By Dr Adrian Mascia(Ph.D Biology, Education. M,

2009, teacher of the year

TYPES OF REPRODUCTION

Reproduction: The creation of a new generation of single cells, single celled organisms or multi-cellular organisms. The production of new organisms will always begin with the division of a single cell.

A–sexual:

Reproduction without the assistance of another organism

Sexual:

Requires two organisms of the same species to combine gametes to form a zygote

A-SEXUAL REPRODUCTIONThere are several methods of A-sexual reproduction

1. Fission2. Spore formation3. Budding4. Fragmentation5. Vegetative reproduction

A-sexual reproduction is very rapid, however does not provide genetic diversity, this can put at species at risk of extinction should conditions change

Fission

• Fission involves the replication of chromosomal DNA

• Once replication occurs, the DNA strands are attached at opposing ends of a cell membrane, and cell division occurs (giving rise to 2 identical cells)

• This is a very rapid process (exponential)• E.G Amoeba

Spore Formation• Spores are hardy, self

contained capsules containing DNA

• Spores are generally mass produced, and are very effective as they will only leave their dormant state when conditions become suitable (increasing chance of survial)

• E.G ferns, mosses, some prokaryotes and protists

Budding• Budding involves the

development of a new organism from the out growth of a parent organism.

• The new organism may detach at some point and become a stand alone organism

• E.G Hydra, some flat worms, yeast cells

Fragmentation• Some organisms such as

sponges have the ability to fragment as well as re-construct themselves

• A sponge can be broken into many pieces, forming many new organisms

• Can also reform a new organism from fragments

Vegetative Propagation• There are some species

of plants from which you can regrow a clone of the original plant by planting cuttings

• This process also allows for a process called grafting, where two different plant cuttings (root and shoot) can be combined to produce a new plant

SEXUAL REPRODUCTION

• Basic process of Meiosis (two gamete cells fusing to form a zygote)

• Creates genetic diversity (essential for the survival of a species)

• Not as fast as A-sexual reproduction

Sexual reproduction in Uni Cellular organisms

• Common misunderstanding that single celled organisms reproduce only A-sexually

• If this were the case we would not see the amazing diversity of single celled organisms

• Several protozoan have the ability to produce gametes

• Generally one gamete is larger and sedentary and one is smaller and mobile (much like in humans)

• Paramecium does not involve gamete production, rather an exchange of genetic material whilst lined up along side one another. This process is called CONJUGATION