grade 8 term 1 natural sciences introduction to...

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GRADE 8 TERM 1 NATURAL SCIENCES INTRODUCTION TO ECOLOGY

Curriculum Skills Resources• Introduction to ecology• Ecosystems• Feeding relationships• Food chains and food webs• Balance in an ecosystem• Adaptations• Conservation of the

ecosystem

• Understanding ecology and the interactions between living things.

• Understanding ecosystems• Understanding feeding

relationships• Food chain vs food web

explanations and diagrams• Understanding the balance in

an ecosystem• Explaining and analysing

adaptations of plants and animals

• Implementing and understanding conservation of the environment.

• Textbook• Worksheets• Pictures of different

ecosystems• Thermometers• Hand lenses• String Rulers• Sieves• Hand lenses• Field guides for identifying

plants and animals

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Watch this YouTube clip on Ecosystems

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Plants and animals live together and interact with one another in ecosystems.

They also interact with non-living parts of the ecosystem such as light and water.

Organisms rely on the ecosystem to live as well as the relationship between the different organisms in the ecosystems.

What is ecology?Ecology is the study of interactions of organisms with one another and with the physical and chemical environment Scientists usually classify the study of ecological interactions into four levels1. Populations 2. Communities3. Ecosystem 4. The biosphere

Interactions between living things1. Population

A population is a group of individuals of the same specifies that live in the same ecosystem at the same time. For example all the lions in the Kruger National Park form a population.

2. Communities The different populations that interact with one another in the same ecosystem are called a community. For example the population of frogs, population of fish, population of reeds and population of algae all interact with one another forming a community within a specific ecosystem.


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EcosystemsAll ecosystems combined make up the biosphere.

There are many different kinds of ecosystems on land and in water.

The non-living parts of the ecosystem influence which living organisms can live there.

The living and non-living parts interact as a system that works together for a common purpose.

3. Ecosystems An ecosystem is all the living and non-living components of an ecosystem and the different ways in which they interact with each other. It is made up of two parts • Non-living part, the habitat where the organisms live. • Living part, consisting of the community.

4. The biosphere The biosphere is all the different ecosystems on the planet. It includes all the areas on Earth where life exits, the lithosphere and the hydrosphere, living organisms and dead or decaying matter.

Activity 11. List the four levels of ecological interaction?

2. Write a short paragraph discussing the list above.

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A forest ecosystem

A desert community


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Network of interactions between organisms and between organisms and their environment.Ecosystems are defined by the network of interactions among organisms, and between organisms and their environment. The different populations in a community depend on each other for food. Feeding relationships are shown in food chains or food webs.

If the population of one organism changes in the ecosystem it will impact the food web or food chain.

Biotic and abiotic parts of ecosystems An ecosystem consists of two ecological communities that include

1. All living organisms (biotic) such as plants and animals.

2. Non-living (abiotic) environment such as temperature, wind and water.

Biotic Living organisms and their different interactions make up biotic factors.

Organisms compete with each other for: food, light, water and space.

Plants competing for light

Animals competing for food

Animals competing for water

Plants competing for space

Abiotic Abiotic form the non-living part of the ecosystem.

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Biotic Abiotic


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Temperature How hot or cold an area is. Temperature varies with seasons, day and night and positioning.

A cactus grows in hot regions.

Wind Wind can be used for pollination and seed dispersal.

It can also hinder plant growth and affect animal activities.

Water Water is needed for survival. In areas with less water plants must be able to reduce water loss.

This Dusty Miller requires very little water.

Light Light is needed for photosynthesis. Some plants grow in full sun and others in shade.

The ponytail palm requires full sun.

Soils Soils can be; sandy, loamy or clayey. Each type of soil has different properties and this affects what will grow.

Grows in loamy soil.

Slope Slope is how steep the land is. Water runs quickly down steep slopes leaving less soil and therefore erosion. Few plants can grow on slopes.

Size of an ecosystemThe size of an ecosystem is not specifically defined and it usually encompasses a specific, limited area (although it can encompass the entire planet). It can be as small as a puddle or as big as a planet.

Survival of individuals and populationsSurvival of individual organisms and populations depends on its ability to cope with changes (adapt) in its habitat (the place where an organism lives) or in the ecosystem.Changes can be sudden for example a fire or they can be gradual such as the change from summer to winter.Some organisms adapt easily to change while others do not.For example; weeds can grow and adapt to a range of different habitats.


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Activity 21. What is the difference between biotic and abiotic factors?

2. Identify and describe the abiotic aspects of the ecosystem such as amount of sunlight, water, wind, temperature, soil type and slope of the area. Describe how the abiotic factors of the ecosystem affect the plants and animal. Describe the plants and animals (biotic factors) in the ecosystem. Describe the relationship between the biotic factors (such as feeding and shelter) in the ecosystem • identify any human interference in the area (such as litter and pathways).

3. Study a small sample of the soil in the ecosystem, using a hand lens, and identify any remains of dead plants and animals.


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Feeding relationshipsProducersGreen plants make their own food through photosynthesis. Plants that make their own food are called producers.The food is either used immediately by the plant or stored for later usage.

ConsumersOrganisms that rely on other organisms for their food and energy are called consumers. They obtain food from plants either directly (such as herbivores) or indirectly (such as carnivores)Consumers are grouped according to what they eat • Herbivores • Omnivores • Carnivores

Category Definition Example ImageHerbivore Animals that feed on

plants.Elephant, cow and horses

Carnivore:

There are three types

Animals that feed on other animals.

Lion

a. Predators A carnivore that hunts other animals called prey.

Leopards prey on zebra

b. Scavenger A carnivore that feeds on deed or decaying meat.

Hyena and vulture

c. Insectivore A carnivore that feeds on insects and other small invertebrates.

Birds, aardwolf and pangolins

Omnivore Animals that eat plants and animals.

Humans, pigs and birds


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DecomposersDecomposers: breakdown (decompose) the remains of dead plants and animals.

They recycle important nutrients in the environment

Examples of decomposers include; bacteria, fungi, earthworms and beetles.

Decomposers vary in size from being so small to very large.

They break down dead matter into simpler substances which are released into the soil, the nutrients are then taken up through the roots therefore being recycled.

Dung beetles are decomposers that feed only on dung of herbivores. They break down the dung which then mixes with soil and improves soil quality = better plant growth.

Fungi (mushrooms and moulds) are decomposers that feed by releasing chemicals called digestive enzymes onto the dead matter. The digestive matter breaks down the leaves, dead matter etc. into simple substances. By doing this nutrients are returned back to the soil.

The importance of decomposersAs the supply on nutrients on Earth is limited, it is essential that they are recycled.

Decomposers are therefore essential by putting nutrients back into soil as well as used to treat sewage. As sewage is human waste bacteria is used to break down sewage into simpler substancesà purified water and fertilisers.

Activity 3Complete the following table:Term Definition ExampleHerbivore

Animals that feed on other animals

Insectivore

Animals that eat plants and animals.

Hyena and vulture

Decomposer

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Mould on bread

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Mushrooms grow on decaying plant matter

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The dung beetle

Earthworm


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Energy flow in a food chain A Food chain shows the flow of energy from one organism to the next. It starts with the producers and moves to the consumers. Animals are consumers as they eat plants.

The à arrows show the direction of the flow of energy.

Scavengers and decomposers are also important in the food chain.

Scavengers get their energy by feeding on dead plants and animals. They break down dead material which is also further broken down by decomposers (bacteria and fungi). Nutrients are then returned to the ecosystem.

Food chains and food websRole of plants in the ecosystemPlants and algae play an important role in the ecosystem.

They are producers which mean that during photosynthesis they take light energy from the sun to produce food.

This energy from the sun is passed along in an ecosystem in the form of a food chain.

What is a food chain?A food chain shows the feeding relationships between living things. It involves a number of steps and shows the transfer of energy between organisms.

It always starts with à a producer; as they can make their own food

and ends with à decomposers; as they return nutrients back to the soil. (These are not always shown on food chains)

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Food Chain

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Trophic levelsTrophic levels are steps or stages in a food chain or web.

First trophic level Producers

Second trophic level Herbivores/ primary consumers

Third trophic level Secondary consumers

Higher trophic levels Tertiary consumers (carnivores)

Each consumer depends on the trophic level below for energy.

Food websA group of food chains connected together is called a food web.

There are many food chains in an ecosystem and most animals do not only eat one thing, therefore food chains are connected.

Food webs demonstrate the different kinds of food eaten by different kinds of animals and how plants and animals are linked.

Watch this YouTube clip on Food Chains

https://goo.gl/HrXoRg


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Energy transfer and energy lossOnly a small amount of energy (10%) is passed from one trophic level to another. This is because most of the energy is used by the organism for life processes such as movement. Some energy is also lost through heat.

Energy pyramids are used to represent the amount of energy that is transferred from level to level. Energy is measured in kilojoules (KJ)

The producer trophic level has the most energy. As energy is lost at each level, the size of each level becomes smaller. (Pyramid shape with 3-4 trophic levels)

Activity 41. What is the difference between a food chain and food web?

2.1 Draw a simple food chain.

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Animals that each other animals e.g. Polar Bear eats seal/fish

Carnivorous fish e.g. Cod, a Fish that eats other fish

Carnivores that eat herbivores e.g. Fox

Herbivores that eat plants e.g. Rabbit

Plants that make their own food


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2.2

Use the image to explain the three food chains, be sure to use accurate terminology.

3.1 Using the food web, clearly explain the interactions between all the organisms.

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3.2 Write down one food chain from the food web.

4. Identify a food chain or food web in an ecosystem in or near the school grounds. Record the observations in the following table.

Date Name of producer

Description and observation.

Name of consumer

Description and observation.

Herbivore/Omnivore or Carnivore

5. Explain the following statements;5.1 On average about 10% of net energy production at one trophic level is passed on to the next level.

5.2 The impact of various factors such as loss of habitat, loss of species, change of weather or climate on ecosystems.

5.3 The impact on a food web when one of the organisms is removed.

6. Complete the following with examples

First trophic level

Second trophic level

Third trophic level

Higher trophic levels


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Balance in an ecosystemAn ecosystem can only accommodate as many organisms as its resources (food, water and shelter) can carry, and it will fail if it does not remain in balance.

Generally there are enough resources in an ecosystem to support the population. However, if there are fewer resources there would be a smaller population.

There may be competition in the ecosystem for resources, for example competing for food. If there is a food shortage the number or organisms will decrease. If there is a surplus of food the number of organisms will increase.

All living organisms in an ecosystem interact with one another, what happens to one population will affect the whole community.

This is how the ecosystem is kept in balance =

If an ecosystem does not remain in balance it will fail.

The balance can be disrupted by the following two factors

1. Natural factors that disrupt the balance There may be changes or disruptions that interfere with the ecosystem and the ecosystem cant cope.

It interferes with the natural functioning and balance.

If it is short term it will recover; if it is long term there may be permanent damage and the ecosystem may not recover.

Natural factors include extreme changes in patterns of weather and climate, such as floods, drought, extreme and sudden changes in temperatures.

2. Human factors that cause disruptionsHuman factors include removing organisms from the ecosystem

1. Human induced pollution Pollution is the damage done to the environment when poisonous substances are released into the atmosphere. Pollutants are the chemicals or wastes that contaminate the water, soil and air.

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Extreme drought


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Farmers use fertilisers which contain harmful substances. These go into the soil and help crops grow. The left over nutrients get washed into rivers and pollute the water.

Burning fossil fuels causes pollutants. These can affect people’s health. Sulphur dioxide is released when fossil fuels are burnt and this produces acid rain. Acid rain can cause serious damage, damaging roads, trees, lakes and ecosystems.

Factories release outflows of warm water. This increases water temperature a reduction of water quality. This is known as thermal pollution. It changes the amount of oxygen in the water and therefore the amount of decay and the type of organisms that live there.

2. Poaching Poaching is the illegal removal of plants and animals from the wild. There are many plants and animals that are under threat of being extinct due to poaching. Animalsà rhino and tortoise Plantsà Cycad and species of orchid

People poach and in exchange get a lot of money. By doing this over an extended period of time the population does not have a chance to recover and the species become endangered.

These factors can contribute to an imbalance in an ecosystem, seriously impacting on its components and altering its natural balance.

Activity 5 1. Why does an ecosystem need to remain in balance?

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Rhinos Cycad OrchidTortoise


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2. Write a paragraph discussing the natural and human factors that disrupt the imbalance.

Adaptations What is an adaptation?Adaptation is the change in the structural, functional and behavioural characteristics of an organism.Adaptation allows the organism to survive as it adapts to changing conditions within the environment.Plants and animals must be adapted to their environment.

Structural This is a special feature on the body. For example a camel has two humps filled with fat tissue to allow it to survive in the hot climate.

BehaviouralMany desert animals go underground where it is cooler to escape the heat of the day.

Many animals have adapted to desert life by living underground, even one species of owl, the burrowing owl.

FunctionalThis relates to the way in which the body works. For example people sweat in order to cool down.

Changing environmental conditions and adaptationsConditions in the environment may change which means that animals need to adapt to these changes.

Organisms that are better adapted have a higher chance of survival and likely chance to reproduce.

Variation helps with adaptations. Variation is a slow process where adaptations are passed down from parents. In other words the differences of the individuals in a population.

Variation can help with survival and the useful characteristics will be passed on to the young. It is a slow process starting with one organism and slowly the whole population will adapt.

Variation can also be negative and make it difficult for the organism to survive.

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Lack of adaptation causes extinctionOrganisms that are unable to adapt to changes within the environment die out (become extinct).

Extinct means that there are no more species left on Earth.

The Dodo, a flightless bird, is extinct. They were hunted for food by farmers, their eggs were eaten by rats and slowly the predators overtook the Dodo population.

Adaptation of plantsSome plants are adapted to their environment; for example can withstand extreme heat or cold.

Some plants are adapted to living in water and others to living in the desert.

Animal adaptations in extreme environmentsAnimals are adapted to live in their habitats.

For example the camel and polar bear have special adaptations, as shown here:

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Catalina Plants Have Adapted to Survive Drought Conditions.

The small ears minimise the amount of water that enters the ear and therefore prevents the freezing of the inner ear.

Hollow fur allows the Polar Bear to float in water when swimming and provides insulation for the Polar Bear.

Big paws allow the Polar Bear to swim easily in the water surrounding its habitat.

Muscle hump over shoulders for catching large prey

Polar Bear

Large, furry feet for walking on ice and snow

Long claws for tearing apart prey

Small, rounded ears

Small tail


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Predator adaptations Predators have adaptations which allow them to catch and hold their prey.

Cheetah Shark

Good eyesight Good sense of smellRun fast Swim fast

Well camouflaged Streamlined shape and muscular tailStrong sharp claws Shake heads from side to side to rip open fleshStrong sharp teeth Sharp teeth

Long and bushy eyelashes to keep out the sand and sun.

Silt-like nostrils which they are able to open and close to prevent sand inhalation.

Tough, leathery mouth for chewing thorny plants.

Webbed, twintoed feet to prevent it from sinking into the sand.

Leathery kneepads for kneeling.

Strong, sturdy thighs.

Hill-like humps used for storing fat, NOT water. They can go without eating food for a long time.

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Camel


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Camouflage:A method used to avoid predators. Colours and shapes help animals blend in with their environment. They keep still and the enemy cannot see them.

Mimicry:Mimicry is when a harmless species copies the behaviour of poisonous species. Some animals resemble other animals or plants in colour or behaviour; this protects one or both of the organisms.

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a red fox with its prey

Here are some adaptations that make animals successful predators:• built for speed• sharp teeth and claws• camouflage to avoid

being seen by prey• eyes to the front of the

head to judge size and distance well.

A goat eating foliage

Here are some adaptations that help animals avoid being caught as prey:• live in groups• built for speed• defences such as poison,

stings or horns• camouflage to avoid

being seen by predators• eyes to the side of the

head to get a wide field of view e.g. like a goat

Camouflage and mimicry

Activity 6 1. Define the following words;

Adaptation

Variation

Extinct

Camouflage

Mimicry

Camouflage in insects

Mimicry in insects


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2. Label the camel and polar bear according to their adaptations.

3. Draw a plant and label how it is adapted to the environment.


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4. Tabulate how the cheetah and shark are adapted to being good predators.

Cheetah Shark

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Alien plant species

Using pesticides

Conservation of the EcosystemConservationMany ecosystems are destroyed due to activities of people. As the population increases so do the activities and therefore the damage.Conservation is the sensible management and use of natural resources in order to protect the habitat and maintain the environment for future generations. It is essential to maintain the biodiversity: this is the total variety of species in an area.

Human activities The following human activities reduce the biodiversity:• Introducing alien species (strange or different) that

compete for resources with the plants and animals that were there originally.

• Polluting the environment.• Using pesticides.• Over harvesting of both plants and animals, particularly for

medicinal purposes.• Replacing natural habitats with monocultures of one

specific plant species. There will be a low biodiversity.

Why conserve species?Conservation is the sensible management and use of natural resources in order to protect the habitat and maintain the environment for future generations.

It is essential to conserve for the following reason;• Regulating the atmosphere and climate (rain and

temperature)• Production of resources à fuel and wood• Recycling of waste to release nutrients back into the soil• Providing shelter• Improve soil quality• Clean water

Why Conserve Water?Water is essential to life on Earth. We need water to grow food, keep clean, provide power, control fire, and last but not least, we need it to stay alive!

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Sustainable use of resourcesSustainable means using resources so that they do not run out and there is enough left for future generations. Enough of the resource should be left so that more can grow and provide enough resources. How environmentalists conserve ecosystemsEnvironmentalists and others work towards managing ecosystems by controlling alien vegetation and preservation of wetlands.Setting aside large areas of land in areas with a vast biodiversity is essential for conservation.The Kgalagadi Transfrontier Park is an area that is being conserved.Legislation can be used to implement rules but it is difficult to maintain.

Controlling alien vegetationSome plants were introduced to South Africa from certain regions that have similar climates and therefore were already adapted to the conditions. There populations increased with no problems

This is not always the case! Alien vegetation compete with the indigenous vegetation

and rapidly take over the area.

Different methods have been introduced to control alien vegetation1. Biological control – the natural enemy of the plant pest such

as insects or fungi is introduced to control the alien plant. It is researched and though through carefully before any action is taken.

2. Chemical control – chemical poisons are sprayed onto alien plants. However this can harm the ecosystem and is expensive.

3. Mechanical control – burning, cutting or uprooting alien vegetation. It is expensive and needs to be repeated every year.

4. Use alien vegetation for practical resources such as making furniture.

Individuals can contribute to conservationIndividuals can contribute to conservation in various ways, such as appropriate waste disposal including recycling and re-using. All people must be involved in conservation.Plastic, paper, glass and metal can be recycled. Recycling means people produce less waste and therefore reducing damage to the environment.Organic waste can be collected and used for compost.

Preservation of wetlandsWetlands include marshes, floodplains, lakes and estuarine systems.

Wetlands are essential to be preserved as they play an important role in the ecosystem.

What do they do?• They filter clean water, store

water and prevent flooding and soil erosion.

• They have a large biodiversity• Used to breed animals • Used for recreation

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Watch this YouTube clip How To Reduce, Re-use, and Recycle

https://goo.gl/933cQj


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Activity 7 1.1. Define;

Biodiversity

Sustainability

1.2. Explain the importance of maintaining biodiversity and sustainable use of natural resources.

2. Explain which irresponsible human practices impact on ecosystems. Suggest possible solutions.

3. How can alien vegetation be controlled?

4. Why is it essential to conserve wetlands?


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ProjectSelecting and studying an ecosystem

Aim: Observing and studying a selected ecosystem

Apparatus: • Thermometer• Hand lenses• String and pegs• Rulers or meter sticks

• Sieves• Field guides to identify

plants and animals.

Method: Select an ecosystem one meter by one meter (measured using a ruler or metre stick) and mark it off with string and pegs.

Make sure to observe and note the following over a period of one week;• Abiotic factors (sun, water, wind, temperature, soil type and slope)• Describe how these abiotic factors affect the ecosystem• Biotic factors (use the field guide to help you identify)• Describe the relationship between the biotic factors.• Identify human interference and the effect on the ecosystem• Study a small sample of soil using the hand lens and explain it in accordance to animals

and plants.

Present your information in clear sections and complete detail.

grade 8 term 1 natural sciences introduction to...

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