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
Testes produce
sperm
Testes produce
testes, as well as providing a sort of climate control system
Sperm duct carries
sperm away from testis, it then join up with the urethra just below the bladder
Urethra
can carry both urine and sperm at different time
Prostate gland
makes semen, a fluid in which sperm can swim in.
Function of penis
to enter the vagina and release sperm.
Ovaries produce
eggs or egg cells.
Oviducts lead the
egg to uterus.
Uterus
nourish the developing fetus prior to birth
Cervix
allows fluids to pass between uterus and vagina
Vagina
the site where sperms are placed after ejaculation
Fertilization is the fusion of the nuclei from a
male gamete (sperm) and a female gamete (egg cell).
Adaptation of sperm:
flagellum to swim
lots of mitochondria to provide energy for swimming by respiration.
enzymes in the acrosome to digest its way through the jelly coat.
Adaptation of egg cell:
energy store to provide energy and nutrients for the growth and development of
zygote after fertilisation.
jelly coat hardens after the entry of one sperm to prevent entry of multiple
sperms.
sperms compared to egg cells
Sperm cells are lot smaller than egg cells. Sperm cells are streamlined and egg cells
are round. Sperm cells can move by themselves but egg cells cannot. There are
millions of sperms deposited at the vagina but there are maximum of 2 egg cells in
female reproductive system.
In early development,
the zygote forms an embryo which is a ball of cells that
implants into the lining of the uterus.
Placenta connects the
embryo to wall of uterus. Placenta is where substances are exchanged between the mother’s blood and the embryo’s blood.
Role of placenta in humans:
gas exchange
transfer of dissolved nutrients, from maternal (circulation)/ to fetal.
transfer of excretory products, from fetal/ to maternal;
by diffusion
produces/ secretes, (named) hormones;
passive immunity/ antibodies, from maternal/ to fetal
prevents/ limits, mixing of blood
regulating blood pressure
maternal/ fetal attachment point
red to counter current flow/ maintains concentration gradient
Role of amniotic fluid:
protection from (mechanical) shock (of fetus)
maintains (constant) temperature (of fetus)
allows movement (of fetus)
prevents dehydration
Amniotic fluid and the amniotic sac:
maintains temperature ;
mechanical shock protection ;
allows movement (of the fetus) ;
provides support (of the fetus) ;
provides a sterile environment / prevents infections ;
(movement) allows for development of bones and muscles ;
ref. to swallowing (of fluid) ;
lubrication / AW ;
Some pathogens and toxins can pass across
the placenta and affect the fetus
Testosterone cause the
secondary sexual characters to develop in boys, like growth
of facial hair and pubic hair, broadening shoulders and general muscular
development and a deepening voice
Oestrogen
cause the secondary sexual characters to develop in girls, like increase
in size of breast, growth of pubic hairs, hips become wide
Site of production of oestrogen and progesterone in the menstrual cycle is the
ovaries. After ovulation site of progesterone production is corpus luteum. During
pregnancy site of progesterone production is the placenta.
Changes to the lining of uterus during menstrual cycle:
loss / thinning, of lining (of uterus), at the beginning of the cycle / during first
week / between day 1–7 ;
regrowth / thickening of, lining (of uterus), during second week / after loss (of
lining) / before ovulation ;
thickness of lining remains constant, in the last two weeks / at the end of the
cycle / after ovulation / if no fertilisation ;
The role of FSH.
FSH stimulates, development / growth / maturation, of follicles (in ovary) ;
-FSH stimulates, development/growth / maturation, of, egg (cell) / ova / ovum /
(female) gamete(s) ;
-FSH stimulates, production / release / secretion, of oestrogen (from ovary) ;
The role of LH.
(FSH and) LH (surge) stimulates, ovulation / release of egg from ovary
LH stimulates (corpus luteum / yellow body / empty follicle), secretion /
production / release, of progesterone
decrease in LH decreases secretion of progesterone (by corpus luteum) ;
The role of estrogen.
Stimulates the uterus to develop a lining (to replace the lining lost during
menstruation)
Post-ovulation, inhibits FSH and LH production in the pituitary gland.
The role of progestogen.
maintains and thickens lining of the uterus
inhibits FSH and LH production
if fertilisation doesn’t occur, levels drop and menstruation occurs.
Sexually transmitted infection (STI)
is an infection that is transmitted through sexual
contact.
Human immunodeficiency virus (HIV)
is a pathogen that causes an STI.
HIV infection may lead to
AIDS
Methods of transmission of HIV:
sexual contact
sharing contaminated needles
sharing contaminated syringes
blood transfusion
breast milk
tissue/ organ transplant
HIV is not spread through
saliva
Methods to stop the spread of STIs:
never have more than one sexual partner use condoms
