Bio- Unit 7

Biological species concept

defines a species as members that have the potential to interbreed in nature and produce viable, fertile offspring, but are not able to produce viable, fertile offspring with members of other populations

Prezygotic barriers

mechanisms that prevent successful mating between species or hinder fertilization of egg

Postzygotic barriers

prevent hybrids from developing into viable fertile offspring

Habitat Isolation

two species occupy different habitats encounter each other rarely, if at all

Behavioral Isolation

specific courtship rituals attract mates

Temporal Isolation

species breed at different times (AM/PM, seasons, years)

Mechanical Isolation

morphological differences, such as sexual organs incompatibility

Gametic Isolation

sperm from one species cannot fertilize egg from another

Reduced hybrid viability

the genes of different parent species may interact and impair the hybrid's development

Reduced hybrid fertility

when hybrid is viable, it may be sterile. Meiosis in the hybrids may fail to produce normal gametes, rendering them incapable of successfully mating with either parent

Hybrid breakdown

some first generation offspring are viable and fertile. However, when mated back to a parent species, offspring of the next generation is infertile

morphological species concept

characterizes a species by its body shape, size, and other features

paleontological species concept

the morphological concept applied to fossils

ecological species concept

defines a species in terms of ecological niche (all biotic and abiotic resources used in an environment)

phylogenetic species concept

defines a species as a set of organisms with a unique derived characteristic (most terminal twigs of tree of life)

allopatric speciation

gene flow is interrupted when a population is geographically divided into isolated subpopulations

sympatric speciation

speciation occurs in geographically overlapping populations

Adaptive radiation

rapid emergence of numerous species from a common ancestor introduced into an environment that presents a diversity of new opportunities and challenges

Habitat differentiation

occupation of a slightly distinct habitat can lead to reproductive isolation

Sexual selection

selection of mates based upon appearance

exaptation

biological adaptation where the function currently performed by the adaptation was not the function performed while the adaptation evolved via natural selections; e.g., feathers