Biology

• Reproduction methods


  • Sexual reproduction
  • Asexual reproduction
• Sexual reproduction


  Fusion of genetic material from two parents
• Asexual reproduction


  New individual produced from part of a single parent
• Sexual reproduction


  • Produces genetically unique offspring
  • Variation in the population
  • Species better able to adapt to environments
  • Disease events less likely to affect entire population
• Asexual reproduction


  • Rapid population of an environment
  • No requirement for mates
  • Able to be enacted under external pressures
  • No requirement for investment in care of offspring
• Disadvantages of sexual reproduction

  • Large time and energy invested
  • Requires a mating partner
  • Fewer offspring produced
• Disadvantages of asexual reproduction

  • Lack of diversity
  • May result in large-scale extinction events
  • Reduced ability to adapt to external pressures
• Animal sexual reproduction


  1. Gametes produced by meiosis

  2. Fusion of gametes forms zygote

  3. Combination of chromosomes increases variation
• Animal asexual reproduction


  1. Binary fission

  2. Budding

  3. Fragmentation

  4. Parthenogenesis
• Internal fertilisation


  Union of egg and sperm inside female body

  
• External fertilisation


  Union of egg and sperm outside female body
• Advantages of internal fertilisation

  • Increased likelihood of fertilisation
  • Embryo protected from environment
• Advantages of external fertilisation

  • Large number of gametes produced
  • Simpler behavioural process
• Disadvantages of internal fertilisation

  • Fewer offspring produced
  • Risk of sexually transmitted diseases
• Disadvantages of external fertilisation

  • Millions of eggs must be produced
  • Offspring must mature rapidly
  • Low survival rate of eggs
• Internal fertilisation


  • Humans
• External fertilisation


  • Salmon, cod, trout, char
• Plant asexual reproduction


  • Vegetative propagation
  • Spore formation

  
• Plant sexual reproduction


  • Flowers are reproductive organs
  • Pollination transfers male gametes to female ovules
  • Fertilisation occurs, ovules grow into seeds in fruit
• Advantages of plant sexual reproduction

  • Creates genetic diversity
  • Higher disease resistance
  • Greater ability to adapt to changing conditions
• Disadvantages of plant sexual reproduction

  • Can prevent favourable genes being passed to offspring
• Budding


  New organism originates from bud-like structure on parent
• Spore formation


  New individuals originate directly from spores of parent
• Fungal sexual reproduction


  1. Plasmogamy - fusion of protoplasts

  2. Karyogamy - fusion of haploid nuclei to form diploid zygote

  3. Meiosis - restores haploid phase
• Fungal asexual reproduction


  • Budding
  • Spore formation
• Bacterial binary fission


  1. DNA replication

  2. Cell elongation and division into two daughter cells
• Advantages of bacterial binary fission

  • Rapid reproduction
  • Only requires single organism
• Disadvantages of bacterial binary fission

  • Lack of genetic diversity
  • Overcome by mutation and horizontal gene transfer
• Protist binary fission


  1. Division of nucleus

  2. Division of organism into two separate organisms
• Protist budding


  New organism grows from body of parent to form new colony
• Fertilisation


  Fusion of haploid gametes to form diploid zygote
• Implantation


  Fertilised egg adheres to uterine wall, establishing pregnancy
• Fertilisation has a 12-24 hour window after ovulation

  
• Blastocyst embeds in uterine wall after fertilisation
• Implantation


  When a fertilised egg adheres to the wall of the uterus. Implantation is the stage of pregnancy at which the embryo adheres to the wall of the uterus. At this stage of prenatal development, the conceptus is called a blastocyst. It is by this adhesion that the embryo receives oxygen and nutrients from the mother to be able to grow.

  
• Sexual reproduction


  1. Development of gametes

  2. In females this occurs in the ovaries, where eggs (ovum) are produced and released into the fallopian tubes

  3. Fertilisation occurs between 12-24 hours after release called ovulation; where the fusion of an egg and a sperm cell can be successful

  4. After fertilisation has occurred the zygote begins to divide and migrate from the fallopian tubes into the uterus

  5. The blastocyst (the ball of divided cells) implants itself into the wall of the uterus called the endometrium

  6. The endometrium provides nutrients and oxygen to the embryo

  
• Fertilisation


  The fusion of two haploid gametes to form a single diploid zygote and in turn, initiate the development of a new organism. Also known as generative fertilisation, insemination, pollination, fecundation, syngamy and impregnation, is the fusion of gametes to give rise to a new individual organism or offspring and initiate its development.
• Hormones


  Chemical messengers produced by the body which travel in the blood to other cells where they have an effect
• Pituitary gland


  • An endocrine gland situated just below the hypothalamus that secretes a number of hormones that regulate other endocrine glands including ovaries and testes
• Hormones play a vital role in all aspects of the development and function of the male and female reproductive systems