Biology Developmental Flashcards
Cleavage increases the ___ ratio of each cell, thereby improving gas and nutrient exchange
surface-area-to-volume
The first complete ___ of a zygote occurs approximately 32 hours after fertilization
cleavage
The second cleavage of a ___ occurs after 60 hours, and the third cleavage after approximately 72 hours, at which point the eight-celled embryo reaches the uterus
zygote
As cell division continues, a solid ball of embryonic cells, known as the ___, is formed
morula
___ begins when the morula develops a fluid-filled cavity called the blastocoel, which by the fourth day becomes a hollow sphere of cells called the blastula (blastocyst in mammals)
blastulation
The outer layer of cells of the ___, called the trophoblast, provides nutrients to the embryo and develops into part of the placenta
blastula
The two components of the fetal circulatory system are the ___ and the umbilical cord
placenta
The placenta and the umbilical cord are outgrowths of the four extra-embryonic ___ formed during development: the amnion, chorion, allantois, and yolk sac
membranes
The ___ is a thin, tough membrane containing a watery fluid called amniotic fluid
amnion
___ acts as a shock absorber of external pressure during gestation and localized pressure from uterine contractions during labor
amniotic fluid
___ formation begins with the chorion, a membrane that completely surrounds the amnion
placenta
The ___ assists with transfer of nutrients from the mother to the fetus
chorion
A third membrane, the ___, develops as an outpocketing of the gut
allantois
The blood vessels of the allantoic wall enlarge and become the ___ vessels, which will connect the fetus to the developing placenta
umbilical
The yolk sac, the site of early development of ___, becomes associated with umbilical vessels
blood vessels
After week two, the embryo is fully implanted in the ___ and cell migrations transform the single cell layer of the blastula into a three-layered structure called a gastrula
uterus
(primary germ layer) ___- “attracto”derm (things that attract us to others, such as cosmetic features and smarts)
ectoderm
(primary germ layer) ___- “means”oderm (the means of getting around as an organism, such as bones and muscle; the means of getting around in the body, such as circulatory system; the means of getting around, such as the gonads
mesoderm
(primary germ layer) ___ - linings of “endernal” organs (the digestive and respiratory tract, and accessory organs attached to these systems)
endoderm
___ (outer layer): the lens of the eye, the retina, and the nervous system
ectoderm
___ (middle layer): portions of digestive and respiratory organs
mesoderm
___ (inner layer): parts of the liver, pancreas, thyroid, and bladder lining
endoderm
By the end of ___, regions of the germ layers begin to develop into a rudimentary nervous system; this process is known as neurulation and starts before week three
gastrulation
A rod of ___ cells called the notochord develops along the longitudinal axis of the embryo just under the dorsal layer of ectoderm
mesodermal
The ___ has an inductive effect on the overlying ectoderm, causing it to bend inward and form a groove along the dorsal surface of the embryo
notochord
The dorsal ___ folds on either side of the groove; these neural folds grow upward and finally fuse, forming a closed tube
ectoderm
After a closed tube is formed with the dorsal ectoderm (neural tube), this gives rise to the ___ and spinal cord (central nervous system)
brain
The cells at the tip of each neural fold are called ___
neural crest cells
Neural crest cells migrate laterally and give rise to many components of the ___ nervous system
peripheral
___: the body organs begin to form
organogenesis
___: the organs increase in size, which is a continual process from infancy through adulthood
Growth
___: eggs develop in women and sperm develop in men, which permits reproduction to occur
gametogenesis
(first trimester) major ___ begin to develop
organs
(first trimester) the cartilaginous ___ begins to turn into bone by the seventh week
skeleton
(first trimester) At the end of the ___ month, the fetus is about 9 cm long
third
(second trimester) The ___ begins to move around in the amniotic fluid, its face appears human, and its toes and fingers elongate
fetus
(third trimester) The growth ___ slows and the fetus becomes less active as it has less room to move about
rate
(labor) In the first stage of birth and maturation, the ___ thins and dilates, and the amniotic sac ruptures, releasing its fluids
cervix
(labor) During the final stage, the uterus contracts, expelling the placenta and the ___
umbilical cord
In ___ (flowering plants), double fertilization occurs - one sperm fertilizes the egg cell, and the other fuses to form the endosperm, which provides nutrients to he developing embryo in the seed
angiosperms
Some plants can produce seeds without ___ or reproduce without the production of seeds by asexual reproduction, which gives rise to individuals genetically identical to the parent
fertilization
In the alternation of generations life cycle, plants can fluctuate between asexual diploid and sexual haploid stages, known as the ___ and gametophyte generations, respectively
sporophyte
The ___ sporophyte produces haploid spores via meiosis, which matures into haploid gametophyte
diploid
The ___ gametophyte goes on to produce gametes via mitosis
haploid
The ___ from mitosis then fuse to produce a zygote
gametes
The embryo (from the zygote dividing mitotically) has the following parts: \_\_\_: precursor of the upper stem and leaves
epicotyl
Plant embryo
Cotyledons: ___ leaves
Hypocotyl: the lower stem and root
Endosperm: feeds the embryo in angiosperms
Seed coat: develops from the outer covering of the ovule
seed
___ is the process of a seed sprouting into a seedling (young plant)
germination
The ___ is involved in plant development, it is found in the tips of roots and stems
apical meristem
The ___ or cambium is located between the xylem and phloem
lateral meristem
