BIO 121 Exam 1 Review Spring 2024
Evolution
The gradual change in a species over time.
Adaptation
When the heritable trait increases an individuals fitness in a particular environment.
Ancestral trait
Is a character that existed in an ancestor.
Derived trait
Is one that is a modified form of the ancestral trait, found in a descendants.
Vestigial trait
A reduced or incompletely developed structure that has no (or reduced) function (e.g.
human tailbone or wisdom teeth).
Homologous structures
Are similarities that exist in species descended from a common ancestor (e.g. humans,
dogs, and birds have similar limb structure).
Convergent evolution
Occurs when similar environmental pressures and natural selection give rise to similar
(analogous) structures in distantly related organisms.
Dispersal
The movement of organisms or individuals from one place to another can result in
Allopatric Speciation (e.g. birds flying to a new island).
Vicariance
The physical splitting of a habitat, some type of geographic barrier can result in
Allopatric Speciation. (e.g. rivers or mountains splitting populations).
Dominant Allele
An allele whose trait always shows up in the organism when the allele is present. (Y)
Recessive Allele
An allele that is masked when a dominant allele is present. (y)
Homozygous genotype
having two identical forms of a gene (e.g. YY)
Heterozygous genotype
having two different forms of an allele (e.g. Yy)
Genetic drift
Is any change in allele frequencies in a population due to chance.
Population bottleneck
Is a drastic reduction in population size brought about by a natural catastrophe or over-
hunting (e.g. elephant seals in the 1800s).
Founder Effect
Occurs when a small number of individuals individuals leave a large population and
establish a new isolated population.
Phylogenetic tree
visual graphic of the evolution of organisms
Systematics
Evolution
The gradual change in a species over time.
Adaptation
When the heritable trait increases an individuals fitness in a particular environment.
Ancestral trait
Is a character that existed in an ancestor.
Derived trait
Is one that is a modified form of the ancestral trait, found in a descendants.
Vestigial trait
A reduced or incompletely developed structure that has no (or reduced) function (e.g.
human tailbone or wisdom teeth).
Homologous structures
Are similarities that exist in species descended from a common ancestor (e.g. humans,
dogs, and birds have similar limb structure).
Convergent evolution
Occurs when similar environmental pressures and natural selection give rise to similar
(analogous) structures in distantly related organisms.
Dispersal
The movement of organisms or individuals from one place to another can result in
Allopatric Speciation (e.g. birds flying to a new island).
Vicariance
The physical splitting of a habitat, some type of geographic barrier can result in
Allopatric Speciation. (e.g. rivers or mountains splitting populations).
Dominant Allele
An allele whose trait always shows up in the organism when the allele is present. (Y)
Recessive Allele
An allele that is masked when a dominant allele is present. (y)
Homozygous genotype
having two identical forms of a gene (e.g. YY)
Heterozygous genotype
having two different forms of an allele (e.g. Yy)
Genetic drift
Is any change in allele frequencies in a population due to chance.
Population bottleneck
Is a drastic reduction in population size brought about by a natural catastrophe or over-
hunting (e.g. elephant seals in the 1800s).
Founder Effect
Occurs when a small number of individuals individuals leave a large population and
establish a new isolated population.
Phylogenetic tree
visual graphic of the evolution of organisms
Systematics
