REPRODUCTION Flashcards
(20 cards)
What is ASEXUAL reproduction?
ASEXUAL REPRODUCTION is a process where genetically identical offspring are produced from one parent plant.
It does not require a gamete or fertilisation.
What is SEXUAL reproduction?
SEXUAL REPRODUCTION is the process of the nuclei of two gametes fusing to form a zygote,
And the production of genetically different offspring.
DIFFERENCES BETWEEN SEXUAL AND ASEXUAL reproduction
-ONE PARENT/ TWO PARENTS
-relatively fast/ relatively slow
-relatively large numbers/ limited offspring produced
-cell division by mitosis/MEIOSIS for gametes, then mitosis after fertilisation
the process of SEXUAL REPRODUCTION
-During sexual intercourse, the sperm is ejaculated into the vagina and
- the sperm travels up through the cervix into the uterus
-the sperm can fertilise an egg in the oviduct around 1-2 days after ovulation
-the fertilised egg, then has a full 46 chromosomes, half from each gamete
DESCRIBE the process of fertilisation in plants:
POLLINATION: a pollen grain is transferred (via wind or insect) from the anther of a flower onto the stigma of a flower,
When succesfully pollinated, a pollen tube begins to grow down the style towards the ovary.
-the pollen grain travels down the tube and enters the ovum through a micropyle (a small opening)
-the pollen grain (containing a male nucleus) fuses with the ovum nucleus to form a zygote (FERTILISATION)
-after fertilisation, the ovule develops into a SEED.
-the flower surrounding the ovule develops into FRUIT
-fruit acts as a mechanism for seed dispersal: -eaten by animals and dispersed through their droppings, -sticky hooks that catch onto passing animal fur
What are the 3 KEY FACTORS needed for GERMINATION?
WATER: swells the seed, bursts it open, activates enzymes for growth
OXYGEN: needed for respiration
WARMTH: boosts enzyme activity
SEED AND FRUIT FORMATION in more detail:
1) the zygote forms into an embryonic plant with a root (radicle) and shoot (plumule)
2) other contents of the ovule develops into a food store for when the seed germinates
3) the ovule wall becomes the seed coat or the TESTA
4) the ovary wall becomes the fruit coat
GERMINATION process
During germination, the embryo is surrounded by a food store called a COTYLEDON
(Some plants have two: DICOTS, some have one: MONOCOTS)
-These provide energy for the radicle and plumule to grow,
-water bursts the testa open, and allows the radicle and plumule to emerge
-The radicle grow downwards and can reach minerals and water, the plumule emerges upwards and can reach light, therefore it can begin the process of photosynthesis for food source
PRACTICAL: INVESTIGATING the conditions needed for germination
C- We are changing the abiotic factors in germinating a seed (water, oxygen, warmth)
O- we are investigating on pea seed
R- repeat
M- record how many seeds germinate
M- measure every day for change in growth for two weeks
S- control the temperature of the room, the pea seeds used, control the type of water used
DESCRIBE THE MENSTRUAL CYCLE
At the beginning of the cycle:
-FSH produced from the pituitary glands support the development of an egg in the ovaries,
-FSH also stimulates the hormone OESTROGEN produced by the ovaries-which thickens the uterus lining
-in preparation for the egg being fertilised to implant into
-OESTROGEN suppresses the release of FSH, preventing any more production of eggs
-when OESTROGEN PEAKS, LH is triggered which causes the egg to be released from the follicle
-this happens at around day,14 and is called OVULATION
-the egg travels through the oviduct, where it can be fertilised from sexual intercourse
-the egg eventually becomes a CORPUS LUTEUM which releases PROGESTERONE (made in the ovaries)
-PROGESTERONE inhibits FSH and LH to prevent repeated ovulation
-PROGESTERONE maintains the uterus lining to stay thick, soft and supple, ready for if the egg becomes fertilised
-if the egg IS fertilised: the corpus luteum continues to produce progesterone, and the uterus lining doesn’t shed, menstruation doesn’t occur, and eventually the placenta will overtake and produce progesterone
-if the egg ISN’T fertilised: the corpus luteum breaks down which stops the release of progesterone, the uterus lining begins to shed and passes out through the vagina, this is called MENSTRUATION and lasts for around 2-5 days,
-the FSH and LH is no longer inhibited by the progesterone, and the cycle repeats again
What is the role of the PLACENTA?
The role of the placenta is to allow the exchange of substances between the mother’s blood and that of the fetus
What makes the placenta an EFFICIENT EXCHANGE SURFACE?
1) the PLACENTAL MEMBRANE + VILLI : provides larger surface area to maximise diffusion
2) THIN PLACENTAL MEMBRANE: shorter diffusion distance
What are the 4 functions of the PLACENTA?
1)RESPIRATORY:
-oxygen from MOTHER, CO2 from FOETUS
2)EXCRETION:
-water, glucose, vitamins, fatty acids, amino acids from MOTHER, urea from FOETUS
3)IMMUNITY:
-antibodies from the MOTHER (circulate around the foetus’s body and protects it from viruses transported from the placenta and directly after birth)
4)ENDOCRINE:
-OESTROGEN + PROGESTERONE ( thickens and maintains the uterus lining + prevents the body from rejecting the baby)
Why does the mother and the foetus’s blood never mix?
The mother and foetus have different blood types,
The mother’s immune system could detect the foetus blood as foreign invader
What is AMNIOTIC FLUID
Amniotic fluid surrounds the baby in the womb and protects it from any injuries
- when body is preparing for bith, the amniotic fluid is expelled, “water breaking”
Why does the UTERUS CONTRACT?
To guide the baby out
What does the umbilical cord do?
Connects the embryo’s blood to the placenta
What are the 3 stages of birth?
1) DILATION OF CERVIX: the cervix dilates to allow the baby to pass through, the muscles of the uterus contract and tears the amnion, “waters broken”
2)DELIVERY OF BABY: strong contractions guide the baby and push the head through the cervix, through the vagina and out
3)AFTERBIRTH: the uterus contracts and pushes the placenta out
FEMALE secondary sexual characteristics?
-voice deepens
-increase in body mass + hips become rounder
-menstrual cycle begins
-breasts develop
-pubic +armpit hair growth
-sex “drive” develops
-growth and development of female sexual organs
MALE secondary sexual characteristics?
-voice ‘breaks’ and deepens
-increase in body mass and muscle growth
-public, armpit, chest, facial hair growth
-sperm production begins
-sex “drive” develops
-growth + development of male sexual organs
