BIO330 Chapter 3: Community Ecology

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30 Questions

What is the primary focus of community ecology?

The study of interactions between populations of different species

What is a key difference between a community and a population?

The number of species living in the area

According to HA Gleason's individualistic concept of community, what is the main reason for species coexistence?

Species have similar abiotic requirements

What is the main difference between a community and an ecosystem?

The presence of non-living components

What is the definition of a community in ecology?

A group of populations of different species

What is the primary unit of study in community ecology?

Group of populations of different species

What is the result of interspecific competition on the realized niche of Chthamalus?

It makes the realized niche smaller than its fundamental niche

What is character displacement?

The tendency for characteristics to be more divergent in sympatric populations of two species

What is the term used to describe populations that occur in the same place at the same time?

Sympatric

What is the difference between the beak sizes of Geospiza fuliginosa and Geospiza fortis in allopatric populations?

They have similar beak sizes

What happens to the Chthamalus population when Balanus is removed from the lower strata?

It spreads into the lower strata

What is the term used to describe populations that are physically isolated from each other by an extrinsic barrier?

Allopatric

What is the main idea behind the competitive exclusion principle?

Two species with similar needs for the same limiting resources cannot co-exist in the same place.

What was the outcome when Gause grew P.aurelia and P.caudatum together in the same culture tube?

The numbers of P.caudatum declined to extinction.

What is an ecological niche?

The sum total of a species' use of the biotic and abiotic resources in its environment.

What did Gause study in his experiment?

Competition among two species of Paramecium.

What is the significance of the competitive exclusion principle in ecology?

It shows how interspecific competitions affect ecological niches.

What can be used to describe an ecological niche?

Space utilization, food consumption, temperature range, and other factors.

What is the primary benefit that cattle egrets receive from their relationship with grazing cattle?

Nutrition from insects and vegetation

What is a characteristic of mutualistic relationships in nature?

Changes in either species can affect the survival and reproduction of the other

What do ants provide to aphids in their mutualistic relationship?

Protection from predators and parasites

What is the benefit that remora fish receive from their relationship with sharks?

Free transport and source of nutrition

What is the role of clownfish in their mutualistic relationship with anemones?

Both A and B

What type of interaction is described in the example of cattle egrets and grazing cattle?

Commensalism

What is an indirect effect of interaction between species?

The presence of one species affects a second species through a third species

What is the result of the presence of rodents on the number of small seeds in a community?

An increase in the number of small seeds

What is a key feature of community structure?

Feeding relationships within communities

What is the term for the diversity of species within a community?

Species diversity

What is the result of the presence of rodents on ant populations in a community?

An indirect positive effect on ant populations

What determines the feeding relationships within a community?

Predator-prey, host-parasite, and plant-herbivory interactions

Study Notes

Competitive Exclusion Principle

  • Gause's hypothesis (1934): two species with similar needs for the same limiting resources cannot co-exist in the same place.
  • Gause studied competition among two species of Paramecium and found that P.caudatum declined to extinction when grown with P.aurelia.
  • This observation led to the formulation of the Competitive Exclusion Principle, which states that no two species can co-exist when resources are limiting.

Ecological Niche

  • Ecological niche is the sum total of the organism's use of biotic and abiotic resources in its environment.
  • Ecological niche includes space utilization, food consumption, temperature range, mating conditions, and moisture requirements.

Mutualism

  • Mutualism is a symbiotic relationship where both species benefit.
  • Examples of mutualism:
  • Aphids and ants: aphids secrete honeydew, which ants feed on, and ants protect aphids from predators.
  • Remora fish and sharks: remora fish clean parasites from sharks, and sharks provide transportation and nutrition.
  • Clownfish and anemones: clownfish nestle into anemone's tentacles for protection, and clownfish keep anemones free of parasites and provide nutrients.

Interspecific Competition and Realized Niche

  • Experimental evidence for competition in nature: removal of Balanus from lower strata allowed Chthamalus population to spread, showing that Chthamalus could survive in areas where it is not normally found.
  • This demonstrates that interspecific competition limits the realized niche of Chthamalus.

Evidence for Competition in Nature

  • Character displacement in Galapagos finches: sympatric populations of Geospiza fuliginosa and Geospiza fortis have more divergent beak sizes than allopatric populations.

Community Ecology

  • Community: an assemblage of populations of different species that interact and inhabit a particular area.
  • Community ecology: the study of interactions or relations between populations of different species living in a particular area.

Community Structure

  • Feeding relationships: trophic structure, predator-prey, host-parasite, and plant-herbivory interactions.
  • Species diversity: species richness and relative abundance.
  • Disturbances and community stability.

Indirect Interactions

  • Indirect effect of interaction: species may not directly interact, yet the presence of one species may affect a second species by way of interactions with a third species.
  • Example: desert rodents and ants interactions, which affect seed populations and, in turn, affect ant populations.

This quiz covers the basics of community ecology, including community interactions, structure, and succession. Learn about primary and secondary succession and more.

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