module 5 and 6

• Mechanisms of reproduction


  • Sexual reproduction
  • Asexual reproduction
• Sexual reproduction


  • Involves two parents and the joining of male and female gametes during fertilisation
  • Produces genetic variation in the offspring
  • The species can adapt to new environments due to variation, which gives them a survival advantage
  • A disease is less likely to affect all the individuals in a population
• Sexual reproduction


  • Time and energy are needed to find a mate
  • It is not possible for an isolated individual to reproduce
• Asexual reproduction


  • There is only one parent and the offspring are clones of the parent and each other
  • The population can increase rapidly
  • Only one parent is needed
  • More time and energy efficient
  • Faster than sexual reproduction
• Asexual reproduction


  • Does not lead to genetic variation in a population
  • The species may only be suited to one habitat
  • Disease may affect all the individuals in a population
• Gametes


  The egg and sperm, sex cells
• Zygote


  The fertilised egg which turns into an embryo
• Types of fertilisation


  • External fertilisation
  • Internal fertilisation
• External fertilisation


  • Female releases the eggs and the male releases the sperm which swim to the eggs in the environment
  • The female releases large quantities of eggs to increase the chance that some will survive, as many don't mate because many are killed/eaten
  • Courtship rituals make sure the male and female sex cells are released next to each other, but even so the chances of fertilisation are very low
• Internal fertilisation


  • Does not require a water habitat/environment
  • Sperm is released inside the female's body in a union called copulation
  • Greater probability of a sperm meeting an egg in the confined space
• Internal fertilisation


  • Humans, birds, insects, reptiles
• External fertilisation


  • Coral, oysters, some fish
• Parts of a plant flower


  • Petals
  • Sepals
  • Stamen - filament and anther (male reproductive part)
  • Pistil/carpel - stigma, style, ovary, ovule (female reproductive part)

  
• Anther


  A sac-like structure that produces and stores pollen
• Filament


  Supports the anther
• Stigma


  Top most part of the flower and is usually sticky to trap pollen
• Style


  The long tube which connects stigma to ovary
• Ovary


  Contains the ovules and is the part of the plant where the seed formation takes place
• Sepals


  Protect both flowers and fruits by producing chemicals that would ward off predators
• Types of flowers


  • Unisexual
  • Bisexual
• Bisexual flower


  • Rose
• Unisexual flowers


  • Papaya, cucumber
• Pollination


  Process of transferring pollen grains from the anther to the stigma
• Pollinators


  • Insects
  • Water
  • Birds
  • Wind
• Types of pollination


  • Self pollination
  • Cross pollination
• Self pollination


  • Pollen transfer takes place between the anther and the stigma of the same flower
  • Can be used to ensure survival if reproductive partners are scarce
• Cross pollination


  • Pollination where the pollen transfer takes place between the anther and stigma of different flowers of the same plant or different plants of the same species
  • Increases genetic variation which is advantageous for evolution
• Asexual reproduction in plants


  • Budding
  • Vegetative propagation
• Budding


  A new plant is developed from an outgrowth plant called a bud
• Vegetative propagation techniques


  • Runners
  • Bulbs
  • Tubers
  • Rhizomes
  • Leaves
• Vegetative propagation techniques


  • Runners: stems which usually grow in a horizontal form above ground
  • Bulbs: bulbs form lateral buds from the base of the mother bulb, which produce new smaller bulbs in subsequent years
  • Tubers: are swollen portions of an underground stem that stores food. E.g potatoes
  • Rhizomes: are root-like stems that grow horizontally under the ground. Like runners but grow underground. E.g. root ginger
  • Leaves: detached leaves from the parent plant can be used to grow a new plant
• Artificial vegetative propagation techniques


  • Cuttings
  • Grafting
  • Budding
• Cuttings


  • Snake plant, Begonia
• Grafting


  • Tree of 40 fruit, Pomato
• Budding


  • Cherry, Citrus fruits, Peach, Apple
• Asexual reproduction in fungi


  • Spores
  • Budding
  • Fragmentation
• Sporangium


  Produces spores by mitosis (underside of the mushroom)
• Hyphae


  Tubular structure of multicellular fungi that form mycelium. Fungal hyphae release digestive enzymes in order to absorb nutrients from food sources.
• Mycelium


  A dense network of filaments produced by the hyphae
• Haploid


  Contains only one set of chromosomes