❤️🔥3- reproduction Flashcards
the reproductive organs of the plant is
flowers
flowers usually contain both
male and female reproductive parts
plants produce
pollen which contains a nucleus inside that is the male gamete
unlike sperm pollen is not capable of
locomotion (moving from one place to another)- this means plants have to have mechanisms in place too transfer pollen from the anther (male part of plant) to the stigma (female part of plant) this process is known as pollination
pollination can occur by
transfer by insects or wind
sepal
protects unopened flowers
petals
brightly coloured in insect-pollinated flowers to attract insects
anther
produces and releases the male sex cell (pollen grain)
stigma
top of the female part of the flower which collects pollen grains
stigma
top of the female part of the flower which collects pollen grains
ovary
produces the female sex cell- ovum
ovule
contains female sex cells found in the ovary
insect pollinated flowers
insects visit flowers to collect nectar, as the insect enters the flowers in search of nectar it often brushes against the anthers which deposit sticky pollen into the insects body. when the insect visits another flower, it may brush against the stigma of this second flower and in the process, may deposit some of the pollen from the first flower resulting in pollination
petals on an insect pollinated plant
large and brightly coloured to attract insects
scent and nectar on an insect pollinated plant
present- entices insects to visit the flower and push past stamen to get to nectar
number of pollen grains on an insect pollinated plant
moderate- insects transfer pollen grains efficiently with a high chance of successful pollination
pollen grains on an insect pollinated plant
larger, sticky and or spikey to attach to insects and be carried away
anthers on an insect pollinated plant
inside flower, stiff and firmly attached to brush against insects
stigma on insect pollinated plant
inside flower, sticky so pollen grains stick to it when an insect brushes past
wind pollinated plants
when ripe anthers open and shed their pollen into the open air, the pollen is then either blown away by the wind or carried by air currents until b y chance they land on the stigma of a plant of the same species, resulting in pollination.
petals on wind pollinated plants
small and dull. often green or brown in colour
scent and nectar wind pollinated plants
absent- no need to waste energy producing these as no need to attract insects
number of pollen grains wind pollinated plants
large amounts- most pollen grains are not transferred to another flower so the more produced, the better the chance of some successful pollination occurring
pollen grains wind pollinated grains
smooth, small and light so they are easily blown by the wind
anthers wind pollinated plants
outside flower swinging loosely on the long filaments to release pollen grains easily
stigma wind pollinated plants
outside flower, feathery to catch drifting pollen grains
cross pollination occurs when
the pollen from one plant is transferred to the stigma of another plant of the same species
cross pollination increases
genetic variation in the offspring
self pollination is when
the pollen from a flower can land on its own stigma or on the stigma of another flower on the same plant
self pollination reduces
genetic variation ion offspring as all the gametes come from the parent
lack of variation in offspring is a disadvantage because
if environmental conditions change it is less likely that any offspring will have adaptations that suit the new conditions well
an ovum is
an egg cell that contains the female nucleus that a male pollen nucleus can fuse with
in plants fertilisation occurs
when the pollen grain nucleus fuses with the ovum nucleus
the growth of the pollen tube
pollen grain has no tail to swim to the ovary of the flower so in order to reach the ovum nucleus the pollen grain grows a pollen tube. this only happens if a pollen has landed on the right kind of stigma. the nucleus inside the pollen grain moves down the tube as the tube grows down the style towards the ovary. once the nucleus of the pollen grain and the nucleus of the ovum have fused that particular ovule has been fertilised and a zygote has been formed. the zygote will then start to divide.
seed and fruit formation
after fertilisation, the ovule that contains the zygote develops into a seed. the wall of the ovule develops into the seed coat known as the testa. the parts of the flower surrounding the ovule develop into fruit which contains the seeds. the fruit provides a mechanism for seed dispersal. some fruits are eaten by animals which then disperse the seeds in their dropping as the tough outer shell of the seed stops them being digested
germination
germination is the start of growth in the seed. the seed contains the zygote which divides into cells that then develop into the embryo plant. when the seed germinates, this embryo beings to grow into a young seedling. cotyledons surround the embryo. cotyledons contain food reserves that supply the young seedling with food when the seeds starts to germinate. the cotyleons fulfil this role until the young plant grows its own leaves and becomes capable of making its own food via photosynthesis. after taking in water, the seed coat splits and this leads to the production of the plumule and radicle
