❤️🔥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
apparatus to investigate conditions for germination
test tubes, test tube holder, cress seeds, cotton wool, fridge
method to investigate conditions for germination
1) set up 4 test tubes, each containing 10 cress seeds on cotton wool
2) label the test tubes A B C D- test tube A leave the cotton wool dry, B add enough water to the cotton wool so that it becomes moist, C add enough water to cover the cotton wool and seeds and carefully add a layer of oil on top, D add enough water to the cotton wool so it becomes moist
3) leave test tubes A B C at room temp or a specific temp
4) place D in the fridge
5) leave all test tubes for a set period
6) compare results on what test tube has the most germinated seeds
corms to investigate conditions for germination
c- we are changing the abiotic conditions in which the seeds are germinating
o- the cress seeds will all be taken from the same parent plant
r- we will repeat the investigation several times to ensure our results are reliable
m- we will record how many seeds in each test tube germinate after a set time period.
s-we will control the temperature for tubes A B C. we will also control the type of water used etc sterile water
artificial way of asexual reproduction
take cuttings to make clones of plants
method to take cuttings
make sure to choose a good parent plant. a section of the parent plant with a new bud is cut off. this cutting can be then placed in water until new roots grow or can be placed directly in soil. these cuttings are then planted and eventually grow into adult plants that are genetically identical to the original plant
benefit of taking cuttings
plants can be cloned cheaply and quickly
prostate gland
produces fluid called semen that provide sperm cells with nutrients
sperm duct
sperm passes through the sperm duct to be mixed with fluids produced by the glands before being passed into the urethra for ejaculation
urethra
tube running down the centre of the penis that can carry out urine or semen, a ring of muscle in the urethra prevents the urine and semen from mixing
testis
contained in a bag of skin and produces sperm and testosterone
scrotum
sac supporting the testes outside the body to ensure sperm are kept at temperature slightly lower than body temp
penis
passes urine out of the body from the bladder and allows semen to pass into the vagina of a woman during sexual intercorse
oviduct
connects the ovary to the uterus and is lined with ciliated cells to push the released ovum down it. fertilisation occurs here
ovary
contains ova which will mature and develop when hormones are released
uterus
muscular bag with soft lining where the zygote will be implanted to develop into a foetus
cervix
ring of muscles at the lower end of the uterus to keep the developing foetus in place during pregnancy
vagina
muscular tube that leads to the inside of the woman’s body where the male penis will enter during sex and sperm will be deposited
human sexual intercorse
during ejaculation in the male millions of sperm cells move along the sperm duct. the sperm are suspended in semen. the semen passes into the urethra. the sperm is then ejaculated into the vagina and the sperm cells then follow a chemical trail and travel through the plug of mucus in the cervix to reach the uterus. the sperm then travels to the oviduct so fetilisation can occur
fertilisation of the sperm and egg
during fertilisation the head of the sperm cell releases enzymes that digest a path through the protective outer layer of the egg cell allowing sperm to pass through the egg cell membrane. once this occurs the egg cell immediately releases a thick layer of material that prevents any more sperm cells from entering ensuring only one sperm cell can fertilise the egg cell
what happens after fertilisation in the oviduct
the zygote travels towards the uterus
how long does it take the zygote to travel to the uterus
about 3 days- during this time the zygote will divide several times to form a ball of cells known as an embryo
what happens wants the zygote travels to the uterus
the embryo embeds itself in the thick lining of the uterus (a process known as implantation) and continues to grow and develop
the placenta forms when
the embryo attatches
the placenta is
an organ that ensures materials can be exchanged between the blood of the mother and the blood of the growing embryo. the umbilical cord joins there embryos blood supply to the placenta for exchange of nutrients and removal of waste products
the embryo is surrounded by
amniotic fluid (a fluid made from the mothers plasma) and is self by the amniotic membrane (also known as the amniotic sac
the amniotic fluid
protects the embryo during development by cushioning it from bumps to the mothers abdomen
gestation period
the 9 months that the embryo grows in the uterus
the major development of the babies organs take place within
the first 12 weeks, during this time the embryo gets nutrients from the mother by diffusion through the uterus lining. after this point the organs are all in place, the placenta has fully formed and the embryo is now called a foetus. the remaing gestation is time for the foetus to grow bigger in size
what does the foetus gain during the gestation period
glucose, amino acids, fatty acids, water, oxygen, mineral ions and vitamins from the mothers blooding
in the placenta the mothers blood
comes into very close proximity to the blood of the foetus but never mixes
what connects the foetus’s blood and placenta
umbilical chord
what does the mothers blood absorb from the foetus’s blood in the placenta
waste products such as carbon and urea so they don’t build up to a dangerous level in the foetus’s blood
the movement of most molecules across the placenta occurs by
diffusion due to difference in concentration gradients- for some substances that need to be moved active transport may be used
the placenta is adapted for diffusion by
having a large surface area and a thin wall for efficient diffusion
the placenta acts as a barrier for
preventing toxins and pathogens getting into the foetus’s blood- not all toxin molecules or pathogenic organisms are stopped passing through the placenta (usually depends on the size of the molecule). this is why women are advised not to smoke during pregnancy as molecules such as nicotine can pass across the placenta
afterbirth
when the placenta detaches from the uterus wall shortly after birth and is pushed out due to contractions in the muscular wall of the uterus
effects of oestrogen
breasts develop, body hair grows, menstrual cycle begins, hips get wider
effects of testosterone
growth of penis and testes, growth of facial hair and body hair, muscles develop, voice breaks, testes start to produce sperm
menstrual cycle
starts at around age 12 and is controlled by hormones, average cycle is 28 days, ovulation occurs at about day 14 and the egg travels down the oviduct to the uterus, failure to fertilise the egg causes menstruation to occur- its caused by the breakdown of the thickened lining of the uterus, menstruation usually lasts about 5-7 days, after menstruation finishes the lining of the uterus starts to thicken again in preparation for possible implantation in the next cycle
the menstrual cycle is controlled by
hormones released from the ovary and the pituitary gland in the brain
oestrogen levels rise
from day 1 and peak before day 14- this causes the uterine line to start thickening and the egg to mature
the peak in oestrogen is just before
the egg is released
progesterone levels
stay low from day 1-14 and start to rise once ovulation has occurred
the increasing levels of progesterone cause
the uterine lining to thicken further- a fall in progesterone causes the uterine lining to break down (period caused)
oestrogen
stimulates the uterus to develop a lining, post ovulation it inhibits FSH and LH production in the pituitary gland
progesterone
maintains and thickens lining of the uterus, inhibits FSH and LH production, if fertilisation doesn’t occur levels drop and menstruation occurs
interaction between the four menstrual cycle hormones
The pituitary gland produces FSH which stimulates the development of a follicle in the ovary
An egg develops inside the follicle and the follicle produces the hormone oestrogen
Oestrogen causes growth and repair of the lining of the uterus wall and inhibits production of FSH
When oestrogen rises to a high enough level it stimulates the release of LH from the pituitary gland which causes ovulation (usually around day 14 of the cycle)
The follicle becomes the corpus luteum and starts producing progesterone
Progesterone maintains the uterus lining (the thickness of the uterus wall)
If the ovum is not fertilised, the corpus luteum breaks down and progesterone levels drop
This causes menstruation, where the uterus lining breaks down and is removed through the vagina - commonly known as having a period
If pregnancy does occur the corpus luteum continues to produce progesterone, preventing the uterus lining from breaking down and aborting the pregnancy
It does this until the placenta has developed, at which point it starts secreting progesterone and continues to do so throughout the pregnancy
