IQ1

• Reproduction


  The process that ensures the continuity of a species
• Sexual reproduction in plants 


  1. Male and female gametes unite to form a single celled zygote which turns into a complete plant

  2. Male gametophytes are produced inside anthers and are pollen grains

  3. Pollen tube enters the embryo sac through the micropyle

  4. One male gamete fuses with the ovum to produce zygote

  5. Second male gamete fuses with the secondary nucleus resulting in double fertilisation
• Asexual reproduction


  1. New plant parts can grow from vegetative organs such as roots, leaves, stems in a process called vegetative propagation

  2. Cutting: Stem from plant is cut and planted in soil to grow into new plant

  3. Layering: Branch is bent and covered with soil to develop roots and grow into new plant

  4. Grafting: Two different plants are joined to grow as one
• Asexual reproduction


  • Does not involve union of male and female gametes
  • Results in formation of new plants to maintain continuity of plant species
• Vegetative propagation


  • New plant parts grow from vegetative organs like roots, leaves, stems
• Vegetative propagation examples:


  • Sweet potato (roots)
  • Ginger (stems)
  • Bryophyllum (leaves)
• Cutting


  • Stem from plant is cut and planted in soil to grow into new plant
• Plants propagated by cutting examples

  • Rose
  • Hibiscus
  • Sugarcane
• Layering


  • Branch is bent and covered with soil to develop roots and grow into new plant
• Plants propagated by layering examples

  • Jasmine
  • Bougainvillaea
• Grafting


  • Two different plants are joined to grow as one
  • One plant serves as the grounded stock
  • The other plant is the desired scion that determines the fruits and flowers
• Sexual reproduction in fungi

  • Plasmogamy: Two genetically different cells fuse
  • Karyogamy: The nuclei fuse
  • Meiosis: Gametes are generated which produce spores
• Asexual reproduction in fungi

  • Fragmentation: Pieces of hyphae separate to form new colonies
  • Budding: Nucleus divides, a bulge forms which is split off by cytokinesis
  • Spores: Mitosis produces genetically identical cells which are distributed by wind or vectors
• Advantages of asexual reproduction in fungi

  • Production of spores allows for wide distribution and colonisation
  • Combination of sexual and asexual methods allows flexibility in propagation
• Disadvantages of asexual reproduction in fungi

  • Offspring may only be suited to one habitat
  • Lack of genetic variability
• Asexual reproduction in bacteria

  • Binary fission: Single cell divides into two identical daughter cells
• Binary fission in bacteria

  1. DNA replication

  2. Cell elongation

  3. Cell splitting into two daughter cells
• Sexual reproduction in protists

  • Haploid protists: Two haploid cells fuse to form a zygote
  • Diploid protists: Adult cells undergo meiosis to produce gametes which fuse during fertilisation
• Asexual reproduction in protists


  • Binary fission: As in bacteria
  • Budding: New organism grows from parent to form colony
• Advantages of sexual reproduction

  • Variation in population
  • Better adaptation to environment
  • Less susceptibility to disease events
• Disadvantages of sexual reproduction

  • Large time and energy investments
  • Requirement for mating partner
  • Fewer offspring produced
• Advantages of asexual reproduction

  • Rapid population of environment
  • No requirement for mates
  • Quick and not energy intensive
  • No requirement for care of offspring
• Disadvantages of asexual reproduction

  • Lack of diversity
  • Potential for large-scale extinction events
  • Reduced ability to adapt to external pressures
• Asexual Reproduction


  Offspring created is identical as it comes from one parent<|>Use of mitosis<|>Individuals have a short lifespan, so for a population or species to survive, genetic material must be passed from one generation to the next
• Types of asexual reproduction

  • Runners
  • Bulbs
  • Cuttings
  • Spores
  • Binary Fission
• Haploid


  Containing one set of paired chromosomes
• Runners


  Side branches with clumps of leaves and roots which grow on the ground, the roots dig down and establish the plant as its own individual plant, i.e. Strawberries
• Bulbs


  Bulbs are underneath certain plants which allow buds to grow from them and then flourish their own individual plant e.g. Daffodil
• Diploid


  Plant classification group where seeds are formed on flowers
• Cuttings


  Branch off a tree is cut and stripped down, then is planted again to grow as its own individual plant
• Gametophyte


  Plant classification group where seeds are formed on cones
• Sporophyte


  Cell division of germ cells that produces four non-identical haploid gametes
• Spores


  Airborne cells that are released from the parent. They are enclosed and developed when the environment is appropriate. E.g., Fungi → Mushrooms
• Binary Fission


  A parent cell divides, resulting in two identical cells, each having the potential to grow to the size of the original cell. E.g., Amoeba, Bacteria, Paramecium
• Meiosis


  Cell division of Somatic cells that produces two identical new diploid cells
• Mitosis


  Gamete-forming haploid stage in a plant's life cycle
• Asexual Reproduction in Unicellular Life

  1. Single-celled organisms such as bacteria reproduce by simply dividing in two by mitosis

  2. Among the single-celled, eukaryotic protists such as Amoeba & Paramecium species binary fission (splitting in two) is also common but is often more complex than simple mitosis division

  3. In single-celled fungi (yeasts) a process called "budding" is very common. This is a form of binary fission in which a new cell is formed as a small "bud" growing on the parent cell. It separates as a new cell and grows to full size. Each budding cycle doubles the population, so a few cells can become millions very quickly
• Angiosperm


  Spore-forming diploid stage in a plant's life cycle
• Asexual Reproduction in Multicellular Life

  1. Many multi-cellular organisms are also able to reproduce asexually

  2. Even some animals can reproduce asexually. Perhaps the best-known example is the small aquatic animal Hydra. This is a relative of jellyfish & coral animals

  3. Hydra can reproduce sexually by releasing eggs or sperm into the water but can also reproduce asexually by a "budding" process. A small out-growth appears on its body and grows into a new little hydra. Eventually this "baby" separates from the parent to live freely as a separate individual
• Fertilisation


  1. Ovary releases an egg (ovulation)

  2. The released egg travels to the fallopian tube via the oviduct

  3. Sexual intercourse occurs and the male releases semen, which is comprised of sperm, directly into the vagina

  4. The sperm swim from the vagina, through the cervix and uterus into the oviduct/fallopian tube

  5. The sperm fuses with the egg to create a zygote (new organism)

  6. Zygote creates a strong membrane which prevents any other sperm fertilising the egg meaning that the remaining sperm will die out

  7. The zygote travels down the oviduct to the uterus where it is implanted