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FOOD CHAINS AND FOOD WEBS GENERAAL HERTZOG: MRS F BEUKES

Food chains & Food webs

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Page 1: Food chains & Food webs

FOOD CHAINS

AND

FOOD WEBS

GENERAAL HERTZOG: MRS F BEUKES

Page 2: Food chains & Food webs

Introduction

Living organisms that live together in an environment are interdependent.

But the environmental conditions, e.g. soil, water and climate also play an important

role. Ecosystems vary in size. Examples are the Kruger National Park, Kalagadi, the

Botanical gardens and the Gariep dam.

ECOLOGY: The study of living organisms and the places where they live..

Page 3: Food chains & Food webs

ECOSYSTEMS are grouped into biomes, namely:

• SAVANNA

• MIDLATITUDE GRASSLANDS

• BOREAL FOREST

• TROPICAL RAIN FOREST

• SCRUBLAND

• OPEN WOODLAND

• DESERT

• TUNDRA

There are various habitats in an ecosystem.

Examples:

A cheetah’s habitat is SAVANNA GRASSLANDS.

ECOSYSTEM: An area where living (biotic) and non-living (abiotic) things live and interact with each other.

BIODIVERSITY: The diverse spectrum of life found in one habitat.

HABITAT: The area in which plants and animals live.

.

Page 4: Food chains & Food webs

Various plants and animals can be found in each habitat.

The plants and animals in a habitat depend on each other for food and protection

and they form a community.

Communities consist of a variety of populations, such as herds of kudu, flocks of sparrows and schools of fish.

COMMUNITY: All the living things in one habitat.

POPULATION: One kind of living organism that is found in one habitat.

Page 5: Food chains & Food webs

Food chainsExample of a food chain:

Page 6: Food chains & Food webs

.

Sun provides energy.

Plants (producers) use this energy to produce their own

food.

Grasshopper (primary consumer) eats the grass.

Frog(secondary consumer) eats the grasshopper.

Frog is eaten by the snake (tertiary consumer).

Snake is then eaten by the falcon.

PHOTOSYNTHES

ISDETRITIVORES EAT ROTTEN FALCON

DECOMPOSERS PROVIDES

COMPOST FOR PLANTS TO GROW

Page 7: Food chains & Food webs

After the falcon dies, its body is broken down by detritivores and decomposers and

energy is released into the soil, atmosphere and water .

Energy is transferred from one organism to the other in this manner.

FOOD CHAIN: It is the relationship where energy (in food) flows between living organisms.

Page 8: Food chains & Food webs

CIRCULATION OF NUTRIENTS:

Consumers: • primary

• secondary • tertiary

Producers

Eaten by

Die and are decomposed by

Die and are decomposed by

Detritivores andDecomposers

Consumed by

Used in photosynthesisNutrients

Page 9: Food chains & Food webs

Exercise 101 Give one word for the following descriptions:

1.1 The relationship where energy (in food) flows between living organisms. FOOD CHAIN

1.2 One kind of living organism that is found in a habitat. POPULATION

1.3 The variety of life found in an ecosystem. BIODIVERSITY1.4 All the living organisms of a specific kind that live

together in an ecosystem. POPULATION

1.5 The diversity of life in a habitat. COMMUNITY1.6 An area where living (biotic) and non-living (abiotic)

things live and interact with each other, e.g. a jungle. ECOSYSTEM

Page 10: Food chains & Food webs

2 Study the sketch below and answer the questions that follow:

2.1 What does this sketch represent?An ecosystem

2.2 Use the sketch as reference and give an example of:2.2.1 a predator: Lion/cheetah/eagle

2.2.2 an omnivore: Ostrich

2.2.3 a herbivore: Giraffe/zebra/springbok/blue wildebeest

2.3 Write down two different food chains that are found in this sketch.grass → springbok → cheetah

tree → giraffe → lion

Page 11: Food chains & Food webs

2.4 Explain why there are so many more herbivores in the habitat than carnivores.

There is more food for the herbivores to eat than for the carnivores.

If there were more carnivores in this habitat, the herbivores would not have

been a sufficient amount of food for the carnivores.

2.5 Explain why giraffes and zebras do not compete for food.

Giraffes eat leaves from trees, while zebras feed on grass. Therefore these

two animals eat different types of food and thus they do not compete for

food.

2.6 Explain why lions and cheetahs compete against each other in this habitat.

Lions and cheetahs are both carnivores. Both these animals may hunt the same

animals and therefore they are each other’s competitors.

Page 12: Food chains & Food webs

3 Study the diagram below and answer the questions that follow

D

C

B

A

plants

soil surface

foodexcretiondecomposition respiration

decomposers

Page 13: Food chains & Food webs

3.1 What does this diagram represent?

A food chain

3.2 What does the arrow at D represent?

Radiation from the sun

3.3 What is another name that can be given to plants? Give a reason for your answer.

Producers, because plants have the ability to produce their own food.

3.4 What does B represent? Give an example.

Secondary consumers for example snakes

3.5 Can C be a herbivore? Motivate your answer.

No, because herbivores only feed on plants (producers) and they are the primary consumers. C is a tertiary consumer.

3.6 Complete A, B and C with your own examples so that the diagrams follow logically.

A: mouse

B: snake

C: eagle

3.7 What do plants, A, B and C release into the atmosphere during respiration?

Carbon dioxide (CO2)

3.8 What does “excretion” mean?

Excretion is waste products that are excreted by humans and animals.

3.9 Give an example of decomposers.

Bacteria/Fungi

Page 14: Food chains & Food webs

Food websFOOD WEB: A variety of interlinked food chains.

Page 15: Food chains & Food webs

Various food chains and how they are linked:

• Worms, grasshoppers, mice, guinea fowls and antelope eat grass and plants.

• Herbivores are a source of food for various predators, carnivores and omnivores.

The grasshopper is eaten by the frog and the bird.

The snake catches the mouse.

The genet catches the mouse, frog, guinea fowl, bird and snake.

The antelope is eaten by the leopard.

The genet, guinea fowl and bird are eaten by the eagle.

• Because the food chains overlap, a food web exists.

• Decomposers are always at the top of the food chain or food web.

• Decomposers recycle the nutrients in dead plants and animals and plough it back

• into the soil.

• These nutrients will make the soil fertile and make it possible for plants to grow.

Page 16: Food chains & Food webs

Activity 13

Investigate your area. See how many different food chains you can identify and

write them down. Food chains in my environment:

Seed → pigeon/mouse → cat/owl

Flowers → butterfly/moth → spider/gecko → crow

Flowers → plant louse → ladybug → spider → crow

Crops → snale → corn cricket → woodpecker

Crops → mouse → cat/owl

Leaves → worms → hoopoe → cat

Determine how many of these food chains are connected, and then draw your own

food web.

WWW.DOCSCIENTIA.CO.ZA

Seed Flowers Crops Leaves

Pigeon Mouse Butterfly Moth Plant-louse Snail Worms

Spider Ladybug Corn cricket Hoopoe

Gecko Wood pecker Cat Crow Owl

Page 17: Food chains & Food webs

3.4 Fossil fuels

There are some circumstances where animals and plants die and it is

impossible for them to decompose and so their remains become

earthbound.

Over a long period of time the remains of these animals and plants are

CONVERTED BY HEAT AND PRESSURE INTO FOSSIL FUELS, e.g. coal and oil

Energy is released when these fuels are burned.

People all over the world are dependent on this energy for electricity, heating,

petrol, etc.

Fossil fuels are non-renewable resources.

NON-RENEWABLE RESOURCES: cannot be replenished (made again) in a short space of time..

Page 18: Food chains & Food webs

The mining and burning of fossil fuels lead to pollution.

Harmful greenhouse gasses are released into the atmosphere – ACID RAIN is formed.

INTERDEPENDENCE IN ECOSYSTEMS

Organisms depend on other biotic (living) organisms and abiotic (non-living)

aspects of their habitat.

These dependencies result in certain relationships better known as SYMBIOSIS.

There are three different symbioses (interdependencies):

GREENHOUSE GASES: Gases whose molecules can absorb harmful infrared radiation from the sun and release them within our atmosphere.

SYMBIOSIS

MutualismCommensalism

Parasitism

Page 19: Food chains & Food webs

MUTUALISM:

Both parties benefit from the relationship that was created

Examples:

Animal-animal crocodile and Egyptian plover

A crocodile lies with its mouth open so that the Egyptian plover is able to get rid of

small pieces of meat that got stuck between the crocodile’s teeth.

The plover feeds on the small pieces of meat that were stuck between

the teeth.

Animal-plant bees and flowers

Bees depend on the flower’s nectar for nutrients.

On the other hand flowers depend on bees to spread their pollen and thus ensure pollination.

Plant-plant lichens

Lichens actually consist of two plants – fungi and algae.

The fungi absorbs water and nitrogenous substances and provide them to the

algae. The algae produce carbohydrates through photosynthesis and provide them to the fungi .

Page 20: Food chains & Food webs

COMMENSALISM:

In this relationship one party will benefit, while the other will not benefit nor will it

be disadvantaged.

Examples:

Animal-animal white egret and cattle

While cattle are grazing, insects are driven into the air and are eaten by

white egret. The white egret is benefitting, but there is no benefit or

disadvantage to the cattle.

Animal-plant finches and trees

Finches build their nests in tall trees. The tree provides protection against predators and floods, so the finch is benefitting. The tree is not at a

disadvantage due to the nest, but it also does not benefit by this relationship.

Plant-plant orchids and trees

Orchids are not fed by the trees. They need the trees so that they may

grow higher and thus get more sunlight necessary for photosynthesis.

Since orchids do not feed on the trees, the tree is not disadvantaged but it

also does not benefit from this relationship.

Page 21: Food chains & Food webs

PARASITISM:

In this instance one party will be disadvantaged while the other benefits.

Examples: Animal-animal ticks and dogs

The tick is benefitting from this relationship since it feeds on the dog.

On the other hand the dog is disadvantaged and may even become infected

with an illness like biliary.

Plant-plant dodder on other plants

Dodder obtains all its water, nutrients and carbohydrates from its host and all of this is to the host’s disadvantage.

The abiotic aspects in a habitat play just as important role in the survival of biotic organisms.

Abiotic factors: Water, soil, oxygen and carbon dioxide.

Page 22: Food chains & Food webs

Exercise 11

1 Consider the diagram below and answer the questions that follow.

1.1 What does this diagram represent?

A food web

1.2 If there was an increase in snakes, which animal will also increase? Give a reason for your answer.

Eagles, because the more snakes there are, the more food there is for the

eagles. The circumstances are favourable for the eagles to increase.

WWW.DOCSCIENTIA.CO.ZA

Seed

SnakeMouseBirds

Eagle

Page 23: Food chains & Food webs

1.3 If there was an increase in snakes, which animal would decrease? Give a reason for your answer.

Birds and mice, because they serve as a food source for the snakes. If there

are more snakes to feed on them, the amount of birds and mice will decrease.

1.4 What animals are the ... in this case:

primary consumer: bird; mouse

secondary consumer: snake; eagle

predator: snake; eagle

herbivore: bird; mouse

2 Give one word/term for the following:

2.1 Fuels like oil, natural gasses and petrol FOSSIL FUELS2.2 Interdependence in ecosystems SYMBIOSIS2.3 One party benefits, while the other does not benefit nor is it

disadvantaged. COMMENSALISM

2.4 These remains of animals and plants have been converted over millions of years.

FOSSIL FUELS2.5 A variety of food chains that are linked. FOOD WEB

Page 24: Food chains & Food webs

3. Match column A to column B. Write down the correct letter next to the description.

The relationship between ants and plant lice.

E A. Parasitism

A variety of food chains that overlap. C B. Ecology

The area where plants and animals live. G C. Food web

The relationship between a clown fish and an anemone. F D. Fossil fuels

A herd of springbok on the grasslands. H E. Mutualism

It is produced from the remains of plants and animals under extreme heat and pressure. D F. Commensalism

The study of living organisms and the places where they live. B G. Habitat

The relationship between humans and tapeworms. A H. Population