This document summarizes key concepts about ecosystems from Chapter 4, including: 1. Ecosystems transfer energy from producers (plants, algae) to consumers (herbivores, carnivores, omnivores, scavengers) to decomposers (bacteria, fungi). 2. Food chains show the transfer of energy between trophic levels, while food webs illustrate the complex feeding relationships. Biological magnification occurs as pollutants accumulate in higher trophic levels. 3. Only about 10% of energy is transferred between trophic levels, limiting food chain length. Ecological pyramids illustrate this energy loss. 4. Chemical cycles like water, carbon, and

1. Chapter 4 (52-71)

2. 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

3. Producer
s
 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.

4. 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.Herbivores
 2. Carnivores
 3. Omnivores
 4.Scavengers

5.  Herbivores: only eat plants; called
primary consumers.
 Examples: many insects and birds, grazing
animals (cows, buffalo, antelope).

6.  Carvivores: eat
herbivores or other
carnivores (eat
animals); called
secondary or
tertiary consumers.
 Examples: lions,
snakes, hawks,
spiders.

7.  Omnivores: eat
plants and animals;
could be primary,
secondary or tertiary
consumers.
 Examples: humans,
bears, chimpanzees.

8.  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.

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

10. 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.

11. 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.
 Consumers
 Heterotrophs: cannot make own food, must
obtain nourishment by eating other organisms.

13. 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?

14. 4.2 Ecosystem Structure

15.  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.
 Producersherbivorescarnivoresdecomposers

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

19. 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.

20. Check for Understanding:
1. What are food chains and food webs
and how are they related?
2. Explain the process of biological
magnification.

21. 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.

22. 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.

23.  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.

25. 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.

26. 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?

27. 4.4 Chemical Cycles
 Most important elements: oxygen,
carbon, hydrogen, nitrogen.
 Elements must be in form cells can use.
 Three important cycles:
 1. Water Cycle
 2. Carbon Cycle
 3. Nitrogen Cycle

28. Water Cycle

29.  Movement of water between ocean, the
atmosphere, and the land.
 Parts of the water cycle:
 Evaporation (Transpiration)
 Condensation
 Precipitation
 Runoff

30.  Evaporation: movement of water into the
atmosphere as it changes from liquid to gas.
 Transpiration: evaporation of water from leaves
of plants.

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

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

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

34. Carbon Cycle

36.  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.

37. Nitrogen Cycle

38.  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.

39. 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?
© Mrs. Paul