Sexual and Asexual Reproduction and Variation

Sexual Reproduction Sexual Reproduction is the creation of offspring using gametes which causes variation. Sexual Reproduction involves two organisms. Male and female gametes (sex cells) join together to create a new cell. This develops into a new individual. The joining of gametes is called fertilisation. Sexual Reproduction causes variation in the offspring because of the gametes. They contain half of the genes from the mother and half from the father. The offspring look a bit like each parent but not identical to them. Variety is important because if a species where all the same, a disease could cause the species to die out.

Advantages and Disadvantages of Sexual Reproduction Variety Reduces the chance of offspring inheriting a genetic disease Leads to continuous evolution Disadvantages There is the chance of not finding a mate Sexually transmitted diseases can be easily contracted There is no guarantee that offspring will be born

Examples of Sexual Reproduction Humans, animals

Gametes Gametes have half of the normal number of chromosomes. E.g.. The human body cell has 46 chromosomes but human gametes have 23. Fertilisation produces a new cell with the normal number of chromosomes- in the case of humans 46. Chromosomes are found in the nucleus of a cell. They contain a lot of genes. The different genes control the development of different characteristics in an organism. A gene is a section of DNA (deoxyribose nucleic acid) that carries the code for a particular protein. In humans and most animals, the female gametes are the eggs and the male gametes are the sperm.

Asexual Reproduction Asexual Reproduction involves only one organism and the offspring are exact clones of the parent. There is no variety in offspring from asexual reproduction because the offspring inherits all of the genes from the one parent, which means it is a natural clone. The differences between a daffodils sexually and asexually produced offspring is the sexually produced offspring contains half the genes of each parent, where as the asexually produced offspring contains all of one parents genes.

Advantages and Disadvantages of Asexual Reproduction More efficient way of passing on genes Don’t need to waste energy looking for a mate Disadvantages Negative characteristics will be passed on All offspring are the same- no variation There isn’t a chance of evolution

Examples of Asexual Reproduction Potatoe Plants, Daffodils, Spider Plant (Chlorophytum)