Unit 7 bio

Artificial selection

The selective breeding of domesticated plants and animals to encourage the occurrence of desirable traits

Evolutionary adaptation

An accumulation of inherited characteristics that enhance organism’s ability to survive and reproduce in specific environments

Homology

Similarity in characteristics resulting from shared ancestory

Biogeography

The study of the past and present distribution of species

Fossil

A preserved remnant or impression of an organism that lived in the past

Natural selection

Differential success in the reproduction of different phenotypes, resulting from the interaction of organisms with their environment. Evolution occurs when actual selection causes changes in relative frequencies of alleles and the gene pool.

Descent with modification

Darwin’s initial phrase for the general process of evolution

Gradualism

A view of Earth’s history that attributes profound change to the cumulative product of slow but continuous processes

Taxonomy

A set characteristics used to assess the similarities and differences between various species, leading to a classification scheme; the branch of biology concerned with naming and classifying the diverse forms of life

Evolution

All the changed that have transformed on Earth from its earliest beginnings to the diversity that characterizes it today

Homologous structures

Structures in different species that are similar because of common ancestry

Vestigial organ

A structure of marginal, if any, importance to an organism. Vestigial organs are historical remnants of structures that had important functions in ancestors.

Balancing selection

Natural selection that maintains stable frequencies or two or more phenotypic forms in a population (balanced polymorphism)

Directional selection

Natural selection that favors individuals at one end of the phenotypic range

Fitness

The contribution an individual makes to the gene pool of the next generation, relative to the contributions of other individuals

Bottleneck effect

Genetic drift resulting from the reduction of a population, typically by a natural disaster, such that the driving population is no longer genetically representative of the original population

Disruptive selection

Natural selection that favors individuals on both extremes of a phenotypic range over intermediate phenotypes

Founder effect

Genetic drift that occurs when a few individuals become isolated from a larger population, with the result that the new population’s gene pool is not reflective of the original population

Gene flow

Genetic additions to or subtractions from a population resulting from the movement of fertile individuals or gametes

Hardy-Weinberg equilibrium

The condition describing a non-evolving population (one that is in genetic equilibrium)

Polymorphism

The coexistence of two or more forms in the same population

Gene pool

The total aggregate of genes in a population at any one time

Greater reproductive access of heterozygous individuals compared to homozygotes; tends to preserve variation in gene pools

Population

A localized group of individuals that belong to the same biological species (that are capable of interbreeding and producing fertile offspring)

Genetic drift

Unpredictable fluctuations in allele frequencies from one generation to the next because of a population’s finite size

Micro evolution

Evolutionary changes below the species level; change in the genetic makeup of a population from generation to generation

Population genetics

The study of how populations change genetically over time

Genetic polymorphism

The existence of two or more distinct alleles at a given locus in a population’s gene pool

Mutation

A rare change in the DNA of a gene, ultimately creating genetic diversity

Relative fitness

The contribution of one genotype to the next generation compared to that of alternative genotypes for the same locus

Geographic variation

Differences between the gene pools of separate populations of population subgroups

Neutral variation

Genetic diversity that confers no apparent selective advantage

Stabilizing selection

Natural selection that favors intermediate variants by acting against extreme phenotypes

Adaptive radiation

the emergence of numerous species from a common ancestor introduced into an environment that presents a diversity of new opportunities and problems

prezygotic barrier

a reproductive barrier that impedes mating between species or hinders fertilization of ova if interspecific mating is attempted

allopatric speciation

a mode of speciation induced an ancestral population becomes segregated by a geographic barrier or is itself divided into two or more geographically isolated subpopulations

morphological species concept

defining species by measurable anatomical criteria

punctuated equilibrium

in evolutionary theory, long periods of apparent stasis (no change) interrupted by relatively brief period of sudden change

biological species concept

Definition of a species as a population or group whose members have the potential to interbreed in nature and produce viable, fertile offspring, but are not able to produce viable, fertile offspring with members of other populations

paleontological species concept

definition of a species based on morphological differences known only from the fossil record

reproductive isolation

the existence of biological factors (barriers) that are members of two impede members of two species from producing viable, fertile hybrids

ecological species concept

defining species in terms of ecological roles (inches).

phylogenetic species concept

definition of a species as a set of organisms with a unique genetic history - that is, as one branch on the tree of life

speciation

the origin of new species in evolution

polyploidy

a chromosomal alteration in which the organism possesses more than two chromosome sets.

species

a group whose members possess similar anatomical characteristics and have the ability to interbreed

macroevolution

evolutionary change above the species level, including the appearance of major evolutionary developments, such as flight, that we use to define higher taxa

postzygotic barrier

any of several species-isolating mechanisms that prevent hybrids produced by two different species from developing into viable, fertile adults

sumpatric speciation

a mode of speciation occurring as a result of a radical change in the genome of a subpopulation, reproductively isolating the subpopulation from the parent population