1. Chapter 20: Community Ecology

2. Community - several interacting populations that inhabit a common environment and are interdependent.
Next level is a community which is several populations living together and depending on each other. What does interdependent mean? An example of a community is shown here with the bear and the salmon. They both live in a common environment and the bear needs the fish for food? How does the salmon need the bear?

3. Predation
Predation is an interaction in which one organism (the predator) captures and eats all or part of another individual organism (the prey).
Adaptations
Predators have adaptations to efficiently capture prey, whereas prey species have adaptations to avoid capture.
How do they trap the sun’s energy? Through what process? What is that process similar to in animal cells?

4. Predation, cont. Adaptations in Prey
Mimicry is an adaptation in which a species gains an advantage by resembling another species or object.
Adaptation in Predators
Speed (i.e., cheetahs)
Sharp teeth and claws
Eyes often at front of the head (useful for judging distance)

5. Competition Competitive Exclusion
Competition may cause competitive exclusion, the elimination of one species in a community.
Resource Partitioning
Differential use of resources to avoid competition is called resource partitioning.

6. Example: Resource Partitioning
Warbler Foraging Zones

7. Symbiotic Relationships
Symbiosis- two species living together
3 Types of symbiosis:
1. Commensalism
2. Parasitism
3. Mutualism
Cleaning shrimp

8. Symbiotic Relationships
Commensalism-
One species benefits and the other is neither harmed nor helped
Ex. Cattle egrets & cattle (birds ride on the cattle; as cattle eat vegetation, insects on the ground get stirred up, which the birds eat)
You can see here that this polar bear is no longer white.

9. Symbiotic Relationships
Parasitism-
One species benefits (parasite) and the other is harmed (host)
Parasite-Host Relationship

10. Symbiotic Relationships
Mutualism-
Beneficial to both species
Ex. Humans & beneficial gut bacteria (i.e., E. coli)
The Egyptian plover takes insects from the backs of buffaloes, giraffes and rhinos. The plover has also been observed taking leeches from the open mouths of crocodiles! In this association the plover receives a supply of food and the other animal rids itself of unwelcome pests

11. = 1 species Type of relationship Species harmed Species benefits
Species neutral
Commensalism
Parasitism
Mutualism
= 1 species

12. Changes in Ecosystems: Ecological Succession

13. What is Ecological Succession?
Natural, gradual changes in the types of species that live in an area
Can be primary or secondary
The gradual replacement of one plant community by another through natural processes over time

14. Primary Succession Begins in a place without any soil:
Sides of volcanoes
Landslides
First, lichens that do not need soil to survive grow on rocks
Next, mosses grow to hold newly made soil
Known as PIONEER SPECIES (the first species to colonize an area)

15. Primary Succession
Soil starts to form as lichens and the forces of weather and erosion help break down rocks into smaller pieces
When lichens die, they decompose, adding small amounts of organic matter to the rock to make soil

16. Primary Succession
Simple plants like mosses and ferns can grow in the new soil

17. Primary Succession
The simple plants die, adding more organic material (nutrients) to the soil
The soil layer thickens, and grasses, wildflowers, and other plants begin to take over

18. Primary Succession
These plants die, and they add more nutrients to the soil
Shrubs and trees can survive now

19. Primary Succession
Insects, small birds, and mammals have begun to move into the area
What was once bare rock, now supports a variety of life

20. Secondary Succession
Begins in a place that already has soil and was once the home of living organisms
Occurs faster and has different pioneer species than primary succession (i.e., weeds)
Example: after forest fires

22. Ecological Succession at Glacier Bay

23. Climax Community
A stable group of plants and animals that is the end result of the succession process
Does not always mean big trees
Grasses in prairies
Cacti in deserts