Natural selection and behaviors Flashcards
What is Natural Selection?
a process whereby which organisms that are better adapted to their environment tend to survive and pass on their genes
What are the 3 key concepts of natural selection
- Natural selection acts on individual, but its consequences occur in populations ( e.g. mean phenotype of the population changes)
- Natural selection acts on phenotypes, but evolution consists of changes in allele frequencies
evolution is not forward looking, adaptation is based on past selection, not future conditions - Natural selection is non random; it increases adaptation to the environment. Mutations is randomly generated
Fitness
ability of an individual to survive and produce offspring relative to other individual in the population (this is relative)
Differential reproduction
some alleles are spread more in a population because the traits they code for are selectively advantageous
Definition of evolution by natural selection
Changes in the frequencies of alleles in a population due to differential survivorship and reproduction of their phenotypes
Three requirements for natural selection:
- variation must exist in the population
- That variation must be heritable
- there must be differential fitness associated with that variation
The result: Organisms become adapted to their environment. Adapted= better able to find food, attract mates, escape from predators, etc.
Stabilizing selection
Alleles associated with mean trait values favored. No change in average trait over time.
*Reduce genetic variability
e.g. birth weight (being too small- premature can be a problem, being to large can be problematic) There is an optimal birth rate.
Directional selection:
Allele frequencies change in one direction. Favors one extreme of a trait distribution
Disruptive selection
Alleles associated with both extremes of a trait favored. Can result in two separate species.
* increase genetic variable
e.g. if your in the middle, you are not good at requiring either resource
Negative Frequency Dependent Selection
being rare is advantageous
Orange Males: Large, dominant, control big territories but struggle to guard them, allowing Yellow males to sneak in.
Blue Males: Medium-sized, good at excluding Yellows and sneaking into Orange territories.
Yellow Males: Smaller, opportunistic, successful at sneaking into Orange territories when unguarded.
Population Cycles:
Morph frequencies shift every 4-6 years; the rarer morph gains an advantage and becomes more common, maintaining the balance among all three morphs.
Positive Frequency Dependent Selection
- Being common is advantageous
if a species does not taste good to predator and they all look the same, the predator will not prey on others that look like that species - looking like other butterflies is advantageous because predator may avoid you at because they tasted another species they didn’t like
Correlational selection:
when two traits interactively affect fitness. some combination work together, well, some do not
eg. color and poison in newt
Tinbergen investigated the behavior of digger wasps.
Hypothesis 1: Wasps rely on visual cues from the burrow’s surroundings while circling above.
Test: Cleared areas around burrow of landmarks.
Result: Wasps appeared confused, stopped mid-air, repeatedly approached, dropped prey, and searched randomly on the ground.
Hypothesis 2: Wasps use landmarks for navigation, and altering these should mislead them.
Test 2a: Moved all landmarks 1 foot southeast.
Result 2a: Wasps landed 1 foot southeast of the nest.
Test 2b: Moved landmarks back to original positions.
Result 2b: Wasps returned directly to their nests.
Hypothesis 3: Wasps can be trained to new landmarks.
Test: Placed a ring of pinecones around the nest and moved it after two days.
Result: Wasps landed within the circle of pinecones instead of at their original nests
How do bees communicate information about the distance and direction of a food source?
Von Frisch
Distance Communication: Bees communicate the distance to a food source through the duration of their waggle dance, with longer dances indicating greater distances.
Direction Communication: Bees convey the direction of a food source by the angle of their dance relative to the sun, with the orientation corresponding to the angle between the food source and the sun.
Do genes alone determine behavior? What are some other factors to consider? Give an example.
No, genes code for many behaviors, genes alone do not produce behavior (nature vs. nurture)
genotype x environment interactions
earning component
ex. Egr1 expression increases in the forebrain of songbirds after they hear the song of another male
