Name_________________________________Biology
44, First Hour Test.
Answer all questions. Each is worth 5 points.
1. You find a population where 36% of all individuals exhibit a dominant trait. If the population behaves according to Hardy- Weinberg predictions,what percentage of individuals would you expect to be heterozygous? (show calculations)
p2 + 2pg = 36; q2 = 64; q = 8, p = 2; 2pq = 32
In the same population, you find that, through several generations, the % of each allele changes by 50% rather than remain constant. Present two possible explanations for this, and the evidence you would look for to prove each of these explanations might be correct.
2.3. for an allele to
change a lot in a short time, cannot be mutation. Could be drift or migration
if small population. Could be selection if environment changed rapidly
4. According to Guthrie, evolution causes humans (and other species) not to get better through time, just older. Explain what is meant by this.
As any species tries to get better, so
does its competition, predators and diseases, and the environment is also changing
= so you don’t get better adapted to the environment, which is a moving target.
You find a population of organisms that exhibit almost no variation for any trait.
Present two possible explanations for this, and the evidence you would look for to prove each of these explanations might be correct.
5.6. reasons for no variation = asexual species, tiny population
and inbreeding, very constant environment for a very long time so already
perfectly adapted
What factors or conditions exist
7.) when the population of a species is at its maximum
birth rate = death rate = population at carrying capacity. Leidig’s law of minimum – some resource is totally used up.
8.) when the number of species in an area is at a maximum
colonization
rate = extinction rate; all resources used or all niches filled.
You find a “living fossil:” a species that in physical appearance is identical to its fossil ancestor that lived millions of years ago. Present two possible explanations for this, and the evidence you would look for to prove each of these explanations might be correct.
9. appearance is similar but other genes have changed – look at
dna
10/ in an unchanging environment for a long
period of time
live on isolated area (island) where it could avoid competition and any need to change.
There is a lake that has within it 200 species of a group of closely related organisms (all with a common ancestor). The lake does not appear to have within it any barriers to movement for this species. Present two possible explanations for this, and the evidence you would look for to prove each of these explanations might be correct.
11.12. – the question
is how the speciation could create 200 species without isolation. plants and sympatric speciation.;, asexual species with individuals adapting to
different environments within the lake;
perhaps there are barriers that we don’t see, or parapatry.
Or perhaps in the past lake level was lower and there were several ponds with
barriers between them
You find a species that seems to be a generalist in terms of its adaptation to its environment. Present two possible explanations for this, and the evidence you would look for to prove each of these explanations might be correct.
13.14. means no
competition – could be on an island or in an extreme environment, or newly
entered the environment and no time yet to specialize.
You calculate the number of species that ought to be on an island of the size you are exploring, but discover that you can find only half the expected number. Present two possible explanations for this, and the evidence you would look for to prove each of these explanations might be correct.
15.16. catastrophy
killed off many species, no time yet to repopulate; island recently got larger
(see level fell) no time yet to adjust; the island is either in the arctic =
fewer species per area, or very isolated in
middle of ocean= hard to colonize
For your Ph.D. thesis, your professor suggests that you search for newly created life forms; life not related to any other species known on earth today.
17. What kinds of environmental conditions would be best to search in, and why.
The key here is not related to existing
life = not dna based. Need lack of oxygen – that will break down
any organic molecules necessary for life
also need lack of existing life that would eat organic molecules. – there are anoxic
environments – deep ocean, deep ground, etc.
18. What kind of things would you be looking for (what would you consider to be life
on a chemical level?
Need a chemical that is not dna or rna
= different, yet can replicate, mutate and carry information.
19. It has been stated that people of who fail to finish high school are more fit than college graduates. What is the basis of this argument and, if it is true, are there any genetic consequences?
Basis is that high school
dropouts have more children on average than college graduates – so are
contributing more to gene pool. Two issues about genes. 1) are
these children in turn having more young (surviving) and are there any genetic
differences (as opposed to simple economics) between the two groups.
20. A high percentage of the population is overweight and being overweight is harmful (decreases life expectancy). Natural selection should not permit such a deleterious trait to exist, yet it does. Present a possible explanation for why natural selection failed in this case.
a) in
the past, binge eating was selected for when food was scarce. Conditions have
changed but genes change more slowly
b) overeating
not under genetic control as never needed to be in the past.
c) availability
of new foods- sugars, etc, that once were scarce so no reason not to eat too
much of them.