Reproduction

• Reproduction


  The process where an offspring with resemblance to its parent is made
• Types of reproduction


  • Sexual reproduction
  • Asexual reproduction
• Sexual reproduction


  Requires fertilization to occur - the union of male and female sex cells
• Fertilization


  The union of a sperm cell and an egg cell

  
• Types of fertilization


  • External fertilization
  • Internal fertilization
• External fertilization


  Gametes or sex cells unite outside the female body, usually in an aquatic environment
• Types of internal fertilization

  • Oviparity
  • Ovoviviparity
  • Viviparity
• Oviparity


  Zygotes are deposited outside the female's body
• Ovoviviparity


  Zygotes are retained inside the female's body and are nourished by the egg yolk
• Viviparity


  Zygotes are retained inside the female's body and are nourished by the female's placenta
• Pollination


  The process of transferring a pollen from the anther of a male flower to the stigma of a female flower
• Double fertilization


  Two sperm cells are released from the pollen - one fertilizes the haploid egg and the other fertilizes the diploid polar nuclei
• Types of asexual reproduction

  • Budding
  • Fragmentation
  • Fission
  • Parthenogenesis
  • Vegetative propagation
• Budding


  An outgrowth develops in the parent organism then detaches itself
• Fragmentation


  A detached piece of an animal develops into an offspring via regeneration
• Fission


  An animal divides into two offspring
• Parthenogenesis


  Unfertilized egg develops into an adult

  
• Vegetative propagation


  The use of vegetative plant parts such as stems and leaves, to grow a new organism
• Comparison of sexual and asexual reproduction

  • Use of gametes
  • Use of vegetative parts
  • Variation of genes in the gene pool
• Embryogenesis


  The process where a zygote develops into an embryo

  
• Embryogenesis


  1. Cleavage

  2. Morula

  3. Blastula

  4. Gastrulation

  
• Embryonic layers in gastrula

  • Ectoderm
  • Mesoderm
  • Endoderm

  
• Ectoderm


  Outermost layer of the gastrula, gives rise to skin epidermis, nervous system, jaws and teeth, pituitary gland, adrenal medulla
• Mesoderm


  Middle layer of the gastrula, gives rise to connective tissues, skeletal system, muscular system, circulatory system, lymphatic system, urinary system, reproductive system (not including cells which give rise to sex cells), adrenal cortex
• Endoderm


  Innermost layer of the gastrula, gives rise to epithelial lining of digestive, respiratory and reproductive systems, parathyroid, thymus and thyroid glands
• Plant zygotes undergo cleavage and divide asymmetrically into a bigger apical cell and smaller basal cell
• Ectoderm


  Outermost layer of the gastrula
• Systems and parts of the body derived from ectoderm


  • Skin epidermis
  • Nervous System
  • Jaws and teeth
  • Pituitary Gland
  • Adrenal Medulla
• Mesoderm


  Middle layer of the gastrula
• Systems and parts of the body derived from mesoderm

  • Connective Tissues
  • Skeletal System
  • Muscular System
  • Circulatory System
  • Lymphatic System
  • Urinary System
  • Reproductive System (not including cells which give rise to sex cells)
  • Adrenal Cortex
• Endoderm


  Innermost layer of the gastrula
• Systems and parts of the body derived from endoderm


  • Epithelial lining of digestive, respiratory and reproductive systems
  • Parathyroid, thymus and thyroid glands
• Majority of the plant embryo arises from the apical cell while the basal cell serves as a suspensor to anchor the developing embryo into the seed

  
• Plant embryo development


  1. Series of cell divisions in both apical and basal cells

  2. Apical cell divides until it reaches the globular stage

  3. Embryo proceeds to the heart stage

  4. Mature embryo contains shoot apical meristem and root apical meristem

  
• Shoot apical meristem (SAM)


  Gives rise to the plant's shoot
• Root apical meristem (RAM)

  Located at the embryo's radicle, gives rise to the plant's roots
• Radicle


  Embryonic root
• Cotyledons


  Provide nutrient to the growing embryo until the plant develops its leaves
• Hypocotyl


  Structure found below the cotyledon, gives rise to the plant's stem
• Organogenesis


  1. Organs start to develop in the embryo

  2. In animals, the three germ layers differentiate and develop into different organs systems and parts of the body

  3. In plants, shoot and root apical meristems develop into the corresponding plant parts