Bot-Lec (Sem-1) - Chapter 3: The Evolution of Populations and Species

species

a group of organisms that can reproduce naturally with one another and create fertile offspring

gene pool

all the alleles of all the genes in a freely interbreeding population

alleles

different versions of a gene

genotype

genetic makeup of an organism; an organism's complete set of genes; the alleles, or variant forms of a gene, that are carried by an organism

Hardy-Weinberg Principle

mathematical prediction that allele and genotype frequencies do not change from generation to generation in the absence of microevolutionary processes; shows that if the population is large, the process of inheritance by itself does not cause changes in allele and genotype frequencies; tells us what to expect when a sexually reproducing population is not evolving

microevolution

small-scale evolutionary changes caused by changes in allele or genotype frequencies in a population over a few generations

mutation

(alteration in a cell's genetic material) is the source of new alleles in a gene pool

Pereskia sacharosa

leaf cactus

Ferocactus wislizenii

fishhook cactus

genetic drift

change in frequency of an existing gene variant in the population due to random chance

gene flow

movement of alleles between local populations due to migration and subsequent interbreeding

natural selection

the principle that, among the range of inherited trait variations, those contributing to reproduction and survival will most likely be passed on to succeeding generations

no selection

all equal in survival and reproduction, phenotype does not affect survival; normal distribution

stabilizing selection

trims off extreme phenotypes, variation about the mean is reduced

directional selection

shifts the curve in one direction, changing the average value of the character

disruptive selection

trims off intermediate phenotypes, results in two or more peaks

biological species concept

concept that a species consists of one or more populations whose members can interbreed to produce fertile offspring and cannot interbreed with individuals of other species

liger

lion + tigress; stronger bite force than tigon due to larger head

tigon

tiger + lioness

reproductive isolation

situation in which reproductive barriers prevent members of a species from successfully interbreeding with members of another species; timing or structure

temporal isolation

form of reproductive isolation in which two populations reproduce at different times

nocturnal

active at night

diurnal

active during the day

plasticity

ability of an organism to change its phenotype in response to different environments

Salvia mellifera

black sage flowers; early spring

Salvia apiana

white sage flowers; unopened in early spring

structural isolation

organisms are unable to reproduce due to differences in their genital organs

allopatric speciation

evolution of a new species that occurs when one population becomes geographically separated from the rest of the species and subsequently evolves

geographic isolation

form of reproductive isolation in which two populations are separated physically by geographic barriers such as rivers, mountains, or stretches of water

clinal variation

gradual change in the phenotype of a species over a geographic gradient

Achillea millefolium

yarrow

sympatric speciation

evolution of a new species that occurs within the parent species' geographic region; may occur as a result of allopolyploidy in an interspecific hybrid

Primula floribunda

orange flower

Primula kewensis

yellow-orange flower

Primula verticillata

yellow flower

Kew Gardens

a botanic garden in southwest London that houses the "largest and most diverse botanical and mycological collections in the world"

interspecific hybrid

the offspring of individuals belonging to different species; usually dies at an early stage of embryonic development; if it survives to adulthood, it usually cannot reproduce successfully

allopolyploidy

situation in which an interspecific hybrid contains two or more sets of chromosomes from each of the parent species; may enable the interspecific hybrid to reproduce successfully as a new species

adaptive radiation

evolution of many related species from an ancestral species

Argyroxiphium sandwicense

Haleakala silversword; only found in the upper slope of the Haleakala Crater in Maui

Wilkesia gymnoxiphium

tarweed species; resembles a yucca; found along the slopes of Waimea Canyon on the island of Kauai

Dubautia platyphylla

a large shrub found in the moist ravines on the island of Maui

extinction

death of every member of a species

mass extinction

death of many species during a relatively short period of geologic time

endemism

a state in which species are restricted to a single region

Tectona philippinensis

Philippine Teak

Bubalus mindorensis

Tamaraw

Strongylodon macrobotrys

Jade Vine

Cinnamomum cebuense

Cebu Cinnamon Tree