plant reproduction

what is pollination

the transfer of pollen from the anther (male RS) to the stigma (female RS)

what’s self pollination

pollen is transferred to stigma of the same plant

what is cross pollination

pollen is transferred to stigma of another plant of the same species —> increased genetic variation

Difference between insect and wind pollinated plants

	Insect pollinated plants	Wind pollinated plants
Petals	Brightly coloured, large + sweet smelling	Small + inconspicuous
Stigma	-small + sticky found inside flower to insects to rub against	-feathery stigma to increase SA and chance of pollen blowing onto it
Filament/Anther	-short filament inside flower	-long filament that allows anthers to hang out
pollen	-sticky -moderate amount produced	-light – easily carried by wind -large amount produced
nectar	-produced by nectaries	-no nectaries à waste energy

what relationship is the pollination of flowers by insects

• mutualistic

• insect - gains energy from nectar or pollen it consumes

• plant - gametes get dispersed by insects

Pros and cons of cross pollination

PROS of cross pollination	CONS of cross pollination
Increases genetic variation + increases gene pool	Needs another plants nearby à not good if plants are far apart
Less homozygous recessive genes that code for disease are expressed	Need pollinating agent e.g wind/insect
Increases allele frequency of advantageous genes à more adapted	May lose advantageous genes
	Genes that code for disease may be transmitted
	Takes longer à fewer offspring

how does pollen form in flowering plants

• occurs in anther of flowering plants

• microspore mother cell (2n) forms

• undergoes meiosis I

• then undergoes meiosis II

• this forms a tetrad of 4 haploid pollen cells

• these develop into separate pollen grains that undergo mitosis

• 2 haploid nuclei forms in each pollen grain

diagram of ovule

describe process of double fertilisation in plants