Bio 112

Exam 1

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