Bio 112

Exam 1

Homology (Homologous Structures)

Homology (Homologous Structures)

• structures derived from a common ancestor but may be modified for different functions

Vestigial Structures

• remnants of ancestral (homologous) structures with no present adaptive function

Cellular & Molecular homologies

• similarity of cell structures, proteins & DNA

Developmental homologies

example) vertebrate embryos

Convergence

• unrelated species have similar adaptations (analogous structures) under similar environmental conditions

Biogeography

• distribution of species (corresponds to geographic history)

Scientific Theory

• broad, well-supported explanation with rich predictive value

Theory of Evolution by Natural Selection

• explains both diversity and unity of life

• accounts for much of form and function

• can predict outcome of environmental change

Apomorphy

• derived characteristic or trait

Plesiomorphy

• ancestral characteristic or trait

Autapomorphy

• a derived but unique characteristic or trait

Synapomorphy

• a derived but shared characteristic or trait

Analogy

• a characteristic that is similar between organisms by convergent evolution, not due to the same evolutionary path.

Morphological Species

• smallest set of organisms that look alike

Ecological species

• a set of organisms adapted to a specific set of resources

Phylogenetic species

• smallest distinct set of organisms that share a common ancestor

Biological Species (our default)

• population whose members potentially interbreed in nature to produce fertile, viable young and do not successfully interbreed with other such groups.

Habitat isolation (prezygotic barriers)

• different species never meet b/c of habitats

temporal isolation (prezygotic barriers)

• different species are active at different times

behavioral isolation (prezygotic barriers)

• courtship cues and other behaviors unique to a specie are effective barriers to mating (dances, songs, etc.)

mechanical isolation (prezygotic barriers)

• parts do not fit each other to “hook up”

gametic isolation (prezygotic barriers)

• sperm of one species may not be able to fertilize eggs of another species

reduced hybrid viability (postzygotic barriers)

• embryo fails to develop or is weak

reduced hybrid fertility (postzygotic barriers)

• hybrid survives but is sterile ( or almost so)

hybrid breakdown (postzygotic barriers)

• 2nd generation hybrid are feeble or sterile

Speciation

• increases diversity of life

Allopatric Speciation

• geographic separation makes a new species

• physical barriers isolate one population and it diverges genetically due to natural selection and/or genetic drift

• biological reproductive barriers evolve, creating separate species

Adaptive radiation

• from one original species multiple others evolved each with its own distinctive characteristics

Sympatric Speciation

• speciation occurs in same geographical area

• (mating behavior & habitat differentiation)

discrete genetic variation

• single gene locus (2 or more alleles)

continuous variation

• phenotypes produced by combined effects of 2 or more genes

Hardy-Weinberg Conditions

• no mutations

• mating is random

• no selection

• very large population size

• no gene flow in or out

Natural Selection

• acts ono-randomly on phenotypes of individuals

• changes allelic & genotypic frequencies of populations non-randomly

• always leads to adaptation of population to current environment

Genetic Drift

• genetic frequency changes due to random events (often occurs in small populations)

• outcomes: reduces diversity, fixed allele

Gene flow

• alleles move in/out of population (migration)

• outcomes: add diversity, reduces differences between populations

Directional selection

• shifts character’s mean value to one direction

Disruptive Selection (Diversifying selection)

• intermediate (heterozygotes) are less fit than extremes (homozygotes)

• maintains diversity

Stabilizing Selection

• intermediate (heterozygote) types more fit than extremes (homozygotes)

• variation reduced

Sexual Selection

• success based on traits related to obtaining mates '

• leads to sexual dimorphism

Diploidy

• less successful recessive alleles are hidden in herterozygotes

heterozygote advantage

• selection favors heterozygote over either homozygote, maintaining both alleles

frequency-dependent selection

• fitness of a phenotype decreases as its frequency increases in population

Binomial nomenclature

• scientific name by Linnaeus

Taxonomy

• grouping species together based on similarities & differences

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

Daring King Phillip Cut Open Five Giant Snakes