exam 6 from lecture slides Flashcards
what are the five conditions for no evolution?
-no difference in viability or fertility
-random mating
-very large population
-no migration
-no mutation
if these conditions for a GENE are met, the allele frequencies do not change and the gene is NOT evolving
if an allele provides an advantage for individuals that carry it…
those individuals have higher reproductive success and the allele will increase in frequency in the population
evolutionary changes require
-heritable variation in a trait
-selection on that trait
what explains the adaptations of organisms and the unity/diversity of life?
descent modification by natural selection
theory of evolution
-descent with modification, species change over time and are related to a common ancestor
-natural selection is the main agent responsible for this pattern
Darwinian fitness
the ability of an individual to survive and reproduce in its environment
-more favorable variations are better at surviving and reproducing and are naturally selected
what is the focus of selection
reproductive success
(NOT survival)
darwin’s theory of evolution four main points
1) individuals within population are variable
2) the variations in individuals are passed from parent to offspring
3) every generation has some individuals more successful at reproducing and surviving than others
4) the survival and reproduction of individuals are not random, but are tied to differences in heritable information
darwins four main points can be tested if
-no hidden assumptions
-nothing has to be accepted uncritically
-many lines of evidence possible
if an environment changes over time…
natural selection may result in the adaptation to the new environment conditions and give rise to a new species
does natural selection make new traits?
NO
it can only edit traits already present in the population
do individuals evolve?
NO
their population evolves over time as natural selection can only increase or decrease with HERITABLE population traits
when does evolution occur?
when one of the HW assumptions is violated
(random mating, no difference in fertility, no migration, no mutation, large population)
how does natural selection occur with the HW assumptions?
when the equal/viable fertility is violated, natural selection occurs
how does sexual selection occur with HW assumptions?
when the random mating assumption is violated, sexual selection occurs
how does genetic drift occur with HW assumptions?
when the large population size is violated, genetic drift occurs
genetic drift
-describes how allele frequencies fluctuate unpredictable from one generation to the next
-the smaller the sample, the more chance for deviation from predicted result
genetic drift tends to
reduce genetic variation through the loss of alleles
driftworms
-reproduce asexually, with all worms producing one offspring, one gene controls color and there are 5 alleles
what are some examples showing how some individuals with reproduce more than others?
-it is by random chance
-so a drift worm eaten= no reproduction
-ant stepped on= no reproduction
etc.
a fixed allele means
the alleles in a population are the same, no variation
founder effect (genetic drift)
-when few individuals become isolated from a larger population
-the allele frequencies is small in the founder population and can be different from those in the main population
bottleneck effect (genetic drift)
-sudden reduction in population size due to a change in the environment
-resulting gene pool may not be reflective of the original populations gene pool
-if the population remains small, it can be further affected by genetic drift
sexual selection is
natural selection for mating success
-when mating is non-random with respect to phenotype or genotype
