Reproduction Flashcards
Definition of sexual reproduction
The joining of two sex cells or gametes during during fertilisation
Two characters of sexual reproduction
- two parents needed
- offspring produced are genetically different to the parent
Two characteristics of asexual reproduction
- One parent needed
- offspring produced are genetically identical to the parent (eg bacteria, production of spores by fungi)
Three advantages of sexual reproduction
- introduces variation into a population
- species can adapt to new environments
- disease is less likely to affect all the individuals in a population
Two advantages of asexual reproduction
- population can increase rapidly
- can exploit a suitable habitat quickly
Two disadvantages of sexual reproduction
- time and energy needed to find a mate
- not possible for an isolated individual
Three disadvantages of asexual reproduction
- does not lead to variation in a species
- species may only be suited to one habitat
- disease may affect all the individuals in a population
Name a natural method for the reproduction of plants
Runners
Name an artificial method for the reproduction of plants
Cuttings
Explain how runners can be used in the asexual reproduction of plants.
- cells split off from the parent plant to grow a radicle (side branch) which forms plantlets
- this forms a plant that is genetically identical to the parent plant via asexual reproduction (cloning)
Explain how cuttings can be used in the asexual reproduction of plants.
- specific plant tissue is selected and sterilised
- tissue sample is taken and grown in a petri dish containing sterile nutrient agar gel
- the explant is treated with auxins to stimulate shoot + root development
- once root and shoot are developed, the cloned plant is then transferred to soil
define fertilisation
the fusion of a male and female gamete to produce a zygote that undergoes cell division and develops into an embryo
Describe the process of fertilisation in plants
- Digestive enzymes are produced by the tip of the pollen tube, enabling it to grow through the style and ovary tissues and reach the ovule.
- The pollen grain enters the ovule through a small gap, the micropyle , to reach the egg cell (the female gamete).
- The male nucleus/gamete is then able to travel down the pollen tube into the ovule, so that it can fuse with the egg cell (fertilisation).
The plant zygote becomes…
The seed
Petals (wind pollinated)
Scentless, inconspicuous or absent (replaced by another structure)
Nectar and scent (wind pollinated)
None
Stamen (wind pollinated)
Long filaments so anthers hang outside flower when ripe.
Pollen (wind pollinated)
Grains with smooth surface to help float through the air. Produced in large quantities.
Stigma (wind pollinated)
Often feathery and hangs outside flower to increase chance of catching pollen in the air.
petals (insect pollinated)
Often scented and brightly coloured
Nectar and scent (insect pollinated)
Insects feed on nectar (a sticky solution) and are attracted by scent.
stamen (insect pollinated)
Enclosed in flower
Pollen (insect pollinated)
Grains with surface features that help to stick to insects and stigma. Produced in small quantities
Stigma (insect pollinated)
Enclosed in flower so that the insect brushes past it when entering flower. Top surface yellow to hold pollen.
what is the plumule
the first emerging shoot
what is the radicle
the first emerging root
what is the cotyledon ?
- contain food reserves that supply the young seedling with food when it starts to germinate
- the cotyledons fulfil this role until the young plant grows its own leaves and becomes capable of making its own food via photosynthesis
describe the order of hormones in the menstrual cycle
(day 1) FSH -> oestrogen -> LH -> progesterone (day 28)
where is FSH released?
in the pituitary gland
what are the roles of FSH in the menstrual cycle?
- causes an egg to develop in the ovaries
- stimulates production of oestrogen
where is oestrogen released?
oestrogen is produced in the ovaries
what are the roles of oestrogen in the menstrual cycle?
- inhibits production of FSH
- causes the uterus lining to thicken and grow
- stimulates the production of LH
where is LH released?
pituitary gland
what are the roles of LH in the menstrual cycle?
- inhibits the production of oestrogen
- stimulates. the release of an egg at day 14 (ovulation)
- stimulates the production of progesterone
where is progesterone released?
ovaries
what are the roles of progesterone in the menstrual cycle?
- inhibits the production of LH
- maintains the lining of the uterus
give 3 adaptations of the placenta
- large SA
- villi
- rich supply of maternal blood vessels
mother -> foetus
water, amino acids, fatty acids, glycerol, glucose, antibodies
foetus -> mother
CO2, urea
what is the role of the placenta?
allows substances to diffuse from the mother’s blood to the foetus and vice versa
what is the role of the amniotic sac?
a membrane that forms around the embryo (made up of mostly foetal urine) which protects the embryo by cushioning impacts.
describe 5 effects of testosterone on males？
- voice breaks
- testes start to produce sperm cells
- hair grows on face and body
- body becomes more muscular
- sexual organs grow and develop
describe 5 effects of oestrogen on females?
- hips get wider
- breasts develop
- ovaries start to release egg cells and menstruation starts
- sexual organs grow and develop
- pubic hair grows
state the functions of the testes
- to produce sperm (the male gametes or sex cells)
- to make testosterone
state the functions of the testes
- to produce sperm
- to make testosterone
state the function of the scrotum
the bag of skin that protects the testicles and keeps them at optimum temperature.
give the function of the sperm ducts
carry sperm from the testicles to the seminal vesicles.
give the function of the seminal vesicles
where sperm is mixed with semen.
