Chapter 16. Reproduction IGCSE BIOLOGY 0610

• 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
• Asexual Reproduction


  • Produces genetically identical offspring
  • Does not involve fusion of gametes or mixing of genetic information
• Gametes


  Sex cells (sperm and ovum in animals, pollen nucleus and ovum in plants)
• Haploid


  Gametes contain half the number of chromosomes of normal body cells
• Diploid


  Zygote and other body cells contain the full number of chromosomes
• Pollination


  Transfer of pollen from anther to stigma
• Insect-pollinated flowers


  • Produce small amounts of larger, spiky pollen grains to stick to insects
  • Have nectar and bright petals to attract insects
• Wind-pollinated flowers


  • Produce large amounts of small, smooth pollen grains
  • Have no nectar or petals, have feathery stigmas to catch wind-blown pollen
• Pollination and Fertilisation


  1. Pollen grain lands on stigma

  2. Pollen tube grows down to ovary

  3. Pollen nucleus fuses with ovum nucleus to form zygote
• Pollination and fertilisation are not the same - pollination is the transfer of pollen, fertilisation is the fusion of nuclei
• Factors affecting seed germination

  • Water, oxygen, warmth (not carbon dioxide)
• Investigating seed germination


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


  Pollen from one flower fertilises the same flower or another on the same plant
• Cross-pollination


  Pollen from one plant fertilises another plant of the same species
• Female reproductive structures


  • Ovaries
  • Fallopian tubes
  • Uterus
  • Cervix
  • Vagina
• Vule followed by fertilisation

  1. Vule

  2. Fertilisation
• Your notes
• Male reproductive system


  Male reproductive structures and their function
• Female reproductive system


  Female reproductive structures and their function
• Fertilisation


  Fusion of the nuclei from a male gamete (sperm cell) and a female gamete (egg cell)
• Fertilisation occurs in the oviducts
• Gametes


  • Adaptations to increase the chances of fertilisation and successful development of an embryo
• 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 continues to grow and develop

  5. Gestation period is 9 months

  6. Major organ development in first 12 weeks

  7. Embryo becomes a fetus
• Amniotic sac


  Surrounds the fetus and contains amniotic fluid
• Umbilical cord


  Joins the fetus's blood supply to the placenta for exchange of nutrients and removal of waste products
• The Placenta & Umbilical Cord: Extended

  1. Fetus develops and grows by gaining nutrients from mother's blood

  2. Bloods run opposite in placenta, never mixing

  3. Fetus's blood connects to placenta via umbilical cord

  4. Mother's blood absorbs fetal waste in placenta

  5. Molecules cross placenta by diffusion due to concentration gradients

  6. Placenta has large surface area and thin wall for efficient diffusion

  7. Placenta acts as barrier to prevent toxins/pathogens entering fetus

  8. Umbilical cord cut after birth, placenta detaches and is expelled
• Exam Tip: Learn at least two specific substances that move across the placenta
• Primary sexual characteristics


  Differences in reproductive organs between males and females, present during development in the uterus
• Secondary sexual characteristics


  Changes that occur during puberty as children become adolescents, controlled by release of hormones
• Female secondary sexual characteristics


  • List of characteristics
• Male secondary sexual characteristics


  • List of characteristics
• Some changes occur to both boys and girls, including growth of sexual organs and body hair. Emotional changes also occur due to increased hormone levels.
• Menstrual cycle


  Controlled by hormones, starts in early adolescence in girls, average cycle is 28 days
• Changes in the lining of the uterus during the menstrual cycle

  1. Uterine lining thickens after menstruation

  2. Egg released around day 14 (ovulation)

  3. Uterine lining breaks down if egg not fertilised, causing menstruation
• FSH (follicle-stimulating hormone)


  Released by pituitary gland, causes egg to start maturing in ovary and stimulates ovaries to release oestrogen
• LH (luteinising hormone)


  Released by pituitary gland when oestrogen levels peak, causes ovulation and stimulates ovary to produce progesterone
• Oestrogen


  Causes uterine lining to thicken and egg to mature
• Progesterone


  Maintains thickened uterine lining, drop in levels causes menstruation