Gen bio2

• Reproduction


  An essential characteristic of organisms to perpetuate their kind
• Types of reproduction


  • Sexual
  • Asexual
• Asexual reproduction


  • Advantageous when adapted to a particular environment and genetic variation is not a necessity
  • Disadvantageous as it lacks genetic variation
• Vegetative reproduction in plants

  1. New plant identical to parent plant

  2. Structures: runners, tubers, corm, rhizomes
• Artificial plant propagation


  1. Plants can grow faster than from seeds

  2. Used for sugarcane, apple, pineapple, ornamental plants
• Grafting in woody plants

  1. Attaches stem from one plant to root or root-bearing of another

  2. Resulting plant has combined vascular system
• Sexual reproduction in plants

  Occurs in the sexual organs of the flower
• Pollination in flowering plants


  1. Pollen transferred from anther to stigma

  2. Aided by insects, animals, wind
• Double fertilization in flowering plants

  Leads to fruit and seed development
• Purpose of fruits


  Protect seeds and aid seed dispersal
• Monocot


  Plant with one cotyledon in seed
• Dicot


  Plant with two cotyledons in seed
• Asexual reproduction in animals

  • Commonly found in lower organisms
  • Resulting offspring are identical to parent
• Fission


  Division of body into two or more equal parts (e.g. Amoeba, Paramecium)
• Budding


  New individual arises as outgrowth from parent (e.g. Hydra)
• Fragmentation


  Body breaks into parts, each fragment can become a complete individual (e.g. Starfish, Earthworms)
• Parthenogenesis


  Modified sexual reproduction resulting in offspring from unfertilized eggs
• Animals that can reproduce asexually

  • Flatworms
  • Roundworms
  • Annelids
  • Crustaceans
  • Insects
  • Fishes
  • Some reptiles
• Sexual reproduction in animals

  Involves two parents and fusion of male and female gametes
• Advantages of sexual reproduction

  • Produces genetic variation in offspring
  • Allows adaptation to new environments
  • Reduces risk of disease affecting whole population
• Disadvantages of sexual reproduction

  • Time and energy needed to find a mate
  • Isolated individuals cannot reproduce
• Components of human reproduction

  • Main reproductive organs
  • Accessory organs
• Testis


  Produce sperm cells
• Scrotum


  Pouch-like sac that holds the testis
• Penis


  Places sperm into vagina during mating
• Vas deferens


  Transports mature sperm to urethra for ejaculation
• Male reproductive glands


  • Seminal vesicle
  • Prostate gland
  • Bulbourethral gland
• Functions of female reproductive system

  • Production of female sex cells
  • Reception of sperm cells
  • Nurturing development of new individual
• Ovary


  Produces egg cells
• Oviduct


  Passageway for eggs from ovary to uterus, site of fertilization
• Uterus


  Place where fertilized egg develops
• Vagina


  Receives penis during mating
• Fertilization and early development

  1. Fusion of sperm and egg to form zygote

  2. Zygote divides and travels to uterus

  3. Implants in uterine lining as embryo
• Monozygotic twins


  One fertilized egg splits to form two genetically identical babies
• Dizygotic twins


  Two eggs fertilized by two sperm to form two genetically unique babies
• Types of contraception


  • Ovulation-suppressing (oral contraceptives)
  • Barrier (condom, diaphragm, cervical cap)
  • Chemical (spermicides)
• Fertilization


  Fusion of sperm and egg cell to form a fertilized egg called a zygote
• Fertilization to implantation


  1. Cell division as zygote travels down fallopian tube to uterus

  2. Zygote attaches to uterine lining (implantation)

  3. Zygote becomes embryo
• Monozygotic twins


  One fertilized egg (ovum) splits and develops into two babies with exactly the same genetic information
• Dizygotic twins


  Two eggs (ova) are fertilized by two sperm and produce two genetically unique children