Sexual Reproduction

Sexual reproduction

Life cycles and the alternation of generations

Sexual reproduction in animals

Animals have diploid body cells and haploid gametes

The diploid body cells are made by mitosis The haploid gametes are made by meiosis At fertilization the haploid sperm and egg

fuse to produce the diploid zygote. This then divides many times by mitosis to

grow into a new individual

Sexual reproduction in plants

In flowering plants there are two distinctive phases of life cycle:

the diploid sporophyte and the haploid gametophyte


The diploid sporophyte produces haploid spores by meiosis.

The spores develop into the haploid gametophyte, which then produces haploid gametes by mitosis


In plants such as mosses and ferns, the main plant is the diploid sporophyte.

It produces (genetically different) haploid spores by meiosis

http://www.mbari.org/~conn/botany/browns/james/Web%20Page%20Work/spora2.htm


The spore grows into the gametophyte, which produces (genetically identical) gametes by mitosis.


In flowering plants the water dependent gametophyte stage in the life cycle is much reduced.

The dominant stage in the life cycle is the sporophyte

Essential terms to know

Spore A haploid cell that can be dispersed It is the product of meiosis of a diploid cell


Gamete A haploid cell, produced by mitosis of haploid cells. It can fuse with another gamete to produce a diploid

zygote


Sporophyte A multicellular plant that is diploid and

produces spores.

http://www.mpm.edu/collect/botany/ferns.html


Gametophyte A multicellular plant that is haploid and

produces gametes


NB These terms have been defined in terms of plant kingdoms. A fungal spore is very different!!!!


Alternation of generations Terrestrial plants that have a life cycle with a

multicellular gametophyte and multicellular sporophyte generation which alternates are said to have a life cycle that shows “alternation of generations”

Health & Medicine

Sexual Reproduction