Biology All Terms

Evolution

any change in the heritable traits within a population across generations, "descent with modification"

Natural Selection

increases the frequency of favorable adaptations to an environment, the mechanism which drives evolution

Taxonomy

The organization of species into a nested classification system

artificial selection

a human-controlled process to produce individuals with certain traits

Homology

Similarity in characteristics resulting from a shared ancestry.

vestigial structures

remnant of a structure that may have had an important function in a species' ancestors.

convergent evolution

Process by which unrelated organisms independently evolve similarities when adapting to similar environments

analogous structures

Body parts that share a common function, but not structure

Biogeography

Geographic distribution of species.

Lamarck's (incorrect) Theory of Evolution

individuals can acquire traits during their lifetime and pass them onto their offspring

3 Domains of Life

Bacteria, Archaea, Eukarya

Eukarya

all organisms that have a nucleus

Prokarya

organisms that do not have a nucleus

Archaea

bacteria that live in extreme environments

Eukarya Kingdoms

Protista, Plantae, Fungi, Animalia

horizontal gene transfer

transfer of genes between cells of the same generation

Phylogeny

Evolutionary history of a species / group of species

Systematics

study of the evolutionary relationships between organisms

Cladistics

classification based on common ancestry

phylogenetic trees

Branching diagrams that depict hypotheses about evolutionary relationships.

analogy

similarity of function and superficial resemblance of structures that have different origins

Molecular Homologies

Similar DNA sequences in different taxa

Molecular homoplasies

shared bases in nucleotide sequences that are otherwise very dissimilar

Genus

A classification grouping that consists of a number of similar, closely related species

Family

Group of genera that share many characteristics

Order

Group of similar families

Classes

In classification, the taxonomic category above order.

Phyla

In classification, the taxonomic category above class.

Kingdom

First and largest category used to classify organisms

Domain

A taxonomic category above the kingdom level. The three domains are Archaea, Bacteria, and Eukarya.

Taxon

any particular group within a taxonomic system

monophyletic

ALL descendants came from one common ancestor

paraphyletic

Pertaining to a group of taxa that consists of a common ancestor and some, but not all, of its descendants.

clades

A group of species that includes an ancestral species and all its descendants.

binomial nomenclature

A system for giving each organism a two-word scientific name that consists of the genus name followed by the species name

Microevolution

Change in allele frequencies in a population over generations.

genetic variation

The variety of different types of genes in a species or population.

population

a group of organisms of the same species populating a given area

gene pool

All the genes that are present in a population at any one time

Hardy-Weinberg equilibrium

condition that occurs when the frequency of alleles in a particular gene pool remain constant over time

genetic drift

A change in the allele frequency of a population as a result of chance events rather than natural selection.

founder effect

Genetic drift that occurs when a few individuals become isolated from a larger population and form a new population whose gene pool composition is not reflective of that of the original population.

bottleneck effect

A change in allele frequency following a dramatic reduction in the size of a population

allele

Different forms of a gene

mutation

A change in a gene or chromosome.

gene flow

movement of alleles from one population to another

adaptive evolution

a process in which traits that enhance survival or reproduction tend to increase in frequency in a population over time

relative fitness

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

directional selection

Natural selection in which individuals at one end of the phenotypic range survive or reproduce more successfully than do other individuals.

disruptive selection

natural selection that favors individuals at both extremes of the phenotypic range

stablizing selection

natural selection where individuals with the average form of a trait have the highest fitness

balancing selection

natural selection that maintains two or more phenotypic forms in a population

heterozygote advantage

occurs when heterozygotes have a higher fitness than do both homozygotes

sexual selection

Natural selection for mating success.

sexual dimorphism

distinct difference in size or appearance between the sexes of a species

speciation

the formation of new and distinct species in the course of evolution.

Macroevolution

large-scale evolutionary changes that take place over long periods of time

biological species concept

Species is a group of populations whose members have the potential to produce fertile offspring.

species

a group of living organisms consisting of similar individuals capable of exchanging genes or interbreeding.

prezygotic barriers

prevent mating between species

postzygotic barriers

Barriers that prevent the hybrid zygote from becoming a fertile adult.

morphological species concept

characterizes a species by body shape and other structural features

ecological species concept

A definition of species in terms of ecological niche, the sum of how members of the species interact with the nonliving and living parts of their environment.

phylogenetic species concept

A definition of species as the smallest group of individuals that share a common ancestor, forming one branch on the tree of life.

allopatric speciation

The formation of new species in populations that are geographically isolated from one another.

sympatric speciation

The formation of new species in populations that live in the same geographic area

Polyploidy

condition in which an organism has extra sets of chromosomes

Autopolyploid

an individual that has more than two chromosome sets that are all derived from a single species

allopolyploid

a species with multiple sets of chromosomes derived from different species

punctuated equilibria

The theory that species evolve during short periods of rapid change

examples of prezygotic barriers

habitat isolation, temporal isolation, behavioral isolation

examples of postzygotic barriers

hybrid sterility

geologic record

a standard time scale that divides Earth's history into four eons and further subdivisions

mass extinction

A large extinction of species in a relatively short period of time

adaptive radiation

An evolutionary pattern in which many species evolve from a single ancestral species

heterochrony

Change in the rate or timing of a developmental event

Paedomorphosis

The retention in an adult organism of the juvenile features of its evolutionary ancestors.

Conditions for Hardy-Weinberg Equilibrium

no mutations, random mating, no natural selection, extremely large population size, no gene flow

2 examples of genetic drift

founder effect and bottleneck effect

Linnaean Classification System

Kingdom, Phylum, Class, Order, Family, Genus, Species

Gene Expression

conversion of the information encoded in a gene first into messenger RNA and then to a protein

Transcription

synthesis of RNA from DNA

Messenger RNA

copies the message from DNA in the nucleus and carries the message to the ribosome

translation

Process by which mRNA is decoded and a protein is produced

ribosomes

site of protein synthesis

primary transcript

The initial mRNA transcript that is produced from DNA synthesis.

triplet code

Three nucleotides that specifies a specific amino acid.

Template Strand

The DNA strand that provides the template for ordering the sequence of nucleotides in an mRNA transcript.

Codons

A three-nucleotide sequence of DNA or mRNA that specifies a particular amino acid or termination signal; the basic unit of the genetic code.

nontemplate strand

the strand of DNA that is not used to transcribe mRNA; this strand is identical to the mRNA except that T nucleotides in the DNA are replaced by U nucleotides in the mRNA

reading frame

Reading mRNA nucleotides in the correct groupings.

RNA polymerase

Enzyme that transcribes DNA.

Promoter

specific region of a gene where RNA polymerase can bind and begin transcription

terminator

A special sequence of nucleotides that marks the end of a genes.

transcription unit

A region of DNA that is transcribed into an RNA molecule.

RNA splicing

Process by which the introns are removed from RNA transcripts and the remaining exons are joined together.

introns

sequence of DNA that is not involved in coding for a protein

exons

expressed sequence of DNA; codes for a protein

spliceosome

complex of enzymes that serves to splice out the introns of a pre-mRNA transcript

ribozymes

RNA molecules that function as enzymes and can splice RNA