Origin of Species and Macroevolution

macroevolution

evolutionary changes that produce new species

species

group of interbreeding natural populations that are reproductively isolated from other such groups

morphology

species vary in physical traits; size, shape, number of parts, color, cell structure

reproductive isolation

sexually reproducing species cannot interbreed with other species

ecology

habitat usage may distinguish species

phylogenetic analysis

algorithmic analysis of morphological and/or molecular characters; often elucidates species boundaries

biological species concept

Ernst Mayr; members of populations that actually or potentially interbreed in nature are reproductively isolated from other populations

morphological species concept

a species has a distinguishing, observable character; applies to a/sexual species

phylogenetic species concept/ general lineage concept

Kevin de Queiroz; a species is a diagnosable population of an independently evolving lineage

prezygotic isolating mechanism

prevent the formation of a zygote; habitat isolation- species ranges do not overlap; temporal isolation- reproductive periods do not overlap; behavioral isolation- species behavior are not compatible; mechanical isolation- genitalia are incompatible; gametic isolation- egg and sperm fail to unite

postzygotic isolating mechanism

block development of a viable or fertile offspring; hybrid inviability- fertilization occurs, but embryo aborts; hybrid sterility- interspecies hybrid viable, but sterile; hybrid breakdown- interspecies hybrid viable and fertile, but subsequent generations degenerate abnormalities caused by chromosomes differing between parents

allopatric speciation

a population becomes isolated, evolves into a new species; slow- mountain building, river formation, glaciers; fast- long distance dispersal, rafting, hurricaines, volcanoes

adaptive radiation

diversification of one species into many species, each adaptively specialized to a specific environmental niche

hybrid zones

areas where related species interbreed; for speciation to occur gene flow must be limited; reinforcement- hybrids are less fit than parent species → outcompeted; fusion- hybrids equally fit as parents → gene flow → 2 species fuse; stability- hybrids continue to occur, but parents remain distinct

sympatric speciation

new species evolve from an ancestral species while inhabiting the same geographic region; less common than allopatric speciation

sympatric speciation: ploidy levels

haploid- sex cells have one set of chromosomes; diploid- one set of chromosomes from each parents; polyploid- cells contain >2 sets of chromosomes (caused by abnormal cell division during mitosis or meiosis; polyploids may have novel variation compared to parental species

sympatric speciation: adaption to local environments

populations inhabiting different local environments adapt and speciate; can happen even if populations are continuous

sympatric speciation: sexual selection

mate choice- species have strong visual, auditory, or chemical cues; a potential mate lacking in one of these signals will have reduced reproductive fitness

gradualism

each new species evolves continuously over time; large phenotypic changes occur because of many small genetic changes

punctuated equilibrium

tempo of evolution can be sporadic; large changes can occur quickly (punctuated) and there can be long periods of stasis (equilibrium)

heterochrony

evolutionary changes in rate or timing of developmental events such as changes can lead to radically different morphologies

hox genes

arose in early ancestor of animals; control the developmental fate of head-to-tail body segments; variation is responsible for different animal bodies; sponges: 1 hox homolog, anemones: 4 hox genes, insects: 9 hox genes, vertebrates: 38 hox genes in four clusters (origin is likely from a tetraploidization event

How do biologists distinguish species?

morphology, reproductive isolation, dna/chromosomes, ecology, phylogenetic analysis

What are the problems with the biological species concept?

it is testable, but is difficult to do so; cannot be applied to asexual species; ignores possibility of hybridization

What are the problems with the morphological species concept?

relies on subjective criteria (which character is important and to whom; does not account for cryptic species, hybrids, variation

What are the problems with the phylogenetic species/ general lineage concept?

this history is unknown for most species

Why tare there disagreements on species concepts?

relative to the number of species, we know too little to generalize; variation is complex, breeding systems are variable; levels of gene flow is variable; speciation is ongoing and all stages are observed

What are the two isolating mechanisms?

prezygotic and postzygotic

Name the prezygotic isolating mechanisms

habitat isolation, temporal isolation, behavioral isolation, mechanical isolation, gametic isolation

Name the postzygotic isolating mechanisms

hybrid inviability, hybrid sterility, and hybrid breakdown

What are the 4 mechanisms of speciation?

allopatric speciation, adaptive radiation, hybrid zones, and sympatric speciation

What 3 mechanisms does sympatric speciation include?

ploidy levels, adaptation to local environments, and sexual selection

What causes phenotypic variation in groups of species?

spatial and temporal expressions of genes affects phenotypes