UW Bio 180 - Exam 3

species

evolutionarily independent population or group of populations

synapomorphy

a trait that is found in certain groups of organisms and their common ancestor, but is missing in more distant ancestors; identifies monophyletic groups; homologous traits that can be identified at the genetic, developmental, or structural level

biological species concept

reproductive isolation between populations (they don't breed and don't produce viable, fertile offspring)

- reproductive isolation = evolutionary independence

- not applicable to asexual or fossil species; difficult to assess if populations don't overlap geographically

reproductive isolation: prezygotic ("before-zygote")

prevents individuals of different species from mating

temporal: populations are isolated because they breed at different times

- habitat: populations are isolated because they breed in different habitats

- behavioral: populations don't interbreed because their courtship displays differ

- gametic barrier: matings fail because eggs and sperm are incompatible

- mechanical: matings fail because male and female reproductive structures are incompatible

reproductive isolation: postzygotic ("after-zygote")

offspring of matings between members of different species do not survive or reproduce

- hybrid viability: hybrid offspring don't develop normally and die as embryos

- hybrid sterility: hybrid offspring mature but are sterile as adults

morphospecies concept

morphologically distinct populations; distinguishing features are most likely to arise if populations are independent and isolated from gene flow

- widely applicable

- researchers disagree how much or what kinds of morphological distinction indicate speciation

- misidentifies polymorphic species; misses cryptic species

polymorphic species

a species with many different morphological types or stages or more than one phenotype

cryptic species

differ in traits other than morphology

phylogenetic species concept

identifies species based on the evolutionary history of populations

- all species form a monophyletic group

- species are defined as the smallest monophyletic group on a phylogentic tree

- widely applicable; based on testable criteria

- relatively few well-estimated phylogenies are currently available

monophyletic ("one-tribe") group

evolutionary unit that includes an ancestral population and all of its descendants but no other (also called a lineage, or clade)

subspecies

populations that live in discrete geographic areas and have distinguishing features, but aren't distinct enough to be called separate species

speciation

a process typically caused by the genetic isolation from a main population resulting in a new genetically distinct species (the first requirement of speciation is the interruption of gene flow)

allopatry ("different-homeland")

condition in which two or more populations live in different geographic areas

allopatric speciation

speciation that begins with geographic isolation, occurs through dispersal or vicariance

vicariance

the physical splitting of a habitat into two or more subgroups that are physically isolated from one another

biogeography

the study of how species and populations are distributed geographically

sympatry

condition in which two or more populations live in the same geographic area, or close enough to permit interbreeding

sympatric speciation

speciation that occurs when there is no geographic barrier present

- based on external events such as disruptive selection for extreme phenotypes based on different ecological niches

- based on internal events such as chromosomal mutations

polyploidy

occurs when an error in meiosis or mitosis results in a doubling of the chromosome number (this is a massive mutation). polyploid individuals are reproductively isolated from the original diploid population and thus evolutionarily independent because breeding between diploids and tetraploids generally results in sterile offspring

1. autopolyploid

2. allopolyploid

autopolyploid ("same-many-form")

individuals are produced when a mutation results in a doubling of chromosome number and the chromosomes all come from the same species

allopolyploid ("different-many-form")

individuals are created when parents that belong to different species mate and produce offspring with two different sets of chromosomes

phylogeny

evolutionary history of a group of organisms

phylogenetic tree

a family tree that shows the evolutionary ancestor-descendant relationships among populations, species, or higher taxa thought to exist among groups of organisms

branch

represents a population through time

node

a fork that within a tree where a branch splits into two or more branches

outgroup

a taxon that is outside of the taxa being looked at; this species diverged prior to the taxa being looked at

root

most ancestral branch of the tree

tip (terminal node)

endpoint of a branch; represents a living or extinct group of genes, species, families, phyla, or other taxa

polytomy

a branch point from which more than two descendant taxa emerge; indicates that the evolutionary relationships among the descendant taxa are not yet clear

ancestral trait

characteristic that existed in an ancestor

derived trait

modified form of an ancestral trait found in a descendant

paraphyletic group

a group that consists of an ancestor and some, but not all, of it's descendants - need to add one clade or tip to get monophyly

polyphyletic group

a group that consists of unrelated tips - need to add more than one clade or tip to get monophyly

sister group

the next most closely related tip or clade; always reciprocal

homology

similarity in organisms due to common ancestry

homoplasy

similarity in organisms due to reasons other than common ancestry

parsimony

the simplest explanation or a pattern that implies the least amount of change

convergent evolution

common cause of homoplasy; occurs when natural selection favors similar solutions to the problems posed by a similar way of making a living in different species

adaptive radiation

when a single lineage rapidly produces many descendant species with diverse adaptive forms

- consist of monophyletic groups that speciated rapidly and diversified ecologically

- triggered by ecological opportunity and morphological innovation

ecological opportunity

the availability of new or novel types of resources

key morphological trait

trait that allowed descendants to live in new areas, exploit new sources of food, or move in new ways

cambrian explosion

great increase in diversity of multicellular life on earth 535-525 million years ago (during the cambrian period)

fauna

collection of animal species

mass extinction

short-term rapid termination of at least 60% of the species present within 1 million years

background extinction

lower, average rate of extinction that occurs when normal environmental change, emerging disease, predation pressure, or competition with other species reduces certain populations to zero

"The Big Five"

- end-Cretaceous extinction

- late-Triassic extinction

- end-Permian extinction

- late-Devonian extinction

- end-Ordovician extinction

impact hypothesis

put for in early 1970s; states that an asteroid struck earth and removed 60-80% of the multicellular species alive

fossil

piece of physical evidence from an organism that lived in the past

fossil record

total collection of fossils that have been found throughout the world

habitat bias

organisms that live in areas like beaches, mudflats, and swamps where sediment is continuously being deposited are more likely to form fossils

taxonomic and tissue bias

organisms with bones or shells are most likely to leave fossil evidence because these provide slow decay

temporal bias

recent fossils are more common than ancient fossils; ancient fossil forms are simpler than more recent forms; more recent forms are more similar to extant species

abundance bias

organisms that are abundant or widespread and/or present on earth for long periods of time leave evidence more often than rare species

radiometric dating

established the absolute ages of the fossil-bearing rocks; decay rate measured in half-lives

precambrian

interval between 4.6 billion - 542 million years ago where life was unicelluar and oxygen was virtually absent

- divided into Hadean, Archaean, Proterozoic eons

phanerozoic eon

interval between 542 mya and the present, divided into paleozoic, mesozoic, and cenozoic eras

paleozoic ("ancient-life") era

origin and initial diversification of animals, land plants, fungi, appearance of land animals

mesozoic ("middle-life") era

begins with end-permian extinction and ends with the extinction of the dinosaurs; gymnosperms and dinosaurs were dominant

cenozoic ("recent-life") era

divided into paleogene, neogene, and quaternary periods; angiosperms and mammals were dominant

"evo-devo" research

study genes and alleles involved in the origin of key synapomorphies (morphological innovations)