Chapter 47 Flashcards
Asexual reproduction
based on mitosis & results in offspring that are
genetically identical to one another and to their parent equivalent to cloning
ex. budding in hydra, fission in anemones and parthenogenesis in lizards
Sexual reproduction
based on meiosis & gamete fusion
▪Due to genetic recombination during meiosis & fusion of haploid gametes( usually from different parents) during fertilization, on results in offspring that are genetically
different from each other & from their parents!
Binary fission
Major type of asexual reproduction
Single parent cell doubles its DNA, then divides into two cells. Usually occurs in bacteria.
Fragmentation
Organisms break into two or more fragments that develop into a new individual. Occurs in many plants, as well as some animals (like coral, sponges, and starfish).
Benefits of asexual reproduction
- all individuals can reproduce
- requires no mates, travel or competition
Budding
Major type of asexual reproduction
Small growth on surface of parent breaks off, resulting in the formation of two individuals. Occurs in yeast and some animals (like the hydra below).
Parthenogenesis
Type of asexual reproduction
An embryo develops from an unfertilized cell. Occurs in invertebrates, as well as in some fish, amphibians, and reptiles.
Gametogenesis
Consists of spermatogenesis: how the sperm is created and oogenesis or how the egg is created
Oogenesis
1 egg ; 4 sperm
- Primary germ cell
- Oogonium through mitotic divisions
- Primary oocyte forms through mitotic divisions
- arrested n prophase 1 of meiosis - Through meiosis I, secondary oocyte and polar body is formed
- Through meiosis II ootid and another polar body is made
- A mature egg ell (ovum is created)
- arrested at metaphase II of meiosis - Sperm enters and fertilized egg
- Completes meiosis II
Spermatogenesis
Male germ cells undergoes meiosis to produce four gametes
- Primordial germ cell in embryo
- Spermatogonial stem cell through mitotic divisions
- Spermatogonium through mitotic divisions
- Primary spermatocyte from mitotic divisions
- Two secondary spermatocyte through
meiosis 1 - Early 4 spermatid through meiosis II
- Sperm through differentiation (Sertoli cells provide nutrients)
Differences between Oogenesis and spermatogenesis
- Oogenesisceases later in
life; spermatogenesis
continues throughout
adult life - Oogenesishas long
interruptions;
spermatogenesis produces
sperm from precursor cells
in continuous sequence
Ovulation
Sperm entry into matured egg cell and becomes a fertilized egg at completion of meiosis II
Scrotum
Holds testes and penis
Penis
organ of copulation needed for internal fertilization
Where are the accessory fluids formed
seminal vesicles, prostate
gland & bulbourethral gland
Where is sperm produced and stored
Produced by testes and stored in epididymis
Vas deferens
tubes that transport sperm from
epididymis to ejaculatory duct.
Ovary
Where meiosis produces egg cells (ova)
Semen
combination of sperm & accessory fluids
Passes through urethra, that services both reproductive & urinary systems in males
Viviparous
Female retains embryo & provides nourishment during development
Humans are viviparous
What happens during ovulation
Egg is expelled from ovary & enters oviduct (fallopian tube), where fertilization may take place
Uterus
Where embryonic development takes place
During childbirth, the baby passes through
cervix & into the vagina
Where does fertilization take place
Oviduct (fallopian tubes)
How puberty is initiated
- Gonadotropin releasing hormone is released from hypothalamus
- Triggers release of
luteinizing hormone
(LH) & follicle-stimulating
hormone (FSH) from
pituitary gland - LH & FSH trigger increases in testosterone
or estradiol
Menstrual cycle
monthly reproductive cycle that occurs in
ovary & uterus (averages 28 days in humans)
Along ovary changes, uterine lining undergoes thickening & subsequently regression.
Menustration
Starts by combined ovarian and uterine cycles
Expulsion of uterine lining through vagina
2 stages of menstrual cycle
Follicular phase
Luteal phase
Follicular phase
14 days, follicle matures &
ovulation occurs (primary oocytes undergo meiosis to produce mature ovum)
Luteal phase
14 days, structure called corpus luteum
forms from ruptured follicle & later degenerates
Cleavage
In most mammals, cleavage (mitosis of the fertilized egg) begins before embryo reaches the uterus
Human Chorionic
Gonadotropin (HCG)
made initially by the embryo stimulates corpus luteum to continue hormone secretion until placenta takes over
Hormones have negative
feedback on LH & FSH as they suppress cycles of ovulation until pregnancy completed
Progesterone
Progesterone stimulates the conversion of the thickened uterine lining to a tissue that can support embryonic implantation and development after ovulation.
Progesterone exerts negative feedback on pituitary hormones.
Which hormone spikes midway through the menstrual cycle and triggers ovulation?
Luteinizing hormone (LH).
Luteinizing hormone (LH)
- secreted by the pituitary gland
- causes the mature ovarian follicle to rupture, a process called ovulation.
Transport and delivery of s
- The vas deferens transports sperm from the epididymis to the ejaculatory duct, which empties into the urethra;
- The urethra carries sperm through the penis to the outside of the body and into the female reproductive tract.
The thickening of the uterine wall, which allows it to support a developing embryo, is triggered by a rise in which of the following hormones?
Progesterone
A rise in progesterone lowers production of LH and FSH and activates the thickening of the uterine lining.
How does testosterone release differ from cortisol release?
Only testosterone is triggered by FSH.
Ovarian cycle
- Hypothalamus secretes GnRh
- Hypothalamus stimulates pituitary gland to secrete LS and FSH
- LS and FSH stimulate follicle growth and secretion of estradiol
- High levels of estradiol increases LH and FSH production
Follicle phase
- Follicle maturation and ovulation
Luteal phase
- Corpus luteum secretes estradiol and progesterone
- estradiol and progesterone inhibit production of LH and FSH - Corpus luteum disintegrates
- causes decline in estradiol and progesterone and ends inhibition of hypothalamus and pituitary
What is placenta composed of?
tissue of maternal and fetal origin.
Why is progesterone production in the corpus luteum important in the first trimester of pregnancy?
To maintain the uterine lining and after this, the placenta will provide enough progesterone
Who produces larger eggs? Viviparous or Oviparous
oviparous populations due to the eggs containing all the nutrients and water required for the entire period of embryonic development
Which structure in the male reproductive tract delivers the sperm from the testis in the scrotum to the base of the penis on its way to ejaculation?
Vas deferens
The vas deferens tube is about a foot long and connects the epididymis to the ejaculatory duct within the prostate gland.
Which structure in the female reproductive system is the longest path for the ovum as it travels from the ovary to the uterus?
Oviduct
What do follicles produce as it matures
As the follicle matures, it secretes estradiol and a small amount of progesterone.
Positive feedback mechanism in hormonal control of human menstrual cycle
High levels of estradiol trigger release of more LH. The follicle can produce high levels of estradiol only if it has grown and matured.
Starting at puberty what happens in spermatogenesis
Starting at puberty, hormones stimulate the primary spermatocytes to undergo meiosis I to form secondary spermatocytes, which then undergo meiosis II to form spermatids.
Start of menstrual cycle characterized by
Endometrium thickens and releases fluids for the first 5 days
What is the role of FSH
Stimulates growth of a follicle that contains an egg cell
Stimulates production of estrogen
What is the role of LH
The LH triggers ovulation mid cycle
Trigger ruptured follicle to develop into lumen corpilus
Effects of estrogen
Stimulates regrowth of linings of uterus
What happens where there is low estrogen
Assures negative feedback so that only one follicle could be created at a time, by decreases FSH
What happens where there is high estrogen
Stimulates high levels of LH and that triggers ovulation
What does the corpus luteum secrete
estrogen and progesterone that maintains the endometrium and inhibits FSH and LH secretion.
What maintains the corpus luteum if there is fertilization
human chorionic gonadotropin
(hcg)
Where does the sperm become capable of movement
epididymis
What does a drop in testosterone do
Stimulate the brain to produce more LH to produce more androgens
What happens when androgens are increased and decreased
inhibits the secretion of releasing hormones by the hypothalamus and LH secretion by the pituitary gland.
A decrease in androgens stimulates the secretion of releasing hormones by the hypothalamus and LH secretion by the pituitary gland.
What pituitary gland hormone stimulates sperm production
FSH
What pituitary gland hormone stimulates the testes to secrete androgens
Luteinizing hormone (LH)
Where do sperm develop
In seminiferous tubules, found within testes.
SEVEN UP
S: Seminiferous tubules, where sperm production takes place
E: Epididymis, where sperm cells are stored
V: Vas deferens, where sperm are transported to the urethra
N: Nothing
U: Urethra, which carries urine from the bladder to outside the body, and also ejaculates semen during orgasm
P: Penis
