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Scala naturae

Aristotle's view of organization of species


layers of sediment


study of fossils


the principle that events in the past occurred suddenly and were caused by mechanisms different from those operating in the present


mechanisms of change are constant over time

use and disuse

lyell's idea that parts of the body that are used become larger and those that are not used deteriorate


characteristic that enhances survival and reproduction in specific environments

natural selection

individuals with certain inherited traits leave more offspring than others

descent with modification

darwin's term for evolution

artificial selection

humans selectively breeding individuals that possess desired traits


similarity resulting from common ancestry

homologous structures

variations on a structural theme present in a common ancestor

vestigial structures

remnants of features that served important functions in organisms' ancestors

convergent evolution

the independent evolution of similar features in different lineages


geographic distribution of species

continental drift

the slow movement of earth's continents over time


found nowhere else in the world


the study of change in allele frequencies in a population over generations

average heterozygosity

the average percent of loci that are heterozygous

discrete characteristics

characteristics classified on an "either-or" basis

quantitative characteristics

characteristics that vary along a continuum

nucleotide variability

differences in nucleotide arrangement

gene variability

differences in genes

geographic variation

differences in the genetic composition of separate populations


a change in the nucleotide sequence of an organism's dna

hardy weinberg principle

the frequencies of alleles and genotypes in a population will remain constant provided only mendelian segregation and recombination of alleles

genetic drift

chance events causing allele frequencies to fluctuate unpredictably from one generation to the next

founder effect

when a few individuals become isolated from a larger population, their gene pool differs from the source population

bottleneck effect

after a severe drop in population size, the resultant population has a differing gene pool from that of the source population

gene flow

transfer of alleles into or out of a population due to the movement of fertile individuals or their gametes

relative fitness

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

directional selection

conditions favor individuals exhibiting one extreme of the phenotypic range

disruptive selection

conditions favor individuals at both extremes of the phenotypic range

stabilizing selection

conditions favors individuals at the intermediates of the phenotypic range

sexual selection

individuals with certain inherited characteristics are more likely than other individuals to obtain mates

sexual dimorphism

marked differences between the two sexes in secondary sexual characteristics

intrasexual selection

individuals of one sex compete directly for mates of the opposite sex

intersexual selection

individuals of one sex are choosy in selecting their mates of the other sex

balancing selection

natural selection maintains two or more forms in a population

heterozygote advantage

individuals who are heterozygous at particular alleles have a greater fitness than both homozygotes

frequency-dependent selection

the fitness of a phenotype declines if it becomes too common in a population

neutral variation

nucleotide differences conferring no selective advantage or disadvantage


the broad pattern of evolution over long time spans

biological species concept

a species is defined as a group of populations that can interbreed to produce viable, fertile offspring but cannot do this with members of other group

reproductive isolation

the existence of biological barriers that impede members of two species from producing viable, fertile offspring


offspring that result from interspecific mating

prezygotic barriers

barriers that block fertilization from occuring

postzygotic barriers

barriers that contribute to reproductive isolation after the zygote is formed

habitat isolation

two species occupy different habitats (prezygotic barrier)

temporal isolation

species breed during different times (prezygotic barrier)

behavioral isolation

courtship rituals unique to a species (prezygotic barrier)

mechanical isolation

morphological differences (prezygotic barrier)

gametic isolation

sperm of one species cannot fertilize eggs of another species (prezygotic barrier)

reduced hybrid viability

hybrid's development or survival is impaired (postzygotic barrier)

reduced hybrid fertility

hybrids are sterile (postzygotic barrier)

hybrid breakdown

hybrids offspring are feeble or sterile (postzygotic barrier)

morphological species concept

characterizes species based on body shape and structural features

ecological species concept

characterizes species based on ecological niche

phylogenetic species concept

characterized species based on the smallest group of individuals that share a common ancestor

allopatric speciation

gene flow is interrupted when a population is divided into geographically isolated subpopulations, causing speciation

sympatric speciation

speciation occurs in populations that live in the same geographic area


a species originating from accident in cell division that causes extra set of chromosomes


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


a viable fertile hybrid with one species that mated having meiotic error

hybrid zone

the region in which members of different species meet and mate


strengthening of reproductive barriers; hybrid gradually cease to be formed


weakening of reproductive barriers; the two species fuse


continued production of hybrid individuals

punctuated equilibria

period of apparent statis punctuated by sudden change


collections of abiotically produced molecules surrounded by a membrane like structure


rna catalysts that can synthesize proteins and carry out catalytic functions

radiometric dating

dating based on the decay of radioactive isotopes

half life

the time required for one 50% of the parent isotope to decay


layered rocks that form when certain prokaryotes bind thin films of sediment together


mitochondria and plastids were formerly small prokaryotes that bean living within larger cells

serial endosymbiosis

mitochondria evolved before plastids


first eon


second eon


third eon


first era


second era


third era

adaptive radiation

period of evolutionary change in which groups of organisms form many new species


an evolutionary change in the rate of development


mature species have body features prevalent in the juveniles of an ancestral species

homeotic genes

master genes that regulate where structures are positioned


the evolutionary history of species


a discipline focused on classifying organisms and determining evolutionary relationships

binomial nomenclature

system of two part names of species


the first part of the name of a species

phylogenetic tree

a branching diagram of the evolutionary history of a group of species


taxonomy through phylogeny

branch points

dichotomies that represents divergences of evolutionary lineages

sister taxa

groups of organisms that share an immediate common ancestor


a branch point from which more than two descendant groups emerge


a branch point within the tree represents the last common ancestor of all taxa


a structural similarity due to convergence

molecular systematic

the discipline that uses dna and other molecular data to determine evolutionary relationships

monophyletic group

consists of an ancestral species and all of its descendants

paraphyletic group

consists of an ancestral species and some, but not all, of its descendants

polyphyletic group

consists of members having different ancestors

shared ancestral character

a character that originated in an ancestor of the taxon

shared derived character

a character unique to the taxon


a species from an evolutionary lineage that is known to have diverged before the group of studied species

maximum parsimony

investigating the simplest explanation for the facts

maximum likelihood

a tree found that reflects the most likely sequence of evolutionary events

phylogenetic bracketing

predicting that features shared by two groups of closely related organisms are present in their common ancestor

orthologous genes

homologus genes found in different species because of speciation

paralagous genes

genes that result from gene duplication

molecular clock

a yardstick for measuring the absolute time of evolutionary change based on the observation that some genes change more rapidly than others

neutral theory

much evolutionary change has no effect on fitness and is not influenced by darwinian selection

horizontal gene transfer

a process in which genes are transferred from one genome to another


study of how animals behave in their natural environments

proximate causation

how a behavior occurs

ultimate causation

why a behavior occurs

behavioral ecology

the study of the ecological and evolutionary basis of animal behavior

fixed action pattern

a sequence of unlearned acts that is unchangeable and carried to completion when triggered

sign stimulus

trigger for a fixed action pattern


a change in activity as a response to a stimulus


an oriented movement towards or away from a stimulus


a regular, long distance change in location


a stimulus transmitted from one animal to another


transmission and reception of signals


chemical substance signals

innate behavior

behavior that is developmentally fixed


modification of behavior through experience


loss of responsiveness to a stimulus


the formation of a long-lasting behavioral response to a particular object or individual

sensitive period

a limited developmental phase when certain behaviors can be learned

spatial learning

the establishment of memory that reflects the organisms spatial structure


location indicators

cognitive map

a representation of the spatial relationships between objects in an animal's surroundings

associative learning

associating one environmental feature with another

classical conditioning

an arbitrary stimulus becomes associated with a particular outcome

operant conditioning

trial and error learning


the process of knowing represented by awareness, reasoning, recollection and judgement

problem solving

the cognitive capacity of devising a method to proceed from one state to or another in the face of an obstacle

cross fostering study

the young of one species are placed in the care of adults from another species

twin study

researchers compare the behavior of identical twins raised apart in different households

optimal foraging model

natural selection maximizes the benefits and minimizes costs of foraging


mating with no strong pair bonds or lasting relationship


one male mates with one female


an individual of one sex having multiple mates


one male has many female mates


one female has many male mates

agonistic behavior

ritualized contest that determines which competitor gains access to a resource



inclusive fitness

the total effect an individual has on proliferating its own genes and by providing aid that enables close relatives to proliferate theirs

coefficient of relatedness

the fraction of genes that are shared

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