Final Exam Short Answer Cumulative

Question 1

What are the five conditions necessary for a population to be in the Hardy Weinberg equilibrium?

Answer 1

• Large population
• Random mating
• No selection
• No mutation
• No migration (gene flow)

If something is violated, it means the population is evolving
(might need to know math)

Question 2

compare top-down and bottom-up models of community organization.

Answer 2

Top down means the predator is gone and bottom up is nutrients gone.

top down: changes in top trophic levels(predators)
(predators> secondary consumers> herbivores> producers)
- Effects on lower levels
- more predators means there will be less of the level below them but more of the level below that and so on.
- herbivores shrink with no predators.
Bottom up: Changes in lower trophic levels

Question 3

Compare exponential and logistic growth. Explain the shape of each graph.

Answer 3

In exponential growth, the rate at the beginning is slow but then it gains momentum as the size of the population increases. In logistic growth(reaches carrying capacity), the rate is fast at the beginning then slows down eventually because many entities are competing for the same space and resources. Carrying capacity is the maximum number of individuals that the environment can support(dictate; natural resources like food, area, space, predation, nesting sites).

Question 4

Provide examples of importance of osmosis in biological systems.

Answer 4

• The diffusion of water across a semi-permeable membrane
• High concentration to low concentration (ex. Movement of water to plant body)

ex: movement of water from the soil to root hairs must cross cell membrane.
- Water hast to move into or out of cells based on consentration levels
ex: kidneys- sodium ions, actively transported out of the loop of Henley and water follows
ex: transport water out of marine fish vs. freshwater fish (too much water, pee a lot)

Question 5

Describe a biogeochemical cycle in which bacteria and plants play a key role

Answer 5

nitrogen cycle:
1) nitrogen fixation: atmospheric nitrogen is fixed into ammonium ion
2) nitrification: ammonium ion turns into nitrite ion, which turns into nitrate ion(NH4+ > NO2- > NO3-)
3) assimilation: when the plant absorbs the nitrate ion into the plant body
4) ammonification: taking the nitrogen and dead organisms or waste products(feces) and converting it into ammonium ion
5) denitrification: turning it into a gas and putting it back into the atmosphere