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Summary Life Science Notes
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Understandable and easily interpreted IEB and NSC Life Sciences summaries for grade 12. All content needed for Final Examinations.
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Reproduction in flowering plantsWhat happens when organisms reproduce?
New generations of the same kind of individuals are formed to
replace those individuals that eventually die.
Reproduction is essential
Places where food shortages are a problem.
FEED MORE PEOPLE PRODUCE MORE FOOD FROM PLANTS AND ANIMALS QUICKLY
2 types of reproduction
1. Asexual reproduction
2. Sexual reproduction
Asexual reproduction: formation of new individuals from a single
parents without the production of gametes.
- offspring carry same genetic material as parents —> clones
Sexual reproduction: fusion of male and female gametes to form a
zygote.
- offspring carry all different combos of the parents genetic
material —> genetically different
Gamete: sex cell
- male: sperm cell
- Female: ovum / egg cell
- Found in multicellular organisms that reproduce sexually
- Produced via meiosis
Meiosis: special type of cell division where number of
chromosomes in the nuclear of the cell is halved.
Haploid: cell contenting half the normal number of chromosomes.
Mitosis: cell division used to produce identical cells called daughter
cells which have identical same genetic material and chromosome
number as the parent cell.
, Diploid: Cell containing the normal number of chromosomes for the
organism
Fertilisation: fusion of gametes.
- when a haploid ovum and haploid sperm join together to make a
diploid zygote.
- External fertilisation: outside the animal body
- Internal fertilisation: inside the female body
Zygote: cell formed from the fusing of an ovum and sperm cell.
- After fertilisation, zygote grows with mitosis into embryo and
then foetus.
Unicellular: organism consisting of one cell
Multicellular: organism consisting of many different cells
ASEXUAL REPRODUCTION
- when a single parent forms new individuals without the
production of gametes.
- Cells divide by mitosis
- Offspring genetically identical to parent
- Clone of parent
ADVANTAGES DISADVANTAGES
Only one parent needs to be present - no energy/ All organisms in population are the same - little
effort needed genetic variation
Desirable characteristics retained Genetic weaknesses of parent present in offspring
Many offspring in a short space of time - rapid Population becomes overcrowded
population growth
Genetically identical individuals adapted to specific
environment
Budding / Fragmentation: yeast, hydra, marine sponges
Binary Fission: Bacteria and Amoeba
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