Reproduction is how organisms produce offspring. There are two main types of reproduction: asexual reproduction, where one parent produces offspring identical to itself, and sexual reproduction, where two parents produce unique offspring. A key part of sexual reproduction is meiosis, which produces gametes (reproductive cells) with half the usual number of chromosomes. During fertilization, a male gamete joins with a female gamete to form an offspring cell containing genes from both parents.
Asexual Reproduction: Reproduction involving a single parent.
Sexual Reproduction: Reproduction involving two parents.
Gamete: Reproductive cells.
Haploid: Cell having only one chromosome of each type.
Diploid: Cell having two of each type of chromosome (twice the amount of chromosomes in haploids).
Fertilization: Process in which two gamete cells unite.
Zygote: A fertilized cell (the result of fertilization).
Meiosis: Cell division where the number of chromosomes is cut in half (results in haploids).
Gametogenesis: Process where haploid cells become gametes.
Crossing-Over: When genetic information is exchanged between homologous chromosomes.
Independent Assortment: When cells divide in meiosis, each individual chromosome is separated randomly and independently.
In asexual reproduction, all offspring produced are identical to the parent and to themselves
Types of asexual reproduction:
Asexual reproduction allows organisms such as bacteria to reproduce very quickly.
Sexual reproduction produces unique offspring whose cells contain a mix of chromosomes from the 2 parents
(both daughter cells from Meiosis I go through this):
At this point after meiosis, the four haploid cells are NOT gametes yet. The cells develop to become gametes in a process called gametogenesis. Male gametes are called sperms, female gametes are called eggs.
Sexual reproduction results in genetic variation for several reasons:
Life cycle of sexually reproducing organisms:
Sexually reproducing organisms can have different types of lifestyles: