reproduction Flashcards
what is asexual reproduction the creation of?
new individuals by the process of mitosis
what does asexual reproduction create?
identical offspring rapidly
asexual reproduction is common with?
many invertebrates
3 types of asexual reproduction
fission
budding
fragmentation
what is fission? examples?
division of parent into 2 genetically identical individuals
amoeba, bactera (bindary fission instead of mitosis)
what is budding? examples?
new individuals pinch off from an existing one to form a colony
yeast, hydra, corals
what is fragmentation? example?
breaking off of the body into smaller pieces that then develop into complete adults through regeneration
sea stars, planaria
advantage of asexual reproduction
animals living in isolation can produce offspring without a mate
many offspring are created in a short amount of time
what is sexual reproduction?
creation of oddspring when 2 haploid gametes come together to form a diploid zygote
when are gametes made?
meiosis
ffemale gamete
ovum/oocyte
male gamete
sperm/spermatozoan `
what does sexual reproduction increase?
genetic variation amongst offspring by inheriting genes from 2 parents
what does the variability in sexual reproduction enhance?
Darwinian fitness and survival when environmental factors change
who can reproduce both sexually and asexually?
freshwater crustacean Daphnia
under favorable conditions, how do Daphnia reproduce?
parthenogenesis/virgin birth
parthenogenesis
mother organisms form genetically identical daughters/clones that d nit need to be fertilized
what is the advantage of parthenogenesis?
allows numbers to increase rapidly in short growing periods
under unfavorable conditions, how do Daphnia reproduce?
give birth to males + sexual females so that mating can occur and some can survive
where is parthenogenesis seen?
species with social organization like bees ad ants
some vertebrates lie fish, birds, amphibians, and lizards
how is parthenogenesis in ants?
male drones develop by parthenogenesis, while female sterile workers and fertile queen develop from fertilized eggs
most animals’ reproductive cycles are linked to?
changing seasons
what does reproductive cycles being linked to season allow?
conservation of energy and reproduce hen condiions are favorable
what does reproductive cycles being linked to season allow?
conservation of energy and reproduce when conditions are favorable
what are reproductive cycles also controlled by?
hormones and environmental cues like temp, rainfall, daylength, and lunar cycles
who is sexual reproduction difficult for?
sessile organisms (dont move) and burrowing animals who may never encounter a member of the opposite sex
how is the prob;em of sexual reproduction for sessile animals solved?
synchronous hermaphroditism
hermaphroditism
having both male and female reproductive systems
-many still must mate with another member of the same species(earthworms)
sequential hermaphroditism
when an individual changes its sex/gonads during its lifetime
male to female
protoandrous
female to male
protogynous
what is sex reversal associated with?
age and size
sequential hermaphroditism in clownfish
in some clownfish species, oldest and the biggest individual can change from male to female is there are not enough females around
fertilization
joining of egg and sperm
external fertilization
eggs and sperm meet in the environment
always occurs in water
environmental cues like, temp, day length and pheromones or nonenvironmental cues like courtship behavior, influence gametes release
produce large numbers of zygotes and few survive
internal fertilization
sperm are deposited in or near female’s reproductive tracts
produce fewer zygotes with more parental care, hence greater survival
gonads
organs that produce gametes
ovaries - female
testicles - male
single opening for both excretion of waste and reproduction
cloaca
examples of organism with cloacas
non mammalian vertebrate - birds and fish
(most mammals have 2 separate openings)
spermatogenesis
production of mature sperm cells
how does structure of sperm fit function?
head region contains 1n nucleus that is tipped with enzymes called the acrosome that help the sperm penetrate the egg
behind the egg are many mitochondria that provide ATP for movement of the flagellum
what parts of the sperm enter the ovum?
head - DNA (nucleus) and centriole
oogenesis
develpoment of ova
ova
unfertilized egg cells
how many follicles do women have?
~400,000
when do women get all their follicles?
formed before birth, but they are not “ready”
follicle
1 egg surrounded by layers called follicle cells
what do follicle cells do?
protect and nourish developing egg
at birth, how are all the eggs in a woman?
diploid and in g1 interphase of meiosis
what happens to the eggs between birth and puberty?
all reach prophase i of meiosis and are essentially stuck there for a while
what happens during puberty?
a single primary oocyte completes meiosis each month
how does a primary oocyte complete meiosis?
FSH hormone stimulates one follicle “the chosen one” to go through meiosis I each month
what happens at the end of meiosis I?
the secondary oocyte is formed and is then released from the ovary with ovulation to go wait in the fallopian tubes/oviduct
how is the meiotic division in puberty?
unequal- the secondary oocyte gets almost all the cytosol and organelles and the 1st polar body is much smaller
how is meiosis II/second mitotic division induced?
when a sperm penetrates the secondary oocyte to produce the haploid ovum/egg
what happenes to the 2nd polar body?
it separates from the ovum, while the haploid ovum and sperm’s nuclei fuse= fertilization
what does the secondary oocyte leave behind when it leaves the ovary during ovulation?
leaves behind follicular tissue
what does the follicular tissue develop into?
corpus luteum in the ovary
what does the corpus luteum do?
secretes hormones estrogen and progesterone that maintain the uterine lining during pregnancy
what happens to the corpus luteum when the secondary oocyte is not fertilized?
it degenerates and the woman has her period then a new follicle matures during the next cycle
principle hormones of males
steroid hormones called androgens
important androgen
testosterone
what does testosterone do?
primary sex characteristics that are associated with the reproductive system
secondary sex characteristics that are not directly related to the reproductive system
primary sex characteristics
sperm production and development of reproductive structures
secondary sex characteristics
deepening of the voice, hair growth, and more muscle growth
how many eggs do females release per cycle?
1 or a few eggs
2 different types of cycles
human and primates - menstrual cycles
estrous cycles - dogs
similarity between menstrual and estrous cycles
ovulation at the endometrium lining of the uterus thickens and develops a rich blood supply in preparation for an embryo
difference between menstrual cycle and estrous cycle
m - if ovum is not fertilized, the uterine lining is shed
e - endometrium is reabsorbed by the uterus
FSH
Follicle Stimulating Hormone
LH
Luteinizing Hormone
how is FSH involved?
involved in the development of the growing follicle
why isnt LH initially helping the growing follicle?
there are no receptors for it on the growing follicle
where are FSH and LH secreted from?
pituitary glands
what do FSH and LSH stimulate?
the release of estrogen and progesterone
does the follicle get receptors for LH?
yes, as it grows larger with the aid of FSH, it eventually develops receptor sites for LH
what type of feedback do LH and FSH have?
positive - it is actually LH that induces ovulation of secondary oocyte
after ovulation, what does LH do?
stimulates the remaining follicular tissue left behind when the secondary oocyte was released to form the corpus luteum
after the corpus luteum is formed, what doesLH do next?
triggers it to secrete estrogen and progesterone
what happens to the hormones when corpus luteum disintegrates?
estrogen and progesterone levels decrease and induces menstruation
what happens to estrogen and progesterone levels when a women is pregnant?
levels remain high
what is estrogen responsible for?
secondary sex characteristics like high water retention, breast development, and calcium metabolism
menopause
women cease to ovulate/menstruate
why do women go through menopause?
ovaries lose their responsiveness to the hormones FSH and LH which then causes the decline of estrogen and progesterone
why do older women tend to have osteoporosis?
estrogen linked to calcium metabolism, so low levels of that causes weak bones
“bone pores”
gestation
pregnancy
is the condition of carrying one or more embryos
conception
fertilization of an egg by a sperm
when does a zygote start cleavaging?
24 hours after fertilization
morula
division of zygote until a forms a solid ball of cells
blastula
morula continues to divide, becoming a hollow ball
gastrulation
cells invaginate to form a gastrula
what begins with the formation of a gastrula?
differentiation of body structures
placenta
disk-shaped organ
what does the placenta contain?
embryonic and maternal blood vessels
what does the placenta exchange? via what?
materials between the mother and embryo like nutrients, respiratory gases
arteries and veins of the embryo’s umbilical cord
what does the placenta dispose?
metabolic waste from the embryo
organogenesis
development of organs
when does organogenesis occur?
first trimester
what is the embryo considered as after the first trimester?
fetus because of all the major structures of the adult are present in rudimentary form
during the 1st trimester, what does the embryo secrete?
hormone human chorionic gonotrophin (HCG)
what does HCG do?
maintains the secretion of progesterone and estrogen by the corpus luteum and keeps the endometrium lining intact
what does a pregnancy test detect in urine?
high levels of HCG
what happens during the 2nd trimester when HCG levels drops?
corpus luteum deteriorates and the placenta secretes its own estrogen and progesterone to maintain the lining
when are estrogen levels the highest?
near the end of the pregnancy in the thrid trimester
what does the high levels of estrogen trigger?
the release of oxytocin receptors on the uterus
local regulator prostaglandins are secreted
what does oxytocin cause?
causes powerful contractions of the smooth muscles of the uterus
what does prostaglandin do?
enhance contractions and cause pain
what happens to mammals after birth?
lactation
what stimulates milk production in the mammary glands?
the pituitary glands produce prolactin that is controlled by the hormone oxytocin
what are birth control a combination of?
synthetic estrogen and progesterone
what feedback are birth control pills?
negative feedback by stopping the release of FSH and LH thus preventing ovulation
what three stages of cell division follow fertilization?
cleavage
gastrulation
organogenesis
cleavage
zygote divides to from the solid morula then hollow/fluid-filled blastula
gastrulation
3 germ layers form
organogenesis
generates rudimentary organs from which adult structures will grow
what does the cell cycle during cleavage consist of?
s-phase of interphase where DNA gets copied
m-phase where mitosis occurs, cytokinesis
what does the embryo do during cleavage?
partitions the cytoplasm of the zygote into many smaller calls called blastomeres and does not enlarge
deuterostomes
second mouth
echinoderms (sea stars) and chordates (humans)
cleavage in deuterostomes
radial - upper four cleavage are aligned directly over the lower four blastomeres
protosomes
first mouth
mollusks (shells)
annelids (segmented worms)
arthropods (insects)
cleavage in protostomes
spiral - blastomere cells of upper tier sit in the grooves between the cells of the lower tier
gastrulation
morula - blastula - gastrula
what is gastrulation?
rearrangement of the cells of the blastula
invagination
cells at one pole of the blastula move inward
gastrula
hollow single layered blastula
where the cells invaginate
blastopore
3 layers in the germ layer
ectoderm - outer layer of the gastrula
endoderm - lines the embryonic digestive tract
mesoderm - partially fills the space between the endo and ectoderms
key body parts that form from ectoderm
epidermis of skin
nervous system
key body parts that form from endoderm
lining of digestive tract
lining of respiratory tract
lining of urethra
reproductive system
key body parts that form from mesoderm
skeletal system
muscular system
dermis of skin
three kinds of morphogenesis changes occurring with organogenesis
folds
splits
condensation/ clustering
first body part to take shape in chordates?
neural tube and notochord
what will the neural tube and notochord become?
spinal cord and backbone/vertebrate respectively
when does the notochord form?
when the mesoderm condenses
if a mother does not get enough folic acid in her diet how will this affect the baby?
neural tube defects - spina bifida
