D3.1 Reproduction Flashcards
Asexual reproduction
not involving gametes and fertilisation
what does asexual reproduction result in
genetically identical offspring
examples of organisms that Asexually reproduce
greenfly - aquatic hydra
yeast cells and amoeba
sexual reproduction
involving the production and fusion of gametes
offspring have 2 sets of chromosomes
Asexual reproduction method
mitosis
sexual reproduction method
meiosis
Fertilisation
fusion of male and female gametes to form a zygote
variability
random fusion of gametes
produced by combining genes in gametes
external fertilisation
fish do it called spawning
internal fertilisation
sperm into body of females
when does sexual reproduction create variation
if environment is changing and they need to adapt
Gamete
haploid male or female sex cell that is able to unite with another of the other sex to form a zygote
male gamete
small
fewer energy reserves
large numbers produced
female gamete
bigger to save nutrients for zygote/ embryo
fewer - one every month
scrotum
- hanging outside main body cavity
- allows testes to be at optimum temperature for sperm production
- 2-3 degrees lower than body temp
produce sperm and testosterone hormone
epididymis
stores sperm
sperm ducts
carry sperm in a fluid - semen
what is the fluid called that sperm is carried in
seminal fluid
endocrine gland in penis
secrete seminal fluid
include seminal vesicles and prostate gland
what does semen contain
sperm and fluid from seminal vesicles and prostate
urethra
duct that carries semen during an ejaculation to outside
runs from bladder to body outside
penis
external male organ used for urination and sexual intercourse
seminal fluid
male reproductive fluid containing spermatozoa in a liquid that supports the sperm
ovary
female reproductive organ in which the female gametes are formed
gland which secretes oestradiol and progesterone
forms ova or egg cells
oviduct
tube connecting ovary to uterus
site of fertilisation
uterus
the organ in which the embryo develops in female mammals
endometrium
lining of the uterus
built up each month in preparation for implantation
if fertilisation doesnt occur it leads to mensuration
mensuration
shedding of the endometrium from the uterus
vagina
muscular canal leading from uterus to outside the body
cervix
ring of muscles at neck of uterus
secretion of which hormones is cyclical
oesteradiol and progesterone is cyclical
follicle stimulating hormone FSH
hormone that stimulates the growth of ovarian follicles in the ovary
lutenizing hormone LH
hormone that stimulates ovulation and corpus leuteum formation
menstural cycle
monthly cycle of ovulation and mensuration in human females consisting of two cycles
ovarian cycle
monthly changes the occur to ovarian follicles leading to ovulation and the formation of a corpus luteum
monthly preparation and shedding of an egg cell
uterine cycle
cycle of changes to the uterus lining
approx 28 days
building up of uterus lining
what is the menstrual cycle controlled by
negative and positive feedback mechanisms
what is FSH secreted by and on which day
pituitary gland on day 1
day 1 of menstrual cycle
shedding of endometrium
FSH does what
stimulates development of several egg cells
only one develops into a mature egg
second stage of menstrual cycle
follicle secretes oestradiol
uterus - build up of endometrium for implantation
increase in FSH receptors, increasing oestradiol
third stage of menstrual cycle
concentration of oestradiol continues to increase
at highest level it inhibits FSH from pituitary
prevents further follicles from development
fourth stage of menstrual cycle - on the 14th day
stimulates ovulation
what stimulates LH
oestradiol
what secretes progesterone
corpus luteum
uterus on fifth stage of menstrual cycle
build up of endometrium preparing for a possible implantation
pituitary gland on fifth stage of menstrual cycle
inhibits LH and FSH
sixth stage of menstrual cycle
FSH and LH levels decrease
allow corpus luteum to degenerate
levels of progesterone and oestradiol fall
hormones are so low that endometrium breaks down and period
seventh stage of menstrual cycle
new cycle underway
eighth stage of menstrual cycle
if egg is fertilised - embryo becomes endocrine gland and maintains corpus luteum as gland for 16 weeks of pregnancy
placenta takes over as corpus luteum
oestradiol and progesterone prevent ovulation and maintain endometrium
ovarian follicle
a fluid filled spherical sac that contains and nourishes an immature egg or oocyte
ovulation
release of oocyte from ovary
corpus luteum
a hormone secreting structure that develops from an ovarian follicle after an oocyte has been discharged. It degenerates after a few days unless pregnancy has begun.
how does fertilisation take place in humans - step by step
- sperm cells membrane fuses with an egg cell membrane
- nuclear membranes of sperm and egg nuclei break down
- homologous pairs participate in joint mitosis to produce 2 diploid nuclei
where is a zygote formed
upper part of oviduct
infertility in males can be due to
- erectile disfunction
- abnormal sperm
- sperm with poor motility
- short lived sperm
- too few sperm
- a blocked sperm duct, prevent semen from containing sperm
infertility in females can be due to
- conditions of the cervix
- conditions in uterus that prevent implantation of embryo
- eggs that fail to mature or be released
- blocked or damaged oviducts preventing egg to reach sperm
in vitro fertilisation IVF
medical procedure in which an egg is fertilised by sperm in a test tube
menstrual activity suspended with hormone based drugs
ovaries induced to produce lots of eggs
step 1 of IVF
down regulation shiftss down period by stopping hormones. process takes 2 weeks
done with a dry nasal spray
step 2 of IVF
superovulation - high doses of FSH injected over 10 day period to stimulate development of multiple follicles
step 3 of IVF
when follicles reach 15-20 mm diameter, HCG is given to start maturation
after 36 hours, follicles are collected
step 4 of IVF
prepared eggs combined with sperm in sterile conditions
step 5 of IVF
successfully fertilised eggs are incubated before implantation
step 6 of IVF
2 weeks before implantation - progesterone to aid implantation
continued till pregnancy testing
step 7 of IVF
embryos at 8 cell stage placed in uterus
if one or more embedden - normal pregnancy
success rate of implantation
40%
hermaphrodite
both male and female parts
ovule
in the flowering plant flower, the structure in an ovary which after fertilisation grows into the seed
pollen
microspore produced in anthers containing male gametes
carried by insects or wind to female parts of the plant
pollination
transfer of pollen from anther to stigma
pollen tube
grows out of a pollen grain attatched to a stigma and down through the style tissue to the embryo sac
what kind of fertilisation is unique to plants
double fertilisation
double fertilisation
one male nuclei fuses with 2 different egg nucleus
1 male with 2 female
sepal
green structures that cover the flower while it is developing
petal
large colourful structures that attract pollinators to the flower
stamen
the male part of the flowers consisting of the anther and filament
anther
produces pollen which contains the male gamete
filament
structure that holds up the anther presenting it to visiting animals
carpel
the female part of the flower made from the stigma, style and ovary
stigma
the part of the female reproductive organs where the pollen lands
style
holds up the stigma and is that path down which the pollen tube grows, carrying the pollen nuclei to the ovum
cross polinate
pollen transfered from the anther of one flower to the stigma of another flower of the same species
often brought by insects, butterflies, bees, birds and bats
why do insects, butterflies, bees, birds and bats assist with pollination
- attracted by colour or scent
- rewarded by nectar and pollen
- accidentaly transfer pollen between flowers
mutualistic reproduction
cross pollination is achieved by
- stamen and stigma maturing at different times
- stigma and anthers at different heights in same flowers
- separate male and female flowers
cross pollination results in
outbreeding
cross pollination advantage
variation and some genomes more successful that others - good if environment changes
cross pollination disadvantage
pollen needs to find the stigma of other flowers - element of chance
self pollination
when pollen is transfered to the stigma in the same flower
what does self pollination result in
inbreeding
advantages of inbreeding
preserves good genomes suited to a stable environment
disadvantages of inbreeding
reduction in variation
- greater chance of two undesirable recessive alleles coming together decreases genetic diversity
self compatibility
recognition and rejection of pollen by the carpel of the same flower
prevents inbreeding and promotes outcrossing
development of seed
seed development from fertilised ovule and contains an embryo plant and food store
process of zygote in a seed
zygote grows through mitosis and forms an embryonic plant
embryo root, embryo stem, single cotyledon or 2 cotyledons
when does formation of stored food reserves occur
can only occur if fertilisation occurs
as seed matures the outer layer becomes
testa
as seed matures the ovary becomes
a fruit
as seed matures
water content decrease
seed dispersal
the carrying of the seed away from the parent plan
germination of seeds
the resumption of growth by an embryonic plant in seed or fruit, at the expense of stored food
how does seed dispersal occur
- moved to new areas, ready for germination
- seeds can be sprung from fruit by an explosive mechanism
- water is used
- all seeds are compact, nutrition and light weight
- seeds taken for food are dropped and lost, or stored and forgotten
why dont many seeds germinate as soon as they are dispersed
have a dormant period
why do sees have a dormant period that can be imposed due to
- incomplete seed development causing embryo to be immature
- presence of a plant growth regulator
- impervious seed coat that is made permeable
- requirement from pre-chilling under moist conditions
after overcoming dormancy
- water uptake so the seed is fully hydrated
- oxygen present at a high partial pressure to sustain aerobic respiration
- a suitable temperature
in germination food reserves are
mobilised
plant growth substance produced by cells of embryo
passes to the food store
protien reserves - hydrolytic enzymes
