reproduction

• Sexual reproduction


  The process involving the fusion of the nuclei of two gametes to form a zygote (fertilised egg cell) and the production of offspring that are genetically different from each other
• Fertilisation


  The fusion of gamete nuclei, resulting in variation in the offspring since each gamete comes from a different parent
• Gametes


  Sex cells, such as sperm and ovum (eggs) in animals, and pollen nucleus and ovum in plants. They contain half the number of chromosomes found in other body cells and are haploid
• Human gametes contain 23 chromosomes, half of the normal 46 found in other body cells because they only contain one copy of each chromosome
• Asexual reproduction


  The process resulting in genetically identical offspring being produced from one parent, without involving gametes or fertilisation
• Offspring produced by asexual reproduction are genetically identical to the parent and to each other, as there is no fusion of gametes and no mixing of genetic information, resulting in clones
• Advantages of sexual reproduction

  • Allows for genetic variation among offspring, which can increase the chances of survival in changing environments and help in evolution
• Disadvantages of sexual reproduction

  • Requires the production of specialised gametes and the search for a mate, which can be energetically costly and time-consuming
• Advantages of asexual reproduction

  • Efficient in rapidly producing numerous offspring, requires only one parent, and ensures the preservation of favourable traits
• Disadvantages of asexual reproduction


  • Lacks genetic variation, making offspring vulnerable to changes in the environment. It may also lead to the accumulation of harmful mutations and limit adaptability to new conditions
• Meiosis


  The type of cell division required for sexual reproduction
• Fertilisation


  The fusion of gamete nuclei, resulting in the formation of a zygote
• Fertilisation in humans


  Involves the fusion of a sperm cell with an egg cell
• Zygote


  A fertilised egg cell formed by the fusion of gamete nuclei
• Fertilisation leads to variation in offspring
• Fertilisation involves the fusion of gametes from different parents
• Embryo


  The early developmental stage of a multicellular organism that is produced after cell division of a zygote
• Pollination


  The process of transferring pollen from the anther (male part) to the stigma (female part) of a flower
• Mechanisms of pollination


  • Insect pollination
  • Wind pollination
• Pollen is not capable of locomotion. It requires a mechanism such as wind, water or insects to transfer it from place to place
• Adaptations of insect-pollinated flowers


  • Sticky pollen and nectar-producing glands to attract insects, brightly coloured petals and attractive smells
• Adaptations of wind-pollinated flowers


  • Produce large amounts of lightweight pollen and have exposed stigmas to catch the pollen carried by the wind
• Cross-pollination


  Pollen from one plant is transferred to the stigma of another plant of the same species
• Self-pollination


  Pollen from a flower lands on its own stigma or on the stigma of another flower on the same plant
• Pollination is crucial for plant reproduction as it facilitates the transfer of pollen, leading to fertilisation and the production of seeds and fruits
• Petals of insect-pollinated flowers tend to be brightly coloured to attract pollinator insects
• Adaptations of anthers in wind-pollinated plants


  • Swinging on long filaments outside of the flower to transfer pollen to the wind
• Fertilisation in plants


  The process in which the nucleus of a male pollen grain fuses with the nucleus of an ovum in the ovary, leading to the formation of a zygote
• Fertilisation in plants


  The pollen grain nucleus fuses with the ovum nucleus, typically in the ovary
• The ovule contains the ovum, which is the female gamete
• Growth of the pollen tube in plants


  The pollen tube grows from the pollen grain towards the ovary, allowing the pollen nucleus to reach the ovum for fertilisation
• What happens after fertilisation in plants


  The ovule develops into the seed, while the ovary forms the fruit
• Fertilisation is essential for plant reproduction as it leads to the formation of a zygote, which develops into an embryo plant within the seed
• Fertilisation occurs when the nucleus of a male pollen grain fuses with the nucleus of the ovum (gametes) in the ovary
• Zygote


  After fertilisation, the zygote develops into an embryo plant
• Ovule


  A structure within the ovary of a flower that contains the ovum, which is the female gamete
• Structures formed after fertilisation in plants


  The ovule develops into the seed, while the ovary forms the fruit
• Germination


  The start of growth in a seed under suitable conditions of water, oxygen, and warmth. It is characterised by the swelling of the seed, bursting of the seed coat, and emergence of the embryo plant
• Factors required for successful germination

  • Water
  • Oxygen
  • Warmth
• Carbon dioxide is not necessary for germination, but its presence does not inhibit the process either