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 The field of science that organizes organisms into phylogenetic trees. Taxonomy The classification of organisms. Taxon Any particular group or branch on a phylogenetic tree. Branch (or Lineages) Represents a population through time. Branch point Represents a point where a branch splits- that is, hypothetical most recent ancestor. Sister taxa Represents two lineages that come from the same branch point (e.g. dogs and humans). Basal taxon Is a taxon that diverged before the taxa that are focus of the phylogeny and helps to root the tree. (oldest on the tree, e.g. lungfish) Homology Traits are similar due to shared ancestry. Parsimony Used to identify the most likely tree, states that the most likely explanation or pattern is the one that implies the least amount of change. natural selection Mechanism for evolution that Charles Darwin and Alfred Wallace independently discovered; "survival of the fittest". What are examples of evolution? -Antibiotic resistance (e.g. TB); -herbicide resistance (e.g. weed killers); -pesticide resistance (e.g. insects that eat crops); adaptation to climate change What situation is most likely an example of convergent evolution? -Squid and humans have eyes similar in structure. -Worms and snakes both move without legs. -Some bats and birds have wings that allow them to fly. What is the main difference between dispersal and vicariance? Dispersal is them physically going somewhere. While Vicariance is being physically split. What is not an example of a prezygotic barrier? Two species of insects produce infertile offspring. What is an example of homologous structures? All vertebrate limbs have similar bone structure. What is an example of reproductive isolation due to temporal isolation? Two species of frogs mate at different times of year. What is an example of postzygotic isolation? Two species of birds can interbred and lay eggs, but the eggs do not hatch (hybrid inviability). Two species of frogs mate and form hybrids, but the hybrids cannot reproduce (hybrid sterility). What is Hardy-Weinberg equilibrium?