4C Flashcards
(19 cards)
Processes that are non-adaptive causes of evolutionary change in a population are:
Migration (gene flow), mutation, and genetic drift
Stabilizing selection
basically heterozygote advantage
Under what circumstances is genetic drift most likely to occur?
A)
In a small population with lots of immigration and emigration
B)
In a large population with lots of immigration and emigration
C)
In a small isolated population
D)
In a large isolated population
C
Resistance to malaria, due to the simultaneous presence of the sickle-cell and the normal alleles for hemoglobin in an individual, is an example of:
heterozygote advantage
bottleneck effect
When a big population suddenly shrinks to a small number — because of something like a natural disaster — and only a few individuals survive by chance.
-Genetic diversity drops.
Ex-
Cheetahs 🐆:
Long ago, cheetah populations crashed (ice age + human hunting).
Today, cheetahs are so genetically similar they can almost be cloned from each other.
Founder effect
When a small group of individuals breaks off from a larger population and starts a new population — and by chance, they carry only a small portion of the original genetic variation.
Populations established on remote oceanic islands by very infrequent colonization events involving only a few individuals initially tend to display __________ relative to the mainland populations from which the colonists came.
Reduced genetic diversity
Processes that are non-adaptive causes of evolutionary change in a population are:
Migration (gene flow), mutation, and genetic drift
Sexual selection in a population can produce extreme phenotypes in one sex. This is the result of:
Non-random mating
What type of microevolutionary change is the founder effect a type of?
genetic drift
genetic drift
Random changes in allele frequencies in a population just by chance, not because the alleles are better or worse.
EX- A tree falls and randomly crushes a few green beetles 🪲 — not because they were weaker, just bad luck! Now green is rarer in the next generation.
Microevolution can be defined as:
A change in the frequencies of alleles in the gene pool of a population
Parapatric speciation
Two populations are next to each other (side-by-side), but they don’t mix much because the environment is different across the area — and over time they become separate species.
Peripatric speciation
A small group breaks off from a larger population and forms a new species, often because they become geographically isolated.
intrasexual selection
Members of the same sex (usually males) compete with each other for access to mates.
So instead of trying to attract a mate directly (like being flashy), they’re fighting or competing to win the right to mate.
Disruptive selection
Both extremes do better than the average.
Intermediate individuals are at a disadvantage.
It increases variation in the population.
Can lead to two distinct forms (sometimes even two new species if it keeps going).
ex-Birds with very small beaks can eat small seeds.
Birds with very large beaks can crack hard seeds.
Birds with medium beaks can’t do either well → selected against.
Directional selection
One extreme phenotype is favored.
The population’s traits gradually shift in that direction.
Happens when environmental conditions change or when new traits give a big advantage
ex- Peppered moths during the Industrial Revolution:
Before pollution: light-colored moths blended into clean trees.
After pollution: dark-colored moths blended into soot-covered trees.
➔ The population shifted from mostly light to mostly dark moths!
Which process below is not a component of natural selection?
A)
Overproduction of offspring
B)
Genetic drift
C)
The favouring of certain alleles by an environmental factor
D)
Genetic variation
E)
Limitation in vital resources
B
Which of the following will not be a possible result of a genetic bottleneck?
A)
A decrease in the frequency of an uncommon allele
B)
An increase in the frequency of the less common allele
C)
Allele frequencies identical to the previous generation
D)
An increase in genetic variability in the population
E)
A decrease in the frequency of the most common allele
An increase in genetic variability in the population
