Reproduction

• Asexual Reproduction


  Does not involve sex cells or fertilisation, only one parent is required, offspring are genetically identical to the parent and each other (clones)
• Asexual Reproduction


  • Bacteria binary fission
  • Plants using bulbs, tubers, runners
• Advantages of asexual reproduction in crop plants

  • Good characteristics (high yield, disease-resistant, hardy) can be reproduced asexually so entire crop will show same characteristics
• Sexual Reproduction


  Fusion of nuclei of two gametes (sex cells) to form a zygote (fertilised egg cell), offspring are genetically different from each other
• Gametes


  Sex cells (sperm and ovum in animals, pollen nucleus and ovum in plants) with haploid nuclei (half the number of chromosomes)
• Zygote


  Fertilised egg cell with diploid nucleus (full number of chromosomes)
• Advantages of sexual reproduction in crop plants

  • Increases variation, may produce genetic variants better able to cope with changes
• Disadvantages of sexual reproduction in crop plants

  • Variation may lead to offspring less successful than parent plant
• Parts of a flower

  • Anther
  • Stigma
  • Style
  • Ovary
  • Petal
  • Sepal
• Pollen of; Insect-pollinated flowers

  • Produce small amounts of larger, heavier pollen grains with spikes/hooks to stick to insects
• Pollen of; Wind-pollinated flowers

  • Produce large amounts of small, lightweight smooth pollen grains
• Pollination


  Transfer of pollen from anther to stigma
• Fertilisation


  Fusion of pollen nucleus and ovum nucleus to form zygote
• Pollen tube grows down style towards ovary containing ovules with female nuclei</b>
• Zygote divides to form seed within ovule
• Factors affecting seed germination


  • Water, oxygen, warmth
• Investigating seed germination


  • 4 boiling tubes with cress seeds, varying water, oxygen, temperature
• Self-pollination


  Pollen from one flower lands on its own stigma or another flower on the same plant
• Cross-pollination


  Pollen from one plant transferred to stigma of another plant of the same species
• Advantages and disadvantages of self- vs cross-pollination

  • Self-pollination reduces genetic variation, cross-pollination relies on pollinators
• Female reproductive structures


  • Ovaries
  • Fallopian tubes
  • Uterus
  • Cervix
  • Vagina
• Fertilisation


  Fusion of the nuclei from a male gamete (sperm cell) and a female gamete (egg cell)
• Comparison of Male & Female Gametes

  • Sperm cell
  • Egg cell
• Pregnancy: Growth & Development of the Fetus


  1. Zygote travels towards the uterus

  2. Zygote divides to form an embryo

  3. Embryo embeds in uterus lining (implantation)

  4. Embryo grows and develops into a fetus
• Placenta & Umbilical Cord

  • Fetus's blood supply connects to placenta
  • Placenta exchanges nutrients, oxygen, and waste between mother and fetus
  • Umbilical cord is cut after birth
• Secondary Sexual Characteristics


  • Changes that occur during puberty as children become adolescents
  • Controlled by release of hormones - oestrogen in girls and testosterone in boys
• The Menstrual Cycle


  • Controlled by hormones released from the ovary and the pituitary gland
  • Ovulation occurs around day 14
  • Failure to fertilise the egg causes menstruation
• Hormones of the Menstrual Cycle

  • FSH (follicle-stimulating hormone)
  • LH (luteinising hormone)
  • Oestrogen
  • Progesterone
• Interaction between all four of the menstrual cycle hormones

  1. FSH stimulates follicle development

  2. Follicle produces oestrogen

  3. High oestrogen triggers LH release, causing ovulation

  4. Corpus luteum produces progesterone

  5. Progesterone maintains uterus lining
• Where hormones involved in the menstrual cycle are made and act

  Pituitary gland, ovary, uterus
• Sexually Transmitted Infections (STIs) & HIV/AIDS


  • Unprotected sex can lead to transfer of pathogens
  • HIV infects and reduces lymphocytes, weakening the immune system
• How HIV Affects the Immune System

  1. Infects lymphocytes

  2. Reduces number of lymphocytes and antibodies

  3. Decreases ability to fight infections, leading to AIDS
• Controlling the Spread of STIs

  • Limiting number of sexual partners
  • Using condoms for protected sex
  • Getting tested after unprotected sex
  • Raising awareness through education
• Advantages of sexual reproduction

  • Increases genetic variation
  • Species can adapt to new environments due to variation giving them a 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
• advantages of sexual reproduction in crop plants

  • increase in variation
  • better able to cope with weather changes
  • produces significantly higher yield
• disadvantages of sexual reproduction in crop plants

  • offspring may be less successful than parent plant at growing well or producing good harvest
• Insect-pollinated flower


  • Large and brightly coloured to attract insects
  • Scent and nectar present - entices insects to visit the flower and push past stamen to get to nectar
• Pollen grains of insect pollinated flower


  • Moderate number - insects transfer pollen grains efficiently with a high chance of successful pollination
  • Larger, sticky and/or spiky to attach to insects and be carried away
• Anther of insect pollinated flower


  • Inside flower, stiff and firmly attached to brush against insects