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.

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?

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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?

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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?

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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?

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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.

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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.

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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?

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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.

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.

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.

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:

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

Interaction:

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The process of interacting/influencing each other.

Organism:

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

Population:

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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:

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

Ecosystem:

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

Biosphere:

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All the ecosystems on Earth combined make up the biosphere.

Let's now take a closer look at ecosystems.

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.

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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

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2. The trees and grass

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3. The mouse

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4. The worm and insect

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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?

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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?

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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?

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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.

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.

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!

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.)

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.

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

Build your own wind meter. http://www.scientificamerican.com/article.cfm?id=bring-science-home-wind-speed

QUESTIONS:

Describe the different habitats in your ecosystem.

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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.

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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?

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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.

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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.

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.

• 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.

• 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.

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).

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/66770481@N02/6741179033/
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/66770481@N02/6741179033/	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 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?

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

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.

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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.

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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.

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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.

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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.

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

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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.

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

What would you classify humans as?

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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.

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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.

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Learner-dependent answer.

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

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Learner-dependent answer.

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

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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.

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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?

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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?

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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?

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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.

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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 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?

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It is called a food chain.

Which organsism is the producer?

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The grass.

Which organisms are the consumers?

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Consumers are the grasshopper, the mouse and the owl.

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

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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.

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

What do the arrows show us?

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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.

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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?

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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.

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.

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?

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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?

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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.

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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.

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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?

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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?

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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?

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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?

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It shows how the different food chains are connected.

Name the producer in this food web.

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Phytoplankton and seaweed

List the herbivores in this food web.

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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.

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.

Learn more about the Riverine Rabbit http://www.edgeofexistence.org/mammals/species_info.php?id=3

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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).

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.

QUESTIONS:

What is a drought?

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

What is a famine?

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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?

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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?

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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.

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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?

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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"

For more information on the bushmeat crisis http://www.bushmeat.org/bushmeat_and_wildlife_trade/what_is_the_bushmeat_crisis

QUESTIONS:

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

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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)?

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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?

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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?

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

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

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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?

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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.

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

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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.

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

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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.

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2. Air pollution.

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3. Land pollution and refills.

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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?

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Learner-dependent answer.

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

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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?

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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.

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.

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.

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.

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.

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.

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

A video on wildebeest migration. http://education.nationalgeographic.com/education/media/wildebeest-migration/?ar_a=1

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 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?

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?

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'!

QUESTIONS:

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

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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?

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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?

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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?

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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.

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

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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?

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?

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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.

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.

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!

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.

Some other people to research include:

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

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