Reproduction

what is a gamete?

a sex cell eg sperm and ovum, pollen nucleus and ovum

how do gametes differ from normal cells?

contain half the number of chromosomes than in other body cells = haploid nucleus

only contain one copy of each chromosome

what happens when male and female gametes fuse?

they become a zygote with 46 chromosomes = diploid nucleus

advantages of sexual reproduction

• increases genetic variation

• species can adapt to new environments due to variation = survival advantage

• disease less likely to affect population

disadvantages of sexual reproduction?

• takes time and energy to find mates

• difficult for isolated members of the species to reproduce

what is asexual reproduction?

• does not involve gametes or fertilisation, only one parent required

• offspring genetically identical to parent and each other

advantages of asexual reproduction

• population can be increased rapidly when conditions are right

• can exploit suitable environments quickly

• more time and energy efficient

• reproduction is completed much faster than sexual reproduction

disadvantages of asexual reproduction

• limited genetic variation in population

• population vulnerable to changes in conditions and may only be suited to one habitat

• disease likely to affect the whole population

features of asexual reproduction

• one parent organism

• offspring produced by mitosis

• offspring genetically identical to each other and the parent

• genetic variation only from mutation

• usually large numbers of offspring produced

• offspring usually produced quickly

features of sexual reproduction

• two parent organisms

• offspring produced from the fusion of two haploid gametes, which are produced by meiosis

• offspring genetially unique and genetically different from both parents

• three sources of variation (50% of dna from each parent, production of gametes by meiosis, random distribution of chromosomes into gametes during meiosis)

• usually limited numbers of offspring produced

• offspring usually produced relatively slowly