Question

1.Natural selection operates at the population level while evolution operates on individuals. True or False

2. Because mules (a cross between a horse and a donkey) are sterile, they cannot be considered a species. True or False

3.Transposable elements are DNA sequences that a. can copy themselves into entirely new areas of the chromosomes. b. occur only on the X and Y chromosomes. c. contain numerous point mutations. d. are not coded to produce proteins.

Answer 1

1. False

the statement is false as natural selection acts on individuals while population evolve and not the individuals. Thus, individual organisms do not evolve and retain same genes throughout the life

2. True

In few cases two different species mate to produce an offspring which is infertile. For example female horse and male donkey reproduce to produce infertile mules. Since mules are sterile, not able to reproduce these cannot be classified as a distinct species.

3 a. can copy themselves into entirely new areas of the chromosomes.

Transposable elements (TEs) are the DNA sequences, able to move from one location to another in the genome and these code for enzymes and cause insertion of an identical copy of themselves into a new DNA site. Transposable elements are of two types (I) simple transposons that do not code for protein and (ii) complex transposons have genes that codes for one or more proteins. Often cause mutations, either by inserting into another gene and disrupting it or by promoting DNA rearrangements such as chromosome deletions, duplications, and inversions.