Environmental Science

Chapter 5 Lecture Notes“How Ecosystems Work”

Chapter 5 Targets1. I can explain how photosynthesis and

cellular respiration are related.

2. I can explain the difference between autotrophs and heterotrophs and list examples of each.

3. I can explain the difference between a food chain and a food web

4. I can diagram a food chain with at least four members and label the trophic level for each member.

5. I can explain the 10% Rule using an energy pyramid

Life Depends on the Sun• Energy from sun enters ecosystem when plants use

sunlight to make sugar molecules.• Photosynthesis: process where plants, algae, and some

bacteria use sunlight, carbon dioxide, and water to produce carbohydrates and oxygen.

Burning the Fuel• Cellular Respiration: process when cells use energy from

carbohydrates; oxygen combines with glucose to form water and carbon dioxide.

• Cellular respiration occurs inside cells of most organisms.

T1

From Producers to Consumers• Producer: organism that can make organic

molecules from inorganic molecules.• also called autotrophs (make their own food)• Consumer: organism that eats other organisms or

organic matter instead of producing its own nutrients.

• also called heterotrophs

Exception to the Rule (or what is common)• Deep-ocean communities of worms, clams, crabs,

mussels, and barnacles, live in total darkness on ocean floor, where photosynthesis cannot occur.

• Producers are bacteria that use hydrogen sulfide in water (not typical, usually use sun)

• Other organisms eat the bacteria

T2

What Eats What?

• Trophic Levels

• Types of Consumers:• Herbivores• Carnivores• Omnivores• Decomposers

T2

Food Chains & Food Webs• Food chain: sequence

in which energy is transferred from one organism to the next

• Food web: shows many feeding relationships possible in an ecosystem.

T3

Trophic Levels

• Trophic level: one of the steps in a food chain or food pyramid.

• Examples include:• Producers • Primary consumers• Secondary consumers• Tertiary consumers

*On the food web, label the trophic levels…

T4

On the food web, label the following:-Producers (Autotrophs)-Carnivores-Herbivores-Omnivores -1st Order Consumers-2nd Order Consumers-3rd Order Consumers-4th Order Consumers

Comprehension Check

Leaves, Berries

fox, frog, owl snake

Grasshopper, squirrel, rabbit

Mouse

Mouse, grasshopper, rabbit, squirrelFox, mouse, frog, snake

Owl, fox, snake

Owl

producer producer

1s

t

1s

t 1s

t

1s

t

2nd

2nd

2nd

2nd

3rd

3rd 3rd

4th

Trip to Neptune

The crew of a space shuttle bound for Neptune is able to grow wheat and corn in its spacecraft. Would they be able to support more crew members by (choose one answer below):1.Eating the corn and wheat2.Feeding the corn and wheat to chickens, then eating the chickens3. Feeding the corn and wheat to chickens, then eating the chickens’ eggs

Trophic Levels• Each time energy is transferred, some is lost as

heat.

• Less energy is available to organisms at higher trophic levels. One way to visualize this is with an energy pyramid.

• Energy loss limits number of trophic levels in an ecosystem

• 10% Rule

T5

Trip to Neptune

The crew of a space shuttle bound for Neptune is able to grow wheat and corn in its spacecraft. Would they be able to support more crew members by (choose one answer below):1.Eating the corn and wheat 2.Feeding the corn and wheat to chickens, then eating the chickens3. Feeding the corn and wheat to chickens, then eating the chickens’ eggs

Comprehension Check

How does energy move through most ecosystems on Earth?

A.From the sun to consumers to producers

B.From the sun to producers to consumers to decomposers

C.From the sun to decomposers to producers to consumers

D.From the sun to consumers to producers back to consumers

Comprehension Check

How does energy move through most ecosystems on Earth?

A.From the sun to consumers to producers

B.From the sun to producers to consumers to decomposers

C.From the sun to decomposers to producers to consumers

D.From the sun to consumers to producers back to consumers

Comprehension CheckWhich of the following statements indicates an understanding of the importance of energy to life on Earth?

A.Many organisms on Earth require energy for their life processes.

B.All organisms on Earth require energy for their life processes.

C.Energy is required for the most important life processes on Earth.

D.The most important organisms on Earth require energy for their life processes.

Comprehension CheckWhich of the following statements indicates an understanding of the importance of energy to life on Earth?

A.Many organisms on Earth require energy for their life processes.

B.All organisms on Earth require energy for their life processes.

C.Energy is required for the most important life processes on Earth.

D.The most important organisms on Earth require energy for their life processes.

Chapter 5 Targets6. I can list and describe the three stages of the

carbon cycle.

7. I can identify two ways humans are affecting the carbon cycle.

8. I can list the three stages of the nitrogen cycle.

9. I can describe the role that nitrogen-fixing bacteria and decomposers play in the nitrogen cycle.

10. I can list the stages of the phosphorus cycle.

11. I can explain how the excess use of fertilizer can affect the nitrogen and phosphorus cycles.

The Carbon Cycle• Carbon cycle: movement of carbon from

abiotic environment into living things and back

• Carbon: main component of proteins, fats, and carbohydrates, which make up all organisms.

T6

1. Humans burn fossil fuels, releasing carbon into atmosphere.

2. Humans destroy forests, preventing uptake of CO2 through photosynthesis

• Increased levels of CO2 contribute to global warming.

• Remember the difference between global warming and the greenhouse effect!

How Humans Affect the Carbon Cycle

T7

Comprehension Check

What is the process that breaks down food to yield energy called?A. cellular digestionB. cellular respirationC. decompositionD. photosynthesis

Comprehension Check

What is the process that breaks down food to yield energy called?A. cellular digestionB. cellular respirationC. decompositionD. photosynthesis

The Nitrogen Cycle• Nitrogen cycle: process when nitrogen

circulates between air, soil, water, plants, and animals in an ecosystem.

• All organisms need nitrogen to build proteins• Nitrogen makes up what % of air we breathe?

T8

Fixing Nitrogen• Nitrogen must be fixed before organisms can use

it.

• Nitrogen-fixing bacteria convert atmospheric nitrogen into useable nitrogen.

• The bacteria live within roots of plants called legumes; which include beans, peas, and clover.

• The bacteria use sugar provided by legumes to produce nitrogen compounds such as nitrates.

• Excess nitrogen fixed by bacteria is released into soil. T9

• Nitrogen stored in bodies of living things is returned to nitrogen cycle once they die.

• Decomposers break down decaying plants and animals and their wastes.

• After decomposers return nitrogen to soil, bacteria transform small amounts of the nitrogen into nitrogen gas, which returns to atmosphere to complete nitrogen cycle.

Decomposers and the Nitrogen Cycle

T9

The Phosphorus Cycle• Phosphorus makes up many molecules in the cells

of organisms.

• Plants get phosphorus from soil and water

• Animals get phosphorus by eating plants or other animals that have eaten plants.

• Phosphorus cycle: cyclic movement of phosphorus in different chemical forms from environment to organisms and back to environment.

T10

Fertilizers and the Nitrogen and Phosphorus Cycles

• Fertilizers contain both nitrogen (N) and phosphorus (P)

• Excess fertilizer can enter land and aquatic ecosystems through runoff.

• Excess N and P cause rapid growth of algae

• Excess algae deplete aquatic ecosystems of nutrients such as oxygen, which fish and other aquatic organisms need

T11

Comprehension Check

What role do bacteria play during the nitrogen cycle?A. Bacteria store nitrogen in wastes.B. Bacteria convert nitrogen into water.C. Bacteria turn nitrogen into phosphates.D. Bacteria transform nitrogen into molecules.

Comprehension Check

What role do bacteria play during the nitrogen cycle?A. Bacteria store nitrogen in wastes.B. Bacteria convert nitrogen into water.C. Bacteria turn nitrogen into phosphates.D. Bacteria transform nitrogen into molecules.

Chapter 5 Targets

12. I can define and list two examples of ecological succession.

13. I can explain how a pioneer species contributes to ecological succession.

14. I can describe how lichens contribute to primary succession.

• Ecosystems are constantly changing.

• Ecological succession: gradual process of change and replacement of types of species in a community.• Each new community often makes it

harder for the previous community to survive.

Ecological Succession

T12

Primary Succession• Primary succession: begins in area that

previously did not support life• Rocks• Cliffs• Sand dunes• Volcanic eruptions

• First species to colonize bare rock will probably be bacteria and lichens, which can live without soil. • growth of lichens breaks down rock,

which with the action of water, begins to form soil.

T13/T14

Secondary Succession

• Secondary succession occurs where an ecosystem previously existed. • One community replaces another that

has been partially or totally destroyed.• Can occur in ecosystems that have been

disturbed by humans, animals, or natural processes such as storms, floods, fires or earthquakes.

T12

Ecological Succession• Pioneer species: species that colonizes

uninhabited area and starts ecological cycle for other species.• Lichens• Bacteria

• Climax community: final, stable community in equilibrium with environment.• Even though a climax community may

change in small ways, this type of community may remain the same through time if not disturbed.

T12

Ecological Succession T12

Comprehension Check

Which of the following shows an effect on the carbon cycle of the increased burning of fossil fuels?

A.More carbonates remain in fossil fuels.B.More carbon dioxide is absorbed by

organisms.C.More carbon dioxide is absorbed by the

atmosphere.D.More carbohydrates remain buried deep in

the ground.

Comprehension Check

Which of the following shows an effect on the carbon cycle of the increased burning of fossil fuels?

A.More carbonates remain in fossil fuels.B.More carbon dioxide is absorbed by

organisms.C.More carbon dioxide is absorbed by the

atmosphere.D.More carbohydrates remain buried deep in

the ground.