mammalian gametes and fertillisation Flashcards
what are the 2 types of gametes in mammals
sperm
ovum
structure of sperm
acrosome
haploid nucleus
midpiece with mitochondria
flagellum
acrosome
contains enzymes to break down the egg’s zona pellucida
midpiece with mitochondria function
provides energy for movement
flagellium function
propels the sperm towards the egg
structure of ovum
nucleus
zona pellucida
cytoplasm with nutrients
cortical granules
zona pellucida
protective coating
- stops more than one sperm fertillising the egg
cytoplasm with nutrients function
supports early embryo development
cortical granules
release enzymes after fertillization to prevent multiple sperm entry
- causes the zona pellucida to harden
what is the acrosome reaction
the release of digestive enzyme from the acrosome, allowing it to penetrate the zona pellucida of the egg
what happens after the sperm penetrates the egg
- cortical reaction occurs
- cortical granules release enzymes to harder zona pellucida
what is the role of meiosis in gamete formiation
halves the chromosome number so that when fertillisation occurs, the diploid zygote is restored
what are the male and female gametes in flowering plants
male: pollen grain
female: egg cell (ovum)
where is pollen produced in plants
in the anther, which constain a pollen sac where meiosis occurs
what are the ovules located in a plant
inside the ovary of the carpel
what happens during the pollen tube formation
- pollen grain germinates on the stigma
- the tube nucleus directs the growth of the pollen tube down the style
- the pollen tube enters the ovule through the micropyle
- the 2 male gametes travel down the tube
generative nucleus
divides to from 2 male gametes
tube nucleus
controls the growth of the pollen tube
what is double fertillisation in plants
- one male gamete fuses with the egg cell -> forms diploid zygote
- the second male gamete fuses with the 2 polar nuclei -> forms triploid endosperm
where does fertillisation occur in plants
inside the embyro sac which is in the ovule
what happens to the ovule after fertillisation
the ovule develops into a seed
- ovary develops into a fruit
function of triploid endosperm
provides nutrients for the developing embryo inside the seed
self pollination
pollen from the same flower fertilises the ovule
cross-pollination
pollen from a different flower fertilises the ovule
