first exam.

done with my first

exam of the Fall Semester

stoked!

ONLY THAT

my mind went blank on this

ONE subject!

isolating mechanisms

straight brain dead.

i knew it like crazy!

just not when i needed it the most.

isolating mechanisms. for reference.

The reproductive characteristics which prevent species from fusing. Isolating mechanisms are particularly important in the biological species concept, in which species of sexual organisms are defined by reproductive isolation, i.e. a lack of gene mixture. Two broad kinds of isolating mechanisms between species are typically distinguished, together with a number of sub-types

Pre-Mating Isolation.
a) Temporal isolation. Individuals of different species do not mate because they are active at different times of day or in different seasons.

b) Ecological isolation. Individuals mate in their preferred habitat, and therefore do not meet individuals of other species with different ecological preferences.

c) Behavioral isolation. Potential mates meet, but choose members of their own species.

d) Mechanical isolation. Copulation is attempted, but transfer of sperm does not take place.2)

Post-mating isolating mechanisms.

Genomic incompatibility, hybrid inviability or sterility.
a) Gametic incompatibility. Sperm transfer takes place, but egg is not fertilized.

b) Zygotic mortality. Egg is fertilized, but zygote does not develop.

c) Hybrid inviability. Hybrid embryo forms, but of reduced viability.

d) Hybrid sterility. Hybrid is viable, but resulting adult is sterile.

e) Hybrid breakdown. hybrids are viable and fertile, but further hybrid generations. may be inviable or sterile.