reproduction Flashcards
(30 cards)
asexual reproduction
1 parent
bacteria, fungi, many plants, some animals
advantages
- less complex and costly in time and energy
disadvantages
- low variation
> decreased genetic diversity
> disastrous when environment changes
> harmful mutations are catastrophic
binary fission
fragmentation
budding
parthenogenesis
sexual reproduction
- 2 parents
- fusion of gametes
advantages
- high variation, better coping in a changing environment
disadvantages
- slow, complex
- costly in energy and time
variation comes from
crossing over in prophase I
separation of homologous chromosomes in anaphase II
fertilization results in a new combination of chromosomes in the zygote
hermaphrodite
organism w both female and male reproductive systems
sperm
male gamete
small
millions produced daily
head
- nucleus
- acrosome (hydrolytic enzymes and paired centrioles)
midpiece
- mitochondria (energy for flagellar movement)
tail
- flagellum (swimming to egg)
egg/ovum
large
immotile
carries food reserves as energy stores for dividing zygote
haploid nucleus
cytoplasm (centrioles, cortical granules, droplets of fat)
1st polar body
plasma membrane
layer of gel
layer of follicle cells
male reproductive system
penis
urethra (sperm urine leave)
sperm duct (transports sperm in ejaculation)
testes (produce sperm)
scrotum (holds testes maintain temperature)
epididymis (store mature sperm)
bulbourethal glands
prostate glands
seminal vesicles
= all produce fluids that help nourish and transport sperm = make up semen
female reproductive system
ovaries (produce eggs and hormones progresterone and oestradiol)
fallopian tubes (eggs travel through, fertilization occurs here)
uterus (nourishes developing fetus)
cervix (widens in birth, menstrual blood passes through)
vagina (muscular canal that extends from the outside of the cervix)
what is not part of reproductive system
anus, urinary bladder, ureter and rectum
menstrual cycle
the monthly series of changes the female body undergoes to prepare for pregnancy
due to variation in ovarian and pituitary hormones
around 28 days
consists of ovarian and uterine cycles that happen simultaneously
controlled by positive and negative feedback mechanisms
- negative: rise in one hormone inhibits another
- positive: rise in one rise in another
ovarian cycle
follicular phase
- 14d, from day 1 of bleeding
- low hormones
- FSH and LH secreted by anterior pituitary
- FSH stimulates the growth of immature eggs in follicles
- growing follicle secretes oestradiol
ovulation
- sharp rise in oestradiol stimulates anterior to secrete more LH and less FSH
- spurt of LH ruptures follicle, egg released
luteal phase
- drop in LH and FSH
- ruptured follicle becomes corpus luteum as it is filled w cells > secretes progre and oestra
- as those hormones rise, LH and FSH inhibited
uterine cycle
proliferative phase (follicular)
- oestradiol from growing follicles causes thickening of endometrial lining of uterus (preparation for pregnancy)
secretory phase (luteal)
- uterine layer thickens further under influence of progresterone
menstruation (end of luteal)
- corpus luteum breaks down die to drop in LH and FSH
- thickened layer breaks down due to drop in progre and oestra
- layers, unfertilized egg and blood are removed from body as menstrual bleeding
what happens in response to the low ovarian hormone levels after menstrual cycle
anterior pituitary secretes FSH and LH causing a new follicle to develop and the cycle starts all over again
ovarian hormones
progresterone and oestradiol
pituitary hormones
follicle stimulating hormone FSH
luteinizing hormone LH
characteristics of egg cell that has been released from a follicle
- has not completed meiosis II yet
- referred to as secondary oocyte
- cortical granules are filled w enzymes in the cytoplasm
- 2 layers outside plasma membrane
- zona pellucida (glycoproteins that prevent sperm entry)
- corona radiata (follicular cells that nourish the egg)
capacitation
the physiological changes sperm undergoes in the female reproductive system that lead to their activation
when the sperm cell reaches the egg
the complementary receptors bind to proteins on the plasma membrane of egg
- membranes fuse together
> egg is activated
series of changes
- rise in intracellular calcium levels
- completion of meiosis II
- cortical reaction
head enters & midpiece and tail are destroyed
> nucleus undergoes changes to form male pronucleus
- nuclear membrane dissolves
- chromatin from both condenses to form chromosomes, fuses and forms a single-celled diploid zygote
zygote undergoes mitotic division
complete flower
contains petals, pistils, stamens, sepals and petals
bisexual flower = perfect flower
has both stamen and pistil
stamen
anther contains pollen grains (consist of a generative cell and a large tube cell)
filament
pistil
stigma style ovary
ovary contains ovules
- inside each ovule is embryo sac w 7 cells and 8 haploid nuclei
pollination
pollen grains are transferred from stamen to pistil (anther to stigma)
- pollen germinates, tube cell grows a pollen tube down the style to ovary
generative cell divides mitotically to form sperm cells - sperm cells move trough micropyle to ovum (tiny opening
fertilization (after pollination)
1 sperm nuclei fuses w egg
diploid zygote develops to embryo
2nd sperm cell fuses w central cell
> triple fusion > triploid cell that gives rise to endosperm that nourishes embryo
= double fertilization
