BIOLOGY 101 Lecture Notes - Lecture 25: Body Plan, Reproductive Isolation, Macroevolution
Document Summary
Macroevolution: evolutionary change above the species level: origins of a new species. Biological: key trait: reproduction, definition: no actual or potential interbreeding, data needed: behavior and offspring fertility, challenges: asexual, rare, and hybrids. Morphological: key trait: appearance, definition: consistently different in body form, data: preserved body forms, challenges: subjective. Phylogenetic: key trait: genetics, definition: divisible into mutually exclusive groups, data: dna sequence, challenges: subjective. Reproductive isolation: when biological factors make two individuals incapable of interbreeding to produce fertile offspring: caused by pre-zygotic and post-zygotic barriers. Mechanical isolation: mating may be attempted, but is prevented by morphological differences. Gametic isolation: sperm of one species cannot fertilize the eggs of another species. Postzygotic barrier: prevents viability or fertile hybrids. Reduced hybrid viability = hybrids have a high mortality rate. Reduced hybrid fertility = hybrids cannot reproduce. Hybrid breakdown: initial hybrids are vigorous and fertile, but subsequent generations are not viable.
