BIOC50H3 Lecture : lecture note 12 for BGYB50

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19 Jul 2010

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1) Explain why we typically find more species under conditions of intermediate disturbance compared to either rare or frequent disturbance. (Ch. 18)

2) Why might you expect communities with fewer species to contain fewer trophic levels? (Ch. 18)

3) How do ecologists distinguish between primary and secondary succession? (Ch. 19)

4) When using a chronosequence to document the pathway of succession, what are the assumptions? (Ch. 19)

5) Why should we not expect a single climax community within a biome? (Ch. 19)

6) Compare and contrast the concepts of facilitation, inhibition, and tolerance in the context of ecological succession. (Ch. 19)

7) When a community experiences succession, why does the species richness of a community initially increase, then plateau, and finally decline? (Ch. 19)

8) Why do early- and late-successional species tend to possess different adaptations? (Ch. 19)

9) Why is the efficiency of energy transfer between two trophic levels generally quite low? (Ch. 20)

10) How do ecologists distinguish between gross primary productivity and net primary productivity? (Ch. 20)

11) Compare and contrast the measurement of primary productivity in terrestrial vs. aquatic systems. (Ch. 20)

12) What factors limit the net primary productivity of terrestrial systems? (Ch. 20)

orangedolphin399

The increased levels of greenhouse gases, particularly carbondioxide, have led some scientists to postulate that terrestrialplants will increase their rates of carbon fixation throughphotosynthesis in response. However, plant physiology experimentsto date show mixed results. One surprising result was that, thoughplants did increase their rates of photosynthesis for a time, withcontinued exposure to elevated levels of carbon dioxide, plantsresponded by actually synthesizing less of the photosyntheticenzyme rubisco and reduced the rates of photosynthesis to ratescomparable with lower concentrations of carbon dioxide. Thisphenomenon is called downregulation. This is of concern becausesome atmospheric scientists are looking to enhanced plant growth toremove the excess carbon dioxide from the atmosphere.

Considering this and the concepts presented in this unit, propose aresponse to the following statement. Explain your answer and givean example supporting your position:

Because of physiological limitations such as downregulation, plantswill not increase their uptake of carbon dioxide in response toincreased levels in the atmosphere, and will not increase theirrelative significance in the removal and sequestration of carbondioxide. Do you agree or disagree?

greendolphin569

Question 402 pts

You go on an expedition to the mountain forests of the remote island of Halmahera, Indonesia. You discover a new species of arboreal primate that is only found deep in the forest. It is endemic to a single mountain range and is found nowhere else. Logging companies are beginning to explore the area and may start building roads soon in order to provide access to the remote forest for logging.

What effects could road building have on the primate population within the next 10 years?

SELECT ALL THAT APPLY (You may need to select more than one answer)

Higher light penetration and lower relative humidity could make areas alongside the roads less suitable for the primates

The likelihood of contracting a new disease would increase in the primate population

Speciation could occur so that populations in isolated forest fragments could split into different species

Its population could increase because of the greater availability of forest edges for foraging

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Question 412 pts

Which of the below is NOT an example of an ecosystem service?

Pollination of crops by native bees

Revenue generated by clear-cutting of tropical dry forest

The presence of an intact forest maintaining constant water flow in streams throughout the dry season in a tropical region

Rainforest trees removing carbon from the atmosphere

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Question 422 pts

Climate change must be factored into the design of new conservation areas and in new land acquisitions made by current reserves. Which of the below types of habitat would be given highest priority for conservation in light of climate change?

SELECT ALL THAT APPLY (You may need to select more than one answer)

Small isolated patches of habitat

Long and narrow areas of habitat that are oriented parallel to latitude

Patches of habitat that join existing conservation areas

Elevational gradients

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Question 432 pts

The Ngorongoro Crater lion population in Tanzania is isolated from nearby Serengeti lion populations. In 1962, the population crashed due to disease, dropping from 90 individuals to less than 20. The population of lions today is currently exhibiting a high rate of sperm abnormalities, which are rare outside the crater population. What is the likely cause of this?

SELECT ALL THAT APPLY (You may need to select more than one answer)

Matings between closely related individuals

Natural selection for fitter sperm phenotypes

Radiation from the crater that is causing new mutations

Lower genetic diversity than normal populations of lions due to a population bottleneck in 1962

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Question 442 pts

What is considered to be the most likely hypothesis for the cause of the extinction of the Pleistocene megafauna?

Hunting by early humans

An asteroid collision that changed the climate

Massive volcanic eruptions that strengthened the greenhouse effect and led to global warming

The global radiation of marsupial mammals that outcompeted the megafauna and made them go extinct