Chapter 53 Reading Quiz 1.A bunch of populations living close together and possibly interacting is called a ____. 2.Which type of interspecific interaction is beneficial to both species? 3.“Cryptic coloration” is also known as… 4.The links in a food chain are also called ____ levels. 5.The sum weight of all individuals in a population is known as the …

1. Explain the relationship between species richness, relative abundance, and diversity. Species diversity  the number and relative abundance of species in a biological community Species richness  the number of species in a community Relative abundance  a measure of the proportion of a species in the community as a whole

2. Distinguish between the “individualistic hypothesis” and the “interactive hypothesis”. The individualistic hypothesis depicted a community as a chance assemblage of species found in an area because they have similar abiotic requirements The interactive hypothesis saw each community as an assemblage of closely linked species having mandatory biotic interactions that cause the community to function as an integrated unit

3. Explain how interspecific competition may affect community structure. Interspecific interactions are those that occur between populations of different species living together within a community Competition will result in one species being dominant over the other “Niches” come into play, and only one species may occupy a niche; the other must adapt to a different niche or not survive 

4. What is coevolution? Coevolution  a change in one species that acts as a selective force on another species - counteradaptation of the second species, in turn, affects selection of individuals in the first species

5. Describe the variations of predation and parasitism. Can have positive, negative, or neutral effects on the species involved Predation and parasitism are both (+/-) interactions Predation Parasitism Parasitoidism Herbivory

6. What are some defenses that animals and plants have against being eaten? Plants: - thorns, spines, hooks - chemicals, hormone analogues Animals: - passive, active, mechanical, or chemical - cryptic coloration, shape - aposematic coloration (bright warning) - mimicry

7. Describe the competitive exclusion principle, what niches are, and the evidence that competition exists in nature. The competitive exclusion principle predicts that two different species competing for the same limiting resources cannot coexist in the same community - one will use resources more efficiently, thus reproducing more rapidly and eliminating the inferior competitor An ecological niche is the sum total of an organism’s use of biotic and abiotic resources in it’s environment - how it “fits into” an ecosystem The weaker organism will become extinct OR One of the species will evolve to the point of using a different set of resources

8. Distinguish between commensalism and mutualism. Commensalism is a (+/0) interaction in which the symbiont benefits and the host is unaffected ex: cowbirds & cattle; sharks & remoras Mutualism is a (+/+) interaction requiring the evolution of adaptations in both species ex: flowers & insects; lichen

9. How do predators, mutualism, and parasitism alter community structure? Predators can alter community structure by moderating competition among prey species (Ex: zebras & lions) Mutualism can have community-wide effects (Ex: mycorrhizae fungi) Parasitic diseases that reduce populations of one species also impact other species

10. Explain how disturbance is one of the most prominent features of most communities. Disturbances are events that disrupt communities - they change resource availability and create opportunities for new species - the impact depends on the size, frequency, and severity of the disturbance - can be caused by natural disasters, overgrazing by animals, alteration on natural ecosystems

11. Why do we consider humans to be the most widespread agents of disturbance? Logging and clearing for farmland has reduced and disconnected forests Agricultural development disrupts grasslands Centuries of overgrazing by animals has contributed to the famine in parts of Africa Human disturbances usually reduce biodiversity 

12. Describe the stages of succession. Primary succession  when life begins in areas essentially barren due to lack of formed soil - volcanoes, retreated glaciers Secondary succession  if an existing community has already been cleared by some disturbance that leaves the soil intact

13. What accounts for the geographical ranges of species? Biogeography  the study of the past and present distribution of individual species and entire communities Limitation of a species to a particular range may be due to: - failure of the species to disperse beyond its current range - failure of pioneer individuals that spread beyond the observed range - the species having retracted from a once larger range to its current boundaries

14. Describe island biogeography. Islands provide opportunities to study factors affecting species diversity of communities due to their isolation and limited size # of species determined by immigration and emigration, which are determined by island size and distance from mainland Smaller islands have higher extinction rates The farther away an island is from mainland, the less species, relative to island size