Biology 1010 @Dalhousie - Evolution

Evolution

Change in biological entities over time/generations

Darwinian Evolution

all species of organisms arise and develop through the natural selection of small, inherited variations that increase the individual's ability to compete, survive, and reproduce.

Tree of Life

the phylogenetic tree that includes all organisms

Carolus Linnaeus

Father of taxonomy; was a botanist who promoted the hierarchical nested classification (and formal ranks)

Linnaen Classification

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

Paleontology

the study of fossils

Lamarckism

An evolutionary theory (proved false by Darwin) stating that species change over time by the use and disuse of structures and the inheritance of acquired traits.

phylogenetic trees

Branching diagrams that depict hypotheses about evolutionary relationships. illustrates descent with modification

Fitness

Ability of an organism to survive and reproduce in its environment

heritable variation

required for a population to evolve by natural selection; in which many traits can be passed on from parent to offspring.

excess production

in any population, more offspring are produced than needed to maintain it

Differential success

the greater survival and reproduction of organisms with some traits compared with organisms that do not have those traits.

Adaptation

A trait that helps an organism survive and reproduce; a result of natural selection over time.

homology

similarity resulting from common ancestry

Biogeography

Study of past and present distribution of organisms

fossil record

Chronological collection of life's remains in sedimentary rock layers

vestigial structures

structures with little or no function derives from more complex structures

molecular homologies

homologies at the biochemical level

Pseudogenes

molecular vestigial features; have a non-functional gene in the same place of the genome that a closely related species has a functional gene

analogous structures

Body parts that share a common function, but not structure

convergent evolution

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

Kingdom

First and largest category used to classify organisms

Phylum

Group of closely related classes

class

in classification, a group of closely related orders

order

in classification, a group of closely related families

family

in classification, group of similar genera

Genus

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

Species

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

transitional forms

fossils that connect ancestral species with their descendants through a series of tiny steps

Hardy-Weinberg Principle

describes expected relationships between allele and genotype frequencies when there is no evolution

gene flow

movement of alleles from one population to another

Allele

Different forms of a gene

Heterozygous

An organism that has two different alleles for a trait

Homozygous

An organism that has two identical alleles for a trait

Population

localized group of interbreeding and interacting individuals

gene pool

Combined genetic information of all the members of a particular population

source of genetic variation

new alleles arise by mutation existing allele, a single mutation can result in a new allele

Microevolution

Change in allele frequencies in a population over generations.

Assumptions of Hardy-Weinberg

1. No net mutations
2. No migration
3. Random mating
4. No natural selection
5. Large population size
6. Random mating

gene flow (migration)

movement of alleles from one population to another; one of the 3 causes of microevolution

genetic drift

A change in the allele frequency of a population as a result of chance events rather than natural selection; one of the 3 causes of microevolution

genetic bottlenecks

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

founder effect (genetic drift)

rare allele occur in a higher frequency in a new population than they do in the general population

polygenetic inheritance

phenotype influenced by several genes, indicating that there are alleles at several loci

quantitative character

a smooth range of phenotypes

Modes of Selection

directional, stabilizing, disruptive

directional selection

in which either end of the distribution curve is selected against

stabilizing selection

extreme phenotypes (middle of distribution curve) is selected against

disruptive selection

intermediate phenotypes selected against

sexual selection

A form of natural selection in which individuals with certain inherited characteristics are more likely than other individuals to obtain mates.

intrasexual selection

competition within one sex (usually males) for mating opportunities

intersexual selection

one sex (typically females) will choose a mate from competing members of the other sex (usually males)

sexual dimorphism

Differences in physical characteristics between males and females of the same species.

interfertility

populations that interbreed to produce fertile offspring

reproductive isolation

Separation of species or populations so that they cannot interbreed and produce fertile offspring

speciation

reproductive barriers inhibit gene flow between populations, allowing evolutionary divergence

prezygotic barriers

prevent mating or fertilization between species

postzygotic barriers

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

Speciation

Formation of new species

allopatric speciation

geographic barrier blocks gene flow between populations

sympatric speciation

a new species arises within the same geographic area as its parent species

speciation and tree of life

each branching on the tree of life began with a speciation event

allopolyploid speciation

occurs when two species hybridize and give rise to a new species

polyphyletic group

A taxonomic grouping consisting of several species that lack a common ancestor

monophyletic group

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

paraphyletic group

A monophyletic group in which some descendants of the common ancestor have been removed.

Cladistic reasoning

shared derived states imply relationships; shared ancestral states do not imply relationships

parisimonious

the most correct

lateral gene transfer

The transfer of genes from one species to another, common among bacteria and archaea.

horizontal gene transfer

The transfer of genes from one genome to another through mechanisms such as transposable elements, plasmid exchange, viral activity, and perhaps fusions of different organisms.

Fossils

Preserved remains of once-living organisms

index fossils

common, widespread fossils characteristic of particular period of deaths history

geological record

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

Cenozoic Era

Age of mammals

Mesozoic Era

Age of reptiles

Paleozoic Era

the part of geologic time 570-245 million years ago ; invertebrates, fishes, amphibians, reptiles, ferns, and cone-bearing trees were dominant

mass extinctions

mass destruction of most species

End-Permian Extinction

Largest mass extinction which resulted in the disappearance of 90% of all species

End-Cretaceous extinction

Mass extinction, 65 MYO, of 60-80% of the multicellular species alive, including the dinosaurs (except birds). Hypothesized to have resulted from the impact of an asteriod hitting the earth.

adaptive radiation

rapid series of speciation events that occur when one or more ancestral species invades a new environment

exaptation

structures adapted to one function can already be somewhat useful for other functions

gene duplication

The generation of extra copies of a gene in a genome over evolutionary time. A mechanism by which genomes can acquire new functions.

Behavioural isolation

when two populations are capable of interbreeding but develop different behaviours such as courtship rituals or feeding.

gametic isolation

A prezygotic reproductive barrier where the sperm of one species may not be able to fertilize the eggs of another species

hybrid inviability

A postzygotic barrier in which hybrid zygotes fail to develop or to reach sexual maturity

habitat isolation

Reproductive isolation in which habitat preferences lower mating probability.

causes of microevolution

natural selection, genetic drift, gene flow