UNIT 4 - D 3.1 - Reproduction Flashcards
What does sexual reproduction require?
both a male and female parent
What does asexual reproduction require?
only one parent
What does asexual reproduction result in?
multiple organisms from the parent that all have the same genetic makeup
Where might asexual reproduction be beneficial?
in a non-changing environment
What are the different mechanisms for asexual reproduction?
binary fission, mitosis, budding, fragmentation, vegetative reproduction, parthenogenesis
What does budding involve?
two genetically identical organisms growing directly from an existing organism
What does fragmentation involve?
the body of an existing organism breaks up into severeal fragments, each growing into a complete organism
what does vegetative reproduction involve?
plants emerging from roots, bulbs, tubers or shoots
what does partenogenesis involve?
in an animal species, growth and development of an egg cell without the involvement of a male gamete
How is asexual reproduction ‘better’ than sexual reproduction?
usually faster, requires less energy expenditure, a single organism can colonize a new area relatively easily
What does each homologous pair of chromosomes have?
a maternal chromosome and a paternal chromosome
When does fertalization occur?
when gametes fuse into a single cell
What is the purpose of fertilization?
to restore the diploid number of chromosomes
What are sperm adapted to provide for a haploid nucleus?
an efficient delivery system
What do egg cells contain?
all the nutrients needed for early embyonic growth and all initial organelles
What provides an embryo with nutrition after the egg?
the uterus then the placenta
How many sperm cells does one ejaculation contain?
millions
What is semen?
the fluid which sperm cells are in
How many sperm cells reach the egg?
100-200
What are the anatomical structures of the female reproduction system?
ovaries, fallopian tubes/oviducts, uterus, endometrium, cervix, vagina
What do ovaries do?
produce and secrete oestradiol, produce and release eggs, the area where ovulation occurs, grows into the corpus luteum
What does the corpus luteum do?
temporarily produce progesterone
What do the fallopian tubes do?
carry the egg or early embryo to uterus
what does the uterus do?
the embryo is implanted inside and develops if fertalized
what is the endometrium?
highly vascular inner lining of uterus
What does the cervix do?
opening to vagina allowing sperm to enter and provides pathway for childbirth
what is the vagina?
muscular tube that leads from external genitals to cervix, semen is ejaculated here during sex
What are the anatomical structures of the male reproductive system?
testes, epididymis, scrotum, vas deferens, seminal vesicles, prostate gland, penis, urethra
What is the function of testes?
location where sperm are produced in seminiferous tubules
what is the epididymis?
area where sperm are recieved, become mature, become capable of swimming
what is the scrotum?
sac that holds the testes outside body cavity so sperm production and maturation can occur at cooler temp
what does the vas deferens do?
carries mature sper from epididymis to urethra during ejaculation
what do seminal vesicles do?
gland that produces and adds seminal fluid to semen
What does the prostate gland do?
produces much of the semen, including carbs for sperm
what does the penis do?
becomes erect as a result of blood engorgement to facilitate ejaculation
what is the urethra?
tube via which the semen leaves the penis after all the glands have added fluids
What is the purpose of the menstrual cycle?
to time the release of an egg for possible fertilization and later implantation in the lining of the uterus
What is ovulation?
release of an egg
what is the uterine lining called?
the endometrium
What is menstruation?
the breakdown of the blood vessels of the endometrium leading to menstrual bleeding
What part of the brain is the regulatory centre for the menstrual cycle?
the hypothalamus
What hormone does the hypothalamus release?
gonadotropin-releasing hormone (GnRH)
What is the result in GnRH reaching the nearby pituitary gland?
the pituitary produces and secretes follicle-stimulating hormone (FSH) and luteinizing hormone (LH)
What is the target tissue for both FSH and LH?
the ovaries
Which hormone’s production and secretion is increased as an effect of FSH and LH on the ovaries?
oestradiol
What is the target tissue of oestradiol?
the endometrium
What effect does oestradiol have on the endometrium?
it increases the density of blood vessels, making the endometrium highly vascular
Why does oestradiol stimulate the pituitary gland to rlease more FSH and LH?
because of a positive feedback loop
What structure does the increase in FSH and LH result in?
graafian follicles
Where are follicle cells located?
within the ovaries
What stage of development are the possible future eggs at in the ovaries?
oocytes
What happens to the randomly arranged follicle cells and oocytes under chemical stimulation of FSH and LH?
they take on a particular cellular arrangement called a graafian follicle
What does a spike in the level of FSH and LH lead to?
ovulation
What is the positive feedback loop between that results in ovulation?
FSH, LH, pituitary gland and oestradiol
What structure is referred to as a single follicle?
the oocyte accompanied by the Graafian follicle’s inner ring of follicle cells
Where does the follicle enter soon after ovulation?
the fallopian tube
What hormone does the remains of the outer ring of follicle cells produce and secrete within the ovary after ovulation?
progesterone
How is the corpus luteum formed?
the cells of the outer ring divide and fill the “wound” area left by ovulation forming a glandular structure
How long does the corpus luteum produce progesterone for after ovulation if fertilization does not occur?
10-12 days
What does progesterone do?
maintains the thickened vascular endometrium
Why does progesterone need to be coninually produced for an embryo to implant?
because the endometrium will break down if progesterone is not produced
What do the high levels of oestradiol and progesterone at the same time do to prevent the production of GnRH?
it provides a negative feedback signal to the hypthalamus
What does the corpus luteum breaking down lead to?
the decline in both progesterone and oestradiol levels
What does the drop in progesterone and oestradiol lead to?
the endometrium breaking down and the hypothalamus begins secreting GnRH beginning another menstrual cycle
What does the ovarian cycle control?
the production and release of eggs and the cyclic release of oestradiol and progesterone
What does the uterine cycle control?
the preparation and maintenance of the lining of the uterus to receive a fertilized egg
Why do the ovarian cycle and the uterine cycle have to be timed synchronously?
because the endometrium must be vascular and ready to receive an early embryo when it enters the uterus from the fallopian tube
What happens as a result of sex?
millions of sperm are ejaculated into the female’s vagina
What do sperm absorb in order to have enough energy to make it to the egg?
some of the sugar in semen
Where is the typical location of fertilization?
within one of the fallopian tubes
waht is the zona pellucida?
a gel composed of glycoproteins which sperm have to penetrate to reach the egg
What helps sperm penetrate the egg’s plasma membrane?
hydrolytic enzymes contained in their acrosomes
What happens after a sperm enters the egg?
vesicles are released from the egg that destroy the sperm flagellum and mitochondria and the haploid chromosomes from the sperm and egg are btoh in the cytoplasm of the egg
What is a pronucleus?
the haploid structure of the paternal and maternal chromosomes remaining seperate with membranes around each
What does the DNA do while in the pronuclei stage?
undergo preparations for mitosis
What happens after preparations have been made for mitosis in the pronuclei stage?
the two pronuclei come together and the temporary nuclear membranes dissolve
How long after fertilization does it take for the first mitotic cell division to be completed?
about 30 hours
what are some possible reasons for inferility?
low sperm counts, impotence (failure to acheive/maintain erection), inability to ovulate normally, blocked fallopian tubes
What is superovulation?
the production of many more eggs than typical of a normal menstrual cycle
Why does in vitro fertilization involve superovulation?
with injections of FSH, the female will produce many graafian follicles in each ovary so there are many potential eggs for harvesting
What happens after harvested eggs are mixed with sperm and observations are made for healthy development of the embryo?
the embryo is implanted into the female uterus
When does the hypothalamus increase the production of GnRH in humans?
during late childhood or early teens
What are FSH and LH classified as?
gonadotropins
Why are FSH and LH classified as gonadotropins?
because their target tissue is the gonads (ovaries and testes)
What do the gonadotropins stimulate?
production of steroids (testosterone, oestradiol, progesterone) by the gonads
What is the physiological result of the enhanced production of the various hormones?
puberty
What are some changes in females during puberty?
increase in height and mass, growth of underarm and pubic hair, development of breasts, menstrual cycle begins, acne may begin, bone structure of hips widens to prepare for possible childbirth
What are the changes in male bodies during puberty?
increase in height and body mass, growth of underarm, pubic, facial, and chest hair, acne may begin, voice deeper, enlargement of testes and penis, erections begin
Where does spermatogenesis occur?
within tubes called seminiferous tubules which are in the testes
Where do cells called spermatogonia lie?
near the outer wall of the seminiferous tubules
Why do spermatogonia undergo mitosis?
to replenish their numbers
When does sperm production occur?
at the start of puberty and throughout life
Why do spermatogonia undergo meiosis?
to produce spermatozoa
What do sperm cells have to do after meiosis?
differentiate
What are the cells inside the seminiferous tubules that developing sperm attach to to gain nutrients called?
sertoli cells
What do the sperm cells do after they have differentiated?
they detach from their sertoli cell and move through the lumen to storage (epididymis)
What are polar bodies?
the three cells that are unusable after oogenesis because they are too small
What is the function of polar bodies?
to be a cellular “container” for the dividing chromosomes during meiosis I and II
What is the fourth haploid cell produced from oogenesis called?
the ovum
Where are the cells oogonia located?
within the ovaries of a female foetus
Why do oogonia under mitosis repeatedly?
to build up their numbers within the ovaries
What do oogonia grow to become?
primary oocytes
What kind of cells are both oogonia and primary oocytes?
diploid
When is meiosis paused for the large primary oocytes?
during prophase I
What surrounds each primary oocyte?
a single layer of follicle cells
What is the structure called when the layer of follicle cells surrounds a primary oocyte?
primary follicle
When will a few of the primary follicles finally finish meiosis I?
during each menstrual cycle
What is the small cell resulting from meiosis I called in oogenesis?
the first polar body
What does the first polar body act as?
a reservoir for half of the chromosomes
What is the other large cell resulting from meiosis I of oogenesis?
the secondary oocyte
What is the structure of a graafian follicle?
an inner ring of follicle cells surrounds the oocyte, then there is a fluid-filled space, then the outer ring of follicle cells
What eventually leads to ovulation?
the increase in fluid between the two follicle cell layers which creates a bulge on the surface of the ovary
When is meiosis II finally completed for oogenesis?
at fertilization
What happens to the released egg cell if it is not fertilized?
it remains a secondary oocyte until the cell dies
What is the difference between spermatogenesis and oogenesis in terms of the amount of gametes produced?
spermatogenesis produces millions daily and oogenesis produces thousands in total
What is the difference between spermatogenesis and oogenesis in terms of number of gametes produced from each cell?
spermatagenesis produces 4 gametes and oogenesis produces one gamete
What is the difference between spermatogenesis and oogenesis in terms of the size of the gametes produced?
spermatogenesis produces smallest cell in the body and oogenesis produces the largest cell in the body
What is the difference between spermatogenesis and oogenesis in terms of the amoung of organelles and cytoplasm in the gametes?
spermatogenesis produces cells with minimal cytoplasm and organelles and oogenesis produces cells with large quantities of cytoplasm, organelles and nutrition
What is the difference between spermatogenesis and oogenesis in terms of motility of the gametes?
spermatogenesis produces motile gametes and oogenesis does not
What is polyspermy?
the rare event of more than one sperm fertilizing the ovum
What does polyspermy result in?
the ovum not developing
What is the cortical reaction?
a series of events initiated by the first sperm that uses the enzymes of its acrosome to penetrate the plasma membrane of the ovum which prevents polyspermy
What are cortical granules?
small vesicles within the cytoplasm of the ovum
What does the initial fertilization caus the cortical granules to do?
fuse with the ovum’s plasma membrane and release their enzymes to the outside
What is the zona pellucida?
the glycoprotein layer surrounding the ovum
How does the zona pellucida become impermeable to more sperm cells?
the enzymes released by cortical granules results in a chemical change in the zona pellucida
What is the resulting fertilized ovum called?
a zygote
what does fertilization stimulate the embryo to do?
begin mitosis
How many cells make up the developing embryo by the time it exits the fallopian tube and reaches the uternine cavity?
about 100 cells
What is an embryo called when it is at the stage of being ready to implant itself into the endometrium?
a blastocyst
What is a blastocyst characterized by?
a surrounding layer of cells called the trophoblast, a group of cells on the interior known as the inner cell mass, and the fluid-filled cavity
What will the trophoblast help to do?
form the foetal portion of the placenta, embryonic membranes, and umbilical cord
What will the inner cell mass end up becoming?
the body of the embryo
What is implantation?
the stage of pregnancy when the embryo stops moving along the endometrium and begins to sink down into the endometrium tissue
What is the main reason for a human ovum being so large?
because it contains the nutrients needed for early embryonic development
What hormone do human embryos produce?
human chorionic gonadotropin (hCG)
Which cells produce hCG?
the trophoblast layer of embryonic cells and later the embryonic placenta cells
What does hCG entering the mother’s bloodstream allow the continuation of?
the corpus luteum in the mother’s ovaries
Why is the continuation of the corpus luteum only necessary for the first stage of pregnancy?
because later the placenta will produce and secrete its own steroids instead of the corpus luteum
What is the basis of early pregnancy tests?
hCG
What are monoclonal antibodies?
antibodies produced by researchers that can recognize hCG
Why were monoclonal antibodies named the way they were?
because the liquid cultures of B-lymphocytes can only secrete antibodies capable of detecting a single antigen
what happens if the monoclonal antibodies detect hCG from female urine?
The antibodies are chemically bonded to an enzyme that changes color when exposed to a select substrate
What does the placenta form from?
the trophoblast layer of the blastocyst and from the tissue of the mother
What is the side of the placenta facing the uterine wall made up of?
connective tissue and blood vessels formed by the mother’s body
What forms the side of the placenta closer to the embryo?
the embryo
What is the umbilical cord?
a protective sheath on the foetal side of the placenta
What, when fully formed, carries foetal blood to the placenta?
two foetal blood vessels within the umbilical cord
What does the blood within the two blood vessels in the umbilical cord carry?
waste products
How does blood return to the foetus oxygenated and filled with nutrients?
a third blood vessel returns blood that has exchanged materials with the maternal bloodstream back to the foetus
What are placental villi?
the foetal blood vessels from the umbilical cord after branching into numerous projections which provides a large surface area for molecular exchange
Which molecules are passed from the foetus to the mother within the placenta?
carbon dioxide, urea, water, hormones
Which molecules are passed from the mother to the foetus within the placenta?
oxygen, nutreints (glucose, amino acids, vitamins, minerals), water, hormones, alcohol and nicotine and other drugs if used by the mother during pregnancy
What are kinds of mammals that lack placentas?
marsupials and monotremes
What acts as a signal for birthing to begin?
less progesterone being secreted by the placenta as the foetus reaches full term
What is parturition?
birth
What is parturition characterized by?
uterine contractions that begin at a relatively low intensity and occur infrequently, then they become more intense and more frequent
What is positive feedback?
a previous event resulting in a more forceful and frequent future event
What hormone is involved in the positive feedback mechanism for parturition?
oxytocin
What is oxytocin produced and secreted by?
produced by the hypothalamus and secreted by the pituitary gland
How does the positive feedback mechanism work for parturition?
when it is time for parturition, a decreased secretion of progesterone stimulates the pituitary gland to secrete a small amount of oxytocin into the bloodstream, then oxytocin receptors in the muscles of the uterus respond with the first contraction which then signals the pituitary gland to release more oxytocin, so on and so forth
Why does the positive feedback loop end at parturition?
because the uterine muscles don’t have anything to contract upon anymore
What is menopause?
the period in a female’s life when her menstrual cycle becomes less predictable and then eventually stops
What is the reason for menopause?
the ovaries stop producing oestradiol and progesterone
How can females alleviate symptoms of menopause?
through hormone replacement therapy (HRT) in the form of oestradiol
Where are gametes of flowering plants produced?
ovules for females and pollen grains for males
What gives rise to ovules and pollent grains vs how are they actually produced?
meiosis gives rise and mitosis produces them
Why is reduction division not required to produce haploid gametes in flowering plants?
because the reproductive structures are already haploid
What are hermaphroditic flowers?
flowers with both male and female structures
What are some hermaphroditic species able to do themselves?
pollinate
Why are both self-pollination and fertilization forms of sexual reproduction?
because the gametes are produced by meiosis and there is a fusion of gamete nuclei to form an embryo
What is the disadvantage of self-pollination?
the loss of genetic variation
What is cross-pollination?
the transfer of pollen produced on one plant with another plant
What are the different shapes and colors of plants meant to do?
attract animals that can transfer pollen from one plant to the next
Where does pollen develop?
whithin structures called anthers
What structure is some pollen transferred to after a pollinator moves on to a different flower?
the stigma
What does pollen that adheres to a stigma begin to grow into?
a structure called a pollen tube
What is a pollen tube equivalent to in animals?
sperm that swim
What do pollen graines do instead of swimming to take male reproductive nuclei to the ovule for fertilization?
they grow into tubes that penetrate other parts of the flower
How do plants use a double fertilization process?
one pollen tube carries two male nuclei which each result in fertilization
How many haploid nuclei are in the ovule of a flowering plant?
3
What do the two male nuclei from the pollen tube fertilize with the three haploid nuclei in the ovule to create?
one pollen nucleus fertilizes with one ovule nucleus to create a zygote while the other pollen nucleus fertilizes the other two nuclei in the ovule to create a tissue called endosperm
Why is endosperm a triploid tissue?
because 3 nuclei were used for its fertilization so it has the chromosome number of 3n
What does the growth of the triploid endosperm tissue produce?
the nutritive endosperm within the seed that will nourish the early plant embryo
What are common insect pollinators?
bees, wasps, flies, butterflies, moths
What do insect-pollinated flowers tend to look like?
large and brightly coloured
What is the reward for insects attracted to insect-pollinated flowers?
nectar
How do insects transfer pollen from flower to flower?
when they drink the nectar, they brush against the pollen grains, the pollen is sticky with numerous spikes so it adheres to the legs or body of the insect, the stigma is also sticky so pollen can be transferred from the insect to the stigma
What is the function of the sepal?
to protect the developing flower while it is inside the bud
What is the function of the petal?
attract pollinators
What is the function of the anther?
the part of the stamen that produces the male sex cells (pollen)
What is the stamen?
the male portion of a flower
What is the function of the pollen?
contain the male nuclei for fertilization
What is the function of the filaments?
stalk of the stamen that holds up the anther
What is the function of the stigma?
the sticky top of a carpel on which pollen lands
What is the carpel?
the female portion of a flower
What is the function of the style?
the part of the carpel supporting the stigma
What is the function of the ovary?
the base of the carpel containing ovule(s)
What is the function of the ovule?
the chamber within an ovary where the female nuclei develop
What are some mechanisms used by plants that promote genetic variation?
different muturation times for pollen and ovules of the same flower, pollen and stigma of flowers in the same plant use chemical self-incompatibility mechanisms, production of flowers that have only male or only female parts, entire plant being only male of female, pollen being transferred by wind
What do some plants having different maturation times for the pollen and ovules of the same flower ensure?
that self-pollination is impossible
What happens if the pollen and stigma of one plant uses chemical self-incompatibility mechanisms when pollen lands on the stigma of a flower on the same plant?
the pollen tube doesn’t grow because of the chemical incompatibility
What is self-incompatibility mechanism in plants with flowers?
pollen landing of the stigma of a flower of the same plant which makes protein interactions occur which reduces/stops the growth of the pollen tube
What does self-incompatibility mechanism of flowering plants include?
the pollen grain on the stigma fails to germinate into a pollen tube, the pollen grain germinates but does not enter through the stigma into the style, the pollen tube enter the ovule but the pollen nuclei degenerates before fertilization, fertilization occurs but the polant embryo degenerates during early growth
When does the most successful pollination occur?
when the pollen is from one plant and the stigma is in the flower of a completely different plant of the same species
What is vigour?
healthy growth of a new plant
What does self-pollination lead to?
inbreeding and decreased genetic diversity and vigour
What happens once a successful double fertilization has occured in a flowering plant?
a seed will begin to develop
What does the ovary grow/ripen to become?
a fruit
What does the number of seeds inside a fruit indicate?
how many ovules the ovary contained
How can animals allow for seed dispersion?
they eat the fruit which containes the seeds and then the seeds may land on the ground far away from the parent plant in the animal’s faeces
What begins once seeds have formed within a flower’s ovary?
dormacy
What happens during dormacy?
the seeds desplay a low metabolism with no growth or development
What does dormacy allow?
for seeds to wait and germinate when conditions are suitable for growth
What is germination?
the early growth of a seed as it develops into a plant
What conditions must be met for a seed to germinate?
water is needed to rehydrate the dried seed tissues, oxygen is needed to allow aerobic respiration to produce ATP, appropriate temperature for the seed
What does a seed contain?
a small plant embryo and the food reserves it needs for early growth
What are food reserves in seeds called?
endosperm tissue
What structures are endosperm tissues transferred to the plant embryo through?
structures called cotyledons
What is imbibition?
how seeds absorb water to begin germination
What is the radicle?
the portion of the embryo that emerges first/the initial root structure
What is the hypocotyl?
cruved portion of the plant shoot found below the cotyledons which is usually the first structure to appear above the ground
