Food Chains, Food Webs, and

the Transfer of Energy

Ecology is the scientific study of interactions between

different organisms and between organisms

and their environment or surroundings

What is Ecology?

Every organism has a habitat and a niche.

A habitat is all the aspects of the area in which an organism lives

biotic (living) factors such as trees, animals

abiotic (non-living) factors such as water, soil, sun, wind

Where are you from?

A niche includes all of the physical, chemical, and biological

factors that a species needs to survive, stay healthy, and reproduce.

What do you do? (behavior)

What do you eat / how do you eat?

Are you the top predator?

You can think of a habitat as where a species lives

and a niche as how it lives within its habitat. Niche Video

All can live in the area because they occupy a different ecological niche

How are organisms classified in an

ecosystem?

What they eat or how they get their

food (producers, consumers, and

decomposers).

The Producers (Autotrophs)

•A group of organisms that can use the energy in sunlight to convert water and carbon dioxide into Glucose (food) through photosynthesis. They make /produce their own food.

•Sunlight is the main energy source for life on earth

•The chemical formula for photosynthesis is:

The Producers (Autotrophs)

• Autotrophs are also called Producers because they produce all of the food that heterotrophs use

• Without autotrophs, there would be no life on this planet

• Ex. Plants and Algae

The Consumers (Heterotrophs)

Organisms that do not make their own food can be referred to as consumers, they consume other organisms for their energy and food supply. Ex. Rabbits, Deer, Mushrooms

Consumers (Heterotrophs)

Scavengers/Detritivores – feed on the tissue of dead organisms (both plants and animals)

• Ex. – Vultures, Crows, and Shrimp

The Consumers (Heterotrophs)

Herbivores – eat ONLY plants

• Ex. – Cows, Elephants, Giraffes

The Consumers (Heterotrophs)

Carnivores – eat ONLY meat

• Ex. – Lions, Tigers, Sharks

Heterotrophs – the Consumers

Omnivores – eat BOTH plants and animals

• Ex. – Bears and Humans

Decomposers

Decomposers – absorb any dead material and break it down into simple nutrients or fertilizers

• Ex. – Bacteria and Mushrooms

Feeding Interactions between organism –

Energy Flow and the Food Chain

Energy flows through an ecosystem in one direction

from the sun or inorganic compounds to autotrophs

(producers) and then to heterotrophs (consumers)

**The sun is the initial source of energy for food chains.

Food Chain—series of steps in which organisms transfer energy by eating and being eaten. Start with producer and end with top consumer or carnivore

FOOD CHAINS

grass

grass- hopper

frog

snake

eagle Keep in mind that the arrow tip

always points towards the “eater”. The direction of how

energy is transferred. .

food

eater

Food Chains

• Question: Which direction does the arrow points ?

• Answer: It points to the direction of the energy transfer, NOT “what ate what”

• Question: What is the primary source of energy for life on earth?

• Answer: The Sun

they must eat or “________” other organisms.

FOOD CHAINS

grass

grass- hopper

frog

snake

eagle

They use the energy in _______ to make their own food

They form the _____ of almost all food chains.

Since they _______ make their own food,

sunlight

cannot

consume

basis

through a process called _____________. photosynthesis

Broken down into

producers and consumers.

It’s at the ___ of its food chain.

FOOD CHAINS

primary consumer

tertiary consumer

quaternary consumer

secondary consumer

grass

grass- hopper

frog

snake

eagle

The ___ consumer in a food chain. It eats _________.

The ___ consumer in a food chain. It eats ________________.

The ___ consumer in a food chain. It eats __________________.

The ___ consumer in a food chain. It eats ________________.

1st

2nd

3rd

4th

producers

primary consumers

secondary consumers

tertiary consumers

any organism that is __________ by any other. not hunted top There are different levels

of consumers…..

Top carnivore:

is the ___________ and _____________ of dead organisms.

FOOD CHAINS

grass

grass- hopper

frog

snake

eagle

All organisms eventually die and

decompose.

are substances needed for an organism’s ______ and _____.

detritus

decomposers

nutrients

Nutrients:

Detritus:

are organisms that ___ _______ and break it down into ________.

Decomposers:

waste matter

rotting remains

eat

nutrients

detritus

growth repair The cycle restarts.

Let’s THINK

What would happen if there were no

decomposers?

HUMANS AND FOOD CHAINS Have you ever eaten one of these?

onion

lettuce

tomato

What is it made of?

wheat

cheese

beef

What food chains did you

participate in when you ate this?

FOOD WEBS No ecosystem is only

made up of only one

food chain. Most

organisms eat more

than JUST one

organism. Members of

___________________

___________________

___________________

____. When you connect all

the food chains of

different organisms

from one ecosystem

together, you form

_______________.

Create a Food Web

• Form groups of 3, create a basic food web for each of the following habitats.

– Freshwater wetland

– Forest

What are Trophic Levels?

• The Energy movement from one organisms to another when it is eaten

• Each step in this transfer of energy is known as a trophic level

3rd trophic level

4th trophic level

5th trophic level

1st trophic level

TROPHIC LEVELS

grass

grass- hopper

frog

snake

eagle

2nd trophic level

phytoplankton

zooplankton

small fish

larger fish

shark

It is the position an organism occupies in a food chain. Each

link in the chain represents one tropic level. The first trophic

level starts with the producers.

This 10 % is used to build

biomass as well as to provide

energy for bodily functions

TROPHIC LEVELS

grass

grass- hopper

frog

snake

eagle

As organisms eat one another,

energy is transferred up the food

chain.

This means that 90 % of the

energy is lost,

1000 kcal

100 kcal

10 kcal

1 kcal

0.1 kcal

- 900 kcal

- 90 kcal

- 9 kcal

- 0.9 kcal

energy mostly in the form of

detritus and as heat used in

metabolic processes.

______________________—

only about 10% of the available

energy within a trophic level is

transferred to the next higher

trophic level

With your group, pick one food chain for your habitat and create a

trophic level.