Which of the following statements about evolution is
correct?
A. Lamarck's theory of use and disuse adequately
describes why giraffes have long necks.
A. Lamarck's theory of use and disuse adequately
describes why giraffes have long necks.
B. Darwin's theory of natural selection relies solely
on genetic mutation.
C. Darwin's theory explains the evolution of man
from present day apes.
D. Darwin's theory of natural selection relies solely
on environmental conditions.
E. Natural selection is the process in which random
mutations are selected for survival by the
environment.
the correct answer is E.
I read the answer key with description but still have no clue.
First, let's discuss evolution. Evolution has 4 primary components:
(1) Variation in a trait in a population
(2) Heritability of that trait
(3) Differential reproductive success
(4) Non-random reproductive success
3 & 4 tend to kind of blur together a bit.
The first step says that our population is not homogenous. For example, not all giraffes have the same length neck. If this is false, there can be no evolution: a trait can not be selected for if all population members have the same trait (we can't select for neck length if everyone has identical necks).
The second says that the trait can, to some degree, be inherited. That is, the children of long-necked giraffes will also tend to have long necks. If this is false, it won't matter how beneficial the trait is, we can't evolve it. I.e., SexyMan allele lets me have 1,000,000 kids. But if my kids can't inherit my sexiness, none of them will have 1m kids - it will have been a blip in the radar, and on an evolutionary timescale, it basically didn't happen.
The third trait says that we don't all have the same success in popping out kids. If we did, traits wouldn't evolve - if long necks and short necks all popped out 2 kids each, no trait would overtake the other, and we wouldn't see a trend of change.
The fourth links 1&2 to 3; it says that these variable traits we have and pass on are *linked to* our reproductive success. Sexiness (which varies and gets passed on) *is linked to* how many kids I pop out, such that sexy alleles can be favored.
The key idea here is very simple:
genes for traits that let me have more kids, will let me have more kids. Those kids will have those awesome traits, and outnumber the other folks. *They* will have more kids, and those kids will have more kids. Genes that let me pop out more kids will thus come to spread through the population. If I pop out 3 kids to your 2, and my kids each pop 3 to each of your kids' 2, and so on, within a hundred generations your 2-kid-genes will be less than 1% of the pop - even if it just started out you and I, 50/50.
So, what did Lamarck propose? Lamarck proposed that things we DO IN LIFE are heritable. I.e., I lift weights, I get strong, I have a kid - he's strong! Obviously bull**** - you should know that the unit of inheritance is the
gene, and your strength-related genes are in no way going to change to reflect whether or not you lift steel. We'll have some pity for Lamarck; they didn't have a good grasp of inheritance and developmental biology back then.
Let's look at your answers:
A. Lamarck's theory of use and disuse adequately
describes why giraffes have long necks.
Clearly not. It doesn't matter how much I use my neck, lift weights, get beat up, over-eat, over-tan, etc. These things do not change the genotype I pass onto my kids; it has no mechanism of inheritance, never mind evolution.
B. Darwin's theory of natural selection relies solely
on genetic mutation.
No. Darwin's theory requires variation in a population, which *mutation can provide*. As you can see from my explanation, however, variation in the population is only 25% of Darwin's theory.
C. Darwin's theory explains the evolution of man
from present day apes.
No. Present day apes are descendants of ancient apes, and so are we. That's like saying that I am descended from my sister; no, we're both descended from our parents. Darwin, in The Origin of Man, argued that we (meaning humans and present day apes) are likely descendants of ancient apes.
D. Darwin's theory of natural selection relies solely
on environmental conditions.
No. Environmentl conditions may determing the non-random differential reproductive success (i.e., a heavy coat is only adaptive in cold weather, for example), but as you can see, that only refers to elements 3 &4 in my initial explanation. This is only 50% of Darwin's theory.
E. Natural selection is the process in which random
mutations are selected for survival by the
environment.
Definitely the best answer. Mutation causes (random) variation in the population, and natural selection is the process by which those variants best suited for survival and reproduction in a given environment do just that - survive and reproduce.
