LO 2 Biological World strand LO 4 Nature of Science strand
Contents
12.1 Types of reproduction. . . . . 126 12.2 Patterns of inheritance . . . . 129
Why it matters
Reproduction is essential for the long-term survival of a species and for life on the planet to continue. Understanding patterns in the inheritance of genetically controlled characteristics is important for the development of agriculture, industry and medicine. Genetic variation within species is the basis for the mechanism of evolution by natural selection.
Sexual
reproduction involves special male and female sex cells called gametes.
Asexual
reproduction A type of reproduction that occurs without using gametes and with only one parent.
Fertilisation is the fusion of male and female gametes to form a zygote.
Female 46 Chromosomes (23 pairs)
Zygote 46 Chromosomes in 23 pairs
Sperm 23 Chromosomes Male 126 46 Chromosomes (23 pairs) Fig. 1 Sexual reproduction in humans.
12.1 Types of reproduction Reproduction is the process by which living organisms produce other organisms of the same kind. Reproduction of new organisms is essential for the survival of a species. The new individuals (children) are often referred to as offspring.There are two main types of reproduction, sexual reproduction and asexual reproduction. Sexual reproduction involves special male and female sex cells called gametes. When
a male and female gamete join (fuse) they form a new cell called a zygote. This is called fertilisation. After fertilisation the zygote divides and grows into a new individual. Sexual reproduction occurs in both animals and plants. In some species, like humans, individual parents are either male or female and produce either male or female gametes. In other species, for example earthworms, individual parents can produce both male and female gametes. Many plants also produce both male and female gametes in their flowers. The offspring from sexual reproduction are genetically different to their parents. The offspring are also genetically different to each other. Sexual reproduction produces variation among offspring.
