BIO 121 Exam 1 Review Spring 2024

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