Natural Selection I and II Flashcards
what is evolution by natural selection
- Darwin’s proposed mechanism explaining how species change
- a process which is the logical outcome of 4 postulates
what are Darwin’s 4 postulates
- variability in traits
- heritability in traits
- variability in fitness
- fitness differences are associated with traits
Darwin’s 4 postulates - variability in traits
- individuals within a population are variable for some trait
- refers to V in VIST
Darwin’s 4 postulates - heritability in traits
- trait variability among individuals are, at least in part, passed from parents to offspring
- refers to I in VIST
Darwin’s 4 postulates - variability in fitness
- some individuals are more successful at surviving and reproducing than others
- refers to S in VIST
Darwin’s 4 postulates - fitness differences are associated with traits
- survival and reproduction of individuals are not random; instead they correlated to variability in traits
- refers to S in VIST
what is Darwinian fitness
- an individual’s ability to survive and reproduce
- in reality, it is the number of copies of genes passed on
Peter and Rosemary Grant experiment
tested if variation and seed availability caused evolution by natural selection in a population of Darwin finches
Grants experiment - what are Darwin’s finches
- a group of very closely related species of birds endemic to the Galapagos Islands
- all descendant of a flock that colonized the islands from the Caribbean
Grants experiment - is P1 true
- observed species and plotted them
- saw a great variability in beak depth
- yes, P1 is true
Grants experiment - how did they check for P2
- they estimated the heritability of beak depth
- plotted it using a parent-offspring regression
Grants experiment : P2 - what is the reasoning behind the parent-offspring regression
- if differences among individuals are due to differences in the alleles they inherited, then offspring will resemble their parents
- heritability may be estimated by comparing parent and offspring traits
Grants experiment : P2 parent-offspring regression - what is heritability
- the proportion of the variation observed in a population that is due to variation in genes
- it can take any value between 0 and 1
- slope on graph = heritability
Grants experiment - is P2 true
- yes- Grants found about 65% of variation in beak depth is due to differences in genes
Grants experiment - is P3 true
- yes
- 84% of the finches disappeared corresponding to the decline in the availability of the seeds (due to a drought)
Grants experiment - is P4 true
- yes
- Grants compared pre-drought and post-drought beaks and saw differences corresponding to the change in seeds
Grants experiment - did the population evolve
yes bc all P’s are met
what can natural selection explain
the observation that organisms are well-suited to their environments and lifestyles (fit between form and function)
define adaptation
- a trait that increases the ability of an individual to survive or reproduce compared with individuals without the trait in a certain environment
define Darwinian hypothesis
a hypothesis about a noteworthy or unusual trait possessed by an organism
what does a Darwinian hypothesis contain?
- hypothesizes that the trait is an adaptation
- explain how the trait evolved from an ancestral condition
- specifically considers the 4 P’s for evolution by natural selection
domestication - what traits may be selected for
- Size – fast growing
- Less aggression
- Friendly: no antipredator behavior
domestication example - Colorado
gave rainbow trout in hatcheries predation cues (alarm and predator cues) to see if they had antipredation behavior
domestication example: Colorado - what was the result
the highly domesticated hatchery-reared fish retain the innate ability to express appropriate responses to the threat of predation
