Biology 115, Sixth Quiz: 2 May 2000

A. Multiple choice questions: 0.5 points each.

• 1. (a)
• 2. (d)
• 3. (b)
• 4. (d)
• 5. (b)
• 6. (b)

B. Definitions: 0.5 points each.

• 7. The demographic transition is the change that occurs as a culture becomes sufficiently industrialized that birth rates decline, generally following a decrease in death rate.

(0.2 for the decrease in birth rate; 0.1 for the fact that it generally involves a decrease in death rate as well; 0.2 for post-industrialization.)
 
• 8. Natural selection is the process by which a population becomes adapted to its environment.
  (full credit even if "species" or "organism" replaces "population".  0.3-0.4 if the words "adapted" and "environment" are used". Extra stuff about Darwin should be tolerated.)

C. Reverse Definitions: 0.5 points each.

• 9. niche.
• 10.  biotic (0.2 for "carrying" or "growth")

D. Fill in the blanks: 0.5 point each.

• 11. death rate; sanitation and living conditions ("death rate" is worth 0.3 and must be worded just that way. For the remaining 0.2, "sanitation", "living conditions", or "technology" are all full credit answers.)
• 12. nitrogen gas; ammonia. (first part is worth 0.3 points: full credit for "nitrogen", "nitrogen gas", or "N₂".

Second part is worth 0.2; "ammonia", "ammonium ions", "NH₃", "NH₄⁺" or "reduced nitrogen" are full-credit answers; "nitrates" or "nitrites" get 0.1).

E. Short answers: 1 point each.

• 13.The amount of energy available to animals that eat plants is smaller than the amount of energy that was obtained from the sun in photosynthesis. No chemical process proceeds with 100% efficiency, so inevitably some energy is lost in the plant in the form of heat. Furthermore, the animal cannot metabolize plant tissue 100% effectively, so some of the energy in the plant cannot be converted to energy that the animal can use. (full credit for the chemical-efficiency argument; partial for the wastage-of- plant-material argument if not accompanied by the chemical efficiency.)
• 14. 3, 4, 1, 2. (Partial credit if A. afarensis is first and H. sapiens is last).

F. Full-paragraph answer: 2 points.

• 15. Less-developed countries have a large percentage of their population in the child-bearing age range, so even if the child-bearers are only replacing themselves, the population will continue to grow until the overall age structure of the population equilibrates.
• 16. A 3.5°C increase in temperature would cause melting of a substantial amount of the water that is currently bound up in ice in the polar ice packs. This will give rise to flooding in many low-lying areas. There are many ecosystems in which even a relatively modest increase in temperature will cause certain species that are currently present in small quantities to out-compete the current occupiers of their ecological niches. Thus many species will die out and be replaced by others. Agriculture would change dramatically as well. Crops that currently grow well but depend on either mild summers or cold winters for some of their growth patterns will not thrive after the changes. Other crops that are difficult to grow now because of cold winters or insufficiently hot summers will do better. So farmers will have to switch to different strains or different crops altogether.