Two species of garter snakes live in the same geographic area. One lives mainly in water and the other mainly on land; therefore, they rarely encounter each other and do not interbreed. What type of isolation is this?

The fish in a certain population average 10 millimeters in length. Imagine that a population of predatory birds arrives in the area, but they cannot eat fish longer than 15 millimeters. After a decade, if the fish average 14 millimeters in length, what probably happened?

The ant Myrmecia pilosula has the smallest number of chromosomes possible in a eukaryote: females possess only one pair of chromosomes, and males have only one chromosome! Put another way, female M. pilosula can be described as having the haploid condition n = 1 and the diploid condition 2n = 2. Based on this scenario as well as your knowledge of gamete formation, a female M. pilosula can produce gametes with ________ different sets of chromosomes. 

If the weather in Virginia changed so dramatically that there was snow on the ground most of the year, what would occur in the local squirrel population?

Based on your understanding of mitosis, explain the function of this process, where it takes place, and the result of this type of cell division.

A farmer noticed that two of her cotton plants produce cotton with a slight greenish hue. By repeatedly crossing the greenish plants, she has produced a variety of deep-green cotton without the use of any dyes. This is an example of:

If the allele for inflated pea pods (I) is dominant to the allele for constricted pods (i), then the cross Ii x ii is expected to produce: 

DNA replication is controlled by enzymes. 1)____________“unzips” the double helix by breaking hydrogen bonds, 2)___________ adds new nitrogenous bases to the exposed single strands, and 3) ____________ bonds short sequences together that are formed from the lagging strand (the strand that is “read” in the opposite direction).

If a bacterial protein is made from 30 amino acids, how many nucleotides are needed to code for its production? 

In the karyotype of a person with Down syndrome, or trisomy 21, an extra copy of chromosome 21 is apparent. This abnormality affects roughly 1 of every 700 children born and is the most common serious birth defect in the United States. People affected by Down syndrome often have cognitive difficulties, heart defects, and shortened life spans. Based on this scenario and your understanding of meiosis, what is the most likely explanation for the extra chromosome 21 in people with Down syndrome?