Chapter 7.1: Reproduction May Be Asexual or Sexual

Flashcards from Chapter 7.1 of Principles of Life, 3rd Edition.

Cell division

The process by which one cell gives rise to two cells; can be:

1. Asymmetrical (mother cell is unchanged and has several differences, like in yeast, plants, or animals)

2. Symmetrical (cells are identical to each other, like in bacteria)

Multicellular organisms may exhibit both types, ranging from reproduction to replenishment

Asexual reproduction

Reproduction through the cloning of a parent organism, with occasional variation arising from mutations

Binary fission

The division of a parent cell to form two identical daughter cells; is a type of asexual reproduction in single-celled prokaryotes

• Similar to mitosis in eukaryotes

Sexual reproduction

Reproduction through cells called gametes that fuse together and create a genetically distinguishable offspring

• Requires that gametes have half the amount of DNA required

• Only occurs in eukaryotes

Meiosis

Cell division that results in the production of gamete daughter cells, with only half the DNA of the original cell

Somatic cell

Any cell in the body of a multicellular organism not specialized for reproduction, derived by mitosis

• Are typically diploid, containing two paired sets of chromosomes

Diploid cells

Cells that contain two paired sets of chromosomes (one from each parent), containing homologous pairs made of homologs

• Has a chromosome number denoted by 2n, containing two sets of n chromosomes

Homologous pairs

A set of two chromosomes nearly identical in length and sequence, with one set coming from the mother, and the other set coming from the father

• In human somatic cells with 46 chromosomes, 23 come from each parent

Homologs

The two chromosomes in a homologous pair, with corresponding (but not identical) genetic information

Haploid cells

Cells that only contain a single set of chromosomes, not containing homologs

• These include gametes

• Has a chromosome number denoted by n, containing one set of n chromosomes

Zygote

A diploid cell formed out of the fusion of two haploid gametes through fertilization

• This then undergoes several mitotic cell divisions, resulting in a mature organism

• Has a chromosome number denoted by 2n, containing two sets of n chromosomes

Fertilization

The process of fusing two haploid gametes into one diploid zygote

Sexual life cycle

In organisms, these are diverse, but essentially break down to one of the two homologs of each diploid chromosome pair to create a haploid gamete for fusion

• Some have gametes that develop immediately after meiosis, and then fuse in fertilization

• Others have haploid cells from meiosis dividing and developing into a haploid organism, that eventually produces gametes by mitosis for fertilization and a diploid life stage

Haplontic life cycle

A type of sexual life cycle where the diploid zygote immediately undergoes meiosis and essentially all of the life cycle is haploid

Diplontic life cycle

A type of sexual lifecycle where the haploid gametes immediately undergo fertilization and essentially all of the life cycle is diploid

Haplo-diplontic life cycle

A type of sexual life cycle where the organism spends significant time in both haploid and diploid stages