Chapter 24: The Origin of Species

speciation

speciation

-An evolutionary process in which one species splits into two or more species. -the origin of new species, is at the focal point of Darwin's evolutionary theory. -Evolutionary theory must explain how new species originate and how populations evolve

microevolution

-consists of adaptations that evolve on the smallest scale within a population, confined to one gene pool; generation-to-generation change

macroevolution

refers to evolutionary change above the species level; large scale

biological species concept

States that a species is a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring; they do not breed successfully with other populations.

species

group of similar organisms that can breed and produce fertile offspring

reproductive isolation

the existence of biological factors (barriers) that impede two different species from producing viable, fertile offspring; keeps two species from interbreeding

habitat isolation

Two species encounter each other rarely, or not at all, because they occupy different habitats, even though not isolated by physical barriers.

temporal isolation

Species that breed at different times of the day, different seasons, or different years cannot mix their gametes.

behavioral isolation

courtship rituals that attract mates and other behaviors unique to a species are effective reproductive barriers, even between closely related species. Such behavioral rituals enable "mate recognition" - a way to identify potential mates of the same species

mechanical isolation

mating is attempted, but morphological differences prevent its 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; WEAK OFFSPRING

reduced hybrid fertility

even if the hybrids are vigorous, they may be sterile. if the chromosomes of the two parent species differ in number or structure, meiosis may fail to produce normal gametes; STERILE OFFSPRING

hybrid breakdown

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

hybrids

are the offspring of crosses between different species

prezygotic barriers

prevent mating or fertilization between species; maintain reproductive isolation; include Temporal, Habitat, Behavioral, Mechanical, and Gamete Isolation. Mneumonic: The Hell Breaking Man Growled

postzygotic barriers

prevent the hybrid zygote from developing into a viable, fertile adult Include: Reduced hybrid viability, Reduced hybrid fertility, and Hybrid breakdown.

morphological species concept

characterizes a species by body shape and other structural features

ecological species concept

defines a species as a set of organisms that are adapted to a particular set of resources

phylogenetic species concept

defines a species as a set of organisms with a unique genetic history

ecological species concept

views a species in terms of its ecological niche, its role in a biological community; i.e.: 2 species of Galapagos finches may look alike but can be distinguished based on what they eat

paleontological species concept

focuses on morphologically discrete species known only from the fossil record; used because their is little to no info about their mating capability

allopatric speciation

The formation of a new species as a result of an ancestral population's becoming isolated by a geographic barrier.

sympatric speciation

The formation of new species in populations that live in the same geographic areas

polyploidy

condition in which an organism has an extra set of chromosomes; result of an accident during cell division

autopolyploid/y

The state of having more than two full sets of chromosomes due to a mutation that doubled the chromosome number; i.e.: a failure of cell division can double a cell's chromosome number from the diploid number (2n) to a tetraploid number (4n)

allopolyploid/y

Various mechanisms can change a sterile hybrid into a fertile polyploid known as a(n) _______. They are fertile with each other but can't interbreed with either parental species- thus they represent a new biological species

hybrid zone

a geographic region in which members of different species meet and mate, producing at least some offspring of mixed ancestry

reinforcement

process by which natural selection increases reproductive isolation

punctuated equilibria

pattern of evolution in which long stable periods are interrupted by brief periods of more rapid change; a new species changes most as it buds from a parent species and then changes little for the rest of its exostence

gradualism model

species descended from a common ancestor gradually diverge more and more in their morphology as they acquire unique adaptations

adaptive radiation

the evolution of many diversely adapted species from a common ancestor upon introduction to various new environmental opportunities and challenges.

heterochrony

an evolutionary change in the rate or timing of developmental events; i.e.: an organism's shape depends in part on the relative growth rates of different body parts during development

allometric growth

proportioning of the relative rates of growth of various parts of the body that helps give a body its specific form

paedomorphosis

a condition in which reproductive development accelerates compared to somatic development, the sexually mature stage of a species may retain body features that were juvenile structures in an ancestral species

homeotic genes

determine basic features such as where a pair of wings and a pair of legs will develop on a bird or how a plant's flower parts are arranged