AP Biology Evolution-Chapters 22-26

descent with modification

a phrase Darwin used in proposing that Earth's many species are descendants of ancestral species that were different from the present-day species

evolution

either descent from modification or a change in the genetic composition of a population from generation to generation

fossil

the remains or traces of organisms from the past

paleontology

the study of fossils

use and disuse

the (false) idea that parts of the body that are used extensively become larger and stronger, while those that are not used deteriorate

inheritance of acquired characteristics

the (false) idea that acquired phenotypic traits could be passed to one's offspring

adaptations

inherited characteristics of organisms that enhance their survival and reproduction in specific environments

natural selection

a process in which individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits

artificial selection

humans modifying other species over many generations by selecting and breeding individuals that possess desired traits

homology

similarity resulting from common ancestry

homologous strutures

anatomical structures that represent variations on a structural theme that was present in their common ancestor

vestigial structures

remnants of features that served important functions in the organisms' ancestors

evolutionary tree

a diagram that reflects evolutionary relationships among groups of organisms

convergent evolution

the independent evolution of similar features in different lineages
(although something may evolve from different ancestors, structures can be formed by means of solving the same problem as opposed to the trait being inherited)

analogous

when species share features because of convergent evolution, not due to common ancestry

biogeography

the geographic distribution of species

Pangaea

Earth's supercontinent

endemic

found nowhere else in the world

microevolution

change in allele frequencies in a population over generations

genetic variation

differences among individuals in the composition of their genes or other DNA segments

average heterozygosity

the average percentage of loci that are heterozygous

mutation

a change in the nucleotide sequence of an organism's DNA

population

a group of individuals of the same species that live in the same area and interbreed

gene pool

all copies of every type of allele at every locus in all members of the population

Hardy-Weinberg principle

a description of the gene pool of a population that is not evolving

adaptive evolution

evolution that results in a better match between organisms and their environment

genetic drift

the result of chance events that can cause allele frequencies to fluctuate unpredictably from one generation to the next

founder effect

when a few individuals become isolated from a larger population, this smaller group may establish a new population whose gene pool differs from the source population

bottleneck effect

a severe and random drop in population size which may result in an under or over represented allele frequency.

gene flow

the transfer of alleles into or out of a population

relative fitness

the contribution an individual makes to the gene pool of the next generation relative to the contributions of other individuals

directional selection

when conditions favor individuals exhibiting one extreme of a phenotypic range, therefore shifting a population's frequency curve for the phenotypic character in one direction or the other

disruptive selection

when conditions favor individuals at both extremes of a phenotypic range over individuals with intermediate phenotypes

stabilizing selection

when conditions favor intermediate variants of a phenotypic trait

sexual selection

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

balancing selection

when natural selection maintains two or more forms in a population (examples: heterozygote advantage and frequency-dependent selection)

heterozygote advantage

when individuals who are heterozygous at a particular locus have geater fitness than do both kinds of homozygotes

speciation

the process by which one species splits into two or more species

macroevolution

the broad pattern of evolution above the species level

biological species concept

defines a species as a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring

reproductive isolation

the existence of biological factors that impede members of two species from interbreeding and producing viable, fertile offspring

hybrid

offspring that result from an interspecific mating

prezygotic barriers

barriers that block fertilization from occurring

postzygotic barriers

reproductive barriers that contribute to reproductive isolation after the hybrid zygote is formed

habitat isolation

two species that occupy different habitats within the same area may encounter each other rarely if at all

temporal isolation

species that breed during different times of day, seasons, or years

behavioral isolation

courtship rituals that attract mates and other behaviors unique to a species and not interspecifically

mechanical isolation

mating is attempted, but morphological differences prevent successful completion

gametic isolation

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

reduced hybrid viability

the genes of different parent species may interact in ways that impair the hybrid's development or survival in its environment

reduced hybrid fertility

even if hybrids are vigorous, they may be sterile (the chromosomes of the two parent species may different in number or structure so meiosis in the hybrids may fail to produce normal gametes)

hybrid breakdown

some first-generation hybrids are viable and fertile, but when they mate with another of either parent species, offspring of the next generation are feeble or sterile

morphological species concept

a concept that characterizes a species by body shape and other structural features

ecological species concept

a concept that views a species in terms of its ecological niche

phylogenetic species concept

a concept that defines a species as the smallest group of individuals that share a common ancestor

allopatric speciation

a population forms a new species while geographically isolated from its parent population

sympatric speciation

a subset of a population forms a new species without geographic separation

cambrian explosion

the "explosion" of new animal phyla forming 535-525 million years ago

plate tectonics

continents are part of gate plates of earth's crust that essentially float on the hot, underlying portion of the mantle

mass extinction

the result of disruptive global environmental changes that have caused the rate of extinction to increase dramatically

adaptive radiations

periods of evolutionary change in which groups of organisms form many new species whose adaptations allow them to fill different ecological roles in their communities

embryonic homologies

anatomical homologies in embryos that are not visible in adult organisms

molecular homologies

shared characteristics on the molecular level

phylogeny

the evolutionary history of a species or group of species

phylogenic tree

a branching diagram grouping organisms according to their common ancestors

comparative anatomy

anatomical features that are similar and that can be compared to each other

analogy

Similarity between two species that is due to convergent evolution rather than to descent from a common ancestor with the same trait.

Binomial nomenclature

Classification system in which each species is assigned a two-part scientific name

Cladogram

Diagram that shows the evolutionary relationships among a group of organisms

What can we learn from the phylogenetic trees and what can't we learn?

Only what common ancestor lived first, though not the time of evolvement. Can not answer what evolved from what, only that they share a common ancestor.

Shared Derived Character

An evolutionary novelty unique to a particular clade. Ex. Mammals have the character of hair which isn't seen in earlier ancestors.

Outgroup

The species or group of species from an evolutionary lineage that is known to have diverged before the lineage that includes the species that is being studied.

Order of Classification

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