Explore energy flow through living systems In this presentation you will: Death and decay...

explore energy flow through living systems

In this presentation you will:

Death and decay

Decomposers release nutrients into the soil

Plants take up the nutrients in the soil

Next > explore recycling of matter in living systems

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The plants and animals within an ecosystem depend on each other for survival.

In just one ecosystem, there are lots of food chains. A food chain can be used to show the transfer of energy from one organism to another, through the ecosystem, by the process of feeding.

An ecosystem is a collection of living things that interact with each other and their environment.

Introduction

The Origin of Energy

Nearly all of the energy found in the different ecosystems on Earth can be traced back to the Sun. Without energy from the Sun, life could not exist on the planet as we know it.

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The Sun gives off energy in the forms of heat and light. Energy from the Sun is known as solar energy.

Plants depend on solar energy.

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Producers are organisms that produce their own food.

They do this by a series of chemical reactions, where radiant energy from the sun reacts with water and carbon dioxide to form chemical energy.

Green plants are producers – they convert sunlight into energy (food).

Photosynthesis

This process is called photosynthesis.

Radiant Energy

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Producers

Carbon dioxide6 CO2

Water6 H2O

Radiant energy (sunlight) +

GlucoseC6H12O6

Oxygen6 O2

+

Carbon dioxide and water are the “ingredients” for photosynthesis, and sugar (glucose) is formed, along with oxygen.

The plants then use these products to carry out the life processes that enable them to survive.

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Energy Transfer

As other organisms, such as snails, feed upon the plants, some of this energy gets transferred to them.

The sugars are rich in chemical energy, and by eating the plants, animalstake in the energy from the sugars.

In the same way, the energy from the snail can get transferred to another animal if it is eaten.

Where does solar energy come from?

Question 1

A) The Sun

B) Food chains

C) The Moon

D) Plants

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Consumers

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Some consumers feed only on producers (plants). These consumers are called herbivores.

Consumer organisms cannot make their own food. They need to get their energy by feeding on other organisms.

Consumers

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Other consumers feed only on other consumers. These are called carnivores.

Depending on how the different consumers feed, they can be arranged into a food chain, to illustrate how energy gets transferred through the ecosystem.

Trophic Levels

Primary consumers are the level above the producers.Secondary consumers occupy the level above the primary consumers.

The different stages of a food chain are called trophic levels. The levels are arranged in order of who feeds on who.Producers are at the lowest trophic level of a food chain.

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Producer

Secondaryconsumer

Primaryconsumer

Trophic Levels

Tertiary consumers are found on the level above the secondary consumers.

There are rarely more than five levels in a food chain. The consumer at the highest level is also known as the top predator.

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Producer

Tertiaryconsumer

Secondaryconsumer

Primaryconsumer

In a food chain, which of the following would you find on the trophic level immediately above producers?

Question 2

A) Carnivores

B) The Sun

C) Secondary consumers

D) Primary consumers

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Food Chains

Arrows in a food chain mean ‘are eaten by’.

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When one organism is eaten by another, chemical energy is transferred between them. The direction of the arrow shows the direction of the energy flow.

For example, berries are eaten by small birds. The berries give the birds the energy they need.

Small birds are eaten by larger birds of prey. Some energy obtained by small birds, from the berries, gets passed to the larger bird.

A food chain

Look at the food chain picture. Energy is passed from:

Question 3

A) small bird to berries

B) bird of prey to small bird

C) berries to small bird

D) No energy is passed along the food chain

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Food Webs

A food web consists of many different food chains. This web contains five food chains that each contain three trophic levels.

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Food webs show the feeding relationships of more species than a food chain does.

Ducks

Snails

Algae onstones

Dragonfly larvaeMinnows

Water fleasTadpoles

Mosquitolarvae

Floatingalgae

Therefore, they give a more complete view of how energy can move through ecosystems.

Food Webs

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Often, if one organism disappears from a food web, other organisms can survive by feeding from different organisms. This will, however, affect the number of organisms elsewhere in the web.

Ducks

Snails

Algae onstones

Dragonfly larvaeMinnows

Water fleasTadpoles

Mosquitolarvae

Floatingalgae

Which of the following provides the most complete view of the feeding relationships in an ecosystem?

Question 5

A) A food chain

B) A food web

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Grass (100,000)

Grasshoppers (50)

Mice (15)

Wild cats (2)

Number Pyramids

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In this food chain, the producer is grass.

A number pyramid shows the number of organisms that make up each trophic level in a food chain.

Number Pyramids

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There are many individual grass plants in this food chain. They occupy the largest section of the pyramid.

As you travel up through the food chain, the number of organisms at each trophic level usually decreases as the organisms increase in size.

The broken lines show that the pyramid is not drawn to scale.

Grass (100,000)

Grasshoppers (50)

Mice (15)

Wild cats (2)

Number Pyramids

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In this case, a massive single producer (the oak tree) can support many thousands of greenfly.

Not all number pyramids have regular pyramid shapes.

Blackbirds (20)

Ladybugs (200)

Greenfly (6000)

Oak tree (1)

However, there are fewer ladybugs than greenfly and even fewer blackbirds, so the top of the diagram is still pyramid shaped.

Energy Pyramids

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Along the way through a food chain, a large percentage of the energy (about 90%) is lost from one trophic level to the next.

Chemical energy is used by an organism for movement, growth, digestion, reproduction and a number of other processes.

Not every living part of an organism is eaten, such as animal skeletons, so the energy contained within these parts cannot be used.

This is because:

Energy Pyramids

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Energy pyramids show the amount of chemical energy that is available at each trophic level of a food chain.

Energy Pyramids

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Energy pyramids take into account the energy production in a food chain.

Each bar represents the amount of energy (measured in joules, J) in each trophic level.

Orange 10,000 J

Oriole 1,000 J

Hawk 100 J

Bobcat 10 J

Energy Pyramids

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The most energy is found at the first trophic level, which contains all the producers in the chain. This is therefore the largest section of the pyramid.

As so much energy is lost at each trophic level, food chains usually consist of no more than four or five trophic levels.

Orange 10,000 J

Oriole 1,000 J

Hawk 100 J

Bobcat 10 J

Energy Pyramids

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On the way up the food chain, the amount of energy at each trophic level decreases. The top predator in the food chain contains the least energy.

Orange 10,000 J

Oriole 1,000 J

Hawk 100 J

Bobcat 10 J

The Recycling of Energy

When a plant or animal dies, it becomes dead organic matter.

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Dead organic matter (biomass) contains stored energy and nutrients of the living organism. This is returned to the food chain through the process of decomposition or decay.

The Recycling of Energy

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Bacteria and fungi (together known as decomposers) break down the tissues of the dead organism, releasing stored energy and nutrients back into the soil.

Composting

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Plants take in the nutrients through their roots and use them for growth, repair and in the making of food.

These released nutrients, for example, as nitrates and phosphates, can then be re-used by plants at the beginning of another food chain.

Death and decay



Decaying Matter

Nutrients

Composting

Gardeners can make use of the decay process by encouraging the process in controlled conditions.

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Death and decay



Decaying Matter

Nutrients

This process is called composting.

Composting

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In a small area, as a heap or in a container, dead organic matter is gathered and left to decompose.The process of decay requires oxygen, and moisture. Gardeners often carefully control these things, by turning the materials and adding measured amounts of water.

Composting

This nutrient-rich material is then added to soils as a fertilizer.

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After a year or more, the contents become a dark, sweet smelling material that is very rich in nutrients.

Which of the following groups of organisms break down dead matter and release nutrients into the soil?

Question 6

A) Consumers

B) Decomposers

C) Herbivores

D) Producers

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Summary

In this presentation you have seen:

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how energy enters and flows through ecosystems

how energy is recycled between food chains

Explore energy flow through living systems In this presentation you will: Death and decay...

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