Bio Midterm 2 Vocab

F₁ Generation

The initial generation from an experimental cross—meaning, the offspring of the original parents.

F₂ generation

The second generation from an experimental cross—the offspring of F₁s.

Recessive Allele

An allele with a phenotype that does not appear in heterozygous individuals.

Dominant Allele

An allele with a phenotype that appears in heterozygous individuals.

Homozygous

Having two copies of the same allele for a gene.

Heterozygous

Having two different alleles for a gene.

Principle of segregation

The observation that alleles of the same gene separate from each other prior to gamete formation. Caused by the separation of homologous chromosomes at the end (anaphase and telophase) of Meiosis I.

Principle of Independent Assortment

The observation that alleles of different genes go into gametes independently of each other, making every combination of alleles from different genes equally likely. Caused by different chromosomes lining up independently of each other in the middle (metaphase) of Meiosis I, and holds if the genes in question are found on different chromosomes.

Wild Type

The typical or most common version of an allele or phenotype, as opposed to novel, unusual, or low-fitness forms.

Co-dominant alleles

Heterozygotes have the phenotype associated with both alleles present.

Loss-of-function alleles

Alleles that lead to a protein or RNA product that cannot function normally or is completely absent.  

Sex chromosome

A chromosome associated with the sex of the individual.

Autosome

Any chromosome that is not a sex chromosome.

Sex-linked genes

Genes found on a sex chromosome.

Linked genes

Genes found on the same chromosome

Polygenic trait

A trait that shows continuous variation—usually normally distributed—due to the involvement of products from many different genes. Also called a quantitative trait.

Genetic Locus

The physical location of a gene on a chromosome. The plural form is loci and is pronounced LOW-sigh.

Genome

All of the DNA, and thus all genes, in an individual of a particular species.

Pedigree

A diagram summarizing the incidence of a genetic disease or other trait in a family. They are used to identify the pattern of inheritance of specific traits and predict how likely offspring from a particular set of parents are to have a specific phenotype.

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

The null model for evolution, 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.

Genetic Drift

Any change that occurs in allele frequencies that is due to chance.

Founder events

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.

Genetic 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.

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.

Maladaptive

Leading to lower fitness.

Mutation

Any change in the sequence of DNA, and thus a change in genetic information. Introduces new alleles into population.

Deleterious mutation

A mutation or other event that lowers fitness. 

Positive assortative mating

 Individuals preferentially mate with others who have genotypes or phenotypes similar to themselves.

Negative assortative mating

Individuals preferentially mate with others who have genotypes or phenotypes different from themselves.

Competition

interactions between two species where each are negatively impacted by the other

Amensalism

interactions between two species where one species is negatively affected while the other is not affected at all

Exploitation

interactions between two species where one species is positively affected while the other is negatively affected

Neutral

two species have no impact on one another

Commensalism

interactions between two species where one species is positively affected by its interactions with the other species while the other is not impacted at all

Mutualism

interactions between two species where both benefit by their interactions with one another

Symbiosis

interactions between two species in which they live in such a close association that one lives on or within the other

Obligate interactions

interactions between species where a particular partner cannot survive or complete its life cycle without interaction with its partner species

Facultative interactions

interactions between species where each species can survive without interacting with the other even though one or both species benefit from their interactions.

Trophic web

are graphical representations of the feeding relationships between multiple species within an ecosystem

Keystone species

a species whose impact on the ecosystem is disproportionately large in comparison to their abundance

Foundation species

a species that plays a significant role in creating, and often defining, the ecosystem in which it inhabits

Ecosystem engineer species

a species that physically alters the ecosystem or habitat in significant ways

Competitive Exclusion Principle

when two individuals or species compete for the same resource and cannot coexist, eventually the stronger one outcompetes the weaker one potentially resulting in its extinction

Resource Partitioning

two individuals or species competing for the same resources subdivide their ecosystem to minimize the degree of overlap, and therefore competition,  between them

Lotka-Volterra Predator-Prey Model

 a mathematical model describing how predator and prey populations influence one another’s growth over time.

Reciprocal Density Dependence

the population density of one species influences the population growth of another species, which in turn influences the population growth of the first.

Character Displacement

 an evolutionary process in which interspecific competition drives heritable changes in traits between two or more species, resulting in greater differences in resource utilization, reduced competition, and potentially facilitating their long-term coexistence.

Sympatry

 the condition where two different populations occupy the same physical space and interact with one another

Allopatry

the condition where two different populations do not occupy the same physical space and do not interact with one another.

Trait Matching

two species have distinct characteristics that evolve in tandem with one another to increase their mutualism and maximize the benefits from their interactions. 

Evolutionary arms race

 two species antagonistically coevolving to produce increasingly specialized offensive and defensive traits creating reciprocal changes over successive generations.

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.

Morphological species concept

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