8.3.1 Sexual Reproduction and the Role of Meiosis

Question 1

asexual reproduction

Answer 1

• involves a single parent that produces genetically identical offspring. Bacteria reproduce asexually
  by a process called binary fission. Corals reproduce asexually by budding off offspring.

Question 2

sexual reproduction

Answer 2

• involves two parents who combine their genes to produce genetically unique offspring.

Question 3

diploid cells

Answer 3

• are cells that have two sets of chromosomes (each set is derived from a parent)

Question 4

somatic cells

Answer 4

• are diploid cells that make up the body of the organism. Early in an individual’s development, a select number of diploid cells will be set aside to undergo a process called meiosis, in which the resulting haploidcells will have only one set of chromosomes
  (half that of diploid cells). The haploid cells that result from meiosis will be able to take part in sexual reproduction, thus they are called sex cells, or gametes
• the cells that make up the body of an organism. Somatic cells cannot take part in sexual reproduction because they have too many chromosomes. In the diagram on the left, two cells with 46 chromosomes will
  produce a cell with 92 chromosomes. The goal of sexual reproduction is offspring that have the same number of chromosomes as the parents, in this case 46.

Question 5

note

Answer 5

• Natural selection can favor sexual reproduction, as opposed to asexual reproduction, because sexual reproduction results in a greater variety of offspring. Sexual reproduction involves combining of genes of two parents and the formation of recombinants, offspring that have a new combination of genes. A greater variety of offspring increases the likelihood of survivorship in an uncertain environment.

Question 6

gametes

Answer 6

• so called sex cells or germ cells) are the cells
  that take part in sexual reproduction. The number of
  chromosomes in a gamete is half of that found in a somatic cell from the same organism. To become gametes, cells must undergo a reductive division called meiosis. After meiosis, human gametes have 23 chromosomes (recall that human somatic cells have 46 chromosomes). A sperm with 23 chromosomes can fertilize an egg that has 23 chromosomes to produce an offspring that has 46 chromosomes.

Question 7

In sexual reproduction

Answer 7

• gametes are usually haploid

Question 8

True or false?

There are no known animal species that reproduce asexually.

Answer 8

• false

Question 9

Bacteria most commonly reproduce by a method called

Answer 9

• Neither A nor B.

Question 10

Yeast, a single-celled fungi, often replicates by pinching off into two unequal sized cells. This process is called

Answer 10

• budding

Question 11

An animal cell with one set of chromosomes rather than two has a ______________ chromosome number.

Answer 11

• haploid

Question 12

__________ cells do not directly take part in sexual reproduction, while __________ cells do.

Answer 12

• Somatic; germ