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Community Ecology

Community Ecology. Remember!. A community includes all organisms that live together in an area. Community Ecology : study of interactions among all populations in a common environment. Ecologists ask - in what ways do the populations interact?. Community Interactions.

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Community Ecology

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  1. Community Ecology

  2. Remember! • A community includes all organisms that live together in an area. • Community Ecology: study of interactions among all populations in a common environment Ecologists ask - in what ways do the populations interact?

  3. Community Interactions • Niche: the role of an organism in an ecosystem • Habitat = address vs. niche = job Bobcat’s Niche: predator, carnivore Rabbit’s Niche: prey, herbivore

  4. Community Interactions • Competition: competing for resources, shelter, space, mates, etc. • Interspecific Competition: between members of different species • Intraspecific Competition: between members of the same species

  5. Niche & Competition • Competitive Exclusion: no 2 similar species can occupy the same niche (compete for the same resources) at the same time The red squirrel is native to Britain, but its population has declined due to competition with the grey squirrel. The grey squirrel was introduced into Britain & has easily adapted, replacing the red squirrel.

  6. Resource Partitioning • Reduces competition through microhabitats

  7. Resource Partitioning Among Dominican Republic Lizards Several species of Anolis Lizards live close in proximity & all feed on insects & other small arthropods. Competition for food is reduced, because each lizard species occupies a different microhabitat.

  8. Interspecific Interactions • Predation: an organism hunts & feeds on another organism

  9. Interspecific Interactions • Symbiosis: the relationship of organisms from different species living closely together

  10. Mutualism • Both species benefit from the relationship Clownfish live within sea anemones, which normally sting other fish. The fish gets protection, & the anemone benefits because the clownfish keep it clean of bacteria.

  11. Mutualism Hummingbirds pollinate flowers. The hummingbirds get food, while helping the flowers reproduce!

  12. Parasitism • One organism gains benefits at the other’s expense. Here, a leech sucks the blood of a human.

  13. Parasitism A wasp lays its eggs in the larva of another insect (a boll weevil). When the wasp eggs hatch, they feed on the boll weevil.

  14. Commensalism • One species benefits and the other is neither hurt nor helped. Epiphytes are plants that grow on other plants without harming them. They never set roots in the ground.

  15. Commensalism Moss growing on a tree

  16. + Benefit - Harmful 0 Neutral

  17. When grazing cows walk around, they disturb the ground, which stirs up insects. Birds follow the cows & eat these insects. The relationship between the bird & the cow is- • Mutualism • Parasitism • Commensalism • Competition Commensalism

  18. Shrimp living in the ocean eat parasites off of larger fish. The shrimp get a meal and the larger fish get rid of a parasite. • Mutualism • Parasitism • Commensalism • Competition Mutualism

  19. A botfly lays maggots inside a man’s head, providing shelter and nutrition for its young. • Mutualism • Parasitism • Commensalism • Competition Parasitism

  20. Populations in Communities • Population sizes can fluctuate (go up or down).

  21. Factors that Affect Population Size • # of births • # of deaths • # of individuals immigrating (entering) & emigrating (leaving)

  22. Exponential Growth • If a population has abundant space & food, no disease or predators, it will grow at an exponential rate. • It is a J-shaped curve resembling y = ax2 + b

  23. Logistic Growth • Population growth slows then stops (stays stable) after a period of exponential growth & resources become less available. • The number at which the environment can support this population is known as the carrying capacity.

  24. Limiting Factors • Factor that causes a population to decrease in size • 2 types: • Density Dependent • Density Independent

  25. Density Dependent Limiting Factors • Relies on how many organisms in a defined space are in that population; can include: • Competition • Predation • Parasitism • Disease Notice the pattern of population size with predator/prey relationship of hares & lynxes.

  26. Density Independent Limiting Factors • Affect all populations in similar ways, regardless of population size • Weather • Natural Disasters • Seasonal Cycles • Human Activities

  27. Before you leave, answer the following question on a sheet of paper (share!) Is Mycorrhizae an example of mutualism, parasitism, or commensalism? Explain your answer!

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