Food Chains ~ Food Webs ~ Energy Pyramids

How does energy flow through an ecosystem?

Energy and nutrients in an ecosystem move…

from organisms that capture energy from the sun and store it in food

to organisms that get energy by consuming other organisms

Why do organisms need energy?

To maintain homeostasis (survive)

To mate (reproduce)

Why do organisms need nutrients?

To build cellular and body structures

Producers = Autotrophs Producers – organisms

that capture energy and store it in the chemical bonds of carbohydrates

Producers/autotrophs are the foundation of all ecosystems because they bring energy into the ecosystem.

How do autotrophs produce food? Photoautotrophs – use solar energy to make glucose

Examples – plants, algae, cyanobacteria

What is the reaction for photosynthesis?

+ CO2 + H2O

C6H12O6 (glucose)

O2 +

How do autotrophs produce food? Chemoautotrophs – use inorganic compounds to make

carbohydrates (chemosynthesis)

Examples - Archaebacteria

Consumers = Heterotrophs

Consumers – organisms that obtain energy and nutrients by eating other organisms

Many different types.

Types of Consumers Herbivore – eats only producers

Examples: cow, rabbit, grasshopper

Types of Consumers Carnivore – eats other

consumers

Examples: lynx, wolf, tiger

Types of Consumers

Omnivore – eats both producers and consumers

Examples: humans and grizzly bears/black bears

Types of Consumers Decomposer – breaks down the

remains of dead organisms

Returns nutrients to the ecosystem

Examples: bacteria, fungi, and worms

Food Chain – a simple pathway that shows how energy flows through an ecosystem

Always begins with a producer

The direction of the arrow shows energy flow.

Simplest food chain = PRODUCER DECOMPOSER

Modeling Energy Flow

Producer Primary

Consumer Secondary

Consumer Tertiary

Consumer

Producers get energy from _________.

Primary consumers get energy from _________.

Secondary consumers get energy from ________________.

Tertiary consumers get energy from __________________.

Quaternary consumers get energy from __________________.

Decomposers get energy from ______________________.

the sun

producers

primary consumers

secondary consumers

tertiary consumers

producers and consumers

Food Web – all the interconnected pathways by which energy flows through an ecosystem

Modeling Energy Flow

Which food chain is the longest? (5 trophic levels)

Which organism consumes the most organisms?

How many producers are found in this ecosystem?

How many consumers are found in this ecosystem?

Food Web

Modeling Energy Flow

Trophic Level – a step (level) in a food chain or food web

A feeding level

Energy is transferred from one trophic level to the next

Modeling Energy Flow Energy changes forms as it moves through the ecosystem.

Energy Pyramids

Energy Pyramid – a triangular diagram that shows an ecosystem’s loss of energy, which results as energy passes through the food chain

Available energy decreases as you move up the food chain

Only 10% of the energy stored in one trophic level can be transferred to the next trophic level

Energy is used during metabolism and released from the organisms as heat.

How does energy flow in an ecosystem?

Energy Pyramids

Which level has the most energy?

Which level has the least energy?