Chapter 52 Flashcards
What is the name for the diploid, fertilized egg?
zygote
Which animals reproduce asexually?
bacteria; archaea; protists; cnidarians; tunicates
(T/F) Multicellular animals only reproduce sexually.
False, cnidarians and tunicates can reproduce asexually.
What is fission?
when a single-celled organism divides and each part becomes a separate but identical organism
What mechanism do Cnidarians use to reproduce?
budding
What is budding?
where a part of the parent’s body becomes separated and differentiates into a new individual
In budding, what are the two options for the offspring?
can become an independent animal or can remain attached to the parent to form a colony
Parthenogenesis is common in
arthropods
What happens in parthenogenesis?
females produce offspring from unfertilized eggs
Can organisms switch between sexual reproduction and parthenogenesis?
Yes, those that are exclusively parthenogenic are all females
The offspring of parthenogenic organisms are
haploid
Explain how the honeybee can switch between sexual reproduction and parthenogenesis.
mates and stores sperm – if she doesn’t release the sperm, the eggs develop into haploid males; if she releases the sperm, the eggs develop into diploid females; if the fertilized egg is exposed to the right hormone, the egg becomes a queen
Give examples of vertebrates that are parthenogenic. (3)
Lacerta lizard; fish; salamanders
Can vertebrates be parthenogenic?
Yes
What is hermaphroditism?
when an individual has both testes and ovaries (can produce sperm and eggs)
Give an example of a hermaphroditic organism.
tapeworm
(T/F) Hermaphroditic animals can self-fertilize.
True (like the tapeworm), but most need another individual to reproduce
How do earthworms reproduce?
hermaphroditically but they need to copulate with another earthworm (as opposed to the tapeworm which can self-fertilize)
What is protogyny?
first female, a change from female to male
What is protandry?
first male, a change from male to female
Where is sequential hermaphroditism found?
in numerous genera of fish
Give an example of a fish that practices sequential hermaphroditism.
coral reef fish
What influences protogyny in fish?
social control
Describe fish that practice protogyny.
live in large groups (schools) where successful reproduction is limited to few large males; if males are removed, largest female changes sex and becomes male
How is an individual’s sex determined in fish, reptiles?
determined by temperature experienced during development - cold temp produces males and warm temp produces females, but can be the opposite OR males produced at both high and low temps and females at temps in between
How is sex determined in birds, mammals?
by genes
In most animals, XX is female except in
birds, where the heterozygous sex is female
When do the reproductive systems of human males/females appear?
40 days after conception
The cells that ultimately become ova/sperm originate in
the yolk sac and migrate to the embryonic gonads
Embryonic gonads are said to be
indifferent, since they can become either ovaries or either testes
What is the sex-determining gene in humans?
SRY (sex-determining region of Y chromosome), which is present in males, which converts the embryonic gonads into testes
What is the “default” mammal sex?
female - the embryo will only become a male if the functional SRY gene is present
How do female marine bony fishes release eggs?
produce eggs in batches and release them into water
How are marine bony fish eggs fertilized?
males release their sperm into water and union of free gametes occurs
What is a disadvantage of dispersing gametes in water? (2)
the release from males and females must be almost simultaneous; release of eggs and sperm must be restricted to well-defined periods
What is one signal that tells marine organisms to reproduce?
tidal cycles of the Moon - when the Moon gets closer to the earth and cause higher tides, it tells marine organisms to reproduce
Internal fertilization occurred in terrestrial vertebrates because
gametes would otherwise dry up and perish
(T/F) Internal fertilization is exclusive to terrestrial vertebrates.
False, some fish use internal fertilization
What are the three strategies for embryonic/fetal development?
oviparity; ovoviviparity; viviparity
Where is oviparity found? (6)
some bony fishes; most reptiles; some cartilaginous fish; some amphibians; a few mammals; all birds
What is oviparity?
after being fertilized internally, eggs are deposited outside the mother’s body to complete development
Where is ovoviviparity found? (3)
some bony fishes; some cartilaginous fish; many reptiles
What is ovoviviparity? (2)
fertilized eggs are retained within mother to complete development, but embryo obtains nourishment from egg yolk; fully independent when hatched
Where is viviparity found? (4)
most cartilaginous fish; some amphibians; few reptiles; almost all mammals
Most cartilaginous fish use what reproductive strategy?
viviparity
Almost all mammals use what reproductive strategy?
viviparity
Most reptiles use what reproductive strategy?
oviparity
Birds use what reproductive strategy?
oviparity
What is viviparity?
young develop within mother and receive all nourishment from mother’s blood via placenta
(T/F) Placenta are exclusive to mammals.
False, they’ve evolved in fishes and lizards
Live birth occurs in which reproductive strategies?
ovoviviparity or viviparity
How has live birth evolved in vertebrates?
one time in mammals, many times independently in fishes/amphibians/reptiles; a one-way evolutionary street
What are amniotes?
reptiles, birds, mammals
How was internal fertilization evolved in vertebrates?
evolved only once in amniotes, evolved multiple times in fishes/amphibians
How do salamanders do internal fertilization?
males deposit sperm on top of mass of eggs and then female positions her cloaca above them, lowers body, picks up fertilized eggs
In cartilaginous fish, what transfers sperm into the female’s body?
modified pelvic fin
A modified cloaca is used to transfer sperm in which animals? (3)
frogs, caecilians, birds
Penises are used in which animals? (3)
turtles, crocodiles, mammals
Hemipenises are used in which animals? (2)
snakes and lizards
Define intromittent organ.
male copulatory organ
Intromittent organs were lost in (2)
birds, rhynchocephalians
External fertilization is found in which general groups of animals? (2)
fishes, amphibians (even though internal fertilization has evolved in these organisms many times)
Describe fertilization and development in bony fish.
external fertilization; eggs contain enough yolk for short time; young fish must seek food from surrounding waters; speedy development
Is fertilization/development in bony fishes particularly efficient?
Not really - thousands of eggs can be fertilized but only a few will grow to maturity since most succumb to predation/infection
Describe fertilization/development in cartilaginous fish.
internal fertilization; viviparous; female gives birth to few, well-developed offspring
The life cycle of amphibians is tied to
the water
From where are gametes released in amphibians?
from the cloaca, in both males and females
In general, the eggs of amphibians develop in
water
What are some exceptions to amphibian eggs developing in water? (2)
some frogs carry eggs on the backs of parents; males can carry tadpoles in vocal sacs
What percent of reptile species are oviparous?
80%
Once oviparous reptiles lay eggs, what happens?
most oviparous reptiles abandon the eggs after laying them
All birds use what kind of fertilization?
internal fertilization
(T/F) Most male birds have penises.
False, most of them don’t, and some have modified cloacas.
Describe the egg shell of reptile eggs.
leathery shell
As the egg passes through the bird oviduct, what happens?
glands secrete albumin proteins
Which protein is responsible for egg whites?
albumin
What is necessary after young birds are born?
development is incomplete, so they need nurturing from their parents
What are amniotic eggs?
eggs in which the embryo develops within a fluid-filled cavity surrounded by a membrane called an amnion
What are the three other extraembryonic membranes (other than the amnion)?
chorion; yolk sac; allantois
What is the chorion?
lines the inside of the eggshell
What is the importance of the extraembryonic membranes?
extraembryonic membranes, combined with the hard shell, prevents the embryo from drying out
Most female mammals are sexually receptive to males
around the time of ovulation
What is estrus?
period of sexual receptivity in females (around the time of ovulation)
What secretes FSH and LH?
anterior pituitary gland
Which two hormones are primarily responsible for driving the mammalian estrous cycle?
FSH and LH
How are humans and apes different from other mammals in terms of estrous cycles?
humans and apes bleed when they shed the inner lining of the uterus; they can engage in copulation during any time of the cycle
How are rabbits and cats different from other mammals?
females ovulate only after copulation as a result of a reflex stimulation of LH secretion
What are the most primitive mammals?
monotremes
What are the only two monotremes?
duck-billed platypus and the echidna
How do monotremes incubate their eggs?
incubate their eggs in a nest or specialized pouch
How do monotreme hatchlings obtain milk from their mothers?
young hatchlings obtain milk from their mother’s mammary glands by licking her skin (because monotremes don’t have nipples)
What are the two subgroups of mammals based on how they care for their young?
marsupials and placental mammals
Describe marsupial offspring.
small, fetuslike offspring that are incompletely developed; complete development in mother’s pouch; obtain nourishment from nipples
Placental mammal fetuses are nourished by
a placenta
The placenta is derived from
the chorion (extraembryonic membrane) and the mother’s uterine lining
On a molecular level, how does the placental mammal fetus obtain nutrients from the mother?
since the fetal and maternal blood vessels are close together, the fetus obtains nutrients by diffusion from the mother’s blood
What are the sites of sperm production?
seminiferous tubules
When do seminiferous tubules develop?
43 to 50 days after conception
Where are Leydig cells located?
located in interstitial tissue between seminiferous tubules
9 to 10 weeks after conception, what happens in the male reproductive system?
the Leydig cells begin to secrete testosterone
What is the general name for male sex hormones?
androgens
What is the purpose of testosterone during embryonic development?
converts indifferent structures into male external genitalia (penis + scrotum)
In adult males, each testis is primarily composed of
highly convoluted seminiferous tubules
Where are testes actually formed?
within the abdominal cavity, but they descend before birth through the inguinal canal into the scrotum
What opening do the testis pass through when moving out of the abdominal cavity?
inguinal canal
What is the temperature in the scrotum?
34 C (lower than 37 C body temperature)
The wall of the seminiferous tubules is composed of (2)
germ cells (spermatogonia) + supporting Sertoli cells
Which cells in the testes are diploid?
the germ cells near the outer surface of the seminiferous tubules are diploid and are the only cells that will undergo meiosis
Where cells in the testes are haploid?
the developing gamete cells located closer to the lumen of the tubule
First, a spermatogonium divides by
mitosis to produce 2 diploid cells - one will go through meiosis and the other will remain a spermatogonium
Adult males, on average, produce how many sperm cells each day?
100 to 200 million sperm
What is a primary spermatocyte?
the diploid daughter cell that begins meiosis
The daughter cell of spermatgonium cell division that eventually undergoes meiosis is called a
primary spermatocyte
What happens in the first meiotic division? (2)
the homologous chromosome pairs are separated which produces 2 haploid secondary spermatocytes; each chromosome still has duplicate chromatids
What are secondary spermatocytes?
the haploid cells that result from the first round of meiotic division
What happens in the second meiotic division?
chromatids are separated to produce 2 haploid spermatids
What are spermatids?
haploid cells that result from the second round of meiotic division
Which cells constitute the germinal epithelium of the seminiferous tubules?
spermatogonia; primary spermatocytes; secondary spermatocytes; spermatids
The seminiferous tubules contain nongerminal cells called
Sertoli cells
What is the function of Sertoli cells?
nurse the developing sperm and secrete products required for spermatogenesis; convert spermatids into spermatozoa by engulfing extra cytoplasm
Spermatids are converted into _____ by ______.
spermatozoa by Sertoli cells
What is the “final” sperm product?
spermatozoa
Spermatozoa are comprised of what three general sections?
head, body, flagellum
The head of the spermatozoon encloses
a compact nucleus
The head of the spermatozoon is capped by
a vesicle called an acrosome
Where does the acrosome derive from?
the Golgi complex
What is the acrosome?
vesicle that caps the head of the spermatozoon
What is the function of the acrosome?
contains enzymes that aid in the penetration of the protective layer surrounding the egg
After sperm are produced in the seminiferous tubules, where do they travel to?
the epididymis
What is the epididymis?
a long, coiled tube
What about sperm needs to be developed when they arrive in the epididymis?
they are not motile when they arrive in the epididymis
How long do sperm wait in the epididymis?
must wait in the epididymis for at least 18 hours to let motility develop
What major function of sperm develops while in the epididymis?
motility
From the epididymis, where do the sperm travel?
the vas deferens
Where does the vas deferens lead to?
passes into the abdominal cavity via the inguinal canal, then to a duct leading to the seminal vesicles
The seminal vesicles produce
a fructose-rich fluid constituting 60% of semen volume
After the seminal vesicles, the vas deferens continues as
the ejaculatory duct and enters the prostate gland at the base of the urinary bladder
How big is the prostate gland in humans?
golf ball
The prostate gland contributes what percentage of semen composition?
30%
From the prostate gland, semen
is carried through the urethra out of the body
What contributes the last 10% of semen?
bulbourethral glands
In addition to contributing part of semen, the bulbourethral glands also secrete
a fluid that lines the urethra/tip of penis prior to coitus
What erectile tissues does the penis contain?
corpora cavernosa; corpus spongiosum
Where is the corpora cavernosa located?
along the dorsal side of the penis
Where is the corpus songiosum located?
along the ventral side of the penis
What causes penile erection?
neurons in the parasympathetic division release NO which causes arterioles in the penis to dilate, flow of blood in compresses veins so blood can’t flow back out
What is the average ejaculate?
2 to 5 mL, 300 million sperm
What is considered sterile?
20 million sperm or lower
Sperm constitutes what percentage of semen?
only 1%
In males, what is the function of FSH?
stimulates spermatogenesis via Sertoli cells
In males, what is the function of LH?
stimulates secretion of testosterone by Leydig cells
In males, what is the function of testosterone?
stimulates development/maintenance of male secondary sexual characteristics, accessory sex organs, spermatogenesis
What are the four male accessory sex organs?
prostate gland, bulbourethral gland, vas deferens, seminal vesicles
What stimulates the anterior pituitary to secrete FSH and LH?
hypothalamic hormone gonadotropin-releasing hormone (GnRH)
How are FSH and Sertoli cells involved in negative feedback inhibition?
FSH stimulates Sertoli cells to secrete inhibin (peptide hormone) which inhibits FSH secretion
How are LH and testosterone involved in negative feedback inhibition?
LH stimulates testosterone secretion, testosterone inhibits release of LH
In females, what is the function of FSH?
stimulates growth of ovarian follicles and secretion of estradiol
In females, what is the function of LH? (3)
stimulates ovulation; conversion of ovarian follicles into corpus luteum; secretion of estradiol and progesterone by corpus luteum
In females, what is the function of estrogen? (2)
stimulates development/maintenance of female secondary sexual characteristics; prompts monthly preparation of uterus for pregnancy
In females, what is the function of progesterone? (2)
completes preparation of uterus for pregnancy; helps maintain female secondary sexual characteristics
In females, what is the function of oxytocin? (2)
stimulates contraction of uterus and milk-ejection reflex
In females, what is the function of prolactin?
stimulates milk production
In the absence of testosterone, the female embryo develops
a clitoris and labia majora from the same structures that produce a penis and scrotum
The penis is analogous to
the clitoris
The scrotum is analogous to
labia majora
The clitoris and penis are similar in that they both contain
corpora cavernosa (both are erectile)
Ovarian follicles contain
primary oocyte + granulosa cells
What is a primary oocyte?
potential egg
At puberty, what do granulosa cells do?
secrete major female sex hormone estrogen
What is menarche?
onset of menstrual cycling
What are the female accessory sex organs? (3)
fallopian tubes; uterus; vagina
Describe the primary oocytes at birth.
the primary oocytes have begin meiosis but are arrested in prophase of the first meiotic division
The human menstrual cycle can be divided into what two phases? What separates these phases?
can be divided in terms of ovarian activity into the follicular phase and luteal phase, separated by the event of ovulation
What happens at the beginning of each menstrual cycle in terms of follicular development?
single dominant follicle emerges and continues development while other follicles in that group head toward destruction
Generally speaking, what happens during the follicular phase?
dominant follicle achieves full maturity as late tertiary follicle under FSH stimulation
What is another name for the late tertiary follicle?
Graafian follicle
What lines the uterus?
simple columnar epithelial membrane called the endometrium
The late tertiary follicle forms as a
thin-walled blister on the surface of the ovary
During the follicular phase, what causes the growth of the endometrium?
estrogen
What is another name for the follicular phase and why?
also known as the proliferative phase because the endometrium grows
During the follicular phase, what happens to the primary oocyte located in the Graafian follicle?
primary oocyte completes first meiotic division to produce one large daughter cell called the secondary oocyte and one small daughter cell called the polar body
What is the polar body?
small daughter cell that results from the primary oocyte completing the first round of meiotic division
What is the secondary oocyte?
large daughter cell that results from the primary oocyte completing the first round of meiotic division
What happens to the polar body?
disintegrates
What happens to the secondary oocyte following the first round of meiotic division?
begins second round of meiotic division but is arrested at metaphase II; will not complete second round of division unless fertilized in the Fallopian tube
The increasing level of estrogen in the blood during the follicular phase stimulates what?
stimulates the anterior-pituitary gland to secrete LH midcycle
The secretion of LH midcycle causes
the sudden secretion of LH causes fully developed Graafian follicle to burst open and release the secondary oocyte (ovulation)
Where does the released secondary oocyte go after ovulation?
enters abdominal cavity near the fimbriae to go into the Fallopian tubes
What are fimbriae?
feathery projections surrounding the opening to the Fallopian tube
What pulls the secondary oocyte into the Fallopian tubes?
ciliated epithelial cells lining the Fallopian tubes draw in the secondary oocyte and propel it towards the uterus
What happens to a secondary oocyte that isn’t fertilized?
if it isn’t fertilized, it disintegrates within a day following ovulation
What happens to a secondary oocyte that is fertilized?
stimulus of fertilization allows it complete second round of meiotic division
Where does fertilization occur in the human female?
upper third of Fallopian tubes
How long does it take for the fertilized zygote to travel to the uterus from the Fallopian tube?
3 days to reach uterus, then another 2-3 days to implant in the endometrium
After ovulation, what happens to the Graafian follicle?
LH stimulates conversion of Graafian follicle into corpus luteum
The second half of the menstrual cycle is called the
luteal phase
The corpus luteum secretes
estrogen and progesterone
What is the purpose of the corpus luteum secreting estrogen and progesterone? (2)
estrogen and progesterone exert negative feedback inhibition of FSH and LH; prevents development of additional follicles
In the luteal phase, what is the effect of progesterone and estrogen on the endometrium?
endometrium becomes more vascular, glandular, and enriched with glycogen deposits
What is another name for the luteal phase?
secretory phase because of the way the endometrium prepares itself for embryo implantation
What happens to the corpus luteum if fertilization doesn’t occur? (3)
degenerates due to decreasing levels of FSH/LH which are caused by estrogen/progesterone feedback inhibition; corpus luteum needs LH for survival but LH is decreased so corpus luteum dies; drop in corpus luteum means abrupt decline in estrogen levels; built-up endometrium is shed
Menstruation is caused by
the corpus luteum disintegrating and estrogen levels decreasing
What happens to the corpus luteum if fertilization does occur?
embryo secretes human chorionic gonadotropin (hCG) to prevent regression of corpus luteum
What is hCG?
LH-like hormone produced by chorionic membrane
What is the purpose of maintaining the corpus luteum after fertilization?
hCG keeps the levels of estrogen and progesterone high which prevent menstruation, which would terminate the pregnancy
Why is hCG used in pregnancy tests?
because it comes from the embryo and not the mother - can better test for pregnancy
What are the four phases of estrous cycles in mammals, in order?
proestrus; estrus; metestrus; diestrus
What are two other names for the Fallopian tubes?
uterine tubes; oviducts
What are the four phases of the menstrual cycle in humans, in order?
proliferative; midcycle; secretory; menstrual
What is the uterus?
muscular, pear-shaped organ that narrows to form a neck (cervix, which leads to vagina)
The entrance to the vagina is initially covered by
the hymen
During sexual arousal, what happens to the secondary female sex organs?
become engorged with bloods
During sexual arousal, what secretes lubricant?
Bartholin’s glands
Describe the female reproductive tracts in cats/dogs/cows.
one cervix but two uterine horns separated by a septum
Describe the female reproductive tracts in marsupials.
two unconnected uterine horns, two cervices, two vaginas
