biology lec 06-07 evidence for evolution

The oak leaf gall fly lays its eggs on the surface of Oak tree leaves.
Larvae feed on the gall that develops around them. The larvae are
typically prey to both parasitoid wasps and to birds; wasps selectively
prey on larvae inside the smallest galls while birds selectively prey on
larvae inside the largest galls. This year a rampant nematode
infection has killed all of the parasitoid wasps. The oak leaf gall flies
will likely experience:

directional selection

In a hypothetical population of 1000 crickets, there exists a gene with two
alleles. 350 Crickets are homozygous dominant (DD), and 200 are
homozygous recessive (dd). What is the frequency of the D allele in the
population?

0.575

why is evolution a theory, not a fact

Scientific theory is different from our everyday use
• In Science:
• Theory is not a guess or a hunch
• Well-established, well-supported, well-documented explanations
for our observations
• Theory becomes Law. No hierarchy
Theories and Laws
• Law of gravity – if you drop something it will fall to the ground
• This is a description, it does not say why
• Theories describe why:
• Newton’s Theory of Gravity (F = G(m₁m₂)/r²)
• Einstein’s Theory of Relativity (E = MC²)
Laws describe, Theories explain
• Gravity is real, it is true, it can be observed,
it can be tested .... this is also the case with evolution!
BIO A01 | Life on Earth: Unifying Principles | Evidence

Predictions based on evolution

If life originated on Earth in the distant past and then evolved, we should see evidence in the fossil record

• If evolution occurred within lineages, and those lineages sometimes split then we should see change in species or morphology through the fossil record
• If organisms share a common ancestry, then we should see transitional forms
• We should see evidence of retrodictions and vestigial characters
• We should be able to see evidence of natural selection

explain variation in beak size between the medium ground finch and the large ground finch 2

• both species eat the same amount of seeds

• there was a massive drought on food

• there was no mating opportunities

• forced to eat tribulus (caltrop) plants which they normally don’t like to eat because the spines are hard and sharp

• the large finch crushed the seeds with its beak, which required more force but they got more seeds

• the small finch braced it against a rock to split it open, less force, but didn’t get as many seeds

• because the small finch had a hard time eating the tribulus, they eat a sticky milky latex plant which would get stuck to their head, cause the feathers on their head to fall off, and then the bald birds would die in the hot sun.

• however, after an el nino event, the food availbility increased, and the seeds were smaller, so the finches with smaller beaks were better suited 

Moral of the story: Rapid natural selection in response to back and forth changing conditions

During good years

• variation fills in

• less selection on the adaptations

during tough years

• adaptations become important

• increased selection

• reduction in variation

role of adaptation ( _______________________) may be evident only during times of stress and competetion

morphology and behaviour