This document contains a very detailed summary of the entire reproduction in plants chapter found in the Mind Action Series Life Science Grade 12 Textbook. The notes are colourful, contain diagrams and are easy to understand.
Module 2.2
= ability of orgs Advantages & Disadvantages
to prod new gen of themselves
➢ NB for survival of species o All individuals o No variation in
reproduce offspring offspring (unless
TWO TYPES: ∴ x expenditure of
energy to prod
gametes / find a
mutation) bcz x
recombo of
alleles
1. Asexual o
mate
Process = simple & o Overcrowding
➢ Prod of new gen of same species by Asexual fast bcz only
involves mitosis
may occur &
resources in
one parent
Reprod o Very useful in
unchanging (stable)
short supply
2. Sexual conditions
o Favourable
➢ Prod of new gen of same species by mutations spread
bringing 2gether genetic materials of rapidly ∴ pop adapt
two parents quickly to new
environ conditions
Similarities: Results in variation
o Basis of evolution
o High expenditure of
energy
o Better chance in o Reproduction
o Prod same kind of orgs to unstable environment process = slower
prevent extinction Sexual o Prevent spread of
disease (offspring
o Unfavourable
mutations &
resistant)
o Result in food production (NB to
Reprod o Reduce the chance of
inheriting disease from
recessive genes
expressed
parent o Outside agents
feed world’s growing population) needed to carry
pollen or seeds
Differences:
Sexual reproduction
Diploid (2n) parents prod gametes (sex
# parents 1 2 (w/ 2
cells) in gonads (sex organs) by meiosis
genders)
Gametes = haploid (n) – have half # of
Processes 1 stage
(mitosis)
2 stages
(meiosis &
chromosomes
fertilisation) Gametes = brought 2together by
Gamete No Yes pollination (plants) / mating (animals)
o Gamete nuclei fuse (fertilisation)
End result Offspring = Offspring = x
genetically genetically o New cell (zygote) = diploid (2n) – has
identical identical 2 set of chromosomes
Value • Unchangi In unstable o Zygote grows by mitotic cell division
ng stable environment
environm can adapt to Gametes
ent = new conditions
good Female gamete = large & x motile
• Reprod = o In animals, male = sperm & female =
possible
where x egg/ovum
mates o In plants, male gamete = nucleus in
Reprod rate Faster slower pollen grain while female gamete =
egg cell (ovum) in embryo sac
Energy input X energy input Energy input
needed needed to
prod gamtes &
find mate
Outside None Pollinators for
agents pollination =
NB
, Module 2.2
Angiosperm Reproduction Pollination vs Fertilisation
= plants w/ flowers = transfer of pollen
that produce their ovules enclosed (containing the male gamete) from
in an ovary the anther to the stigma of the
➢ not naked on a cone scale (like a female organ for fertilisation
gymnosperm)
When anther = mature; splits open &
Flowers explained: discharges pollen
Pollen = carried to stigma
= the organ of sexual
reproduction. It contains the
Types of pollen transfer
reproductive organs & will attract 1. Cross pollination - when pollen =
pollinators transferred from anther of 1 flower
➢ If make male & female gametes = of 1 plant to stigma of flower of
hermaphrodite (bisexual) another plant, of same species
➢ Male gametes = inside pollen grains ➢ = offspring genetic variation
produced by anthers
2. Self pollination - pollen =
➢ Female gametes = inside ovules which =
enclosed by ovary transferred from anther to stigma
of same flower / another flower on
the same plant
{ structure } ➢ X offspring genetic variation
Flower has 4 whorls
{ prevent self-pollination }
1. Calyx (green) In Nature:
2. Corolla (coloured) ➢ in bisexual flowers, anthers and
3. Stamens (male whorl) stigmas ripen @ diff times
➢ stigma positioned above the anthers
4. Carpels (female whorl) ➢ flowers = unisexual ∴ x pollinate
themselves
➢ plant breeders remove anthers ∴
prevent self pollination
Fertilisation:
= the joining of two
haploid cells, the male gamete & female
gamete, to form a diploid zygote
Takes place after pollination
o Pollen grain lands on stigma &
develops a pollen tube (which grows
along style into ovule)
o Pollen tube carries male gamete
o Once gamete enters ovule,
fertilisation can occur
o After fertilisation, development
of embryo & seed begins
carpel = ovary, style & stigma
o Ovary = main part of the carpel, containing ovules
o Each ovule contains a female gamete
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