Leader: Kirsten Karkow
Course: Biol 211 - Wilsey
Date: 3/30/2012
Worksheet 24
Supplemental Instruction
Iowa State University
Define the following terms:
Sexual Dimorphism – when males and females of the same species have two distinct forms.
Biological Species Concept – individuals capable of successful reproduction are of the same
species.
Morphological Species Concept – individuals that look the same are of the same species.
Ecological Species – individuals adapted to the same niche are of the same species.
Hybrid Vigor – refers to the improved function of hybrid offspring.
Speciation – process by which one species splits into two or more species.
Allopatric Speciation – speciation occurring due to the formation of some geographical barrier.
Sympatric Speciation – speciation occurring while inhabiting the same geographical region
(usually due to the exploitation of different niches).
What process leads to speciation?
ISOLATION!
1. Gene flow between two populations is interrupted
2. Genetic differences gradually accumulate between the two populations.
3. Reproductive isolation evolves as a consequence of this divergence.
Describe the following PREZYGOTIC barriers:
1.
2.
3.
4.
5.
Habitat Isolation: living in different areas, so never mate
Temporal Isolation: mate at different times of the year, so never mate
Behavioral Isolation: have different displays (mating behavior), so never mate
Mechanical Isolation: have noncompatible anatomy, so never mate
Gametic Isolation: have noncompatible gametes, so fertilization never occurs
Describe the following POSTZYGOTIC barriers:
1. Hybrid Inviability: reduced ability of hybrid offspring to survive/grow
2. Hybrid Sterility: hybrid offspring survive/grow normally, but are sterile
3. Hybrid Breakdown: hybrid offspring are normal/vigorous, but F2 are inviable/sterile
Supplemental Instruction
1060 Hixson-Lied Student Success Center  294-6624  www.si.iastate.edu