bio final ch24.txt

The process by which one species splits into two or more species.

A species is a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring, but do not produce viable, fertile offspring with members of other such groups.

The existence of biological factors (barriers) that impede members of two species from interbreeding and producing viable, fertile offspring.

Offspring that result from an interspecific mating.

• Prezygotic barriers block fertilization from occurring. Barriers are:
• 1. Habitat Isolation
• 2. Temporal Isolation
• 3. Behavorial Isolation
• AFTER MATING ATTEMPT
• 4. Mechanical Isolation
• 5. Gametic Isolation

• Postzygotic barriers prevent a hybrid zygote from developing into a viable, fertile adult. Barriers are:
• 1. Reduced Hybrid Viability
• 2. Reduced Hybrid Fertitlity
• 3. Hybrid Breakdown

The morphological species concept characterizes a species by body shape and other structural features.

The ecological species concept views a species in terms of its ecological niche, the sum of how member of the species interact with the nonliving and living parts of their environment.

The phylogenetic species concept defines a species as the smallest group of individuals that share a common ancestor, forming one branch on the tree of life.

In allopatric speciation (latin for "other country"), gene flow is interrupted when a population is divided into geographically isolated subpopulations. Remember the fish in different ponds graphic.

In sympatric speciation (latin in "same country"), speciation occurs in populations that live in the same geographic area. Remember the fish in different ponds graphic.

A species may originate from an accident during cell division that results in extra sets of chromosomes.

An autopolyploid (from the Greek autos, self) is anindividual that has more than two chromososme sets that are al derived from a single species.

In subsequent generations, various mechanisms can change a sterile hybrid into a fertile polyploid.

• - Extinction
• - Speciation
• 1. Anagenesis
• 2. Cladogenesis

- Gradualism - change of time

- Puntuated Equilibrium - change at a specific point in time