2. Forces of evolutionary change
__________________________
traits that improve survival
or reproduction will accumulate
in the population
adaptive change
___________________________
frequency of traits can change
in a population due to
chance events
random change
AP Biology
3. Natural Selection
Selection acts on any trait that affects
survival or reproduction
predation selection
physiological selection
sexual selection
AP Biology
4. Predation Selection
Predation selection
act on both predator & prey
behaviors
camouflage & mimicry
speed
defenses (physical & chemical)
AP Biology
5. Physiological Selection
Acting on body functions
disease resistance
physiology efficiency (using oxygen, food, water)
biochemical versatility HOT STUFF!
protection from injury Some fish had the
variation of producing
anti-freeze protein
5.5 mya
The Antarctic Ocean
freezes over
AP Biology
6. Physiological selection
Dogs pee on trees…Why don’t trees pee on dogs?
plant nutrient
NH3
animal waste
One critter’s trash
is another critter’s treasure!
AP Biology
7. Sexual Selection
Acting on reproductive success
attractiveness to potential mate
fertility of gametes
successful rearing of offspring
Survival doesn’t matter
if you don’t reproduce!
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
AP Biology
8. Sexual selection
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
It’s FEMALE CHOICE, baby!
AP Biology
9. The lion’s mane…
Females are attracted to
males with larger, dark
manes
Correlation with higher
testosterone levels
better nutrition & health
more muscle & aggression
better sperm count / fertility
longer life
But imposes a cost to male
AP Biology
HOT! Is it worth it??
10. Sexual selection
Acts in all sexually
reproducing species
the traits that get you mates
sexual dimorphism
influences both morphology &
behavior
can act in opposition to natural
selection
Jacanas
Is there a testable
hypothesis in there?
AP Biology
11. Sexual selection
Sexual selection acts in all
sexually reproducing species
___________________________
it influences both morphology
& behavior
it acts on both
males and females
Is there a testable
hypothesis in there?
AP Biology Jacanas
14. Genetic Drift
____________________________________
____________________________________
not adaptation to environmental conditions
not selection
_____________________
small group splinters off & starts a new colony
_____________________
some factor (disaster) reduces
population to small number & then
population recovers & expands
again but from a limited gene pool
AP Biology
15. Founder effect
__________________________________
__________________________________
just by chance some rare alleles may
be at high frequency;
others may be missing
skew the gene pool of
new population
human populations that
started from small group
of colonists
example:
AP Biology colonization of New World
albino deer Seneca Army Depot
16. Distribution of blood types
Distribution of the O type blood allele in native
populations of the world reflects original settlement
AP Biology
17. Distribution of blood types
Distribution of the B type blood allele in native populations
of the world reflects original migration
AP Biology
18. Out of Africa
Likely migration paths of humans out of Africa
10-20,000ya
10-20,000ya
50,000ya
Many patterns of human traits reflect this migration
Many
AP Biology
19. Bottleneck effect
____________________________________
__________________________________
famine, natural disaster, loss of habitat…
loss of variation by chance event
alleles lost from gene pool
not due to fitness
narrows the gene pool
AP Biology
20. Cheetahs
All cheetahs share a small number of alleles
less than 1% diversity
as if all cheetahs are
identical twins
2 bottlenecks
10,000 years ago
Ice Age
last 100 years
poaching & loss of habitat
AP Biology
21. Evolution is "so overwhelmingly
established that it has become
irrational to call it a theory."
-- Ernst Mayr
What Evolution Is
2001
Professor Emeritus, Evolutionary Biology
Harvard University
(1904-2005)
AP Biology 2007-2008
Even though it’s very hot to have a large mane the benefit of attracting mates and successfully producing & rearing young since you have that large mane outweighs the costs. Females who chose these males were more “successful” (more, healthier young) and therefore had a greater opportunity to pass on the trait of being attracted to longer darker manes to their daughters and the trait of having longer, darker manes to their sons.
Small founder group, less genetic diversity than Africans All white people around the world are descended from a small group of ancestors 100,000 years ago (Chinese are white people!)
South & Central American Indians were nearly 100% type O for the ABO blood system. Since nothing in nature seems to strongly select for or against this trait, it is likely that most of these people are descendants of a small band of closely related "founders" who also shared this blood type
The global frequency patterns of the type B blood allele: Note that it is highest in central Asia and lowest in the Americas and Australia. However, there are relatively high frequency pockets in Africa as well. Overall in the world, B is the rarest ABO blood allele.
Migration Paths According to the "Out of Africa" theory, modern humans appeared as a single African species nearly 100,000 years ago, then spread throughout the world (K.Wong, Is Out of Africa Going Out the Door?, Scientific American 281(2), August 1999).
Born in 1904 in Germany, Mayr trained as a medical student but realized he had a greater passion for studying birds and biology. Emigrating to the United States, he became a curator at the American Museum of Natural History, working on bird classification while formulating his key ideas about evolution. In 1942 he published his most important work, Systematics and the Origin of Species . Mayr moved to Harvard University in 1953 and served as director of the school's Museum of Comparative Zoology from 1961 to 1970. Since then, he has published a number of books and chapters and received the prestigious Japan Prize for Biology in 1983. In his landmark 1942 book, Mayr proposed that Darwin's theory of natural selection could explain all of evolution, including why genes evolve at the molecular level. On the stubborn question of how species originate, Mayr proposed that when a population of organisms becomes separated from the main group by time or geography, they eventually evolve different traits and can no longer interbreed. It's this isolation or separation that creates new species, said Mayr. The traits that evolve during the period of isolation are called "isolating mechanisms," and they discourage the two populations from interbreeding. Moreover, Mayr declared that the development of many new species is what leads to evolutionary progress. "Without speciation, there would be no diversification of the organic world, no adaptive radiation, and very little evolutionary progress. The species, then, is the keystone of evolution."
