Mechanisms of reproduction

• Each sperm cell has half the number of chromosomes as the original parent cell (23).
• Reproduction is the process of creating new offspring/individual organisms from a parent.
• Sexual reproduction is a process that requires two parents.
• In sexual reproduction, a haploid gamete from each parent combines to produce Genetically unique diploid offspring.
• Asexual reproduction is a process that requires one parent.
• Through cell division, asexual reproduction produces Genetically identical offspring.
• Internal fertilisation is a process where the union/combining of gametes occurs inside the female body.
• Examples of animals that undergo internal fertilisation include reptiles, mammals, and birds.
• External fertilisation is a process where the union/combining of gametes occurs outside the female body.
• Examples of animals that undergo external fertilisation include amphibians and fish.
• Advantages of external fertilisation

  • Little energy required to find mate 
  • Large numbers of offspring produced 
  • Offspring can be spread widely = less competition 
• Disadvantages of external fertilisation

  • Many gametes go unfertilized 
  • Offspring often not protected by parents ; many die
• Advantages of internal fertilisation

  • Fertilization more likely to occur 
  • Embryo protected from predators 
  • Offspring more likely to survive
• Disadvantages of internal fertilisation

  • Higher energy requirement to find mate 
  • Less offspring produced 
  • More energy required to raise/care for young 
• BUDDING IS A FORM OF ASEXUAL REPRODUCTION IN ANIMALS

  Bud forms on parents, develops, then breaks off and a new unique offspring is formed 

  E.g. Coral
• REGENERATION/FRAGMENTATION IS A FORM OF ASEXUAL REPRODUCTION IN ANIMALS

  Part of the parents breaks off → new organisms is able to form from broken part 

  E.g. flatworms & sea sponges
• PATHOGENESIS IS A FORM OF ASEXUAL REPRODUCTION IN ANIMALS

  Development of an organisms from a female gamete without fertilization from a male gamete 

  E.g. honey bees/insects
• SEXUAL REPRODUCTION IN ANIMALS

  Haploid male and female gametes unite to produce a genetically unique offspring 

  E.g. dogs
• FORMS OF ASEXUAL REPRODUCTION IN FUNGI

  • Budding
  • Fragmentation
  • Spores
• SPORES ARE A FORM OF ASEXUAL REPRODUCTION IN FUNGI

  They Produce haploid spores via mitosis in the fruiting body (genetically identical to parent)
• Fungi undergo sexual reproduction in repsonse to adverse environmental conditions
• HOMOTHALICS IS A FORM OF SEXUAL REPRODUCTION IN FUNGI

  Self fertile - can produce sexual reproducing colony
• HETEROTHALLICS IS A ANOTHER FORM OF SEXUAL REPRODUCTION IN FUNGI

  Require haploid a and a alpha cells to fuse 

  - Specialize haploid cells form to produce a diploid cell (genetically unique) → undergo meiosis to produce new haploid spores
• BINARY FISSION IS A FORM OF ASEXUAL REPRODUCTION IN PROTISTS

  Division of parent body into 2 equal daughter individuals through mitosis
• MULTIPLE FISSION IS A FORM OF ASEXUAL REPRODUCTION IN PROTISTS '

  Division of parents organisms into multiple daughter cells
• SYGNAMY IS A FORM OF SEXUAL REPRODUCTION IN PROTISTS

  Complete/permanent fertilization of 2 haploid gametes → form a diploid organism
• CONJUGATION IS A FORM OF SEXUAL REPRODUCTION IN PROTISTS

  Union of 2 individuals to exchange their haploid pronuclear to form a zygote nucleus → Produce daughter cells through binary fission
• ASEXUAL REPRODUCTION OCCURS IN BACTERIA THROUGH BINARY FISSION

  1. Cell elongates (builds more cell wal) 

  2. Bacteria genome replicates/remains attached to membrane (plasmid s replicate as well if present)

  3. Duplicated DNA begins to seperate/moves towards poles a sit further elongates 

  4. Cleave furrow behind to form/cell wall forms in cleavage furrow 

  5. 2 identical daughter cells are produced
• Bacteria DNA genetic variation occurs to increase genetic diversity and survival
• CONJUGATION AS A SEXUAL REPRODUCTION METHOD IN BACTERIA

  Direct transfer Of DNA from one bacterial cell  to another (can be same or different species)
• TRANSFORMATION AS A SEXUAL METHOD OF REPRODUCTION IN BACTERIA

  Naked DNA taken from environment by bacterial cells
• TRANSDUCTION AS A SEXUAL REPRODUCTION METHOD IN BACTERIA

  Uses a bacteriophage (bacterial virus) to transfer DNA from one bacterial cell to another 
• BULBS ARE A FORM OF ASEXUAL REPRODUCTION IN PLANTS

  They are undergorund storage organs with a short stem and fleshy leaves

  E.g. Onions
• RUNNERS ARE A FORM OF ASEXUAL REPRODUCTION IN PLANTS

  They are side branches which grow close to the  ground and develop new plantlets generically identical to parent plant

  E.g. Strawberry
• SEXUAL REPRODUCTION IN PLANTS OCCURS THROUGH FLOWERS

  The male sex cell (pollen grain) and the female sex cell (ovum) meet in pollination

  • Pollinators land on flower stigma with pollen → travels to ovum/fertilization occurs →  Seed/fruit produced + genetically unique offspring fr