Evolution 3 exam review

Heterochrony

Evolutionary change caused by changes in the timing or rate of developmental events

Paedomorphosis

Retention of juvenile traits in the adult form

Neoteny

Slowing of developmental rate causing juvenile traits to remain in adults

Peramorphosis

Descendants develop beyond the adult form of ancestors

Recapitulation

Developmental pattern where ancestral adult traits appear during descendant development

Axolotl

Example of paedomorphosis because it retains larval aquatic traits as an adult

Biological Species Concept

Defines species based on reproductive isolation

Phenetic Species Concept

Defines species based on overall morphological similarity

Phylogenetic Species Concept

Defines species as the smallest monophyletic group with shared derived traits

Evolutionary Species Concept

Defines species as lineages with their own evolutionary trajectory and fate

Speciation continuum

The gradual process by which populations become reproductively isolated species

Prezygotic isolation

Barriers that prevent fertilization from occurring

Precopulatory isolation

Prezygotic barrier where organisms do not mate

Postcopulatory isolation

Prezygotic barrier where mating occurs but fertilization fails

Postzygotic isolation

Barrier where hybrid offspring have reduced fitness or sterility

Hybrid sterility

Postzygotic isolation where hybrids cannot reproduce

Geographic isolation

Physical separation of populations preventing gene flow

Secondary contact

When diverged populations come back into contact after isolation

Background extinction

Normal low rate of extinction over time

Mass extinction

Rapid widespread extinction event affecting many species

Phylogenetic diversity

Measure of evolutionary history represented by a group of organisms

Most recent common ancestor (MRCA)

The most recent shared ancestor of a clade

Parsimony

Principle favoring the evolutionary explanation with the fewest changes

Time-calibrated phylogeny

Phylogenetic tree scaled to geological time

Twofold cost of sex

Disadvantage of sexual reproduction because only half of offspring can directly reproduce and meiosis passes only half of genes

Cost of males

Sexual females produce sons that do not directly bear offspring

Cost of meiosis

Sexual reproduction transmits only 50 percent of parental genes

Red Queen hypothesis

Sexual reproduction is favored because it creates novel genotypes that parasites cannot easily exploit

Sexual reproduction

Favored in variable environments with high parasite pressure

Asexual reproduction

Favored in stable predictable environments

Intersexual selection

Mate choice where one sex chooses mates based on traits

Intrasexual selection

Competition within the same sex for access to mates

Sexual selection

Natural selection acting on traits that improve mating success

Direct benefits

Mate choice benefits involving resources protection or territory

Indirect genetic benefits

Mate choice benefits involving good genes for offspring

Sexual conflict

Antagonistic evolutionary interests between males and females

Independent assortment

Formation of different gamete combinations during meiosis

Gamete

Reproductive cell carrying one allele for each gene

Multicellularity

Evolutionary transition from single cells to cooperative groups of cells

Convergent evolution

Independent evolution of similar traits in unrelated lineages

Come together model

Multicellularity evolving when independent cells aggregate

Stay together model

Multicellularity evolving when daughter cells remain attached after division

Group living

Living in social groups that provide costs and benefits

Kin selection

Selection favoring behaviors that increase reproductive success of relatives

Hamilton’s Rule

Altruism evolves when rB is greater than C

Relatedness coefficient (r)

Probability that two individuals share a gene through common ancestry

Altruism

Behavior that benefits another individual at a cost to the actor

Reciprocal altruism

Cooperation among unrelated individuals based on future repayment

Economies of Scale

Groups performing tasks more efficiently than individuals

Group selection

Selection acting on differences among groups

Coevolution

Reciprocal evolutionary change between interacting species

Antagonistic coevolution

Coevolution where one species benefits at the expense of another

Mutualistic coevolution

Coevolution where both interacting species benefit

Evolutionary arms race

Escalating adaptations between interacting species

Host-parasite coevolution

Reciprocal adaptations between hosts and parasites

Cospeciation

Parallel speciation of hosts and their associated parasites or symbionts

Phylogenetic congruence

Matching host and parasite phylogenies indicating shared evolutionary history

Vertical transmission

Symbionts passed directly from parent to offspring

Horizontal transmission

Symbionts acquired from the environment or unrelated organisms

Genome reduction

Loss of genes in symbionts due to host dependence

Obligate symbiont

Symbiont that cannot survive independently of its host

Mutualism

Symbiotic relationship where both species benefit

Commensalism

Symbiotic relationship where one species benefits and the other is unaffected

Parasitism

Symbiotic relationship where one species benefits and the other is harmed

Endosymbiosis

Symbiosis in which one organism lives inside another

Mitochondria

Organelle thought to originate from bacterial endosymbiosis

Chloroplast

Photosynthetic organelle derived from bacterial endosymbiosis

Nitroplast

Nitrogen-fixing organelle formed through endosymbiosis

Black Queen hypothesis

Organisms lose costly genes and depend on other organisms for functions

Holobiont

A host organism together with its microbiome

Phylosymbiosis

Pattern where microbiome relationships mirror host phylogeny

Host-filtered microbial community

Microbial community shaped by host traits and selection

Rhizosphere

Region of soil influenced by plant roots and microbes

Phyllosphere

Microbial habitat on plant surfaces such as leaves

Endosphere

Interior tissues of plants colonized by microbes

Rhizobium

Nitrogen-fixing bacteria associated with plant roots

Mycorrhizae

Mutualistic fungi associated with plant roots

Microbiome

Community of microorganisms associated with a host

Buchnera

Bacterial symbiont living in aphids and providing nutrients

Wolbachia

Bacterial symbiont commonly infecting insects

Termite gut microbiome

Microbial community that helps termites digest cellulose

Human microbiome

Microbial community living in and on the human body

Competitive exclusion

Microbes preventing pathogens from establishing in the host

Antibiotic resistance

Evolutionary increase of resistant bacteria under antibiotic selection

Selection pressure

Environmental factor favoring certain traits over others

Human evolution

Evolutionary history of the genus Homo

Out-of-Africa hypothesis

Model proposing modern humans evolved in Africa and later dispersed

Multiregional Evolution Hypothesis

Model proposing humans evolved regionally with gene flow among populations

Serial founder effect

Loss of genetic diversity as populations migrate farther from Africa

Heterozygosity

Measure of genetic variation within a population

Incomplete lineage sorting

Retention of ancestral genetic variation across descendant lineages

Deep coalescence

Another term for incomplete lineage sorting

Neanderthal introgression

Transfer of Neanderthal DNA into modern humans through hybridization

Denisovans

Extinct hominin group that interbred with modern humans

Homo habilis

Earliest recognized member of the genus Homo

Homo heidelbergensis

Hominin closely related to Neanderthals Denisovans and modern humans

Australopithecus afarensis

Early hominin species not belonging to genus Homo

Paranthropus boisei

Robust hominin species outside genus Homo

Chimpanzees

Sister group most closely related to humans

Bonobos

Primate species closely related to chimpanzees and humans