When the Most Recent Glacial Period Ended, Ice Sheets That

question 17

Multiple Choice

When the most recent glacial period ended, ice sheets that had covered most of Canada retreated, and landscapes were opened up for plants and animals to colonize.In British Columbia, rivers and lakes were colonized by small fish called three-spined sticklebacks about 15,000 years ago.They swam upstream and became relatively isolated populations, each in their own small lake, separated by streams from other lakes.In each of at least six lakes in which they have been studied, there are species pairs; one species swimming close under the surface, snatching insects, the other swimming near the bottom, eating small crustaceans in the mud.This appears to be an example in which _______ may have led to rapid speciation.

• A) polyploidy
• B) sexual selection
• C) dietary specialization
• D) dispersal ability
• E) pollination type

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Definitions:

Heterozygous

Having two different alleles of a particular gene, one inherited from each parent.

Homozygous

An organism that has two identical alleles for a trait on both homologous chromosomes.

Dihybrid Cross

A genetic cross that takes into account the behavior of alleles of two loci. Compare with monohybrid cross.

Loci

Fixed positions on a chromosome where specific genes or genetic markers are located.