Biology: Asexual Reproduction (Chp 1.1)

A. Introduction
A.1 Definition:

  • Reproduction: a characteristic of living things which involves production of offspring from (a) mature parent(s) –  in infertile period if sexual – to maintain continuity of life
  • In sexual reproduction, a parent needs to enter a fertile period and be mature first (able to produce gametes) to be able to reproduce. If in asexual, mature means already grown to original size.

 A.2 Purposes

  • To make sure a species can continue (preservation and continuation)
  • To ensure the survival of a species
  • Pass on our own genetic identity

A.3 Characteristics

Category

Asexual

Sexual

Parent 1 parent. 2 parents, same species, one male and one female.
Offspring The offspring is genetically identical to the parent and other offspring, called a clone Similar to parent (show variations)
Advantages
  • Requires less energy
  • No need to search for a mate
  • Time efficient
  • Have more genetic variation that is vital for evolution
  • Promote diversity (cara lain) evolution, mutation
  • Improve survival chance of organisms: can adapt and survive when environement change
Disadvantages
  • Lack of genetic variation causes them to share same weaknesses
  • Population can go extinct with dramatic changes in environment, cannot adapt
  • Need to attract mates
  •  “expensive”
  • Competition is costly
  • Recombination is risky
Examples
  • Budding by Hydra
  • Gemmules by Sponges
  • Fragmentation by Planarians
  • Regeneration by Echinoderms
  • Rhizome, plant propagation (“stek”, “cangkok”), in plants
  • Tissue culture
  • Binary fission by amoeba
  • Spores
  • Autogamy in plants/earthworms
  • Laying eggs by chickens, birds, fishes, frogs
  • Giving birth
    y human, mammals
  • Spores
  • Pollination in plants (“serbuk sari” dan “pistil”)
  • Conjugation: make a junction for exchanging genetic material, no fertilisation but make genetic variation

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

A.4 Cell Division

Mitosis Meiosis
  • General cell division method
  • Have 2 identical daughter cells, where the genetic material is 2n (for ex. Parent have 46 chromosome offspring also have 46)
  • Sex cells
  • Have 4 daughter cells, where the genetic material is n (for ex. Ovum have 46 chromosome = 2n, daughter cell 23)

B. Types Of Asexual Reproduction

B.1 Binary Fission

  • Pembelahan biner 1 -> 2 -> 4 -> 8 -> 16
  • Pembelahan ganda: multiple fission
  • Amoeba, Paramecium, Euglena (protozoa -> monera)

11-02_BinaryFission_0_L

B.2 Budding

  • Bertunas
  • Yeast (unicellular organism): ragi, Hydra
  • Diff with fragmentation: kl budding: grow -> separate, fragmentation: separate directly

HydraBuddingB.3 Spore

  • By sporulation: fern (paku), moss (lumut), mushroom (cendawan), mold (kapang)
  • Spore stored in sporangiummoldspores
  • Spore can grow by itself without the need of other spre -> no sex type, although it is call a reproductive cell

B.4 Fragmentation

  • Broken can grow into new organism
  • Planaria, Starfish
  • Cicak isn’t fragmentation since the tail cannot produce new offspring: regenerationfragmentation-in-planaria

B.5 Parthenogenesis

  • Virgin Birth -> no fertilization by male
  • Produce offspring from unfertilized egg
  • Why choose this? Because sexual need limited mating season, need to find mate, have to be mature
  • Example: komodo, wasp, aphid, lizard, snake

Continued in next post…….

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