1. Food Webs and Food Pyramids in Ecosystems

2. General Definitions
Ecology: The study of the relationships between organisms in the environment
Ecosystem: a community of organisms and the physical space surrounding them
Food webs: A system of interlocking, interdependent food chains

3. Biomes Ecosystems exist in five biomes Deserts Tundras Forests
Marine/Aquatic
Grasslands

4. Ecosystems Examples of ecosystems include:
Pond within a national forest
The “watering hole” in the savannah
Coral reef in Belize

5. Factors Ecosystems are comprised of two types of factors
Biotic – living factors
Trees, animals, bacteria, fungi, plants
Abiotic – non living factors
Sunlight, Wind, Rain, Soil

6. KEY CONCEPT Life in an ecosystem requires a source of energy.

7. Producers provide energy for other organisms in an ecosystem.
Producers get their energy from non-living resources.
Producers are also called autotrophs because they make their own food.

8. Producers provide energy for other organisms in an ecosystem.
Consumers are organisms that get their energy by eating other living or once-living resources.
Consumers are also called heterotrophs because they feed off of different things.

9. Energy Flows Through Ecosystems
sun
secondary consumers
(carnivores- eat animals)
loss of energy
loss of energy
primary consumers
(herbivores-eat plants)
producers (plants)

10. KEY CONCEPT Food webs model the flow of energy in an ecosystem.

11. Trophic levels are the nourishment levels in a food chain.
Primary consumers are herbivores that eat producers.
Secondary consumers are carnivores that eat herbivores.
Tertiary consumers are carnivores that eat secondary consumers.
Omnivores, such as humans that eat both plants and animals, may be listed at different trophic levels in different food chains.

12. Trophic Levels
We describe the different classifications of organisms in a food web or Energy Pyramid in terms of levels

13. Correct Names of Trophic Levels

14. A food chain links species by their feeding relationships.
A food chain is a model that shows a sequence of feeding relationships.
A food chain links species by their feeding relationships.
A food chain follows the connection between one producer and a single chain of consumers within an ecosystem.
DESERT COTTONTAIL
GRAMA GRASS
HARRIS’S HAWK

15. Consumers are not all alike. Herbivores eat only plants.
Carnivores eat only animals.
Omnivores eat both plants and animals.
Decomposers break down dead organic matter into simpler compounds.
carnivore
decomposer

16. A food web shows a complex network of feeding relationships.
An organism may have multiple feeding relationships in an ecosystem.
A food web emphasizes complicated feeding relationships and energy flow in an ecosystem.

17. Example Food Web What do arrows point towards?
Why is there more than one arrow pointing to a single circle sometimes?
Why is there a sun in every food web?

21. KEY CONCEPT Pyramids model the distribution of energy and matter in an ecosystem.

22. Ecological Pyramid sun Loss of energy between levels of food chain
can feed fewer animals in each level 1
100
100,000
1,000,000,000

23. An energy pyramid shows the distribution of energy among trophic levels.
energy transferred
energy
lost
Energy pyramids compare energy used by producers and other organisms on trophic levels.
Between each tier of an energy pyramid, up to 90 percent of the energy is lost into the atmosphere as heat.
Only 10 percent of the energy at each tier is transferred from one trophic level to the next.

24. Other pyramid models illustrate an ecosystem’s biomass and distribution of organisms.
Biomass is a measure of the total dry mass of organisms in a given area.
tertiary
consumers
secondary
primary
producers
75 g/m2
150g/m2
675g/m2
2000g/m2

25. An energy pyramid can show the numbers of individual organisms at each trophic level in an ecosystem.
tertiary
consumers
secondary
primary
producers 5
5000
500,000
5,000,000
A vast number of producers are required to support even a few top level consumers.

26. Humans In Food Chains
Dynamics of energy through ecosystems have important implications for human populations
how much energy does it take to feed a human?
if we are meat eaters?
if we are vegetarian?

27. KEY CONCEPT Populations grow in predictable patterns.

28. Changes in a population’s size are determined by immigration, births, emigration, and deaths.
The size of a population is always changing.
Four factors affect the size of a population.
immigration
births
emigration
deaths

29. Population growth is based on available resources.
Exponential growth is a rapid population increase due to an abundance of resources.

30. Logistic growth is due to a population facing limited resources.

31. KEY CONCEPT Ecological succession is a process of change in the species that make up a community.

32. Succession occurs following a disturbance in an ecosystem.
Succession regenerates or creates a community after a disturbance.
a sequence of biotic changes
damaged communities are regenerated
new communities arise in previously uninhabited areas