MATTER AND ENERGY IN THE ECOSYSTEM

Chapter 4 (52-71)

Mrs. Paul

4.1 Roles of Living Things

All organisms need energy to live. In ecosystem, energy moves in ONE

direction:Sun Organisms

Energy from sun enters ecosystem via PHOTOSYNTHESIS!

Organisms gather food by:Producing, Consuming,

Decomposing

Producers Producers: organisms that make their own

food using the sun’s energy. Produce sugar using carbon dioxide, sunlight

and water (in a process called Photosynthesis).

Examples: plants, algae, some bacteria.

Consumers Consumers: organisms that

cannot make their own food. Must eat other organisms. Examples: fungi, many

protists and bacteria, animals.

4 ways consumers gather food:1.Herbivores2. Carnivores3. Omnivores4.Scavengers

Herbivores: only eat plants; called primary consumers. Examples: many insects and birds, grazing

animals (cows, buffalo, antelope).

Carvivores: eat herbivores or other carnivores (eat animals); called secondary or tertiary consumers.Examples: lions,

snakes, hawks, spiders.

Omnivores: eat plants and animals; could be primary, secondary or tertiary consumers.Examples: humans,

bears, chimpanzees.

Scavengers: feed on the bodies of dead plants or dead animals; secondary, tertiary or higher consumer. Return nutrients to the environment.Examples: vultures,

hyenas, many insects.

Decomposers

Decomposers: bacteria and fungi that consume the bodies of dead plants and animals or other organic waste. Recycle nutrients back into environment.

In your notes: Make a list of 10 organisms

(living things) you saw on your way to school today.

Label each one as a producer, consumer, or decomposer.

Trophic Levels

Trophic Level: a layer in the structure of feeding relationships in an ecosystem. Levels get smaller and smaller.Producers, primary consumers, secondary

consumers, tertiary consumers, etc. Producers

Autrotrophs: make their own food.Puts energy into the ecosystem.

ConsumersHeterotrophs: cannot make own food, must

obtain nourishment by eating other organisms.

Check for Understanding:1. List the different groups of organisms in

an ecosystem, and explain how each type gathers food.

2. How do autotrophs and heterotrophs differ?

3. In most ecosystems, the first trophic level contains more organisms than the second trophic level. Can you suggest a reason that explains this pattern?

4.2 Ecosystem Structure

Producers and consumers depend on each other.

Changes in population of one organism affect all other organisms in the ecosystem.

Food Chain: a series of organisms that transfer food between the trophic levels of an ecosystem.Producersherbivorescarnivoresdecomposers

Food Web: a network of food chains representing feeding relationships among organisms in an ecosystem.More complex and more realistic.Show interdependence of organisms.

Biological Magnification

Humans affect environment-add pollution.

This is magnified in a food web.The higher up the trophic levels you

look, the more pollution you will find (it accumulates).

Example: DDT and bald eagles. Biological Magnification: the

increasing concentration of a pollutant in organisms at higher trophic levels in a food web.

Check for Understanding:1. What are food chains and food webs

and how are they related?

2. Explain the process of biological magnification.

4.3 Energy in the Ecosystem Energy from sun enters ecosystem via

photosynthesis. Energy then passed from producers to

consumers. No food = no survival. Amount of energy available limits the

structure of the food web.

Energy and Food Producers absorb only 1% of

sunlight that reaches earth to make 170 billion tons of food per year!

Energy used to make cells. Biomass: total amount of

organic matter present in a trophic level. The amount of energy available to the next level.

Much of energy in each level is lost before it can reach following level (power the animal, in the form of heat, to make shells, fibers, bones, etc)Only 10% energy transfer.Limits the length of food chains.

Ecological Pyramids Ecological Pyramid: diagram that shows

amount of energy in different trophic levels in ecosystem.Can show energy, biomass, number of

organisms in each level.Producers are on the bottom (largest level).Tertiary consumer are on the top (smallest level).

Growth of producers limited by lack of elements (carbon, hydrogen, nitrogen, oxygen) – not by energy from the sun.

Check for Understanding:1. How much of the energy that appears

in one trophic level will appear in the next?

2. What is an ecological pyramid?

3. Where is energy lost between trophic levels? Where does this energy ultimately go?

4.4 Chemical Cycles

Most important elements: oxygen, carbon, hydrogen, nitrogen.

Elements must be in form cells can use. Three important cycles:

1. Water Cycle2. Carbon Cycle3. Nitrogen Cycle

Water Cycle

Movement of water between ocean, the atmosphere, and the land.

Parts of the water cycle:Evaporation (Transpiration)CondensationPrecipitationRunoff

Evaporation: movement of water into the atmosphere as it changes from liquid to gas.

Transpiration: evaporation of water from leaves of plants.

Condensation: change of water from gas to water as it cools; leads to formation of clouds.

Precipitation: the product of condensation falling to the earth in the form of rain, snow, sleet, hail, etc.

Runoff: water flowing downhill and eventually returning to the ocean.

Carbon Cycle

Movement of carbon from the atmosphere, into the food chain, into the environment and back into the atmosphere.

Photosynthesis and Respiration are the most important parts.Photosynthesis uses carbon dioxide and sunlight

to make sugars.Respiration breaks down the sugars to remake

carbon dioxide and energy. Ocean and rocks are another good source of

carbon.

Nitrogen Cycle

Organisms need nitrogen to make amino acids. Movement of nitrogen from the atmosphere, into

the food chain and back into the atmosphere. Steps:

Nitrogen-fixing bacteria use nitrogen to make ammonia.

Ammonia gets consumed by more bacteria to make nitrogen compounds plants can use.

Animals get the nitrogen we need from proteins in the plants we eat.

Decomposers return nitrogen to the soil in the form of ammonia.

Check for Understanding:1. What are the four most common

elements in the human body?

2. How do transpiration and evaporation differ?

3. Humans are releasing large amounts of carbon dioxide into the air by burning fossil fuels like coal and oil. What effect might this carbon have on the carbon cycle?