Biodiversity chapter 20

Describe the biological species concept

The biological species concept defines a species as a group of populations whose members interbreed in nature to produce fertile offspring and are reproductively isolated from other such groups

list two potential problems with the biological species concept

It does not apply to asexually reproducing organisms or extinct species, some different species (such as wolves and coyotes) can interbreed successfully, blurring species boundaries

Explain the significance of reproductive isolating mechanisms

Reproductive isolating mechanisms prevent gene flow between species, allowing them to remain genetically distinct and enabling speciation

prezygotic barriers prevent

mating or fertilization

postzygotic barriers occur

after fertilization

prezygotic barriers ex

Habitat isolation, temporal isolation, behavioral isolation, mechanical isolation, gametic isolation

postzygotic barriers ex

Hybrid unviability, hybrid sterility, hybrid breakdown

Explain the mechanism of allopatric speciation

Allopatric speciation occurs when populations become geographically isolated, and gene flow stops. Natural selection and genetic drift cause populations to diverge until reproductive isolation evolves

example of allopatric speciation

Pupfish species that evolved in isolated desert pools after lakes dried up, or species on the Galápagos Islands

Explain the mechanisms of sympatric speciation

Sympatric speciation occurs within the same geographic area and happens through: Ecological shifts (change in resource use), and Polyploidy (especially in plants)

sympatric speciation ex

Plant example: Allopolyploid flowering plants that form new species through chromosome doubling.

Animal example: Apple maggot flies that shifted from hawthorn trees to apple trees

describe punctuated equilibrium

Long periods of little change interrupted by short bursts of rapid speciation

describe phyletic gradualism

Evolution occurs slowly and continuously over long periods

Define macroevolution

large-scale evolutionary change at or above the species level, including the origin of new species and major groups

Discuss macroevolution in the context of novel features and allometric growth

Macroevolution produces evolutionary novelties, which are modified pre-existing structures (preadaptation’s), such as feathers evolving from reptile scales

Allometric growth occurs when

different body parts grow at different rates, and small changes in developmental timing can result in major evolutionary differences

Adaptive radiation

the rapid diversification of a lineage into many species that fill different ecological niches, such as Hawaiian honeycreepers.

Extinction eliminates

species and creates empty adaptive zones, allowing surviving species to diversify; mass extinctions are often followed by adaptive radiation