BIO 141: Natural Selection 1 & 2

what are darwin 4 postulates

1. individuals vary

2. some of the variable traits are heritable

3. there is struggle for existence; not all individuals survive and reproduce

4. individuals with favorable traits survive and reproduce

what do his four postulates lead to

evolution which is an inherited change in a group of organisms over time

graph shows number of finches over time in the population

there is a struggle for existence; not all individuals survive and reproduce

graph shows the different beak sizes

individuals vary

graph shows very strong beak depth relationship with offspring and parent; peak size very heritable

some of the variable traits among individuals are heritable

graph shows population before the drought and after the drought bigger beaks to crack big nuts

individuals with favorable traits survive and reproduce

adaption

a heritable trait increases the fitness of an individual in a particular environment relative to individuals without the trait

fitness

the ability of an individual to produce surviving fertile offspring relative to other individuals in the population

t or f survival of the fittest is inadequate description of natural selection

true

sexual selection

ability to obtain a mate, remember quality of offspring in the sense that the traits the parent passed on will be be passed to child’s offspring

misconception: evolution does not mean that individuals change

instead, it is the population that changes over time

selection did not cause neck length individual giraffes to increase

giraffes with slightly longer necks had a greater probability of survival and reproduction, and because neck length is heritable, populations harbored more long necked giraffes over time

misconception: no goal in evolution

individuals with favorable traits that survive and reproduce, over time this leads to organisms that are better adapted to their environment

natural selection is not random

generation of variation is random, but natural selection results in increased matching between organism and environment over time

misconception: evolution does not lead to perfection

evolution results in organisms that are better at surviving and reproducing relative to other individuals

what do you think happens among lizards of a certain species when the food supply is limited

the lizards least successful in competition for food are likely to die of starvation and malnutrition

According to the theory of natural selection, where did the variations in body size in the three species of lizards most likely come from

random genetic changes and sexual recombination both created new variations

what could cause one species to change into three species over time

groups of lizards must have been geographically isolated from other groups and genetic changes must have accumulated in these lizard populations over time

fitness is a term often used by biologists to explain the evolutionary success of organisms

lizard b is the most fit because it has mated with many lizards

in lizard populations, what are the primary changes that occur gradually over time

the proportions of lizards having different traits within a population change

what type of variation in lizards is passes to the offspring

all characteristics that were genetically determined