Reproduction

• Define sexual reproduction

  The fusion of male and female gametes to produce offspring which are genetically different
• How many chromosomes does a gamete have and what is it called?

  23

  Haploid
• How many chromosomes does a zygote have and what is it called?

  46

  Diploid
• How does sexual reproduction occur? Define it.

  Meiosis - egg and sperm dude to form a cell with full chromosomes.
• Advantages and disadvantages of sexual reproduction

  - can adapt to new environments due to variation

  - disease less likely

  
  

  -limited number produced

  -takes time and energy to find mates
• Define asexual reproduction


  Only one parent involved, in which offspring are genetically identical to (clones)
• How does asexual reproduction occur? Define it.

  Mitosis: cell division
• Advantages and disadvantages of mitosis

  - large numbers produced

  
  

  - disease is likely to affect population due to no genetic variation

  - may only be suited for one habitat/vulnerable to change in conditions
• Differences between sexual and asexual reproduction

  Sexual: - genetic variation

  - offspring inherits features from both parents

  
  

  Asexual: - no fusion of gametes

  - no variation
• What is the role of the placenta and why is it important?

  Supplies the baby with food and oxygen

  Mother's blood absorbs waste products from fetus' blood (CO2, urea)
• What is the role of FSH?

  Stimulates egg cell to develop

  Stimulates ovaries to release oestrogen
• What is the role of LH?


  Stimulates release of egg (ovulation)
• Describe the role and trend of oestrogen


  - rises from day 1-14

  - simulates the uterus to develop a lining to replace the lining lost during menstruation

  - peaks just before egg is released

  - stimulates release of LH and inhibits release of FSH
• Describe the role and trend of progesterone


  - low from day 1-14

  - maintains uterus lining.

  - fall in progesterone levels causes the uterus lining to break down (menstruation)

  • inhibits release of LH and FSH
• How is the sperm adapted?

  - flagellum (tail): swim to egg

  - many mitochondria: provide energy or flagellum to move back and forth

  - enzymes in head: digest through the jellycoat and cell membrane of egg cell
• What is the function of the oviduct?

  Eggs released into it, site of fertilization
• What is the function of the uterus?

  Where fertilized egg implants
• Characteristics of insect-pollinated plants

  - bright petals and sweet smelling nectar: attract insects

  - large and sticky pollen grains

  - anther inside flower, stiff and firmly attached: brush against insects

  - stigma inside flower, sticky: so pollen grain sticks to it when insect brushes past
• Describe the process of insect pollination

  - insect lands on flower to collect nectar, and pollen grain from anther brushes onto insect

  - insect moves to another flower and transfers pollen grain to stigma which is sticky
• Characteristics of wind-pollinated plants


  - No scent and lightweight: no need to attract insects

  - anther outside flower, on long filaments: to release pollen grain easily

  - small and light pollen grains

  - stigmas outside flower, long and feather: catch pollen
• Describe the process of wind pollination


  Wind carries the small and light pollen to the stigma of another flower
• Describe the process of fertilization in plants

  - pollen grain lands on stigma

  - pollen tube grows down the style, to ovary

  - it penetrates the ovule

  - nuclei fuse and form a zygote

  - ovule develops into seed, ovary wall develops into fruit
• Describe a natural method of asexual reproduction in plants

  Strawberry runners

  - grow side branches which young plants grow from

  - once they touch the soil, they grow roots
• Describe an artificial method of asexual reproduction in plants

  Cuttings

  - remove a branch from the parent plant

  - dip the end in rooting powder which contains plant hormones that encourage root growth

  - the cutting is planted and grows
• State the conditions needed for germination

  Water

  Oxygen

  Warmth
• Why is water needed for germination?

  Allows the seed to swell up, and the seed coat to burst, and the growing embryo plant to exit the seed
• Why is oxygen needed for germination?

  For respiration, so that energy can be released for germination
• Why is warmth needed for germination?


  Enzymes work faster at high temperature