Unit 7 Objective Questions and Answers

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1. What is the difference between community composition, and species abundance, richness, diversity and evenness?

Community composition: what species are in a community Species abundance: number of individuals of a species Species richness: number of species within a community, does not take abundance into

account Species diversity: abundance + richness Evenness: how even the community is; so if you have the same number of individuals in

each species you would have a very even community

2. What are the four main factors that determine distribution and abundance of species? Natural selection – niche based factors, abiotic characteristics that determine which

species can and cannot live there Genetic drift Gene flow Mutation

3. Compare deterministic and stochastic effects. Stochastic – things happen by chance Deterministic – perfect curve (even though no population is ever perfect)

4. What is a niche? Which is larger, fundamental or realized?Niche is all the resources an organism needs to live. Fundamental niche is larger than realized.

5. What are intraspecific and interspecific factors limiting distribution and abundance of species?

Intraspecific – limits distribution and abundance of species WITHIN the species (abiotic factors, behavioral differences, and density dependent.

Interspecific – limits distribution and abundance of species outside of species (commensalism, competition, consumption, and mutualism)

6. Describe commensalism, competition, consumption and mutualism. Commensalism: (+,0). One organism benefits from the relationship and the other is not

affected at all. Competition: (-,-). Both organisms are harmed. Each species does worse when they’re

together Consumption: (+,-). One benefits and one is harmed Mutualism: (+,+). Both organisms benefit from their relationship

7. What is Gause’s competitive exclusion principle?Complete competitors cannot coexist. One will be at least a little better than the other and the other will go extinct.

8. What is resource partitioning?Allows multiple species to coexist in same environment. Species divide a niche to avoid competition.

9. Describe constitutive vs inducible defenses. Constitutive: defense that an organism has at ALL TIMES (ex: shells). This is good for

when you have a constant threat. Inducible: defense is turned on when there’s a threat; does not have this defense active

at all times

10. What are fitness tradeoffs?A situation that involves losing one quality or aspect of something in return for gaining another quality or aspect. More colloquially, if one thing increases, some other thing must decrease.

11. How does Batesian differ from Mullerian? Batestian: a harmless species mimics a harmful species. Ex: Coral snake (venomous) vs

Scarlet King Snake. “Red on yellow will kill a fellow. Red next to black is a friend of Jack.” Mullerian: two or more harmful species mimic each other. The purpose of this is that if a

predator learns to avoid one of the species, it will learn to avoid the mimic species as well. Ex: two species of venomous wasps that have the same color pattern.

12. Describe how the top-down control and bottom-up limitation hypothesis. Which is correct?

A top-down cascade is a trophic cascade where the food chain or food web is disrupted by the removal of a top predator, or a third or fourth level consumer. On the other hand, a bottom-up cascade occurs when a primary producer, or primary consumer is removed, and there is a reduction of population size through the community.

13. What is coevolutionary arms race?In evolutionary biology, an evolutionary arms race is a struggle between competing sets of co-evolving genes, traits, or species, that develop adaptations and counter-adaptations against each other, resembling an arms race.

14. Why are mutualisms sometimes referred to as “mutual parasitisms”?Because they both happen to benefit from the other but they’re just trying to get the most out of each other. “Using” each other for their own good.

15. Differentiate between deterministic and stochastic. Stochastic is due to random chance alone.Deterministic is nonrandom factors that determine the distribution and abundance of species (intraspecific and interspecific). Leads to nonrandom and predictable patterns over time. Opposite of stochastic.

16. What is the difference between Gleason and Clements views on plant community succession? Which is supported by the evidence?

Gleason = random chance. The community found in a particular area is neither stable nor predictable. It is largely a matter of chance whether a similar community develops in the same area after disturbance occurs.

Clements = predictable. Biological communities are stable, integrated, and and orderly entities with a highly predictable composition. They develop by passing through a serious of predictable stages dictated by interactions among species. This development culminates in a stable final stage called a climax community.

They’re predictable up to a certain point then are no longer predictable.

17. Describe and draw a figure depicting the theory of island biogeography.

18. Can speciation affect ecology in the short-term (e.g. decades)? Give an example. Yes it can affect it in short-term. The example is the soapberry bug.

19. What is a disturbance regime?

Disturbance regime = most communities experience a characteristic type of disturbance. In most cases, disturbances occur with a predictable frequency and severity.

20. What is the difference between primary and secondary succession? What are pioneer species? What is the successional pathway for temperature grasslands/forests?

-Succession is the recovery, the development of communities, that follows a severe disturbance -Primary succession occurs when a disturbance removes the soil and its organisms, as well as organisms that live above the surface -Secondary succession occurs when a disturbance removes some or all of the organisms from an area but leaves the soil intact-Pioneer species are hardy species which are the first to colonize previously disrupted or damaged ecosystems, beginning a chain of ecological succession that ultimately leads to a more biodiverse steady-state ecosystem.

21. What are keystone species?Keystone species - a species on which other species in an ecosystem largely depend, such that if it were removed the ecosystem would change drastically.

22. What are the hypotheses describing the latitudinal gradient in diversity?1) High-productivity hypothesis – high productivity promotes high diversity.2) Energy hypothesis – high temp increases productivity and the likelihood that organisms

can tolerate the physical conditions in a region3) Area and age hypothesis – tropical regions have had more time and space for speciation

than other regions4) Intermediate disturbance hypothesis – regions with a moderate type, frequency, and

severity of disturbance should have high species richness and diversity Each of these factors may influence diversity, but no single hypothesis offers a convincing explanation for the global diversity gradient

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23. What is the role of primary producers?A primary producer, or autotroph, is an organism that can synthesize its own food from inorganic sources Primary producers form the basis of ecosystems by transforming the energy in sunlight or inorganic compounds into the chemical energy stored in sugars (in other words – turning energy into plant tissue) Primary producers use this chemical energy for maintenance and/ or growth

24. What is gross primary production? Net primary production? NPP = Net Primary Productivity... Net primary production is the rate at which all the

plants in an ecosystem produce net useful chemical energy; it is equal to the difference

between the rate at which the plants in an ecosystem produce useful chemical energy (GPP) and the rate at which they use some of that energy during respiration.

GPP = Gross Primary Productivity (assimilation) R = cellular respiration (and waste/heat loss) NPP = GPP – R

25. What does this mean – “Energy flows, nutrients cycle”?Energy dissipates as it flows through ecosystemsNutrients cycle through the ecosystems

26. What does the direction of arrows indicate in food web?Arrows show direction of energy flow: from organism consumed to consumer

27. What are production efficiency and trophic level transfer efficiency?Production efficiency = percentage of energy assimilated by an organism that becomes incorporated into new biomassTrophic level transfer efficiency = amount of energy at one trophic level that is acquired by the trophic level above and incorporated into biomass. Examines energy flow between trophic levels, not just individual species

28. What is a trophic cascade?A trophic cascade occurs when changes in topdown control cause conspicuous effects two or three links away in a food web – For example, the reintroduction of wolves in Yellowstone National Park has led to far-reaching changes in the food web

29. How does biomagnification work?

the concentration of toxins in an organism as a result of its ingesting other plants or animals in which the toxins are more widely disbursed. One organism eats another organism that has toxins in it and therefore the toxins are now in its system

30. What are global patterns in productivity?• NPP on land is much higher than it is in the oceans, because more light is available • The terrestrial ecosystems with highest productivity are located in the wet tropics • Marine productivity is highest along coastlines, and it can be as high near the poles as it is in tropics

31. Which biomes have the highest productivity per unit area? Overall?Per unit = tropical wet forests and tropical seasonal forests Overall = oceans

32. Why is productivity important for higher trophic levels?There needs to be high productivity at lower levels in order for there to be any at the higher levels.

33. What factors control the rate of nutrient cycling? How does it differ between temperate and tropical areas?

Boreal forests: accumulation of detritus and organic matter (better to farm here)Tropical wet forest: almost no organic accumulation

34. Describe the nitrogen cycle.

Nitrogen makes up 78% of atmosphere. Gets fixed by nitrogen fixing cyanobacteria. Can also be fixed by nitrogen-fixing bacteria in roots and soil.Nitrogen can be returned back up to the atmosphere as well. She said you don’t need to know all of the details about this… but you might want to look over it just in case.

Too much nitrogen can cause “dead zones” in aquatic systems which leads to decreased species diversity which is obviously very bad.

35. Describe the water cycle. The global water cycle begins with water evaporating out of the ocean and precipitating back into it. Evaporation exceeds precipitation over oceans. When this water vapor moves over the continents, it is augmented by water transpired by plants. Precipitation falls on the continents, and flows back to ocean via rivers.

36. Describe the carbon cycle. CO2 is stored in atmosphere, taken up through photosynthesis and respired. Lots of carbon stored in the ocean(largest reservoir by far), some stored on land and atmosphere as well.

In both terrestrial and aquatic ecosystems, photosynthesis is responsible for taking carbon out of the atmosphere and incorporating it into tissue. Cellular respiration releases carbon to the atmosphere as CO2.

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37. How many species are there?8-9 million eukaryotic species… we’re not including bacteria and archaea

38. Why is biodiversity important?Biodiversity can be thought of as the tree of life. It describes the evolutionary relationships among all life forms. Biodiversity has both economic and biological benefits. Communities that are more diverse appear to be more productive, more resistant to disturbance and invasion, and more resilient than communities that are less diverse. Increased species richness increases the surfaces provided by ecosystems.The prosperity, health and happiness of humans are dependent upon the preservation of biodiversity and functioning ecosystems. Collectively, all the direct and indirect benefits that humans derive from organisms and ecosystems they compose are called ecosystem services.

39. What are the 5 major threats to biodiversity? Describe each.

Habitat destruction: 50% of total land surface has been altered by humans. Humans cause habitat destruction in many ways: logging, burning forests, grazing livestock, filling in wetlands, development. One of the worst is deforestation. Habitat fragmentation is one of the most pervasive forms of habitat degradation. It’s the breakup of large, continuous areas of natural habitat into small, isolated pieces. Overexploitation = harvesting of wild organisms by humans faster than the population can reproduce. This is the dominant threat for marine species.

Invasive species = new organism introduced to environment that causes damage to it.

Pollution = industrial pollutants can cause acid rain and contribute to greenhouse gases. Pharmaceutical drugs are released in human urine and pass through wastewater plants into streams and rivers.Pesticides and herbicides can biomagnify in food chains Nutrient runoffs can cause eutrophication, which is excessive richness of nutrients in a lake or other body of water, frequently due to runoff from the land, which causes a dense growth of plant life and death of animal life from lack of oxygen.

Climate change = the average global temps increased 0.74 degrees Celcius during the 20th century. Oceans are becoming more acidic, precipitation patterns change, severity of extreme weather events is increasing, sea levels are rising, melting ice caps.

40. Describe some of the conservation successes. Give Swordfish a break!! Stopped eating swordfish and restored the population. Clean water act made regulations for factories so they stopped polluting water.

Clean air act made LA go from smog filled air to having relatively clear air now! Kids were getting asthma and are now healthy.

41. Which species are at greatest risk?Amphibians. 41% are threatened.

42. How do we protect and restore biodiversity?Read, think, and talk with others to develop your knowledge and beliefs about human’s role in the world. Consider what you do with your money and time. – Reduce, reuse, recycle – Reduce meat consumption – Reduce flying – Walk or bike more often – Choose a career in line with your beliefs Realize that your choices may not be the same as others, so lead by example. Take the long view…. Ask yourself how your actions might affect the experiences of your great-grandchildren. Be active in the political process.