Principles of Ecology

Chapter 2.2: Flow of Energy in Ecosystems

Student Performance Standards• SB4. Students will assess the dependence of all

organisms on one another and the flow of energy and matter within their ecosystems.– A. Investigate the relationships among organisms,

populations, communities, ecosystems, and biomes.– B. Explain the flow of matter and energy through

ecosystems by:• Arranging components of a food chain according to energy flow.• Comparing the quantity of energy in the steps of an energy

pyramid.• Explaining the need for cycling of major nutrients (C, O, H, N, P).

– C. Relate plant adaptations, including tropisms, to the ability to survive stressful environmental conditions.

Essential Question• How does energy flow through an ecosystem?

Ecosystems are Open Systems!

• Ecosystems are not isolated from each other.• They do not have clear boundaries.• Things move from one ecosystem to another.• Example: A green turtle that lives off the

shores of Miami, Florida swims 90 miles to an island off the coast of Cuba to lay her eggs every summer. She travels from one ecosystem to another.

Chapter 2, Section 2: Flow of Energy in Ecosystems

• Organisms cannot survive without a constant source of energy.

• You are a living organism. You get your energy from the foods you eat.

• Many of the foods you eat come from plants.• Where do plants get their energy?

Life Depends on the Sun• Plants use sunlight to make sugar molecules in

a process called photosynthesis:Sunlight + carbon dioxide + water = sugar molecules

(called carbohydrates), and oxygen gas

Flour Production

Wheat Products: Pizza Dough Pretzels Breads Pasta Cookies Cakes

Photosynthesis Equation:

6CO2 6H2O Solar energy C6H12O6 6O2

carbohydrate

The Flow of Energy from Plants to Animals:

When animals eat a plant…….

• Some of the energy is transferred from the plant to the animal.

• Organisms use this energy to move, grow, and reproduce.

From Producers to Consumers• A producer is an organism that makes its own

food.

– Also called autotrophs – use sunlight to make and store their own food.

– Ex: Plants, bacteria, algae– In places where sunlight is unavailable, some

bacteria use hydrogen sulfide and carbon dioxide to make organic molecules as food.

From Producers to Consumers

• A consumer is an organism that gets its energy from eating other organisms.– Also called heterotrophs.

• Name the producer.• Name the consumer.

4 Types of Consumers:1. Herbivores – eat only producers.

2. Carnivores – eat other consumers.

3. Omnivores – eat both plants and animals.

4. Detritivores (decomposers) – eat fragments of dead matter; help break down dead organisms.

Ex: centipedes, woodlice, earthworms, bacteria, and molds

Models of Energy Flow

• Ecologists often use models to show the flow of energy through an ecosystem.

• Food Chains• Food Webs• Ecological Pyramids

A Food Chain is……• Energy is transferred from one organism to

the next as each organism eats another:

Food Chain

Food Web• Energy flow in an entire ecosystem.• A food web shows many possible feeding

relationships in an ecosystem:

Ecological Pyramids

• An ecological pyramid is a diagram that can show the relative amounts of energy, biomass, or numbers of organisms at each trophic level in an ecosystem.– Energy Pyramid– Biomass Pyramid– Pyramid of Numbers

Energy Pyramids

Times

Times

Times

Times

Trophic Levels• Each step through which energy is transferred

is called a trophic level:– Primary– Secondary– Tertiary– Quaternary

• Each time energy is transferred from one organism to another, some of the energy is lost as heat and less energy is available to organisms at the next level.

Chemical Equation for Cellular Respiration:

6CO2 6H2O energyC6H12O6 6O2

Cellular Respiration:Carbohydrates + oxygen = carbon dioxide + water + energy

How Energy Loss Affects an Ecosystem:

• The decreased amount of energy at each trophic level affects the organization of an ecosystem.– Because so much energy is lost at each level, there

are fewer organisms at the higher trophic levels.

Biomass Pyramid• Biomass – the total mass of

living matter at each trophic level.

• In a pyramid of biomass, each level represents the amount of biomass consumed by the level above it.

Pyramid of Numbers