Exam 1 Flashcards
What were Darwin & Wallace’s thoughts on evolution?
Species change over time based on select traits that provide an advantage in survival and reproduction (fitness)
Descent with modification
New species form from the continued evolution of their ancestors based on selected traits
How does the vastness of geologic time help prove the theory of evolution?
rock layers and fossils
What are transitional features?
They link older and younger species by serving as a middle ground between the current anatomy of a population and the anatomy of its ancestors
What are homologies?
a structure that is similar across species and is derived from a common ancestor
Structural homology
Similarities in adult structures across species that are derived from a common ancestor
Genetic homology
Similarities in genetic code across species that derive from a common ancestor
plasticity
different phenotypic expressions of the same allele based on environmental factors
directional selection
shifts the average expression of a trait in a population over to one extreme or the other
stabilizing selection
selection against the extremes
disruptive selection
favors BOTH of the extreme phenotypes
what form of selection can be the first step in speciation?
disruptive
what form of selection causes a loss of variation in the gene pool?
stabilizing
balancing selection
no phenotype has a distinct advantage
which form of selection maintains variation?
balancing
frequency dependent selection
fitness depends on the rarity of the phenotype
intersexual selection
mate choice
intrasexual selection
competition for mates
sexual dimorphism
differences between the sexes
________ is the only evolutionary process that results in adaptation.
natural selection
genetic drift
random events cause allele frequencies to fluctuate randomly from generation to generation
what causes genetic drift?
sampling error
Sampling error causes a loss of ______ and is more common in ______ populations.
heterozygosity, smaller
founder effect
a few individuals get separated from the original group –> new population is started with a differing gene pool
bottleneck effect
sudden change in environment drastically reduces the size of a population –> surviving alleles are a result of chance
gene flow
movement of alleles between two separate populations
What is the ultimate source of genetic variation?
mutation
describe the biological species concept
-(a mechanism used to differentiate species)
-a population (or a group of populations) that are reproductively isolated from other groups.
describe the morphospecies concept
-(a mechanism used to differentiate species)
-species are identified by differences in size, shape or other morphological features
describe the phylogenetic species concept
-(a mechanism used to differentiate species)
-identifies species based on the evolutionary history of populations
monophyletic group
an ancestor + all the descendants
synapomorphy (shared derived trait)
a trait that is found in certain groups of organisms + their common ancestors, but not in its more distant ancestors
What are the two causes of speciation?
-genetic isolation
-genetic drift: mutation, selection, and genetic drift in isolated populations cause divergence
speciation
the process of creating a new species
What are the two kinds of reproductive isolation?
-prezygotic isolation
-postzygotic isolation: zygotes are formed, bot offspring do not survive or are infertile
allopatry
when populations become geographically isolated
what are the two kinds of allopatric speciation?
dispersal + vicariance
describe allopatric speciation by dispersal
-a few individuals leave the main population
-these individuals have a small portion of the genes in the original population
-due to genetic drift, mutation, and selection they become 2 different species
describe allopatric speciation by vicariance
-a chance event physically separates a population (can be fast or slow)
-due to genetic drift, mutation, and selection they become 2 different species
What were Plato’s thoughts on evolution?
He thought everything was created and stayed exactly as it was
What were Aristotle’s thoughts on evolution?
He thought there was a hierarchy of organisms, with humans at the top
What were Lamarck’s thoughts on evolution?
He thought the actions of parents changed the traits of the offspring
What are Darwin’s postulates (conditions for evolution)?
- individuals within species are variable
- some of these variations are heritable
- individuals that reproduce the most are the ones with the most favorable variations
