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8/3/2019 Teacher's Slides

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Energy Transfer in Ecosystem

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Menu for todayMenu for today

You will learn about Producers and consumers how energy is transferred from one

organism to another. constructing and interpreting food

chains/ food webs food pyramid- energy

about the consequences of adding orremoving an organism from anenvironment

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14.1 Energy in Ecosystem

14.1 Energy in Ecosystem

In order to live, plants and animals in anecosystem need energy.

How can energy be transferred within theecosystem?

Energy flows within an ecosystem whenorganisms feed on each other or in terms offood

The energy transferred decreases as it passesfrom one organism to another.

In order to live, plants and animals in anecosystem need energy.

How can energy be transferred within theecosystem?

Energy flows within an ecosystem whenorganisms feed on each other or in terms offood

The energy transferred decreases as it passesfrom one organism to another.

SUNSUNGREEN

PLANTS

GREEN

PLANTS

PLANT-

EATERS

PLANT-

EATERS

MEAT-EATERSMEAT-EATERSphotosynthesisphotosynthesis foodfood foodfood

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Definition:Definition:

A food chain consistsofa seriesoforganismsthrough whichenergyistransferred.

Eachorganism (plantor animal) iscalled a

link.

What is aFood Chain???

What is aFood Chain???

Food ChainFood Chain

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Green leaf Caterpillar Bird

Each arrow ( )means iseaten by. A threelink foodchainorthreetropic

levels.

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seaweed water snail fish bird

An example of a food chain in a local

rocky shore ecosystem:

An example of a food chain in a local

rocky shore ecosystem:

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Link Organism in Food Chain Example

Producer

Green plants that produce their own food; mostfood chains start with green plants; theyprovide food and energy for animals in the foodchain.

Seaweed,water snail,fish, bird

Consumer

Animals cannot make food, so they consumeother plants or animals.

primary: animals that eat plants only Water snail

secondary: animals that eat other animals Fish, bird


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Energy transfer in a food chain.

In a food chain, energy is passed from one organism toanother.

Energy transfer in a food chain.

In a food chain, energy is passed from one organism toanother.

producerproducer

primary consumerprimary consumer

secondary

consumer

secondary

consumer

tertiaryconsumer

tertiaryconsumer

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Food WebsFood Webs

An ecosystem is made up of many interconnected foodchains.An ecosystem is made up of many interconnected foodchains.

This is because manyanimals eat more thanone type of food. The

network of food chainsis called a food web.

As there are many food chains in thefood web, the energy flow through theecosystem takes many different paths.

As there are many food chains in thefood web, the energy flow through theecosystem takes many different paths.

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Green plants

Earthworms Grasshoppers Field mice

Toads Lizards

Snakes

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(a) Fromthefood web shown above,constructa foodchain with

(ii) four links.

green plant earthworm toad snakegreen plant grasshopper toad snake

green plant grasshopper lizard snake10


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(b) Namethe producer.

green plants

(c) Nametheherbivores.

earthworm, grasshopper, field mice

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14.2 Energy Loss in Food Chains14.2 Energy Loss in Food Chains

As energy passes along a food chain, the amount ofenergy transferred gradually decreases.

Energy is lost to the environment at each link in thefood chain.

As energy passes along a food chain, the amount ofenergy transferred gradually decreases.

Energy is lost to the environment at each link in thefood chain. movement and breathing

(energy released)

movement and breathing

(energy released)

waste

(energy dissipated)

waste

(energy dissipated)

body

(energy stored)

body

(energy stored)

Energyis lost :

throughrespiration

asheatInurine andfaeces.

tocarryoutactivities.

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Because the amount of energy transferreddecreases along the food chain, there arerarelymore than four links in a food chain. Therewould not beenough energy to support the fifthpopulation of consumers.

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Leaves caterpillars bird

The Pyramid of NumbersThe Pyramid of Numbers

What is aPyramid of Numbers???

What is aPyramid of Numbers???If the pyramid isrepresented in

numbers we call it a

Pyramid of Numbers

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Whentheconsumers arein largenumbers,the pyramidisinverted as

shown below.

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Pyramid of Biomass

Biomassisthemassof livingmatter.

A Pyramid of Biomass showsthemassof livingmatter ateachtrophic level.

Thearea ofeach box representstheamountofbiomass ofeach linkinthefoodchain.

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A frogfeedon 200 caterpillars. The 200caterpillarsfeedon 15 000 leaves. Draw

a pyramidofbiomasstorepresentthefoodchain,ifa froghas a massof250 g, a caterpillar 30 g and a leaf

10 g.

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Leaves caterpillars frogs

1 frog = 250 g 200 caterpillars = 200 x 30 = 6 000g

15 000 leaves = 15 000 x 10 = 150 000g

150 000 g

6 000 g

250 g

leaves

caterpillars

frog

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14.3 The Balance of Nature14.3 The Balance of Nature

The numbers of animals and plants in a food web are finelybalanced so that each animal in the food web has enoughfood to eat.

The balance between the number of plants and animals inan ecosystem is called the balance of nature.

Some ways that the links in food webs can be changed:

Diseases can kill one kind of plant or animal

Animals and plants are introduced into the habitat

Human activities often break the links in food webs

The numbers of animals and plants in a food web are finelybalanced so that each animal in the food web has enoughfood to eat.

The balance between the number of plants and animals inan ecosystem is called the balance of nature.

Some ways that the links in food webs can be changed:

Diseases can kill one kind of plant or animal

Animals and plants are introduced into the habitat

Human activities often break the links in food webs

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Green plants

Earthworms Grasshoppers Field mice

Toads Lizards

Snakes

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EXAMPLE

Refertothefood web above.

Insecticides are sprayed to killearthworms, grasshoppers and field

mice feeding on the plant. Explain howthis might result in the death of thesnakes.

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ANSWER

Snakesfeedontoads, lizards and fieldmice.

Thedeathoftheearthworms,grasshoppers andfieldmicereducesthenumberoftoads and lizards astheyhavelessfoodtoeat.

Intheend,thesnakes will die becauseofinsufficientfood.

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What have you learnt?

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What is the difference between a food chain

and a food web?

What is the difference between a primary

and secondary consumer?

In what ways are energy lost in a food

chain?

Why is there rarely food chains with more

than 4 links?

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