reproduction Flashcards
what are the advantages of asexual reproduction?
- useful when the environment is stable
- completed much faster
- enables an organism to quickly populate
- more time + energy efficient
- if it’s well adapted to its environment, successful characteristics are carried on
what are the disadvantages of asexual reproduction?
- disease likely to affect the whole population as there is no genetic variation
- population is only suited to one habitat
- population is vulnerable to changes in conditions
- limited genetic variation in population
what are the two types of cell division?
mitosis and meiosis
what is the use of meiosis?
to produce gametes for sexual reproduction
what is the use of mitosis?
growth and repair
how many daughter cells are made in mitosis?
two genetically identical daughter cells
are offsprings from sexual reproduction genetically identical?
no, they are genetically different
how many chromosomes do the daughter cells contain and why is this important?
- 23 (a haploid amount)
- important so zygote has correct number when gametes fuse
how many daughter cells are produced in meiosis?
4 genetically different daughter cells
how many cell divisions occur in mitosis and meiosis?
- 2 cell division in meiosis
- 1 cell division in mitosis
how does sexual reproduction lead to variation in offspring?
there are two parent cells, so two sets of genetic information
where does mitosis occur?
all body cells, except the gametes
where does meiosis occur?
only in the gametes
what is the function of the sepal?
to protect the unopened flower
what is the function of the petal?
may be brightly coloured to attract insects
what is the function of the stamen?
male part of the flower, comprising an anther attached to the filament
what is the function of the anther?
produces the male sex cells (pollen)
what is the function of the stigma?
the top of the female part go the flower, which collects pollen grains
what is the function of the ovary (plants)?
produces the female sex cells (contained in the ovules)
pollination definition.
pollination is the transfer from anther to stigma of a plant
position of stamen in insect pollinated plants
enclosed so the insect has to make contact
position of stamen in wind pollinated plants
exposed so pollen can easily blow away
position of stigma in insect pollinated plants
enclosed so insect has to make contact
position of stigma in wind pollinated plants
exposed to catch pollen blowing in the wind
type of stigma in insect pollinated plants
sticky so pollen grains can attach from insects
type of stigma in wind pollinated plants
feathery so it can catch pollen grains blown by
size of petals in insect pollinated plants
large and colourful to attract insects
size of petals in wind pollinated plants
small because it doesn’t need to attract insects
colour of petals in insect pollinated plants
bright and colourful to attract insects
colour of petals in wind pollinated plants
dull, green mostly
nectary’s in insect pollinated plants
present - they produce nectar, a sweet liquid containing sugars as a reward for insects
nectary’s in wind pollinated plants
not present - don’t need to attract insects
pollen grains in insect pollinated plants
sticky and large
pollen grains in wind pollinated plants
smaller, smooth, inflated grains to carry in the wind
what is self-pollination?
when pollen goes from the anther to the stigma of the same plants, this can result in a genetically weaker plant
what is cross-pollination
when pollen goes from one plant to another of the same type, this results in stronger plants
fertilisation definition
the fusion of gametes to form a zygote
the order of pollination and fertilisation in a plant.
- a pollen grain on the stigma grows a tiny tube, all the way down the style to the ovary. (pollen tube releases digestive enzymes to digest way through tissue of style into ovary)
- the pollen tube carries a male gamete to meet a female gamete in an ovule
- the pollen tube curves around the ovule to enter the opening in an ovule
- the tip of the tube dissolves and allows the pollen grain nucleus to move out of the tube and into the ovule
- the nucleus of the pollen grain MUST fuse with the nucleus of the ovum for fertilisation to occur
- the two gametes join and their chromosomes combine, so that the fertilised cell contains a normal complement of chromosomes, with some from each parent flower
- after fertilisation, female parts of the flower develop into a fruit seed
- the rest of the carpel becomes a fruit
name 4 methods of seed dispersal
- wind dispersal
- water dispersal
- animal dispersal
- bursting
what does a seed contain?
- a plant embryo
- root (radical)
- shoot (plumule)
- one or two seed leaves
- starch
what 3 factors are required for successful germination?
- water
- oxygen
- warmth
what are the male gametes called?
sperm cells
when are male gametes produced?
always, continuously from birth
where are the male gametes produced?
testes
function of the bladder
the body’s urine storage tank
function of the sperm duct
sperm passes through and mixes with fluids containing nutrients
function of the testes
exocrine gland - produces sperm via meiosis
endocrine gland - produces testosterone
function of the seminal vesicle
produces a fluid which mixes with the sperm to form semen
function of the urethra
tube inside penis which carries urine/semen - contains ring of muscle which prevents them mixing
function of the penis
passes urine out of the body and passes semen into the vagina
function of the scrotum
pouch which holds the testes - must be held outside body as sperm production requires a lower temperature of 35 degrees
function of the prostate gland
produces seminal fluid
what are the female gametes called
egg cell
where are the female gametes released from?
ovary
function of the fallopian tube
connects the ovary to the uterus, lined with cilia that waft the egg along and into uterus, site of fertilisation
function of the uterus
a muscular bag with soft lining, where foetus develops until birth
function of the cervix
a ring of muscle - keeps foetus inside uterus
function of ovaries
have hundreds of undeveloped ova - one is released per month
function of the vagina
muscular tube that leads from the cervix to outside the body
what is the purpose of the villi in the placenta?
- increases surface area:volume
-> increases rate of diffusion
-> nutrients can be transported faster
why should the blood flow in opposite directions in the placenta?
- to stop it mixing
-> possibility of different blood types
-> the body will try fight the other blood type - maintain concentration gradient across whole blood vessel
adaptations of the placenta
- large surface area with villi
- good blood supply -> maintain concentration gradient
- keeps harmful molecules out
where its produced and function of testosterone
testes - to produce sperm
where its produced and function of FSH
pituitary gland - stimulates egg development and ovulation
where its produced and function of oestrogen
ovaries - stimulates thickening of uterus lining
where its produced and function of LH
pituitary gland - surges to stimulate ovulation, causes egg to mature
where its produced and function of progesterone
ovaries - maintains uterus lining, stops production of FSH and LH
which hormones increase on day 4 of menstruation
FSH and ovulation
which hormones increase of day 14 of ovulation
LH and progesterone
how can plants reproduce asexually
BUDDING
- process in which a new plant grows out of the bud on the parent plant
RUNNERS
- grow side shoots called runners via mitosis
role of the amniotic fluid in protecting the foetus
- protects the foetus from jolts and bumps
- keeps temperature fairly constant
how is the foetus protected by amniotic fluid
- a membrane called amnion (amniotic sac) encloses the foetus
- this secretes a fluid called amniotic fluid
