Codon Midterm 1 Flashcards
Natural Selection
The process that changes allele frequencies when certain heritable traits are associated with different levels of reproductive success.
Evolution
A change in allele frequencies.
Stabilizing selection
Natural selection that favors the average phenotype in the population and acts against extreme phenotypes.
Directional Selection
Natural selection that favors an extreme phenotype.
Adaption
A heritable trait that increases fitness in a particular environment
Fitness
The ability to produce viable offspring
Theory
An explanation or set of hypotheses that attempt to explain a large and pervasive phenomenon, meaning they that tie together a large suite of observations about how the natural world works
DNA
A molecule that stores hereditary information in code form
Gene
Segments of DNA that contain the information that molecular machines use to make a product—an RNA or protein—that functions in the organism
Mutation
Any change in DNA. Mutations create new alleles
Allele
Versions of a gene. Different alleles have different variations of the coded information in the gene
Genotype
A listing of the alleles present in an individual
Phenotype
What an individual looks or acts like
Fitness
The ability to produce viable offspring
Hypothesis
A proposed explanation for something that researchers have observed.
Prediction
A statement of an outcome that should occur if a hypothesis is correct.
Null Hypothesis
A hypothesis that represents the “not” or “no-effect” contrast to the hypothesis being tested.
Treatment (or experimental) group
A group that experiences experimental conditions that conform to the mechanism proposed in the hypothesis.
Control Group
A comparison group that represents the normal or no-treatment condition to contrast with groups that experience experimental manipulation.
Controlled Conditions
Aspects of an experimental design that are used in both control and experimental treatments to eliminate bias among treatments and reduce influence from confounding factors.
Outcome variable
The variable that is measured in an experimental or observational study. It represents a quantity that is relevant to the hypothesis being tested.
Genetic Drift
Any change that occurs in allele frequencies that is due to chance.
Founder Effects
One of the several types of events that can cause genetic drift. They occur when a relatively small number of individuals disperse to a new habitat and found a completely new population.
Gene bottlenecks
One of the several types of events that can cause genetic drift. They occur when a species undergoes a large and rapid decrease in population size due to a disease epidemic, catastrophic storm, or other change.
Maladaptive
Leading to lower fitness.
Gene flow
An evolutionary process that changes allele frequencies through the movement of individuals and their alleles from one population to another. Homogenizes allele frequencies among populations.
Mutation
Any change in the base sequence of DNA, and thus a change in genetic information. Introduces new alleles into population.
Null Model
A model that predicts the data you should expect to see if a process is not working—meaning, when a particular causative agent is not impacting the situation.
Hardy-Weinberg Principle
A null model stating that if no selection, drift, gene flow, or mutation occur, and if mating is random with respect to the gene in question,
then allele frequencies will not change from one generation to the next and
genotype frequencies will be in the proportions p2, 2pq, q2, where p and q are the frequencies of two alleles at that gene.
Assortative mating
Mate choice based on similarities or dissimilarities in phenotype.
Inbreeding
Mating among relatives.
Gene Pool
A concept used in predicting the results from random matings among all of the individuals in a population, by supposing that all gametes are tossed into “pool” and then drawn out at random to produce offspring.
Anthropocene
A proposed interval in Earth’s history where environments and species are undergoing massive and widespread change due to human activities.
Inbreeding depression
Reductions in the average fitness of individuals in a population, due to the increased prevalence of homozygous recessive genotypes that have deleterious effects.
Extinction vortex
In some genetically isolated populations, a self-reinforcing cycle that lowers fitness and population size.
Wildlife corridor
A physical connection between habitat patches.
Speciation
The process of genetic isolation and genetic divergence that is responsible for the creation of new species.
Species
An evolutionary independent unit in nature—meaning, a population or group of populations that is genetically isolated from others and is thus changing under the effects of natural selection, genetic drift, and mutation independently of others.
Population
A group of individuals from the same geographic region that regularly mate together.
Phylogenetic tree
A graphical depiction of evolutionary history, or phylogeny.
Homologous traits
Any characteristic, ranging from a single nucleotide in DNA to body parts, that is observed in multiple species and inherited from the same common ancestor.
Root (of phylogenetic tree)
The base of a tree, indicating the common ancestor of all the taxa indicated at the tips.
Node (of phylogenetic tree)
A split where a speciation event occurs, so one species splits into two.
Branch (of phylogenetic tree)
A species or other group changing through time.
Tip (of phylogenetic tree)
The end of a branch, representing a taxon
Taxon
A named group of organisms (plural is taxa)
Monophyletic group
An ancestor and all of its descendants.
Synapomorphy
A trait that one group has that no one else does. Synapomorphies define monophyletic groups.
Homoplasy
Similarity in traits that is not due to common ancestry but due to independent evolution.
Outgroup
Any lineage that is not part of the monophyletic group that is the focus of a phylogenetic tree.
Parsimony
A criterion in logic that states that the simplest explanation is the most likely to be correct.
