evolution unit review

natural selection

natural selection

organisms adapted to their environment are more likely to survive and pass on genes that aided success (ex. giraffes; long necks allow them to reach food from branches)

artificial selection

evolutionary process in which humans consciously select for or against particular features in organisms (ex. choosing which individuals to breed from one generation to the next)

Darwin

British naturalist who proposed the theory of biological evolution by natural selection — “descent with modification”

fitness

all physical traits & behaviours that enable organisms to survive & reproduce in their environment

adaptation

single trait/behaviour that gives the organism an advantage over others in the same environment

common ancestor

an ancestral group of organisms that is shared by multiple lineages

fossil record

preserved remains of ancient organisms; often found in sedimentary rock

DNA

deoxyribonucleic acid; polymer of nucleotides. deoxyribose sugar + nitrogenous base + phosphate group

double helix

physical structure of DNA; two linked DNA strands wind around to resemble a twisted ladder in a helix-like shape

sugar phosphate backbone

forms the structural framework of nucleic acids, including DNA and RNA; composed of alternating sugar and phosphate groups

nucleotides

molecule that is the basic building block of the nucleic acids (nitrogen base + phosphate + sugar)

complimentary base pairing

occurs between A-T, C-G; gives double helix shape of DNA

nitrogenous bases

adenine, guanine, thymine, cytosine — nitrogenous compounds that form an important part of the nucleotides

A, G

adenine & guanine: nitrogenous bases (purines)

T, C

thymine & cytosine: nitrogenous bases (pyrimidines)

allele frequency

represents the incidence of a gene variant in a population

mutation

molecular alteration in genetic material; a change in the nucleotide sequence. most happen in ‘junk’ DNA. must happen in sex cells to be passed down

gene flow

exchange of alleles between populations & increases genetic diversity (ex. migration, when humans marry different cultures)

genetic drift

random fluctuation in allele frequencies; can go in both directions

founder effect

new colony of small population; frequency of deleterious trait (causes disease/deformity) is high

bottleneck effect

large population is reduced to small population — overhunting, disease, lack of habitat/resources. survivors possess traits of rebounded population

non-random mating

purposeful selection of mates based on the presence or absence of certain traits in potential mates

microevolution

gradual change in a single population

macroevolution

changes in an entire species over time

divergent evolution

evolution of single species into a wide variety of descendant species

convergent evolution

when organisms that aren't closely related evolve similar features or behaviours because they live in similar ecologies

adaptive radiation

common in periods of environmental change or when new ecological opportunities occur

character displacement

tendency of closely related species who live together to diverse rapidly; minimizes competition and occurrence of hybrid organisms in nature

speciation

formation of new species; result of geographic, physiological, anatomical, or behavioural factors

allopatric populations

populations living in areas separated by geography (ex. oceans, mountains, rivers)

sympatric populations

populations living in the same area

pre-mating isolation mechanisms

1. seasonal/habitat isolation (ex. 2 plants: one grows in sun = blooms May, other grows in shade = blooms June)

2. behavioural isolation: court rituals are different, prevent mating (ex. bird song)

3. mechanical isolation: genitalia do not fit (ex. chihuahua & great dane)

post-mating isolation mechanisms

1. gametic mortality: sex cells die in hostile environment

2. zygotic mortality: egg fertilized, offspring doesn’t develop

3. hybrid sterility: offspring produced but can’t reproduce itself (ex. horse x donkey = horse [sterile])

equilibrium

a species that does not change very much over time (ex. horseshoe crab)

gradualism

theory that evolution causes changes slowly over time

punctuated equilibrium

evolution occurs rapidly after long periods of no change (equilibrium); allows for ancient and modern species to co-exist

extinction

when a species can’t adapt fast enough to a changing environment; 5 major mass extinctions

homologous structures

an organ, system, or body part that shares a common ancestry in multiple organisms

evolutionary change

heritable change in populations and species over time due to natural selection, genetic drift, and sexual selection

analogy

similarity of function resemblance of structures that have different origins (ex. wings: fly, bird, moth = analogous)

inbreeding depression

the reduced survival and fertility of offspring of species

intelligent design

theory that some features of organisms are so complex that they could not possibly have come into existence through normal causes