Reproduction Flashcards
Asexual reproduction
process resulting in the production of genetically identical
offspring from one parent
Advantages of asexual reproduction:
wild species that are adapted to
the environment can survive.
isolated wild species can
reproduce because only single
parent is required.
crop plants are genetically
identical therefore they have the
same yield and characteristics.
require less energy.
quick
no gametes
favourable characteristics of
parent passed on
dense colonies outcompete other
species
no pollinators required
reliable
no harmful variation
Disadvantage of asexual
reproduction:
less variation
lack of diversity in wild plants
risk of overpopulation in wild
plants
competition for resources as all
individuals are close together in
wild plants
wild plants and crops are less
likely to survive to change
environment
no adaptive features in wild
plants
all individuals are susceptible to
the same, diseases/pests in wild
plants
higher risk of extinction in the wild
plants
no evolution in wild plants
genetically identical so higher risk
of inheriting genetic diseases in
both wild and crop plants
Sexual reproduction
process involving the fusion of the nuclei of two gametes to
form a zygote and the production of offspring that are genetically different from each
other.
Fertilisation
fusion of the nuclei of gametes.
Nuclei of gametes are
haploid
nucleus of a zygote
is diploid
Advantages of sexual reproduction
maintain/ increase, the population in wild plants
allow variation in wild plants
allow adaptation to, new/ changed
environment(s) in wild plants
allow natural selection/ evolution/ formation
of new species in wild plants
random fusion of gametes in wild plants
ability to express recessive trails in wildplants
allows to use of selective breeding in crop
plants
Disadvantages of sexual
reproduction
Slow
Lots of energy is
needed
Need 2 parents
Sepals:
Protect the flower while it is a bud
Petals:
Brightly coloured and attract insects to flowers
Stamen
It is male part of flower, consists of long filament and anther at the top which contain pollen grain, which contain male gametes
Carpel:
It is the female part of flower. It contains ovary, which contains ovules,
which contains female gamete. At top is style with stigma at the top. function of
stigma is to catch pollen grains.
Insect pollinated flower
large, brightly coloured petals, strong scent, nectar to
attract insects towards them. The anther and stigma are inside the flower so that the
insect brush past them and some pollen stick onto them. The insect then goes to
another flower, looking for more nectar. Pollen grains are sticky and spiky so, some
of the pollen it picked up at the first flower sticks onto the stigma of the second
flower when the insect brushes past it. The stigma is sticky, and many pollen grains
get stuck on it.
wind pollinated flower
produce much more pollen than insect pollinated flowers.
This is because a lot of the pollen doesn’t land on another flower, so huge amounts
are wasted. Usually no petals because there is no need to attract insects. Their
anthers and stigmas dangle outside the flower, to catch the wind. The filaments of
the anthers are very flexible, so they can swing in the wind and release their pollen.
The feathery stigmas have a large surface area, increasing the chances of catching
pollen.
Pollination
transfer of pollen grains from an anther to a stigma.
Self-pollination
transfer of pollen grains from the anther of a flower to the
stigma of the same flower or a different flower on the same plant.
Cross-pollination
transfer of pollen grains from the anther of a flower to the
stigma of a flower on a different plant of the same species.
Self-pollination doesn’t produce
lots of variation. Less capacity to respond to changes in the environment. They don’t rely on pollinators
Cross-pollination produce
variation. More capacity to respond to changes in the
environment. They rely on pollinators.
Fertilization occurs when
a pollen nucleus fuses with a nucleus in an ovule
Events which occur between pollination
and fertilisation.
pollen lands on stigma
pollen (grain) germinates/ pollen (grain)
grows pollen tube
pollen tube grows down the style
reaches the ovule
(tip of) pollen tube breaks open
male gamete travels down the pollen
tube
male gamete enter ovule
(male gamete) fuse with female
gamete
zygote forms.
Events which occur between
fertilisation and production of
seed.
zygote (is formed)
divides by mitosis
to form embryo
formation of radicle and
plumule
formation of, cotyledons/
seed leaf/ food reserve
formation of teste/ seed
coat
ref to endosperm
seed formed form ovule