Interactions and interdependence within the environment

Chapter overview

5 weeks

Learners are introduced to the basic concepts of ecology and the four levels in which ecological interactions are grouped for research and studying purposes. This is made explicit in the text in this introductory section and learners are given short activities to allow for meaningful engagement with these concepts. Visit http://www.slideshare.net/elmochem/chapter-3-5-lecture-ecology-population-growth.. The slides contain an overview of the concepts introduced in this section.

2.1 What is Ecology (0.5 hours)

Tasks

Skills

Recommendation

Activity: What is a population?

Identifying, observing, analysing, describing, writing

Optional

Activity: Check your understanding

Describing, writing, recalling

Suggested

2.2 Ecosystems (4 hours)

Tasks

Skills

Recommendation

Activity: Abiotic components in a grassland ecosystem

Identifying, listing, describing, writing

CAPS suggested

Activity: Studying an ecosystem

Investigating, observing, taking measurements, describing, analysing, writing, working in groups

CAPS suggested

Activity: Identify the type of interaction between organisms

Identifying, writing

Optional

2.3 Feeding relationships (2 hours)

Tasks

Skills

Recommendation

Activity: Different types of consumers

Identifying, describing, writing

CAPS suggested

Activity: Different decomposers

Identifying, describing, writing

CAPS suggested

2.4 Energy flow: food chains and food webs (3 hours)

Tasks

Skills

Recommendation

Activity: Energy transfer in an ecosystem

Classifying, identifying, evaluating, describing, writing

CAPS suggested

Activity: Studying energy pyramids

Constructing, describing, writing

CAPS suggested

Activity: Identifying food chains and food webs

Identifying, describing, writing

CAPS suggested

2.5 Balance in an ecosystem (2 hours)

Tasks

Skills

Recommendation

Activity: The critically endangered Riverine Rabbit

Identifying, describing, writing

CAPS suggested

Activity: Assessing the impacts of a natural disaster

Describing, writing

CAPS suggested

Activity: Poaching in Southern Africa

Reading, interpreting, writing

CAPS suggested

Activity: Assess your impact on the environment

Identifying, interpreting, writing

Optional

2.6 Adaptations (2 hours)

Tasks

Skills

Recommendation

Activity: Distinguish between types of adaptations

Reading, identifying, describing, writing

Optional (Suggested)

Activity: Why do animals migrate?

Identifying, describing, writing

Optional (Suggested)

Activity: Living stones

Describing, writing, drawing, labelling

CAPS Suggested

2.7 Conservation of the Ecosystem (1.5 hours)

Tasks

Skills

Recommendation

Activity: Why should we care?

Group work, research, public speaking, debating

CAPS suggested

Activity: Finding solutions to environmental problems

Writing, reflecting

CAPS suggested

Activity: Individuals who make a difference

Research, describing, writing

Optional (Extension)

  • What is ecology?
  • We talk about the population of people in South Africa, but do other animals live in populations?
  • What makes up an ecosystem? Are we part of an ecosystem?
  • How are organisms linked by their feeding relationship to make food webs?
  • Why do we need many more producers and fewer carnivores in a food web?
  • How does an ecosystem remain balanced so that it can support all of the organisms that live there?
  • We know that natural disasters can have a huge impact on ecosystems, but what are we as humans doing that upsets the fine balance in ecosystems?
  • What does it mean if an organism is adapted to its environment?
  • Why have some organisms become extinct?
  • During the course of Earth's history, many organisms have become extinct, so what is different and worrying about the decreasing numbers of rhinos and elephants?
  • How can we make a difference to conserve our own environments?

What is ecology?

Learners have already studied the biosphere in detail in Gr. 7. They have also looked at the concept of an ecosystem in the younger grades. We will now put these different levels together in a hierarchical organisation representing the study of ecology.

  • biosphere
  • community
  • ecologist
  • ecology
  • ecosystem
  • interact
  • population
  • population ecology
  • species

If you want to check the definitions of a New word, check the glossary at the back of this strand.

Every living organism on earth depends on and interacts with other living and non-living things to stay alive. Organisms depend on other organisms for food for example, and also depend on their environment for protection and a place to stay. The particular branch of Science that studies how organisms interact with other organisms and their environment is called ecology. Someone who studies these relationships and interactions is called an ecologist.

Ecological interactions

The ecological interactions that take place within a specific area are generally classified into four levels: populations, communities, ecosystems and the biosphere.

Look at the following illustration which shows the levels of organisation.

Individuals live together in populations. Different populations together make up a community. Communities together with the non-living things in their surroundings make up an ecosystem. All the ecosystems on Earth make up the biosphere.

You may have heard of terms such as the biosphere and ecosystems in previous grades. What about populations and communities? You may have also heard about the population of people in South Africa, or when someone talks about your local community at home. What do we mean when we use these terms in ecology? Let's take a closer look.

Population

The website link provided in the visit box for our 'Breathing Earth' provides a very interesting simulation of how the population of the Earth, and also individual countries changes every second. If you have internet access in your classroom and a projector, you could put this website up when you first introduce population and then leave it running during the lesson. At the end of the lesson, bring it up again to see how much the Earth's population has increased in just a short time such as your lesson.

A simulation of different real-time changes in Earth's human populations. http://www.breathingearth.net/

In the previous illustration, we can see that the individual impala make up a population in the game reserve. On a large scale, we can also say that the 50 million people in South Africa make up our country's population.

What is a population?

INSTRUCTIONS:

  1. Look at the following examples of populations.
  2. Answer the questions which follow.

Discuss this with your class first and get their opinions. They should note that all the animals in a population are the same species and they can interact as they live in a specific area.

http://www.flickr.com/photos/amanderson/4686389576/
A population of hippos in the St Lucia estuary (river mouth) in Kwa-Zulu Natal. http://www.flickr.com/photos/amanderson/4686389576/
http://www.flickr.com/photos/amanderson/4685773273/
A population of zebra in Kruger National Park. http://www.flickr.com/photos/amanderson/4685773273/
A population of seals on Seal Island in False Bay.
A population of penguins at Boulders Beach.

QUESTIONS:

Learners might not know the answers to these questions as we have not yet given the definition of a population, but this is meant as a discussion and for them to come to the conclusion of what defines a population without stating the definition up front.

What do you notice about all the animals that make up a population?



All the animals are of the same species in a population. They are different ages, there are males and females.

In each of the photos, the populations of animals are found in a specific area. Do you think the zebra in Kruger National Park and the zebra in Hluhluwe-Umfolozi game reserve in Zululand are from the same population? Why do you say so?



No, they are not from the same population. Individuals in a population all live in a specific area and they can interact and breed with each other. They are not able to interbreed if they live in different areas.

How big is a population?


A population does not have a specific size. Rather, it is defined by the area that you are talking about and whether the individuals can interact.

Do you think the seals that lived on Seal Island 100 years ago are part of the same population as the seals that live there now in the photo? Why do you say so?



No, they are not from the same population. A population consists of organisms that live in the same space and at the same time. Individuals in a population interact with each other and are able to interbreed. Since the seals lived at different times, they cannot be part of the same population.

What do you think would happen to the population of hippos in the estuary at St Lucia if the river dried up? Explain your answer.



The number of hippos in the population would decrease. They might not necessarily all die, but the numbers would decline. The decline may be due to some individuals of the population migrating to other areas. The population would decrease because the environment cannot support the hippos anymore as there is not enough water in their habitat. (We will look more at balance in an ecosystem later in the chapter.)

A group of scientists is studying a population of zebra in the Kruger National Park. They notice that over the last 4 years, the population has grown quite rapidly. Why do you think this might be the case? What are some possible reasons for this? Discuss this with your class.





Some possible reasons include: there are perhaps fewer predators and so less of the zebra are being eaten. There might perhaps be an increase in the number of females that are born and so more are reproducing. There might be an increase in the amount of food available, perhaps other populations of herbivores have decreased or there might have been particularly rainy seasons so there is lots of food (green grass). Disease may have decreased so fewer animals are dying, or the amount of hunting or poaching by humans may have decreased.

Discuss this with your learners and see what they come up with. They have looked at feeding relationships and ecosystems in previous grades and so this also links back to what they have studied before and requires them to apply what they already know to new situations.

Extension question to ask your learners: Another group of scientists wants to compare the population of penguins at Boulders Beach in Cape Town with another population in Antarctica. What are some aspects of each population that they could compare?

Discuss this with your learners. You can help them come to the answers by asking leading questions, such as, how would the scientists compare the habitats of the two populations? How would they compare how well the penguins are doing in each population?

Answer: Some aspects that they could compare between the populations are: growth rate of the population, the number of deaths and births in a given time frame, what the penguins in each population eat, what are the natural enemies/ predators of each population of penguins, which other species do the populations of penguins interact with in their environment, how many times per year do they reproduce, do they build shelters, is there any human impact on the penguins etc.

A population is a group of organisms of the same species that live in the same area at a specific point in time and they can interbreed with each other. When a scientist studies a population they might study how the population grows and the factors that affect how the population increases or decreases. They will also look at how the population interacts with the environment.

Community

In ecology, a community refers to all the populations of organisms that interact in a certain area. Community ecology is the study of how they interact. For example, what feeding relationships occur in the area? What types of grasses do specific herbivores eat and what eats the herbivores? Turn back to the illustration of the wildlife in the game reserve. Which animals make up the community?


Lions, wildebeest, zebra, impala and vulture.

This is a possible extension activity if you would like to do it with your learners. This has only been included in the Teachers Guide as many learners might not be familiar with an underwater environment.

Identify organisms in a community

INSTRUCTIONS:

  1. Study the photo below.
  2. Answer the questions that follow.
http://www.flickr.com/photos/38485387@N02/3580781379/
An underwater community. http://www.flickr.com/photos/[email protected]/3580781379/

QUESTIONS:

  1. Identify the different populations of organisms that make up this underwater community which is part of the ocean.

Different fish populations, turtles, seaweed, corals, sponges, plankton.

  1. Which other types of organisms would you expect to find in this community, but you cannot see in this photo?

Some other examples include: crustaceans such as crabs or crayfish, jellyfish, octopus, other fish species, perhaps a reef shark.

  1. How would describe the specific area that this community inhabits?

It is a coral ree f.

  1. Identify some possible feeding relationships between the different populations of organisms in this community.

Some types of fish could eat other types of fish, the fish can eat the seaweed, the turtles eat the seaweed, the sponges filter the water for plankton.

Ecosystem

Turn back to the illustration of the wildlife in a game reserve. The different populations interact with each other to form a community. When we look at how the communities interact with the non-living things in their environment, then we are looking at ecology at the ecosystem level.

Think of the different populations of organisms making up a community in Kruger National Park, such as the zebra, elephant, lions, springbok, different trees and grasses. Now look at the photo of some of these populations at a watering hole. In this photo we are studying how the living things interact with the non-living things. For example, the zebra and springbok are drinking water, whilst the elephant is splashing mud over itself to cool down. This is an ecosystem.

http://www.flickr.com/photos/34731946@N00/335133573/
An ecosystem in the game reserve consist of the living and non-living things interacting with each other. http://www.flickr.com/photos/[email protected]/335133573/

Biosphere

All the ecosystems on Earth combined make up the biosphere. At the biosphere level, we can study how the living and non-living things interact on a much larger scale. This includes climate changes, how the Earth has changed over history and even how the movement of planet Earth affects different ecosystems, wind patterns as well as rock and soil formation.

All the ecosystems on Earth make up the biosphere.

Check your understanding

This can be done as a short revision task in class or as homework to check what learners understand so far, or you can ask learners the questions orally in class. Suggested answers have been give, but learners must be encouraged to use their own words.

Write your own definitions and explanations for the following terms.

Ecology:


The particular branch of science that studies how organisms interact with other organisms and their environment.

Interaction:


The process of interacting/influencing each other.

Organism:


An individual life form, either a plant, animal, fungus, protist or bacteria.

Population:


A group of organisms of the same species that live in the same area at a specific point in time and they can interbreed with each other.

Community:


All the populations of organisms that interact in a certain area.

Ecosystem:


The different living things interact with the non-living things in their environment to make up an ecosystem.

Biosphere:


All the ecosystems on Earth combined make up the biosphere.

Let's now take a closer look at ecosystems.

Ecosystems

  • abiotic
  • biotic
  • habitat
  • migrate
  • predator

The living organisms on Earth live and interact in different ecosystems around the planet. Together all these ecosystems make up the Earth's biosphere. An ecosystem consists of the abiotic (non-living) environment and the biotic (living) organisms.

Interested in a career in Green Science? Discover the possibilities here! http://www.sciencenewsforkids.org/2013/03/cool-jobs-green-science/

The article in the visit box is about scientists working in 'Green science', particularly studying the interactions between plants and their environment. A possible enrichment activity, or homework task is to get learners to read the article, and then this webpage has questions that you can ask your learners in an informal discussion: http://www.sciencenewsforkids.org/teachers-questions-for-cool-jobs-green-science/

Biotic and abiotic components in an ecosystem

We have looked a lot at the living organisms in different ecosystems in the last section, but what are some of the abiotic things in ecosystems? And how do the biotic things interact with the abiotic environment in a system?

Abiotic components in a grassland ecosystem

INSTRUCTIONS:

  1. Look at the following image of a grassland ecosystem.
  2. Answer the questions that follow.

QUESTIONS:

List some of the abiotic things in the grassland ecosystem shown in the image.



Soil, rocks, water, wind/air, sunlight/temperature, clouds.

For each of the animals, discuss how you think the organisms below are interacting with the abiotic environment.

  1. The eagle
  2. The trees and grass
  3. The mouse
  4. The worm and insect

  1. The eagle uses the wind and air to soar and glide while hunting.
  2. The trees and grass are rooted in the soil so that they do not blow over and they can get water and use sunlight and carbon dioxide to make food.
  3. The mouse creates its home in the ground/dead stick/grass, it can store seeds and food in the soil and hide from predators.
  4. The worm and insect live in the soil.

In the picture, the blue arrows show the movement of water through the ecosystem. What do we call this movement of water?


The blue arrows describe the water cycle.

You can revise the water cycle here, namely: The water in the pond/dam evaporates as it changes from a liquid to a gas. The water vapour then condenses to form clouds as fine droplets of water. When the water droplets become big enough, they precipitate as rain. The water runs down the slopes and collects in the lower regions such as the pond.

Temperature is an abiotic factor in an ecosystem. What can affect the temperature in the grassland ecosystem?




The time of day will affect the temperature as this will affect how much heat energy the ecosystem receives from the Sun depending on the Earth's position. The time of year will also affect the temperature as the ecosystems distance from the sun changes. Weather conditions will also affect the temperature, for example if there are clouds, wind, or it is raining. The direction the area faces will also affect the temperature, for example if it is on a slope.

Another abiotic factor which affects ecosystems is the slope of the land. For example, is it flat or are there hills or mountains. How would you describe the land in the grassland ecosystem? How do you think this contour affects the ecosystem?




This grassland ecosystem has a sloped surface. There is a hill on the right hand side and the ground slopes downwards towards the pond. This shape and slope enables the water to run down when it rains and collect in the pond, thereby providing a collection of water for the ecosystem.

Play a game to identify specific habitats on Earth. http://www.curriculumbits.com/prodimages/details/biology/where-on-earth.html

Apart from the recycling water, biotic and abiotic factors also interact to recycle carbon dioxide and oxygen in ecosystems. Photosynthesis in plants uses carbon dioxide to produce glucose. The plants and animals then break down the sugars and release carbon dioxide again during respiration. Photosynthesis releases oxygen, while plants and animals take it in for respiration. Look at the following illustration which shows how the gases are cycled through a pond ecosystem.

There are two labels missing, but lines have been provided for you to fill them in on the diagram. Discuss this with your class and write them in.

The arrow starting on the right above the buck should read 'Carbon dioxide released during respiration in plants and animals.' The arrow ending on the right below the buck should read 'Oxygen used by plants and animals during respiration.'

Now that we know a bit more about the different biotic and abiotic factors in an ecosystem and how they interact, let's study an ecosystem!

You can find out lots more online by visiting the links provided in the Visit boxes. Be curious and discover the possibilities!

Studying an ecosystem

This activity may be given to learners as a project. Learners will mark off parts of an ecosystem and must ideally be able to return to it regularly. You as the teacher must pre-visit the area and find a suitable area for marking off and studying, preferably near a stream or shore. Ensure that there is enough space for several classes to study the same area without damaging it. Identify organisms and find possible relationships between them. Show learners before the visit how to use equipment correctly and how to keep records. If you have microscopes, teach them how to use these to study soil samples and small organisms. During the visit, you will have to circulate and check on the groups of learners.

As many of the measurements taken will be new concepts and practices, you should explain the reasons for measuring different environmental conditions in the ecosystem. During the investigations it is also important to walk between groups to ensure that they are applying the newly learnt skills appropriately and taking accurate measurements.

The leaf litter and soil samples may be studied in the field but could also be studied in the class. If teachers have taught learners to use basic light microscopes they should encourage them to study these with the use of a microscope too.

MATERIALS::

  • 60 m long string
  • pegs or stakes
  • measuring tape (10 m long)
  • old material for flags on pegs
  • thermometer
  • rulers
  • trowel
  • sieve
  • insect nets
  • large plastic ziploc bags
  • marking pens
  • forceps
  • gloves
  • hand lens
  • clipboard, paper and pens or pencils
  • camera (if possible)

Optional materials are: rain gauge, wire ring, binoculars, field guides.

INSTRUCTIONS:

  1. Work in groups of five. Your teachers will help you to select a site to study.
  2. Stake out a square measuring 10 m x 10 m. Use the 10 m measuring rope and knock the stakes or pegs into the ground to mark the corners of the square. Tie a flag to the stake to make it more visible. (You will use this square to study different things in the next few weeks so make sure that you choose an appropriate site that does not overlap with another group's site.)
An example of a square with four quadrants.

  1. Try to identify as many plants as possible. Use the following space to record your findings about the plants. You can even draw some illustrations.





Learner-dependent answer. If you can find moss or lichen, point out this interaction to learners which shows how a plant grows on a rock (interaction between biotic and abiotic). Similarly, plants (biotic) interact with the soil (abiotic) when they draw mineral salts and water from the soil.

  1. Use the net to capture a few small invertebrates. Try to identify them (ask for help if you need it), then release them unharmed. Use the following space to record your observations. You can use illustrations.





Learner-dependent answer. Perhaps there are ants building a nest - point out these interactions to learners.

  1. Look for evidence of bigger animals. Are there any dropping, tracks, or birds in the trees? Record what you find.





Learner-dependent answer. Lookout for any interactions between animals and with their abiotic environment and point these out to learners.

  1. Measure the temperature.
    1. Measure the air temperature in your square.
    2. Measure the temperature of the soil about 5 cm below the surface.

If you are able to take the temperature several times over the course of a day, use this information to plot a graph to show how the temperature changes over the course of the day.

  1. Take a soil sample by putting one scoop of soil into a plastic bag. Determine whether it is sand, loam or clay soil. Compare your sample with those of other groups. The following illustrations give an idea of the different types of soil.
Different soil types.

Learners might have learned about soil types in previous grades in Earth and Beyond. This acts as a revision of what they have learned.

Use the hand lens to see if you can find any plant or animal remains in the soil.

  1. Use the following space to write about your observations and draw images. (Optional: Measure the rainfall and wind speed. Measure the rainfall over the next few weeks.)





Learner-dependent answer. You can easily make your own rain gauges by cutting the top off a 2 litre plastic bottle and inverting the top half into the bottom half to form a tunnel. You can use a marker pen to write measurements on the side of the plastic bottle. See this link: http://www.rain-barrel-world.com/homemade-rain-gauge.html

QUESTIONS:

Describe the different habitats in your ecosystem.




Learner-dependent answer. They may describe the habitats/ecosystem as aquatic, terrestrial, or even a pond, grass, forest, etc.

Explain how you think the abiotic factors of the ecosystem you studied affect the plants and animals in your ecosystem.




Learner-dependent answer. Learners should take note of the water resources in their square, the slope of the land, and the type of soil and how this affects the organisms.

What relationships did you notice between the plants and animals in the area you studied?




Learner-dependent answer. Learners should take note of any feeding relationships that may exist. We will be studying this in more detail next, but learners would have done this in previous grades.

In the area that you studied, was there any evidence of human interference? For example, rubbish or a pathway? How did this impact on the living organisms and also the abiotic factors in your square? What suggestions can you make to prevent this kind of interference.




Learner-dependent answer. Perhaps there is litter which is blocking a stream, or that animals can eat and choke on. Perhaps there is a path that humans walk on, resulting in them trampling the plants so that nothing grows there. Learners could suggest putting some rubbish bins nearby, or perhaps mark off the area so that people have to walk around, etc.

Do you think that your presence while you made your observations had an influence on the animals or plants in the quadrant that you observed?

Learner-dependent answer. Learners may observe that insects or other small animals scurried away from them when they approached their quadrant. or perhaps insects were drawn to the stakes and rope that was used to demarcate their area.

You may choose to use this practical activity for learners to submit a written account/ report of their work and to present their findings to the class in the form of a powerpoint presentation. Possible areas to evaluate might include:

  • Title and purpose
  • Procedures followed by the group (as awarded from observations by the teacher)
  • Comparative data similarities to other groups in the class that measured in similar areas.
  • Answer to the questions above.
  • Oral presentation of their research as presented in their powerpoint slideshow to the class. They could include the different activities that will be conducted throughout this chapter, such as their work on the different food chains and the food web that exists in their marked off ecosystem and work on conservation of their marked off ecosystem.

We studied relatively small ecosystems. How big can an ecosystem be? Does size in an ecosystem matter?

Ecosystem size

The size of a real ecosystem is not defined in terms of area, but rather by the interactions that occur inside it. It can be as small as a river bank or as large as the Kruger National Park.

Types of interactions

Within an ecosystem the species living in a particular area can interact in different ways with each other. We can classify the interactions between organisms as follows:

1. Competition

When two species in an ecosystem need to share a valuable and often limited resource. such as food or water, they are in competition with each other. The two different species compete with each other for the same resources, especially food.

http://www.flickr.com/photos/dalangalma/8197670802/
Hyenas and vultures are both scavengers and compete for the same food. http://www.flickr.com/photos/dalangalma/8197670802/

2 . Symbiosis

Symbiosis describes the way in which two different species living together in the same community, interact with each other over a long time period. This can occur in the form of parasitism, mutualism or commensalism.

  • Parasitism: Parasitism is when the one species benefits or gains something from the relationship and the other species is harmed in some way. The host may die in some interactions.
http://www.flickr.com/photos/31031835@N08/6368338667/
Ticks are parasites and feed off the blood of many animals, for example dogs, cows, buck and humans. http://www.flickr.com/photos/[email protected]/6368338667/

  • Mutualism: Mutualism occurs between any two species where both of the individuals benefit from the interaction. Both species gain something from the other, so we can say it is mutually beneficial.
http://www.flickr.com/photos/dejeuxx/6924771739/
Pollination is an example of mutualism as the bee gets food (nectar) from the flower and the flower is pollinated by the bee so that it can reproduce. http://www.flickr.com/photos/dejeuxx/6924771739/

Some ants have fungi farms that they carefully look after and protect, providing the fungi with organic matter to fertilse it, while the fungi provides the ants with nutrients.

A video of leaf cutter ants tending to their fungi farm

  • Commensalism: In some interactions between individuals from different species, the one species benefits, while the other one is unaffected by the relationship. Unlike parasitism, in commensalism the other species is not harmed or benefited in any way.
http://www.flickr.com/photos/marcelekkel/4803634603/
A whale shark with remora fish. The remora fish get scraps of food that fall out of the shark's mouth. The whale shark is unaffected. http://www.flickr.com/photos/marcelekkel/4803634603/

3. Feeding: Different species in an ecosystem are related and interact when one species can use the other species as a food source. For example, in predator-prey relationships, the one species (predator) will hunt another species (prey).

http://www.flickr.com/photos/thomson-safaris/8377408989/
Lions and zebras have a predator-prey relationship. http://www.flickr.com/photos/thomson-safaris/8377408989/

Identify the type of interaction between organisms

This is an optional activity.

INSTRUCTIONS:

  1. Study the photos and information in the following table.
  2. Identify the interdependence in each case and give a reason for your choice.

Type of interaction

Explain this kind of interaction

A hummingbird feeding. http://www.flickr.com/photos/mark233/6338069992/

Plants on a forest floor. http://www.flickr.com/photos/[email protected]/6741179033/

Flea bites on a human.

Clownfish in an anemone.

An egret waiting for the rhino to disturb insects to eat.http://www.flickr.com/photos/dkeats/8040036825/

Type of interaction

Explain this kind of interaction

A hummingbird feeding.http://www.flickr.com/photos/mark233/6338069992/

Mutualism

The bird receives nectar from the flower and pollinates the flower at the same time.

Plants on a forest floor.http://www.flickr.com/photos/[email protected]/6741179033/

Competition

The plants are competing for light, space and water.

Flea bites on a human.

Parasitism

The fleas bite the human and feed, and the human is harmed in the process.

Clownfish in an anemone.

Mutualism

The sea anemone protects the clown fish from predators, the clown fish feeds on small invertebrates which might harm the anemone and the anemone also gets nutrients from the fish's fecal matter.

Teacher note: Discuss this with your class, especially if you do not live by the sea.

An egret waiting for the rhino to disturb insects to eat.http://www.flickr.com/photos/dkeats/8040036825/

Commensalism

The egret benefits as it waits for the rhino to disturb insects in the grass as it moves along feeding. the bird then catches the insects as they fly up. The rhino is not harmed and does not benefit from the relationship.

Now that we know how organisms interact with each other, we will take a closer look at the feedings relationships between different organisms.

Feeding relationships

Learners should have learned about food chains and food webs in previous grades. Therefore, some of this content is revision, but the concepts have also been extended to make it more engaging at this level.

  • carnivore
  • consumer
  • decomposers
  • herbivore
  • insectivore
  • omnivore
  • producer

In the last section we saw how organisms from different species interact within an ecosystem. Let's now take a closer look at how organisms interact through their feeding relationships.

Feeding types

Living organisms need to feed to be able to perform the other life processes. Some organisms can produce their own food, such as plants, while other organisms cannot do this and need to feed on other organisms to obtain their energy.

We can therefore identify different feeding types in an ecosystem, based on how the organism obtains (gets) its food. There are producers and consumers.

Producers

Producers are organisms that are able to produce their own organic food. They do not need to eat other organisms to do this. Producers are also called autotrophs. Which organisms have you come across that can make their own food?

The term autotroph comes from the Greek words autos meaning 'self' and trophe meaning 'nourishing'. So autotroph means 'self-feeding'.

Plants are producers because they make their own food during photosynthesis. What do plants need in order to photosynthesise?



Plants need water from the soil, carbon dioxide from the air, and sunlight energy from the sun.

http://www.flickr.com/photos/mickers/7896129722/
Plants produce food through photosynthesis. http://www.flickr.com/photos/mickers/7896129722/

In 2011, deep sea researchers discovered mussels living in symbiosis with bacteria that use hydrogen as a fuel source in chemosynthesis. These are the first organisms discovered to do so!

Consumers

Organisms which cannot produce their own food need to eat other organisms to get food. These organisms are called consumers. All animals are consumers as they cannot produce their own food. Consumers are also called heterotrophs.

The term heterotroph comes from the Greek wordsheteros meaning 'different' and trophe meaning 'nourishing'. So heterotroph means 'different-feeding' or feeding on different things.

There are many types of consumers and we can classify them into specific groups depending on the food that they consume. These are:

  • herbivores
  • carnivores
  • omnivores
  • decomposers

: Different types of consumers

This activity is intended to build on previous knowledge of herbivores, omnivores and carnivores, and introduces concepts of insectivores and scavengers, which learners might have incidental knowledge of but might not have defined themselves. The activity requires that they engage with their existing knowledge and use this to define the terms. Teachers should walk between groups and ensure that they use scientific vocabulary as taught in this and previous sections as well as the New Word List, in their definitions.

INSTRUCTIONS:

  1. The following image shows a variety of different animals found in South Africa.
  2. Study the illustration and then answer the questions that follow.

QUESTIONS:

What is a herbivore? Write a definition below and then give four examples of animals from the images which are herbivores.



A herbivore is an animal which feeds on plant material. Examples of herbivores are: elephant, duck, horse, buffalo, squirrel, grasshopper, rhino, zebra, cow, mouse, etc.

What is a carnivore? Write a definition below and then give four examples of animals from the images which are carnivores.



A carnivore is an animal which eats other animals (living or dead). Examples of carnivores are: lion, jackal, dolphin, crocodile, shark, leopard, mosquito, vulture, crab, seal, etc.

There are different types of carnivores. Some carnivores hunt other animals. They are called predators. The animals that they hunt are called prey. A lion is an example of a predator. Give three examples from the images of animals which are prey of the lion.


Buck, zebra, buffalo.

Other types of carnivores are called scavengers as they eat dead meat, for example a hyena. There are three other scavengers in the images. Identify them and write the names below.


Vulture, jackal, crab.

The following animals are also all carnivores. They all have a similar diet. Do you know what they all eat? Find out what these animals eat. Discuss this with your class.

http://www.flickr.com/photos/42244964@N03/4325982802/
A chameleon. http://www.flickr.com/photos/[email protected]/4325982802/
http://www.flickr.com/photos/chimothy27/3642531568/
A bat. http://www.flickr.com/photos/chimothy27/3642531568/
http://www.flickr.com/photos/twbuckner/4056556245/
A praying mantis. http://www.flickr.com/photos/twbuckner/4056556245/
http://www.flickr.com/photos/j\_benson/2545246443/
A swallow. http://www.flickr.com/photos/j_benson/2545246443/

Write down below what these animals all eat and what we call this type of carnivore.



These animals all eat insects and other small invertebrates. They are called insectivores.

What do we call animals that eat both plants and other animals? Give one example from the pictures.


An animal which eats both plants and other animals is an omnivore. Examples are: pig, flamingo, mouse/rat.

What would you classify humans as?


Humans are omnivores.

The last group of animals that we can discuss from this image are the decomposers. Decomposers break down the remains of dead plants and animals. Give an example of a decomposer from the image.


An earthworm is a decomposer.

Refer to the study of an ecosystem in or near your school that you are busy with.
  1. List the producers in your ecosystem. Explain how you know they are producers.

Learner-dependent answer.

List the herbivores that you found in your ecosystem. Explain how you know they are herbivores.



Learner-dependent answer.

Did you find evidence of or find examples of carnivores in your ecosystem? List them below.



Learner-dependent answer.

Study the soil again. Use the hand lens to see if there are any decomposers that you can see or see evidence of in your ecosystem. Describe any decomposers that you found below.



Learner-dependent answer.

They might have seen earthworms or fungi.

In the last activity, we looked at different consumers. The examples that we studied were all different types of animals. But what about the other kingdoms, such as fungi?

You might remember learning about fungi in previous grades. Fungi are not plants. Fungi cannot photosynthesise as they do not have chlorophyll. So where do fungi get their food from?

Different decomposers

INSTRUCTIONS:

  1. Look at the following photographs of different fungi.
  2. Answer the questions that follow.

QUESTIONS:

What kingdom do the above organisms belong to?


They are mushrooms so they are part of the Fungi kingdom.

What do you notice about where these mushrooms are growing? What are they mostly growing on? Is it dead or alive?



The mushrooms are mostly growing on dead plant matter, such as dead tree logs and humus.

The mushrooms get their nutrients from what they are growing on. At the same time, they are breaking down this dead matter. What can we therefore call fungi?


We can call them decomposers.

When fungi, and other decomposers, break down dead material, they help to return nutrients to the soil. Write a few sentences where you explain why you think decomposers are important in an ecosystem and how they help an ecosystem to function.





Decomposers break down the matter in dead organisms to release the nutrients such as water and carbon, back into the ecosystem. These nutrients are therefore recycled and made available for other organisms to use. They also help to keep an ecosystem 'clean' as they make sure that dead and decaying material is not left lying around in an ecosystem for an extended period.

We now know that the different organisms in an ecosystem are related by how they feed. There are producers and consumers. We have seen that organisms from one species eat other organisms from another species. How can we link these feeding relationships together to describe how the energy is transferred in an ecosystem from the producers to the consumers?

Energy flow: Food chains and food webs

  • energy pyramid
  • food chain
  • food web
  • primary consumer
  • secondary consumer
  • tertiary consumer
  • trophic level

The flow of energy from the sun to different organisms in an ecosystem is very important as it supports all the life process of living organisms. In this section we will look more closely at the way in which energy flows from the sun to different organisms in order to support and sustain life on Earth.

Energy transfer

Energy is vital for organisms to carry out their life processes. All energy in food webs comes from the sun. Plants trap sunlight energy during photosynthesis and convert it to chemical potential energy in food compounds, which are available to animals. Herbivores get energy directly from plants, but carnivores and omnivores eat animals for energy. This energy transfer is shown by food chains.

Energy transfer in an ecosystem

INSTRUCTIONS:

  1. Study the following diagram which describes the feeding relationships between different organisms in an ecosystem.
  2. Answer the questions which follow.

QUESTIONS:

What can we call this diagram?


It is called a food chain.

Which organsism is the producer?


The grass.

Which organisms are the consumers?


Consumers are the grasshopper, the mouse and the owl.

Out of the consumers, identify the herbivore and the carnivores.


The grasshopper is the herbivore and the mouse and the owl are the carnivores.

The rat also actually eats seeds and other plants. Therefore, what do we call the rat? Give a reason for your answer.



The rat is an omnivore as it eats both plants and animals.

What do the arrows show us?



The arrows show the transfer of energy from one organism to the next.

Do you think it makes a difference which way the arrows are pointing? Explain your answer.




Yes, it does make a difference. The arrows show the direction in which the energy is transferred as one organism eats the other one, always from the producers to the consumers.

Use the following space to draw three more food chains. Use organisms from the ecosystem that you are studying at or near your school in at least two of the food chains you draw.







Learner-dependent answer. Learner's food chains must start with a green plant (producer), or part of a green plant, such as a fruit or wheat. Make sure they have used the arrows in the correct direction, and that they have three levels of consumers.

Where would you place decomposers in a food chain? Why do you say so?



Learner-dependent answer. They could say that decomposers would come at the end of the food chain as they break down the bodies of the dead organisms. Or they are often put at the side, with many arrows from all levels of the food chain as they break down all the dead organisms at every level.

Can you see how the above food chain describes how the energy is passed along from the producer to the consumers? But, there are three different consumers in this food chain. How can we distinguish between the different consumers?

  • Animals that eat plants are primary consumers. (Primary means first.)
  • Animals that eat primary consumers are called secondary consumers.
  • Animals that eat the secondary consumers (mostly predators) are the tertiary consumers.

Identify the different levels of consumers in the food chain in the activity.

Encourage learners to write the levels into the diagram. The grasshopper is the primary consumer, the rat is the secondary consumer and the owl is the tertiary consumer.

Each of these levels in the food chain is called a trophic level. The organism uses up to 90% of its food energy itself for its life processes. Only about 10% of the energy goes into new body cells and is available to the next animal when it gets eaten. This loss of energy at each trophic level can be shown by an energy pyramid. But, why do we show it in the shape of a pyramid? Let's find out.

A video on energy pyramids

Studying energy pyramids

MATERIALS:

  • cardboard
  • scissors
  • glue
  • coloured pens and pencils

INSTRUCTIONS:

  1. Have a look at the following energy pyramid for a marine and a savanna ecosystem. Pay careful attention to the number of organisms in each level.
  2. Answer the questions that follow.
  3. At the end, you can make your own energy pyramid.

QUESTIONS:

Which organisms are the producers in the marine ecosystem and in the savanna ecosystem?


The phytoplankton in the marine ecosystem and the trees in the savanna ecosystem.

Which organisms are the primary consumers in the marine ecosystem and in the savanna ecosystem?


The crustaceans in the marine ecosystem and the giraffe in the savanna ecosystem.

90% of the energy is lost and only 10% is made available to the next trophic level. Why do you think this happens? Discuss this in your class and write your answer down below.



The organisms in each level use most of the energy (\(\text{90}\)%) to sustain their own life processes (such as breathing, moving, reproducing etc). Therefore, only \(\text{10}\)% is available to the next level which feeds on them. Learners might need help with this question, so ask them leading questions such as, what do the organisms in each level need energy for?

Give possible reasons why you think there needs to be so many producers in these ecosystems.



Energy flow in an ecosystem is very inefficient and only \(\text{10}\)% of the energy from a trophic level is passed to the next level. Therefore, to provide enough energy for the subsequent trophic levels, there needs to be many plants as primary producers.

How many trophic levels are there in each of the ecosystems?


There are 5 in the marine and 3 in the savanna ecosystem.

Compare the amount of producers with the amount of secondary consumers. Why does there seem to be such a large difference in numbers?



Since only \(\text{10}\)% of the energy produced by the consumers is passed on to the next level, the primary consumers need to eat a large amount of producers to get enough energy to live. In the same way, each level needs to be supported by a larger population that it feeds on as only \(\text{10}\)% of energy is passed on to each level.

Read the following quote and draw an energy pyramid with five trophic levels in the space provided:

"Three hundred fish are needed to support one man for a year. The trout, in turn, must consume 90 000 frogs, that must consume 27 million grasshoppers that live off 1000 tons of grass."







Learner-dependent answer

Now let's make our own energy pyramids. Follow the steps:

  1. Use an A4 sheet of cardboard and cut out a square. Do this by folding one corner to the opposite side and cutting off the rectangle sticking out.
  1. Next, fold the square in half the other way so that you have two folds diagonally across the square.
  1. Cut along one fold to the centre.
  1. Fold the one of the triangle sides underneath the other one to make a pyramid.
  1. Before gluing the two sides together, draw three lines to divide the sides into 4 layers.
  2. Now you need to design your energy pyramid. Decide on the organisms that will go into each level. You will need producers, primary consumers, secondary consumers and a tertiary consumer.
  3. In one of the triangles, draw images of each of the organisms in the different levels.
  4. In another triangle write the names of the organisms.
  5. In the last triangle, write whether the organism is the producer or which type of consumer.
  6. Now glue the triangle together.
  7. Have a look at the following example. You must come up with different organisms!

Food webs

Consumers have different sources of food in an ecosystem and do not only rely on only one species for their food. If we put all the food chains within an ecosystem together, then we end up with many interconnected food chains. This is called a food web. A food web is very useful to show the many different feeding relationships between different species within an ecosystem

Identifying food chains and food webs

INSTRUCTIONS:

  1. Study the food web below.
  2. Answer the questions that follow.

Plankton is a term to describe organisms that live in the water and can't swim against a current. Phytoplankton are microscopic plant-like organisms and zooplankton are tiny animal-like organisms.

QUESTIONS:

What sort of ecosystem does this food web describe?


A marine ecosystem.

Use the following space to write down 4 different food chains from this food web.



There are several answers. Some examples include:

phytoplankton ⇨ krill ⇨ fish ⇨ penguin ⇨ leopard seal

phytoplankton ⇨ zooplankton ⇨ fish ⇨ sea gull ⇨ leopard seal

phytoplankton ⇨ krill ⇨ blue whale

seaweed ⇨ crab ⇨ squid ⇨ penguin ⇨ leopard seal

seaweed ⇨ crab ⇨ squid ⇨ elephant seal ⇨ killer whale

What does a food web show?



It shows how the different food chains are connected.

Name the producer in this food web.


Phytoplankton and seaweed

List the herbivores in this food web.


Krill, zooplankton and crab

Name two species in this food web that are top carnivores.

Killer whale and blue whale.

Refer to the ecosystem that you are currently studying. See if you can identify the food web that is applicable in your marked off ecosystem. Draw it below.









What do you think would happen to the marine ecosystem in the last activity if we removed the phytoplankton? This brings us to the next section.

Balance in an ecosystem

  • endangered
  • extinct
  • limit

In this section will examine the balance between the different trophic levels in ecosystems, since all organisms in the ecosystem have to rely on the resources the area can supply. Any area can only support a limited number of animals. Look at the ecosystem below and decide which resources the organisms depend on. Remember to take some notes.

Use this as an entry point into this section.The resources that organisms depend on are food, shelter and water. Ask learners questions such as, what would happen if there was a drought and all the grass died, or there was a fire that swept through and burned all the plants, or what happened if all the zebra got a disease and died? The ecosystem would become imbalanced in some way.

A balanced savanna ecosystem.

If all the grass and trees die, what would happen to the zebra and elephants? What would later happen to the cheetah and hyena? Why is this? The balance in an ecosystem refers to how many animals it can support for long periods. If the balance is upset, the whole system could fail.

In Gr. 7 Life and Living, learners studied Biodiversity and Sexual Reproduction in Angiosperms, (including sections on pollination). If there is time, show learners this brief video about the mysterious disappearance of honeybees that has many people worried and alarmed! Afterwards, lead a class discussion in which you ask the learners what effect the loss of honey bees would have on the ecosystem.

Try your hand at balancing a jungle ecosystem! http://revolution.caret.cam.ac.uk/flash/ecosystems_younger.swf

One of the factors that we can look at within an ecosystem to see if it is balanced is the population growth of different species over time.

Population growth

Over time ecological populations interact and change within a community. All populations change over time and grow. The population growth of a species in the wild is kept in balance by a number of different factors.

Human intervention can sometimes cause serious damage to an animal population, such as the critically endangered Riverine Rabbit. There are fewer than 200 individuals left in South Africa. It only eats from a few plant types, so its habitat is restricted to where these plants are found, like small areas of the Karroo. During the day, it hides under bushes on the river banks, but many of its home areas have been invaded by humans or destroyed.

The critically endangered Riverine Rabbit

INSTRUCTIONS:

Teachers should if possible download the poster about the Riverine Rabbits and the information leaflet at http://www.capenature.co.za/resources.htm?sm%5Bp1%5D%5Bcategory%5D=341 to discuss in class.

  1. Study the diagram that shows the threats to the Riverine Rabbit.







Explain the different limiting factors on the population growth of the Riverine Rabbit using the information in the diagram.

  • Habitat destruction is one of the main reasons, due to farming, fire and livestock (which may also may cause erosion)
  • Other animal species compete for their food
  • Floods kill their young and destroy their habitat
  • Natural predators kill them
  • They are killed in the road and by 4x4 vehicles in river beds
  • Hunters accidentally kill them, thinking they eat crops

The main goal of any species is to reproduce and ensure the survival of the species. Factors beyond the control of the species often influence this and limit the growth of the population, as with the Riverine Rabbit. These disruptions cause an imbalance in the ecosystem and can affect the organisms that live there as well as the ecosystem as a whole.

Factors that disrupt a balanced ecosystem

We can group these factors as:

  1. natural factors; and
  2. human factors.

We have already discussed this in some detail, but let's take a closer look.

Natural factors

Natural disasters like floods or hurricanes can cause severe disruptions to ecosystems, but the ecosystems recover eventually. If the change occurs over long periods, like climate change and global warming, the damage may not be reversible. For example, there are many different theories about why the dinosaurs become extinct. One of the main theories is a sudden change in climate. This sudden change, whether it was due to a meteor striking earth or not, disrupted the balance in the ecosystems. It was to such an extent that all the dinosaurs died out.

A simulation of a meteor striking Earth (video).

http://www.flickr.com/photos/usace-kcd/5846530366/
A sudden natural disaster, such as flooding, can disrupt an ecosystem. http://www.flickr.com/photos/usace-kcd/5846530366/

Assessing the impacts of a natural disaster

In the 1980s a devastating drought and famine raged in Ethiopia and caused the death of 400 000 people. Many animals, plants and microorganisms also died and species that depend on water for their reproductive cycle, like amphibians, were particularly badly affected.

http://www.flickr.com/photos/ctsnow/95573879/
The dry landscape in Ethiopia. http://www.flickr.com/photos/ctsnow/95573879/
http://www.flickr.com/photos/oxfameastafrica/5933226731/
People trying to collect water. http://www.flickr.com/photos/oxfameastafrica/5933226731/

QUESTIONS:

What is a drought?


Drought is water shortage, when there is no rain for a long time.

What is a famine?


A famine is a scarcity of food when there is starvation.

How do you think a drought and famine in a particular area, such as in Ethiopia are linked?


Drought makes plants die, so animals that eat them also die. This decreases food for humans, as crops and farm animals die as well.

A famine is often accompanied by the spread of diseases amongst animals and humans. Why do you think this is so?


Hungry and malnourished animals and humans are too weak to fight off disease.

Do you think the effects of a drought and famine on an ecosystem are reversible or irreversible? Give a reason for your answer.



It is usually reversible, but ecosystems can take a very long time to recover from severe droughts.

Why is a drought more likely to cause an imbalance rather than a month which receives a lower rainfall than usual?



Droughts last much longer than just one season of low rainfall. Water resources are so low during a drought that most organisms die.

Perhaps discuss this with your learners before they write their answer down. Ecosystems are fairly robust and can cope with fluctuations in climate over the year. However, an imbalance results if the climate changes very suddenly or else changes and remains like that for a long period of time.

Human factors

Many years ago, people like the San had little impact on their environment, as they lived in harmony with the land and only took what food they could carry. Modern man has, however, had a huge effect on nature. We clear land to build cities, roads and farms, we pollute the environment and produce waste and litter. Humans also poach endangered animals and over-harvest marine animals, causing lasting damage to ecosystems.

Poaching in Southern Africa

In 2012, 668 rhinos were poached in South Africa for their horns. By late June 2013, only half way through the year, 446 rhinos had already been poached! This is a massive increase since 2000, when only 7 rhinos were poached.

INSTRUCTIONS:

  1. Read the following newspaper article.
  2. Answer the questions that follow.

Hunting and bushmeat - the road to extinction

19 October 2012

Illegal hunting (poaching) of animals and the killing of wild animals for 'bush meat' in many parts of Southern Africa is of serious concern to environmentalists and is driving some species close to extinction. Poor communities often rely on small wild animals they can trap for food, but removing too many of the smaller animals could force the carnivores (like lions, leopards and wild dogs) that eat them to turn to domestic animals like sheep or cattle for food. For this reason, farmers may go out and shoot even more of them. The carnivores themselves sometimes get caught in the traps. Although hunting and finding bushmeat have been traditional ways of getting food for many generations, the current 'over-hunting' is causing concern. Dr Rene Czudec of FAO commented: "There is an urgent need to look for solutions to ensure the sustainable use of SA's wildlife, while still helping to develop poor communities"

QUESTIONS:

After reading this article, explain what you think bushmeat is.



Any meat obtained from wild animals that were trapped / snared/ poached, often illegally.

How did the hunting of the San differ from today's removal of bush meat?

The San only took what they needed, their traps were well set and their numbers were small. Today's people set traps badly, so the wrong animals are killed and then often not eaten. There are also a lot more people doing it now.

Why do you think there is a market for bushmeat (people who buy the bushmeat)?



Many people are poor and cannot afford to buy the more expensive meat in stores so rather buy much cheaper meat from illegal traders.

Some people from local communities that live on the edge of protected reserves, sneak into the reserves and illegally kill wildlife for food. Do you think this is justified? Discuss this with your class. What do you think some solutions to the problem could be?





Learner-dependent answer. Note: Encourage learners to express their opinion about this and have a debate in class. Some will feel it's wrong to exclude people from traditional food sources, others feel it's more important to protect the animals and find other ways of helping people. Ask for suggestions to solve the problem: quotas / education programmes / help people to grow food or keep animals etc.

What is poaching?


The illegal hunting of wild animals in areas for food or money.

Why do you think poaching causes an imbalance in an ecosystem?



When animals are poached, they are killed at a faster rate than their population can grow. They may become extinct.

In the article, wildlife is poached for the meat to be sold as food. What two other animals that are poached in southern African game reserves and why are they poached?



The rhino is poached for its horn, elephants are poached for their tusks.

Abalone (Perlemoen) are edible sea snails sold as a delicacy in Asia. Although they are farmed, many are removed illegally by divers, causing a serious decrease in their numbers.

http://www.flickr.com/photos/dkeats/5327947094/
A perlemoen in its natural environment. http://www.flickr.com/photos/dkeats/5327947094/
http://www.flickr.com/photos/smwhang/3783672117/
Perlemoen served as a delicacy. http://www.flickr.com/photos/smwhang/3783672117/

How do you think the illegal poaching of perlemoen is affecting our marine ecosystems?



The natural predators of abalone have too little food so other species are eaten instead. this affects other populations too. Note: Local people who use Perlemoen as food for their families are also stopped from removing them. Cape gangsters have taken over the illegal Perlemoen trade because of the huge amounts of money involved. It is illegal to buy or sell Perlemoen!

In the northern provinces in South Africa, Mopani worms are a traditional source of high protein seasonal food found in the area. But. they have also become a favourite of tourists and visitors of the area. Each year, more and more are being eaten so that they are now hard to find. We say they are becoming locally extinct.

http://www.flickr.com/photos/fifikins/4213181845/
A Mopani worm. http://www.flickr.com/photos/fifikins/4213181845/

Describe the impact that this could have on the rest of the food chain or food web.




The secondary consumers that eat them will have less food, so they eat more of other animals, which also become endangered. Secondary consumers that eat only these worms may become extinct directly.

Another way in which humans have a huge impact on the environment and cause disruption to ecosystems is through pollution. There are many different types of pollution. Are you aware of the ways in which you are contributing to pollution?

Assess your impact on the environment

QUESTIONS:

There are different types of pollution, as listed below. For each one, discuss it with your partner and write a short description of the pollution, where it can come from.

  1. Water pollution.


  2. Air pollution.


  3. Land pollution and refills.


You can also start this first part of the activity as a class discussion. Ask learners what types of water resources are polluted and how. What pollutes the air? Where does our waste from our homes go? Below are some points for the discussion.

  • Land pollution: In spite of recycling, much rubbish still goes to landfill sites, where chemicals seep into soil water and poison food chains.
  • Water pollution: Can be caused by car oil, people washing in rivers or using rivers as toilets. Some municipalities allow raw sewage into rivers / sea, others treat sewage first but still spill chemicals into rivers. Farmers spray crops to kill pests, but this also washes into rivers and damages ecosystems.
  • Air pollution: Comes from chemicals burnt by factories, coal stoves, car exhausts, insecticide sprays and burning old tyres, etc.

Assess your own life. Where have you perhaps contributed to the types of pollution mentioned above?




Learner-dependent answer.

Brainstorm ways in which you can reduce each of these types of pollution.




Learner-dependent answer.

Study the following posters made by a Gr. 8 class.

What do you think they are trying to encourage us to do? What is the message of the posters?





This links to the last section on conservation of ecosystems. Note: Some answers include that the first poster is trying to convince us to think twice before throwing something away. We should rather recycle it or think of how it can be reused. We can also buy things with the minimum packaging and reduce the number of plastic bags we use. The second poster is playing on the words of having a 'plan B'. In this case however, we have no plan B for planet Earth - there is no second Earth or any other planet that we can live on. We only have this planet and we need to look after it.

Adaptations

A very important note about this section is to point out the misconception that organisms adapt. This is incorrect as individual organisms do not adapt, it is the populations or species which adapt over time. Individual organisms have adaptations which make them better suited to their environment. The points in CAPS are a misconception and should be reworded as follows:

  • Adaptation is the change in structural, functional and behavioural characteristics of organisms in a species. Adaptation usually takes place over many generations.
  • Adaptation, over time, allows a species to survive in response to changing conditions in the environment
  • Species that are unable to adapt to changes within the environment die out (become extinct)

Be sure to make it clear that it is species or populations of organisms that adapt, and not individual organisms.

  • adapt
  • camouflage
  • hibernation
  • instinct
  • migration
  • mimicry
  • terrestrial environment

Organisms in ecosystems face competition, predation, parasitism and human influence, all of which could affect them negatively, forcing them to adapt, move away or die. It is well known that SA has undergone big climatic changes in the past. For example, the dry Karoo was once swampy and the Cango Caves in Oudtshoorn were once under water.

Rock formations inside the Cango Caves show that they were once under water.

Cango is a KhoiSan word and means 'Place of deep water'.

What is adaptation?

When Southern Africa rose out of the sea millions of years ago, organisms that could not adapt to the new, drier terrestrial environment became extinct, but individuals that could adapt, survived and formed new populations. These adaptations could be changes in the organism's structure, function or behaviour over very long time periods. Only populations of organisms that happen to have suitable characteristics are able to survive in changing conditions within an environment. They are 'selected by nature' to survive. Those species that do not adapt will die out and become extinct.

As we have said, adaptation in species can occur in three main ways:

  1. Structural: the physical characteristics of a species such as having long legs and strong muscles.
  2. Functional: a species may have special way of carrying out its life processes such as being able to produce eggs with a hard shell , so that the embryos can grow and hatch even if the climate changes.
  3. Behavioural: the species can have special behaviours that are instinctive (which they know by instinct) or can be learned such as making safe nests for protecting their babies

These changes take place over a long time period within a species and must be passed on from generation to generation. Over time and over many generations, these adaptations in the individual organisms will allow the species to evolve and adapt to its changing environment. Let's have a look at some of the adaptations of plants and animals.

Adaptations in animals

Animals have different adaptations which have enabled different species to live and function in different areas. Let's look at some of the animals that live in our country and how they have adapted to live in their environments.

Distinguish between types of adaptations

INSTRUCTIONS:

  1. We will work through different adaptations in South African animals that have enabled them to survive in the environment they live in.
  2. In each of the examples, say whether you think it is a structural, functional or behavioural adaptation and give a reason for your choice.

QUESTIONS:

Record your work in the table below each set of animals.

Aardvark: It has a flexible, tubular tongue up to 30cm long as well as thick skin and short, powerful legs with strong claws for digging into termite mounds, its favourite food. These ants are then collected by the tongue - up to 50 000 in one night! It hides underground in daytime to escape heat and predators.

http://commons.wikimedia.org/wiki/File:Porcs\_formiguers\_\%28Orycteropus\_afer\%29.jpg
Two aardvarks in an enclosure. http://commons.wikimedia.org/wiki/File:Porcs_formiguers_%28Orycteropus_afer%29.jpg

How is the species adapted to life in its habitat?

What type(s) of adaptation is this?

How is the species adapted to life in its habitat?

Body adapted to dig and reach into nests to get prey; little hair as lives in hot climate; has shovel-like claws and powerful short limbs, long sticky tongue to pick up and eat the ants.

What type(s) of adaptation is this?

Structural: longer snout and tongue; thick skin to protect it from termite and ant bites; powerful limbs to dig in any soil

Behavioural: nocturnal - hunts at night when cool; hides in tunnels from predators

Desert beetles :They have ridges on their backs for collecting mist in the Namib Desert at night. Long back legs tilt the body, so mist is collected, condenses and runs via channels and grooves into their mouths.

http://www.flickr.com/photos/pedronet/3203851713/
A desert beetle. http://www.flickr.com/photos/pedronet/3203851713/

How is the species adapted to life in its habitat?

What type(s) of adaptation is this?

How is the species adapted to life in its habitat?

Body adapted with grooves and ridges to channel tiny droplets to the mouth; the hind legs are longer and stronger to keep the beetle in this position for a long time.

What type(s) of adaptation is this?

Structural: grooves on body form channels to mouth; strong hind legs

Behavioural: nocturnal habits, it stands in the specific position all night while water droplets condense on its body

Gemsbok :This striking antelope from the Kalahari Desert prefers grass and shrubs, but will dig for roots and tubers if it needs water. They save water by not sweating and sleep in the shade during the day. If they can not find shade, they turn the body's lightest side to the sun.

http://www.flickr.com/photos/mister-e/3051915461/
Gemsbok standing in the Kalahari. http://www.flickr.com/photos/mister-e/3051915461/

How is the species adapted to life in its habitat?

What type(s) of adaptation is this?

How is the species adapted to life in its habitat?

Body colour pattern help it to blend into surroundings; also lighter colouring can face the fiercest angles from the sun if no shade; can extract water from plants that it eats

What type(s) of adaptation is this?

Structural: body colouring

Functional: extract all available water from plants it eats; does not lose much water or energy as it does notr sweat

Behavioural: seeks shade during hottest hours of the day; turns the lightest part of its body to the sun if no shade is available; can change eating patterns if normal diet of grass is not available

Ostrich: These are the biggest and heaviest birds, but they can't fly. To avoid predators, they fight with strong clawed toes or run away, up to 70km/hr! Ostriches swallow small stones to help digest any food they find. Male ostriches get red beaks in the mating season. The female lays eggs and she sits on them during the day, while the male incubates them at night - examine their colour differences to see why.

http://www.flickr.com/photos/jonasb/6987050666/
A female ostrich. http://www.flickr.com/photos/jonasb/6987050666/
http://www.flickr.com/photos/jonasb/6987048092/
A male ostrich. http://www.flickr.com/photos/jonasb/6987048092/

How is the species adapted to life in its habitat?

What type(s) of adaptation is this?

How is the species adapted to life in its habitat?

Ostriches have a long toe and claw to fight predators and escape; eggs remain dormant until heat of breeding male and female's bodies starts their development. Male and female share nesting duties. Their bodies are specially camouflaged: male has black feathers to be camouflaged at night when it is on the nest; female has speckled dusty coloured feathers to be camouflaged during the day when she is on the nest.

What type(s) of adaptation is this?

Structural: strong toe and leg muscles help it to run fast; male beak turns red to signal female that it is ready to breed.

Behavioural: male sits on nest at night and female on nest during day as they take turns to nest; ostriches eat pebbles to help digestion as they do not have teeth; female lays just enough eggs to cover with body

Stick and leaf in sect:These insects look like leaves or sticks to avoid predators - this is calledmimicry. They feed on plant materials at night and move very slowly to avoid being seen. Female stick insects can reproduce without mating.

http://www.flickr.com/photos/nh53/6061103659/
A stick insect. http://www.flickr.com/photos/nh53/6061103659/

How is it adapted to life in its habitat?

What type(s) of adaptation is this?

How is it adapted to life in its habitat?

Body adapted to mimic leaf or stick; moves very slowly to seem like a branch or leaf moving; nocturnal to avoid being seen in daylight by predators; stick insects can reproduce without male insects

What type(s) of adaptation is this?

Structural: body structured to resemble leaf or stick

Behavioural: nocturnal as it feeds under cover of darkness; moves slowly to not attract predators

Other behavioural adaptations

Many species of animals display an interesting behavioural adaptation called migration. This occurs when an animal or a group of animals move between different areas at different times or periods.

Why do animals migrate?

INSTRUCTIONS:

  1. Have a look at the following animals.
  2. Think of reasons why they would want to migrate from their present habitat.

Animals

Description

Reason to migrate

Wildebeest migrating in the Masai Mara. http://www.flickr.com/photos/scubagirl66/7929201230/

Wildebeest migrate long distances each year which coincides with the pattern of rainfall and grass growth.

The sardine run as sardines migrate along the South African coastline. http://www.flickr.com/photos/tanaka_juuyoh/1775405862/

The sardine run occurs along the African coast during May to July each year when billions of sardines migrate to the north east coast of South Africa.

Animals

Description

Reason to migrate

Wildebeest migrating in the Masai Mara. @@BYhttp://www.flickr.com/photos/scubagirl66/7929201230/

Wildebeest migrate long distances each year which coincides with the pattern of rainfall and grass growth.

Find where the grass is growing and there are water sources

The sardine run as sardines migrate along the South African coastline. @@BYhttp://www.flickr.com/photos/tanaka_juuyoh/1775405862/

The sardine run occurs along the African coast during May to July each year when billions of sardines migrate to the north east coast of South Africa.

There are actually many theories about why the sardine run occurs, and it is still poorly understood. The most likely reason is that it is a seasonal reproductive migration.

Watch underwater footage of the amazing sardine run that occurs each year from May to July

Animals that don't migrate sometimes go into an inactive state called hibernation in winter. Some of them sleep through a whole winter, while some frogs hibernate by burrowing into the mud when the pond dries up, until the rains return.

Frogs have a special chemical in their bodies that prevents their blood from freezing completely - a kind of natural antifreeze!

Adaptations in plants

Several local plants are also adapted to their environment.

The umbrella thorn in the African savannah can survive temperatures ranging from 50°C to below freezing. Its deep roots reach ground water easily and the small leaves prevent dehydration, while still being well exposed to light due to the umbrella shape of the tree. Why does it need light?


The more exposure to sunlight, the higher the rate of photosynthesis. Encourage your learners to take notes when you discuss topics in class.

An umbrella thorn acacia.

The Baobab tree survives in dry areas, since it stores water in the thick trunk and spongy wood. The smooth bark reflects heat, making it cooler, but also helps protect the fruits from monkeys. How can it do this?

http://www.flickr.com/photos/dkeats/5643928782/
The sun setting behind a baobab tree. http://www.flickr.com/photos/dkeats/5643928782/
http://www.flickr.com/photos/kelsiedipernaphotography/3800104410/
This baoba is over 3000 years old! Take note of its width and the reflective bark. http://www.flickr.com/photos/kelsiedipernaphotography/3800104410/

The slippery surface also helps prevent monkeys and other small animals from climbing up and eating its leaves and fruit!

The flowers smell like rotting meat to attract bats, flies and moths at night. Why do you think the baobab tree needs to attract these animals to its flowers?


The fruit bats come to feed on the flowers and the nectar and in turn they pollinate the baobab flowers.

http://www.flickr.com/photos/tgerus/3613267071/
A baobab flower which smells like rotting meat. http://www.flickr.com/photos/tgerus/3613267071/

We are now going to look at some very unique plants, which are only found in South Africa.

Living stones

INSTRUCTIONS:

  1. Study the following photographs. They show different types of plants. These plants actually look like pebbles. They are from the genus Lithops and they succulent plants, meaning they have parts that can store water.
  2. Answer the questions which follow.

The name 'Lithops' comes from two Ancient Greek words lithos meaning 'stone' and ops meaning 'face'. So, Lithops means 'stone-faced'!

http://www.flickr.com/photos/yellowcloud/3862534417/
Lithops plants growing in dry rocky ground. http://www.flickr.com/photos/yellowcloud/3862534417/
http://www.flickr.com/photos/yellowcloud/4673616905/
Different patternedLithops plants. http://www.flickr.com/photos/yellowcloud/4673616905/
A very camouflagedLithops plant. Can you see it?
http://www.flickr.com/photos/yellowcloud/4239972017/
A floweringLithops. http://www.flickr.com/photos/yellowcloud/4239972017/

QUESTIONS:

Why do you think these plants are commonly referred to as 'living stones' or 'pebble plants'?



This is because they are plants but they are camouflaged to look like stones or pebbles.

Why do you think the plants have such different patterns on their surfaces? How does this help them to survive in their environment?



The Lithops plants are camouflaged to look like stones and blend in with their rocky soil that they grow in. The patterns look like different rocks/pebbles. They are therefore not usually seen by herbivores which might eat them. This adaptation protects them from being eaten.

Lithops plants are classified as succulents. What does this mean? What type of environment are succulents adapted to live in?



Succulents are plants which are adapted to live in hot, arid environments and they have thickened, fleshy leaves and stems to store water.

Lithops leaves are fleshy and mainly underground, and the stem is short. Flowers grow between the leaves, which shrink to below ground level during drought. How does this help the plant survive?



The fact that the leaves are mostly underground helps the plant to conserve water because as little as possible is exposed to the hot environment so this reduces water loss. During drought, the leaves shrink even further underground to try to conserve water even more.

If the leaves are reddish-brown and mainly underground, where is the chlorophyll? Examine these dug-up stone plants.

http://www.flickr.com/photos/yellowcloud/4240758668/
The upper surfaces ofLithops plants. http://www.flickr.com/photos/yellowcloud/4240758668/

http://www.flickr.com/photos/yellowcloud/4239988271/
The underneath surfaces of theLithops plants. http://www.flickr.com/photos/yellowcloud/4239988271/

Where is most of the green part of the plant located?.


Most of the leaf and hence the green chlorophyll is located on the underneath side of the plant underground.

This is a thin section of a stone plant under a hand lens. Draw a diagram of it and label the top of the leaves, the split between the leaves and the stem. Indicate where the soil level would be. What is stored in the clear area of the leaves?

http://commons.wikimedia.org/wiki/File:Dissected\_Lithops\_0133\_\%283137859955\%29.jpg
A cross section of aLithops plant viewed under a microscope. http://commons.wikimedia.org/wiki/File:Dissected_Lithops_0133_%283137859955%29.jpg

Learner-dependent answer

The labelled micrograph should look something like this:

The upper patterned surface acts as a window. Can you see the clear, fleshy middle parts of the leaves? Do you think light can travel through this? How does this allow the plant to photosynthesise?




The upper part of the leaves acts as window and lets light through. As the interior of the leaves is transparent, the sunlight can travel through to the bottom parts of the leaves which are underground and contain the chlorophyll in order to photosynthesise. This allows the plant to have a coloured, patterned upper surface to camouflage it from herbivores, but still allows that sunlight to travel through for photosynthesis.

Conservation of the ecosystem

Our country is one of the most naturally diverse in the world. This means that we have many different species and habitats and ecosystems here, more than most other places in the world.

Our country's natural beauty and diversity attract thousands of tourists each year, but it is under severe threat from poaching, pollution and other human influence. Ecosystems are able to naturally recycle materials like water, carbon dioxide and other gases and the remains of organisms, if they are left alone. But ecosystems cannot do this effectively if we interfere. These human interferences include:

  • Habitat destruction like deforestation and burning
  • Pollution causing global warming
  • Alien invasive plants taking over ecosystems
  • Hunting, poaching and other killing of wildlife

These pressures have caused great loss in biodiversity. Some ecosystems are under strain and others have already collapsed.

Video on rhino poaching in South Africa.

For more information on how you can get involved in the efforts against rhino poaching http://www.stoprhinopoaching.com

Why should we care?

There are many reasons why it is important for humans to care about the environment. As we have learnt, everything in an ecosystem is connected. Therefore harming one component of the ecosystem will have a ripple effect that can damage all the other systems.

Finding solutions to environmental problems

INSTRUCTIONS:

  1. The following table is a list of environmental issues.
  2. Do some research on air pollution, water pollution, landfills and climate change.

INSTRUCTIONS:

Write down the effect (consequence) of this issue on the ecosystem (or on humans). Write down a possible solution or a simple action that you can take to help.

Environmental Issue

Consequence

Action

Inappropriate waste disposal: Air pollution

Inappropriate waste disposal: Water pollution

Inappropriate waste disposal: Landfills and littering

Carbon emissions and climate change

There are many possible answers in this activity. Learners may be incredibly specific or they may prefer to answer generally. They can be creative with their suggestions. Below are some example answers, but learners may come up with many more.

Environmental Issue

Consequence

Action

Inappropriate waste disposal: Air pollution

1) Harmful chemicals in the air cause a range of allergic and degenerative lung diseases as well as cardiovascular disease and many cancers.

2) Air pollution can also cause acid rain, which can destroy forests and poison lakes.

Support companies and products that use cleaner production methods. Do not use products known to cause pollution. Develop cleaner technologies.

Inappropriate waste disposal: Water pollution

Water pollution can be cause by factories or farms allowing their waste to run off into streams or water sources, or it can be caused by the accumulation of many people discarding their waste into rivers. This may cause the spread of disease or poison aquatic plants and animals.

Do not throw harmful chemicals down the drain or into rivers and streams. Support companies that dispose of their waste responsibly.

Inappropriate waste disposal: Landfills and littering

Litter builds up and can take many thousands of years to degrade. Due to inappropriate waste disposal, plastic is ending up in the oceans, and in many animals habitats. Animals who mistake litter for food often end up choking and dying.

Reduce, reuse and recycle wherever possible. Do not throw litter onto the ground. Look after your belongings so that they last longer. Purchase responsibly- don't buy packaging that does not degrade (like polystyrene).

Carbon emissions and climate change

Excessive burning of fossil fuels is a type of air pollution that contributes to global warming and climate change. Climate change has an effect on habitats as animals and plants cannot adapt fast enough to the rapid changes in their habitats. This may result in many species going extinct.

Try to limit your use of electricity- switch off lights, put on more clothes instead of using a heater, turn off the geyser for some hours each day. Don't overfill the kettle. Use public transport. Share lifts and carpool. Don't drive excessively. Walk when you can. Use less plastic.

Some people and organisations like Greenpeace, fight for environmental conservation. There may be groups in your local area that also promote environmental conservation - do not think that you can not make a difference if you are just one person!

http://www.flickr.com/photos/jemanlin/1417937089/
The Greenpeace ship,Arctic Sunrise, which is used in many environmental awareness campaigns and research. http://www.flickr.com/photos/jemanlin/1417937089/

Why should we care?

This is an optional, extension activity.

INSTRUCTIONS:

  1. Divide the class into two teams. One group supports environmental conservation and the other believes we should use all earth's resources as we like.
  2. Both groups must research their topics beforehand and gather relevant points.
  3. The teacher can lead the debate and ensure it proceeds in an orderly way.

QUESTIONS:

After the debate, write down 3 points about each viewpoint that you can remember.







Learner-dependent answer.

Below is some extra information on the types of individuals who are actively involved in conservation, if you wish to discuss this further with your learners:

  • Park rangers and conservationists work to save the environment. Research scientists inform park managers about conservation and investigate how climate change affects populations.
  • Economists and scientists are trying to work out the 'costs' of big cities on the environment and how to sustain healthy ecosystems so that we and all living things can enjoy the benefits of healthy food, clean water and air.
  • Other groups remove alien plants or track down poachers, especially regarding cycad and rhino poaching, which is escalating. You can help!
  • Some people run campaigns to raise awareness about different environmental concerns, for example the poaching of endangered animals, or the drive to recycle cans, paper, bottles and plastic. Get involved!
  • Climate change activists inform the public about global warming and the damages we are causing to our world by deforestation and pollution.

Learn about actions that you can take at home to help the environment. YOU can make a difference http://www.wwf.org.za/act_now/green_living/at_home/

Your photos can help scientists to map where mammals are in South Africa and help guide their conservation efforts http://mammalmap.adu.org.za/index.php?serial=1

There are all ordinary people who feel passionate about saving the only world we have. It takes the combined work of many concerned people to maintain healthy ecosystems - you can also make a difference!

Individuals who make a difference

This is an optional, extension activity to create awareness about what other individuals have done. If you do not have time to do it in class, learners could do it as a homework exercise.

INSTRUCTIONS:

  1. Below are some photos of various individuals who have contributed to environmental conservation and awareness in some way.
  2. Research what each individual has done.
  3. Then, chose one who you find most inspiring and write about them, identifying what is is you admire.
  4. You do not have to stick to the people who have been identified here. You can write about someone else too who you have identified with.
  5. Lastly, reflect on how you can make a difference in your own life and what you could do to conserve you own local environment. Write about this too.
http://www.flickr.com/photos/jrscientist/4379034881/
Sir David Attenborough. http://www.flickr.com/photos/jrscientist/4379034881/
http://www.flickr.com/photos/nickstep/5072666287/
Jane Goodall. http://www.flickr.com/photos/nickstep/5072666287/
Jacques Cousteau.
http://commons.wikimedia.org/wiki/File:Al\_Gore.jpg
Al Gore. http://commons.wikimedia.org/wiki/File:Al_Gore.jpg

Some other people to research include:

  • Wangari Mathai
  • Lawrence Anthony
  • Steve Irwin
  • Diane Wilson
  • Dian Fossey
  • Ian Player
















A short tribute film on Wangari Mathai.

Summary

Ecosystems

  • Ecology is the study of interactions of organisms with one another and with the physical and chemical environment.
  • The study of ecological interactions is conducted at four levels:
    • populations
    • communities
    • ecosystems
    • biosphere(s)
  • All ecosystems combined make up the biosphere.
  • An ecosystem consists of a community that includes all living organisms (biotic) such as plants and animals, together with the non-living (abiotic) environment and climatic conditions such as temperature, air and wind, water, interacting as a system.
  • An ecosystem can refer to a specific area on Earth or the entire biosphere can be regarded as one large ecosystem.
  • The survival of populations and species depends on whether enough individuals are suited to the environmental conditions at the time. As conditions do change over time only those better suited to the changed environment will be able to continue the species. And so over time species adapt.

Feeding relationships

  • Plants are producers. They make their own food.

  • Animals are consumers. They obtain food from plants either directly (such as herbivores) or indirectly (such as carnivores).

  • Herbivores feed on plants.

  • Carnivores feed on other animals (living or dead). This group includes:

    • Predators hunt other animals, their prey, for example lions and leopards.
    • Scavengers that eat dead animals, for example hyenas and vultures.
    • Insectivores that eat insects and other small invertebrates such as worms
  • Omnivores feed on plants and animals. Humans are generally omnivores.
  • Decomposers break down (decompose) the remains of dead plants and animals. They recycle important nutrients in the environment.

Energy flow: food chains and food webs

  • Plants and some algae play a very important role in the ecosystem because they capture the radiant energy from the Sun and use it in the process of photosynthesis to produce glucose that the plant and other animals can use to gain energy.
  • This energy is passed along a food chain from producers to consumers; decomposers are the last link in this transfer of energy. They release energy as heat to the environment.
  • Each stage of a food chain is called a trophic level.
  • Energy transfer and energy loss occur at each trophic level.
  • Interlinked food chains together form food webs.

Balance in an ecosystem

  • An ecosystem can only accommodate as many organisms as its resources (food, water and shelter) can carry.
  • The balance can be disturbed by natural or human factors:
    • natural factors include extreme changes in patterns of weather and climate, such as floods, drought, extreme and sudden changes in temperature.
    • human factors include removing organisms from the ecosystem (such as poaching), human-induced pollution.
  • These factors can contribute to an imbalance in an ecosystem, seriously impacting on its components and altering its nature.

Adaptations

  • Adaptation is the change in the structural, functional or behavioural characteristics of a species over many generations.
  • Adaptation allows the species to survive as it adapts to changing conditions within the environment.
  • Species and populations of organisms that are unable to adapt to changes in the environment will die out and become extinct.

Conservations of ecosystems

  • People can work towards managing and sustaining natural ecosystems.
  • Individuals can contribute to conservation in various ways such as appropriate waste disposal (including recycling and reusing).

Concept map

This concept map shows how the concepts in this chapter on the 'Interactions and interdependence within the environment' link together. Complete the concept map by filling in the 2 levels which are missing for the study of ecology. Also, fill in the 4 types of consumers that you have learned about in this chapter.

Can you see how the arrows show the direction in which you must 'read' the concept map?

Teacher's version

Remember that concept maps are different to mind maps in that concept maps have a hierarchical structure and show how concepts link together using arrows and linking words. Whereas mindmaps generally contain a central topic and individual branches coming out which do not necessarily link together. Mindmaps can also be a useful way of summarizing information and studying, however, we are using concept maps as they help to show linkages, which is very important in science. Help your learners to 'read' the concept map by showing them that the arrows show the direction in which concepts progress and are linked to each other. Learners might battle to find the other 2 levels in which we study ecology - help them by reminding them of the 4 levels, namely; populations, communities, ecosystems and the biosphere.

Revision questions

Match the columns in the following table to link the description to the term. Write your answers on the lines below. [9 marks]



1. Producer

A. Organisms that eat other organisms to obtain food

2. Carnivore

B. Feeds on plants and animals

3. Consumer

C. Organisms that make their own food.

4. Omnivore

D. Organisms that eat only plant material

5. Predator

E. A carnivore that eats dead animals

6. Decomposer

F. An organism which feeds on other animals (living or dead)

7. Insectivore

G. An organism that breaks down the remains of dead plants and animals

8. Scavenger

H. A carnivore that hunts other animals

9. Herbivore

I. A carnivore that eats mainly insects and other small invertebrates

1 - C

2 - F

3 - A

4 - B

5 - H

6 - G

7 - I

8 - E

9 - D

Distinguish between abiotic and biotic factors in the environment. [4 marks]





Abiotic factors are the non-living elements in the environment that have never and will never live. This includes gases, rocks and soil, water, temperature and weather conditions. Biotic factors are those factors that have once lived or that are living today. This includes past and present plants and plant materials, animals and microorganisms.

There are different levels of ecological organisation between an individual organism and the biosphere of the Earth. List and describe the levels in between the two mentioned here. [6 marks]







Population: the individuals of the same species that live in the same space and time and breed with each other form a population.

Community: different populations of different species within the same area at the same time form a community.

Ecosystem: all the communities within the larger area that interact with and are interdependent on each other and the abiotic factors within the area.

Discuss the different types of interaction that exists between species. [9 marks]









  • Competition: when organisms from different species compete for the same limited resource
  • Feeding relationships: there are many different types of feeding relationships between different organisms in an ecosystem, such as herbivory, predation, scavenging.
  • Symbiosis: when two (or more) organisms' actions have a positive, negative or neutral effect on other organisms from a different. The way in which they interact and the influence this has on the other species leads us to identify
    • mutualism
    • parasitism
    • commensalism

Explain what the different trophic levels represent in an ecosystem and why we can represent the levels as a pyramid with the bottom layer being the largest. [8 marks]









Producers: are organisms / plants that are able to produce their own energy from sunlight, water and carbon dioxide and do not need to consume other organisms to get energy.

Primary Consumers: need to consume plants in order to get energy.

Secondary Consumers: need to consume primary consumers to get energy.

Tertiary Consumers: consumers secondary consumers to get energy.

The trophic levels can be represented as a pyramid as there needs to be more organisms in the bottom layer than in the layer above it. This is because only about \(\text{10}\)% of the energy in each trophic level is available to the next level. The rest is used by the organisms for their own processes.

Evaluate this statement: An insectivore is a carnivore.' [2 marks]




An insectivore eats insects and small invertebrates and is therefore a carnivore, as it eats other animals, thus the statement is correct because carnivores get their energy from eating other animals and not plants.

Identify the following in this food web. [7 marks]

  1. Producers:
  2. Primary consumers:
  3. Secondary consumers:
  4. Scavengers:
  5. Decomposers:

  1. trees, shrubs, grasses
  2. zebra, elephant, termites
  3. cheetah, hyena
  4. vultures, hyenas
  5. bacteria, fungi

There are more zebra than cheetah in this balanced ecosystem. Explain why this is so. [3 marks]





The zebra are primary consumers and use about \(\text{90}\)% of the energy that they get from the grass, transferring about \(\text{10}\)% to the cheetah to consume. There therefore needs to be more zebra than cheetah in order to make sure the cheetah are supported in terms of food supply, and also that they do not eat all the zebra so that the zebra population does not die out.

Describe the work of the producers in this ecosystem. [2 marks]



The producers capture the energy from the sunlight and convert it to chemical potential energy in the form of glucose through the process of photosynthesis. In this way they place energy into the ecosystem which animals cannot do.

Based on this picture, evaluate how active the decomposers are in this environment. [2 marks]



Learners should be able to identify the lack of dead animal carcases and manure, which indicates that the decomposers are working efficiently.

What do you think would happen to this ecosystem if all the zebra got a disease and died? [2 marks]



If all the zebra died, the ecosystem would become unbalanced. Firstly, the cheetah would not have a food source anymore and they would also in turn suffer and starve. The hyena would also have a depleted food source. There might perhaps be less dung for the dung beetle to use to lay its eggs. The grazing of the zebra also has an effect on the plants and so if the zebra all die out, the grass growth will increase.

What do you think would happen to this ecosystem in the short term and in the long term if a big fire came through and burned most of the grass and some of the trees? [2 marks]



In the short term, many of the animals would battle as the zebra and the elephant would have a reduced food source, especially the zebra which eat grass. Some of them might die. This in turn will affect the other predators. Many of the smaller organisms would also be burned. However, in the long term, this imbalance will normally be restored as the landscape recovers and the plants start to grow again after the first rains.

The following food web shows the feeding relationships between organisms in another savanna ecosystem.

Use this food web to write down three food chains. [6 marks]

There are multiple food chains here. Some examples are:

tree \(\rightarrow{}\)\(\rightarrow{}\)

tree\(\rightarrow{}\)\(\rightarrow{}\)

shrub\(\rightarrow{}\)\(\rightarrow{}\)

grass\(\rightarrow{}\)\(\rightarrow{}\)\(\rightarrow{}\)

grass \(\rightarrow{}\)\(\rightarrow{}\)\(\rightarrow{}\)\(\rightarrow{}\)

Describe how the different organisms in the table below are adapted to live in their specific environments. [4 X 3 marks = 12 marks]

Organism

Adaptations

A leopard.http://www.flickr.com/photos/safaripartners/4838390161/

A whale.http://www.flickr.com/photos/eguidetravel/8058729536/

A Venus Flytrap.

A dung beetle.http://www.flickr.com/photos/amylovesyah/3945525048/

Organism

Adaptations

A leopard.http://www.flickr.com/photos/safaripartners/4838390161/

The leopard is camouflaged due its colouring and spots. This helps it to hide away from prey so that it can get as close as possible before chasing. The leopard is adapted to run fast over short periods in order to catch its prey. It has a light, streamlined body with strong legs. It has a tail for balance to turn sharp corners while chasing.

A whale.http://www.flickr.com/photos/eguidetravel/8058729536/

The whale is a mammal so it does not have gills, but it can hold its breath for a long time underwater so that is can dive down and also catch prey/filter feed. It has a blowhole on top of its head for breathing. The blubber keeps it warm as it insulates it and also provides energy when diving and swimming in very cold seas. It has a strong tail, stream lined body and its forelimbs are flippers for swimming.

A Venus Flytrap.

This plant has adapted as it is carnivorous. It catches flies and has adapted to digest them. The red colouring inside the 'catchers' attracts the flies as it looks like meat. As soon as the flies land on the surface, the plant is triggered and the catchers clamp shut, catching the fly. The catchers are adapted with the spikes on the end to form a cage around the fly and keep it there while it is digested. The plant can also photosynthesise as it is green and contains chlorophyll

A dung beetle. http://www.flickr.com/photos/amylovesyah/3945525048/

A dung beetle has adapted to its environment by using the dung from other big herbivores as a food source and to lay their eggs. They have adapted by being able to collect the dung and roll it into balls so they can transport it to where it is needed. This also creates a warm, safe chamber in which to lay their eggs, feed the young and protect them. The dung beetles have strong front legs so that they can do the rolling. Their back legs have fine control of the dung ball.

Read this paragraph about the Quiver tree of the Kalahari and Namib desert.

The Quiver tree lives in the Namib and Kalahari deserts, where the heat and lack of water makes it extremely difficult for plants to grow and survive. It stores its water inside green succulent leaves and bloated branches. The San used to hollow out the branches and use them for their quivers, which is where the tree gets its name from. The branches are covered with a white powder that reflects the heat and the leaves have very few pores to minimise water loss through evaporation. During extremely harsh weather conditions, the tree can amputate (remove) its own branches and reduce the leaves to minimise water loss even further, then when the conditions improve, it sends out new shoots and grows a rich leafy top again.

A quiver tree.

How is this species adapted to life in its habitat? [4 marks]





The quiver tree has thick bloated branches and succulent leaves so that it can store water for the dry months. Its branches are covered in white powder to reflect heat away from plant which helps to reduce water loss. The leaves have few pores to also minimise loss of water. The tree can amputate leaves and branches if water is scarce.

A group of poachers recently made the following statement when they were arrested: ""Why is it so important to conserve the biodiversity and the environment? Surely there are enough wild animals and plants that it doesn't matter if some of them die and become extinct?" Write 3 - 4 sentences to explain to them why we need to care about the biodiversity in our country. [6 marks]

Learners need to display the following:

  • recognition of the importance of valuing each species and their specific niche in their ecosystem
  • recognition that each species fill a specific place in the food chain and if one is removed it affects all the other species in that food chain / web / pyramid.
  • each organisms needs to be protected in order to preserve the entire ecosystem
  • the importance of preserving our diversity to ecotourism and for future generations to enjoy (we have not INHERITED the earth from our parents, we are CUSTODIANS of the earth for our children!)

Total [84 marks]