1. Community Ecology
Biology 1 Chapter 20

2. Do Now
The main predators of field mice in a certain ecosystem are rattlesnakes and foxes. Suppose humans begin building neighborhoods in the ecosystem, driving out many of the indigenous rattlesnakes and foxes. What will most likely happen to the field mice's population?
A. The population will not be affected by the change.
B. The population will decrease in size.
C. The population will increase in size.
D. The population will occupy an entirely new niche.
Answer: C

3. Predation
Predation-an individual of one species, the predator, eats all or part of an individual of another species, the prey.
Carnivores-predators that eat animals
Herbivores-predators that eat plants.
All heterotrophs are either predators or parasites or both.

4. Adaptations in Animal Prey
Escape
Hiding
Produce toxins
Mimicry-one species closely resembles another species

5. Batesian mimicry-harmless species resembles venomous species
Ex. Harmless king snake & venomous coral snake
Mullerian mimicry-two or more dangerous or distatesful species look similar
Ex. Bees and wasps

6. Adaptations in Plants Physical defenses Chemical defenses
Thorns, spines, sticky hairs, tough leaves
Chemical defenses
Secondary compounds-chemicals that are byproducts of the plants’ metabolism and are harmful or distasteful to animals.

7. Competition
Intraspecific competition-interactions between members of the same species competing for the same resources.
Interspecific competition-a type of interaction in which two or more species use the same limited resources.
Ex. Lions & hyenas compete for zebras
Competitive Exclusion-one species is eliminated from a community because of a competition for the same limited resource.

8. Reduced Niche Size
Niche-the role that the species plays in its environment.
Fundamental niche-the range of conditions that the species can potentially tolerate
Realized niche-the part of the niche that the species uses.

9. Character Displacement-the evolution of differences in a characteristic due to competition.

10. Competition is the most intense between similar species that require the same resources.
Resource Partitioning-similar species coexist so that each species may avoid competition with others by using a specific part of an available resource.

11. Symbiosis
Symbiosis-a close, long-term relationship between two organisms

12. Types of Symbiosis
Parasitism-one individual is harmed while the other benefits; does not usually result in the immediate death of the host.
Host-is harmed
Parasite-benefits
Ectoparasites-Remain on the outside of the host
Endoparasites-Live inside the host’s body.

13. Types of Symbiosis
Mutualism-two species derive benefit from each other
Some mutualistic relationships are so close that neither species can survive without the other.
Ex. Pollination

14. Types of Symbiosis
Commensalism-one species benefits and the other species is not affected.
Ex. Species that scavenge for leftover items
Crash Course-Intro to Ecology

15. Do Now
The Toolache Wallaby was a kangaroo species in Australia that became extinct in the 20th century. The wallaby was hunted by humans, as well as animals brought to Australia by humans. Humans also cleared the land where the wallaby lived and foraged for food. Given this information, which of the following environmental changes caused the Toolache Wallaby to become extinct?
I. loss of habitat
II. climate change
III. introduction of non-native species
IV. pollution
A. I and III only
B. II and IV only
C. I, II, III and IV
D. I, II, and IV only
Answer: A

16. Species Richness
Species richness-the number of species in the community
Varies with latitude (distance from the equator)
Closer to the equator has more species richness.
Species evenness-the relative abundance of each species

17. Habitat Size and Species Richness
Species-area effect-Larger areas usually contain more species than smaller areas do.
Most often applied to islands, where area is limited by geography.

18. Community Stability & Species Richness
Disturbances-events that change communities, remove or destroy organisms, or alter resource availability.
Abiotic-drought, fire, flood, volcanic eruption, earthquake, storms
Biotic-elephants tearing up trees or prairie dogs moving soil, humans bulldozing, clear-cutting, paving, plowing, or mowing.

19. Stability-the tendency of a community to maintain relatively constant conditions; a community’s resistance to disturbances

20. Successional Changes in Communities
Ecological succession-the gradual, sequential regrowth of a community of species in an area

21. Primary Succession-the development of a community in an area that has not supported life previously, such as bare rock, sand, island formed by volcanic eruption.
Soil is not initially present.

22. Secondary succession-the sequential replacement of species that follows disruption of an existing community
Ex. Fire, storm, human activity

23. Pioneer Species-the species of organisms that predominate early in succession
Tend to be small, grow quickly, and reproduce quickly.

24. Climax Community-The community proceeds through a predictable series of stages until it reaches a stable end point.
Succession
Crash Course-Succession

25. Do Now
Microorganisms can mutate and evolve very quickly compared to most multicellular organisms. This allows pathogenic microorganisms to infect new species. Suppose a very harmful microorganism that is quite successful at infecting hardwood trees is introduced into a forest ecosystem. What effect would this pathogenic microorganism most likely have?
A. It would maintain the balance of the ecosystem by reducing the populations of all the species.
B. It would maintain the balance of the ecosystem by reducing the population of one species.
C. It would disrupt the ecosystem by infecting and killing the populations of all the species.
D. It would disrupt the ecosystem by greatly reducing the population of a few species.
Answer: D

26. Finding Nemo Activity Predator-Prey Mutualism and Niches Commensalism
Coexist
Parasitism
Competition
Competetive Exclusion