Tuesday, July 19, 2011
Monday, July 18, 2011
Sunday, July 17, 2011
Asexual reproduction
Asexual Reproduction
= formation of new individuals from the cells of a single parent. Offspring are identical to their parent. Does not involve meiosis.
Advantages
- Allows an organism to rapidly produce many offspring, saving time and energy for courtship,finding a mate,and mating.
- Combination of genes to be handed down unchanged.
Disadvantages
- Reduces genetic variation, disadvantage in the long term for the evolution and adaption of a species to its changing environment.
- Harmful mutation sometimes pass on to progeny.
(1) Binary fission
(2) Fragmentation
- parts of plant break off and grow into new plant.
(3) Sporulation
- formation of spores
- haploid
(4) Budding
- a small protuberance on the surface of parent cell increases in size until a wall forms to separate the new individual or bud from the parent.
(5) Regeneration
- ability of body to replace lost parts of an organism
(6) Vegetative reproduction
- that describes all the natural methods of asexual reproduction used by plants.
(7) Parthenogenesis
- an individual develops from an unfertilized egg.
- in most species, reproduction by parthenogenesis occurs when conditions are right and food is plentiful, at other times, sexual reproduction takes place.
(8) Polyembryony
- ability of fertilised egg to develop into mass of cells that will then form numerous embryos.
- e.g.: identical twins
(9) Paedogenesis
- reproduction by an animal that still in larvae form or pre-adult
- e.g.:Lancelet (amphioxus)
Saturday, July 16, 2011
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