Variation Variation is a name given to differences in a species, e.g. dogs: Variation is due to each animal having different GENETIC INFORMATION in their cells.
Where is this information stored? Section of a chromosome: Genes for blood group: Genes for eye colour Genes for hair colour Genetic information is stored by genes which are arranged on chromosomes: Different species have different numbers of chromosomes. Humans have 46 (23 pairs) in every cell.
Environmental differences Clearly, not all differences are due to just our genes…
Sexual reproduction Sexual reproduction involves two organisms of the same species. Each organism produces a GAMETE. For example, in animals the gametes are the egg and the sperm: When the sperm penetrates the egg the egg is fertilised and cells start to reproduce to form a new individual:
Sexual reproduction Fertilisation In plants, the gametes are the egg and pollen: Any type of sexual reproduction helps a species to become more varied because the offspring inherit characteristics from both parents.
Selective breeding I raise cows. Each type of cow is good at a certain job. The Friesian cow produces large quantities of milk, the Jersey cow produces very nice milk and the Hereford cow produces lot of beef. Friesian Jersey If, for example, I want lots of milk I would only breed Friesian cows with each other – this is SELECTIVE BREEDING. Hereford
Asexual reproduction Plants can reproduce ASEXUALLY. The offspring are genetically ________ to the parent plant and are called _________. Two examples: 1) This spider plant has grown a rooting side branch (“stolon”) which will eventually become __________. 2) A gardener has taken cuttings of this plant (which probably has good characteristics) and is growing them in a ____ atmosphere until the ____ develop. Words – clones, damp, independent, roots, identical
Cloning 1) Cloning plants: 2) Cloning sheep: