ch8 sexual reproduction Flashcards
what is asexual reproduction
process resulting in the production of genetically identical offspring from one parent only
what are the types of asexual reproduction
- binary fission
- spore formation
- vegetative reproduction
what is binary fission
- single parent cells divides into two daughter cells
- examples is bacteria
what is spore formation
- reproduction by forming spores, which, under favorable conditions, form new organisms
- examples are fungi and fern
what is vegetative reproduction
organisms produce a new individual from a vegetative part of the plant
examples are potato and ginger
what are bulbs and tubers (and how do they help asexual reproduction)
- food storage organs
- budding can occur here to produce new genetically identical plants
what are runners and how do they help aseual reproduction
- side shoots that have tiny plantlets on them
- plantlets grow roots and develop into seperate but gentically identical plants
what are the advantages of asexual reproduction
- quick
- only one parent needed
- no gametes needed
- all good characterisitcs are passed on
- no dispersal leads to plants growing in the same beneeficial environment as parents
- can store large amounts of food leading to rapid growth
disadvantages of asexual reproduction
- little variation leads to difficulties in adapting to new environments
- offsprings inherit al bad characteristics
- lack of dispersal leads to competition for sunlight, nutrients and water
what is sexual reproduction
process involving the fusion of the nuclei of to gametes to form a zygote to form a offspring that is genetically different
what are the advantages of sexual reproduction
- variation makes adaptation easier
- disease resistance
disadvanatges of sexual reproduction
- 2 parents needed
- growth is slow
- might be less successful than parent is at growing
what is gametes
- sex cell
- haploid nucleus (half of normal cell chromosomes, for humans its 23)
what is zygote
- fusion of male and female gametes
- fertilised egg cell
- contains full set of 43 chromosomes
what are flowers
- reproductive organ of the plant
- contain male and female reproductive parts
what is pollen
- contains nucleus that is male gamete
- relies on plants mechanisms to be transferred from anther to stigma
what are the two pollination proccesses
- by wind
- by insects
what is sepal
protects unopened flower (bud)
what are petals
bright colored and sometimes scented to attract insects
what is anther
produces and releases male sex cell (pollen grain)
what is stigma
top of the female part of the flower that collects pollen grains
what is ovary
produces female sex cell (ovum)
what is ovule
contains female sex cells
found in ovary
features of insect pollinated flower (6)
- petals to attract insect
- scent/nectar to attract insect inside the flower
- moderate pollen grains - transfer is already effiecient
- large sticky/spiky pollen grains to stick to insect
- stiff anthers to brush against insects
- sticky stigma so pollen sticks to it
features of wind pollinated flower (6)
- dull petals
- no scent/nectar waste of energy to produce as no insects
- large number of pollen grain szo hhigher chance of stigma catchin
- smooth small light pollen grins to be carried by the wind
- anthers swinging loosely outside flowers to release pollens easily
- stigma outside flower and feathery to catch drifting pollen
what is cross pollination
pollen from one plant is transferred to stigma of another plant from the same species
advantage of cross pollination
improves genetic variation
disadvantage of cross pollination
relies completley on presence of other pollinators
what is self pollination
pollen lands on stigma of own flower or different flower of same plant
advantage of self pollination
does not rely on presence of pollinators
disadvantage of self pollination
no variation
what is fertilisation
pollen fuses with an ovum in the ovule
how does the pollen reach the ovule from the stigma
- grows a pollen tube
- nuleus in pollen grain slips down the tube
- fuses with one of the ovums in the ovary
how is a seed formed
- zygote is formed after fertilisation
- zygote divides and forms seeds
- different plnts had different numbers of ovules so different number of seeds
what is germination
start of growth in the seed
what is needed for germination
- water for seed to swell up and start enzymes in embryo for growth
- oxygen for energy for growth
- warmth - optimum temperature for enzymes
parts of female reproductive system
- ovaries
- oviduct/fallopian tube
- uterus
- cervix
- vagina
parts of male reproductive system
- testes
- scrotum
- sperm ducts
- prostate gland
- urethra
- penis
function of ovaries
- contains follicles that develop the ovum
- produces oestrogen and progesterone
funtion of oviduct/fallopian tube
- carries ovum to the uterus
- fertilisation usually occurs in the first third of the oviduct
function of uterus
- site for zygote implantation after fertilization
- where fetus develops
- during pregnancy, uterus increases in volume
function of cervix
- ring of muscle that keeps baby in uterus
- relaxes during childbirth
function of vagina
- recieves penis during intercourse
- baby comes out of at birth
function of testes
produces sperm and testosterone
function of scrotum
holds testes outside body for ideal temperature for production of sperm
function of sperm ducts
carries sperm from testis to urethra
function of prostate glands
produces seminal fluid (makes up most of semen)
function of urethra
carries semen from sperm duct to penis
function of penis
- becomes erect when filled with blood
- penetrates vagina to deliver sperm
size of ovum (female gamete)
biggest cell in body
size of sperm (male gamete)
smallest cell in body
amount of ovum produced
smal numbers, only once amonth
amount of sperm produced
produces in large number
mobility of ovum
no mobility
mobility of sperm
can swim using flagellum
chromosomes of gametes
23 each (haploid nucleus)
specilaized features of ovum
- cytoplasm contains food stores for development of zygote
- jellycoat that initiates acrosoe reaction in sperm and changes at fertilisation
specialized features of sperm
- flagellum for mobility
- mitochondira for energy for mobility
- acrosome for enzymes to penetrate egg
what happens before fertilization in humans
- cilia cells of oviduct + peristalsis move egg towards uterus
- sperm swims up uterus towards oviduct
proccess of fertilization in humans (8)
- The sperm reaches the ovum
- The acrosome secretes enzymes which allows it to burrow through the jelly coat
- The sperm’s head will disconnect with its flagellum (tail) by binding to the plasma membrane
- The sperm’s cell membrane then fuses with the ovum’s plasma membrane
- This releases the sperm’s nucleus into the ovum
- A fertilization membrane forms to prevent other sperms from entering
- When the sperm’s nucleus and the ovum’s nucleus fuse together, this is called fertilization
- A haploid sperm and a haploid ovum fuse together to form a diploid nucleus
process of implantation (3)
- The zygote starts dividing into several cells by mitosis as it travels down to the uterus
- The zygote will become a ball of cells (blastocyst) and is considered an embryo
- When the embryo reaches the uterus, it will sink and bury into the uterus lining
function of umbilical cord
Connects the fetus to the placenta
Contains 2 arteries that deliver blood from the fetus to the placenta for material exchange
Contains one vein, delivering the blood back from the placenta to the fetus
function of placenta
Has finger-like projections called villi that burrows into the uterus lining that is rich in blood supply
Villi - provides a thin, large surface area to allow efficient material exchange between the fetus’ blood and the mother’s blood via diffusion
There is no mixing of blood as the mother’s blood and the babies blood could be different and incompatible, which could result in blood clotting
what is amniotic sac
The fetus is surrounded by the amniotic sac (amnion)
The amniotic sac is a membrane that encloses the amniotic fluid
The sac ruptures just before birth
function of amniotic fluid
The amniotic fluid protects the fetus from
Mechanical shock
Drying out
Temperature fluctuations
what is antenatal care
Guidance on motherhood
Checks on foetus and mother including: weight check, blood tests, urine tests, blood pressure checks, ultrasound scanning etc.
mothers diet during antenatal care
More proteins → growth of foetus
Slightly more fat → the new cells’ cell membrane
More vitamin C and D → blood vessel walls and bones
Iron → haemoglobin
Calcium → growth of bones and teeth
things to avoid during pregnancy
Drugs: aspirin, heroin - damage fetus’ nervous system, babies born addicted
Smoking: nicotine (can cross the placenta)
Smoking: CO - reduce oxygen transport across placenta (babies born to smokers may have low birth weight, foetal brain damage, increased risk of lung infection)
Alcohol drinking: premature babies, reduced birth weight
Viruses: HIV, rubella (can pass across the placenta)
process of labour and birth
Birth begins when the muscle of the uterus starts to contract. (this is triggered by the hormone oxytocin)
The pressure causes the amniotic sac to break and release the amniotic fluid (water break)
The contractions become more powerful and more frequent to push the baby down while the cervix dilates until it is wide enough for the baby’s head to pass through
advantages of breast feeding
- antibodies so no harmful bacteria
- correct proportion of nutrients
- correct temperature
- builds emotional bond
- no cost/preparation
- reduces uterus size after birth
disadvantages of breast feeding
- painful
- need for mother
- damages beauty
advantages of bottle feeding
- no pain
- no need for mother
- may contain supplement nutrients
disadvantages of bottle feeding
- expensive
- risk or wrong mixture
- risk of illness
what is fsh and roles
FSH (follicle-stimulating hormone) is released by the pituitary gland and causes an egg to start maturing in the ovary
It also stimulates the ovaries to start releasing oestrogen
what is lh and roles
The pituitary gland is stimulated to release luteinising hormone (LH) when oestrogen levels have reached their peak
LH causes ovulation to occur and also stimulates the ovary to produce progesterone
what is oestrogen and roles
Oestrogen levels rise from day 1 to peak just before day 14
This causes the uterine wall to start thickening and the egg to mature
The peak in oestrogen occurs just before the egg is released
what is progesterone and roles
Progesterone stays low from day 1 – 14 and starts to rise once ovulation has occurred
The increasing levels cause the uterine lining to thicken further; a fall in progesterone levels causes the uterine lining to break down (menstruation / ‘period’)
interaction with all 4 hormones(10)
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
what is the male hormone
testosterone
what is the female hormone
oestrogen
what is pirmary sexual characteristics
diiferences in sexual organs that ppl ar eborn with
what is secondadry sexual characteristics
diifereneces between male anf female that develop during puberty
what is ovulation and when does it occur
its release of egg and occurs halfway through cycle at 14 days
what does failure to fertilise egg result in
break down of uterus lining (menstruation)
what is mensturation controlled by
hormones secreted from pituary gland in brain and ovary (oestorgen and progesterone)
descirbe oestrogen levels
rise from day 1 and peak around day 14
describe progesterone
low from 1-14 and rise after ovulation
what are the 4 methods of birth control
Natural
Chemical
Barrier
Surgical
methods of natural birth control
- abstinence
- monitoring body temersture
- monitoring cervical mucus
- calendar/rhythm method
methods of chemical birth control/hormone
- IUD (intrauterine devices)
- IUS
- Contraceptive pills
- implant in arm (stops ovulation)
- injection of projesterone
methods of barrier
- condom
- femidom
- diaphragm/cap
surgical birth control methods
- vasectomy (men)
- sterilization (women)
fertility treatment - hormones
- use of drugs containing fsh and lh to increase chance of pregnancy
- may reuslt in twins and triplets
fertility treatment - artifical insemination
- sperm inseted into womans uterus close to time of ovulation
IVF (in vitro fertilisation)
egg is taken out and fertilised with sperm in petri dish then placed back for implntatgion
what are stis/stds
Infection that is transmitted via body fluids through sexual contact
how is hiv aids transferred
Unprotected sex with an infected person
Contact with an infected person’s blood through blood transplants, organ transplants etc.
From mother to child, during pregnancy, childbirth and breastfeeding
Sharing syringes while injecting drugs
how does hiv affect
The virus slowly destroys the lymphocytes and reduces its numbers
Also decrease the ability of the body to produce antibodies
Body has no immune system and cannot fight against other infections such as pneumonia and tuberculosis
May develop cancer cells
There is still no cure, antiviral treatment may allow down progress of full blown AIDS
why do gametes have to be haploid
so that chromosome number does not double (at fertilisation) ;
so that chromosome number remains constant from generation to generation
