sexual reproduction life cycles and the alternation of generations

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

Sexual reproduction in plants The diploid

sporophyte produces haploid spores by meiosis.

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

Sexual reproduction in plants In plants such as

mosses and ferns, the main plant is the diploid sporophyte.

It produces (genetically different) haploid spores by meiosis

Sexual reproduction in plants The spore grows

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

Sexual reproduction in plants 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 knowSpore A haploid cell that can be dispersed It is the product of meiosis of a diploid cell

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

zygote

Essential terms to knowSporophyte A multicellular plant that is diploid and

produces spores.

Essential terms to knowGametophyte A multicellular plant that is haploid and

produces gametes

Essential terms to knowNB These terms have been defined in terms of

plant kingdoms. A fungal spore is very different!!!!

Essential terms to knowAlternation 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”