Sexual Reproduction

• Sexual reproduction - the process involving the fusion of the nuclei of two gametes (sex cells) to create a zygote (fertilised egg cell) where the offspring is genetically different from eachother

  • involves two parents
  • offspring is similar but not identical
  • variation comes from the different DNA in the two gamete combining
• Fertilisation - the fusion of gamete nuclei
• Zygote - fertilised egg/ovule cell
• Gamete - a sex cell

  • animals - sperm and ovum/egg cell
  • plants - pollen nucleus and ovum
• Haploid - the presence of only one set of chromosomes in a cell

  • nuclei of gametes are haploids
  • half the chromosomes of a normal body cell
  • humans - 23 chromosomes, half set of chromosomes
• Diploid - the presence of two sets of chromosomes where one set comes from each parent, two of each chromosome

  • same number of chromosomes as a normal body cell
  • humans - 23 PAIRS of chromosomes, full set of chromosomes
  • nuclei of zygotes are diploids
  • a zygote is still a diploid when its developing into a fetus or embryo during the pregnancy
• • Haploid and Diploid comparision

  A) haploid

  B) diploid

  
• Gametes only have half of the chromosomes than other cells in the body aka haploid nucleus

  • only contain one copy of each chromosome unlike two copies found in other body cells
  • normal body cell contains 46 chromosomes while gametes only contain 23 - half of a normal body cell
• Male and female gametes fuse to create a zygote, allowing them to create the full 46 chromosomes aka diploid nucleus

  • half from father and half from mother
• • Advantages and disadvantages of sexual reproduction:
  • For plants, energy is used to improve appearance or pollen volume which wastes energy (disadvantage)

  A) genetic variation

  B) adapt

  C) variation

  D) survival advantage

  E) diseases

  F) variation

  G) time and energy

  H) maters

  I) isolated members

  J) reproduce

  
• Advantages and disadvantages for species in the wild:

  • advantages:
  • more pest and diseases resistant which gives them greater survival advantage
  • there’s variation which allows them to adpat quickly to conditions
  • disadvantages:
  • requires 2 parents which is difficult in the wild
  • the process can be too slow
• Advantages and disadvantages for farming:

  • advantages:
  • variation is increased which allows crops to better deal with weather changes and create higher yields
  • has more resistance so a whole population won’t die out
  • selective breeding - can increase food production
  • disadvantages:
  • variation can create offspring that isn’t as good as the parent, leading to a bad harvest
  • takes too long and energy costly
• Meiosis - a type of cell division that results in the production of four genetically different daughter cells from a single parent cell

  • creates the gametes
• Sexual reproduction allows natural selection and evolution (advantage)
• Sexual reproduction can maintain or increase a population (advantage)
• Sexual reproduction increases genetic diversity within populations (advantage)
• Sexual reproduction takes place in:

  - animals

  - plants

  - fungi
• remember the haploid is always half of normal body cells and this applies to all types of organisms
• Define Sexual reproduction

  The fusion of the nuclei of two gametes (sex cells) to create a zygote which leads to the production of a genetically different offspring
• Define Diploid

  the presence of two sets of chromosomes where one set comes from each parent, two of each chromosome. Its usually 23 PAIRS of chromosomes aka a full set.
• Define Haploid


  The presence of only one set of chromosomes in a cell. 23 chromosomes which is a half set.
• What are the differences between asexual and sexual reproduction?

  Asexual: One parent, offspring identical to parent, gametes aren't needed Sexual: Two parents, offspring genetically unique, gametes are needed
• Phenotype - observable features of an organism
• Define meiosis


  A reduction division that turns diploid cells to haploid cells for the production of gametes