5 Modes of Evolution Flashcards
Change in allele frequency
Evolution
Natural Selection
Best suited for the environment have a higher probability of survival and reproduction.
Natural selection requires ____ in the population. “If everybody is the same, then no one is best suited because everyone is equally suited.”
Variation
What are the three modes of natural selection?
Directional Disruptive Stabilizing
Directional selection
one extreme phenotype is favored
Disruptive selection
both extreme phenotypes are favored
Stabilizing selection
No extremes are favored (average is favored)
Bimodal distribution
Disruptive selection
Directional selection
Stabilizing Selection
Mate choice; results in evolution
(change in allele frequency)
ex. male peacock
Non-random mating
Random chance and sampling error rcause low repitition or unpredicted results.
Causes change in allele frequency
Genetic drift
New population doesn’t resemble the original population
Founder effect
When “N” decreases or only a few are allowed to reproduce.
ex.) Lions, wolves
Population bottleneck
Movement of alleles between populations.
Changes allele frequencies.
Gene flow
Error in copying DNA for gametes
(Only way to get brand new alleles.)
Mutation
Mutations are ___.
1% per million years (vertebraes)
rare
Mutations are ___ ___ helpful.
very rarely
Mutations are rarely ___.
(can’t reproduce)
fatal
Often silent mutations that ___ __ phentotpye
don’t affect
5 Modes of Evolution
Natural Selection
Non-random mating
Genetic drift
Gene flow
Mutation
2 rates of evolution
Punctuated Equilibrium
Gradualism
Huge evolutionary events (very fast) but, they are rare.
Punctuated Equilibrium
Small, constant evolutionary events.
Gradualism
Population
all members of a species that interact with one another.
Type 1 Survivorship
ex. elephants, bears, whales, humans
- High Probability of surviving in early life
- High parental care
- Few offspring at a time
Type 2 Survivorship
ex. pigs, domestic cats, ducks, spiders
- Probability of survival is constant
- Moderate parental care
- Moderate number of offspring
Type 3 survivorship
ex. sea turtles, frogs, salmon, most insects
- Low probability of survival in early life
- No parental care
- Many offspring at a time
Doubling time ___ as N increases
____ growth
Decreases
Exponential growth
Maximum number of individuals of a species that can be sustained by the environment indefinitely
“K”
Carrying capacity
How can you oscillate above and below “K”
Limiting resource is not always needed.
How can you greatly exceed “K”
Very rapid population growth or large lag in demand for the limiting resource.
Do not increase in frequency or severity as N changes
ex. fires, ice ages, drought, hunting, tornados, deforestation, pesticides
(Control of Population Size)
Density independent factors
Get worse and more frequent as N approaches K
ex. disease, parasitism, famine
(Control of Population Size)
Density dependent factors
