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The proposal that a human sperm contained a miniature human being is consistent with the now-discredited
theory of development known as
A) epigenesis.
B) preformation.
C) cell differentiation.
D) morphogenesis.
E) cell theory.

preformation.

You buy a pie that contains a swirled mixture of chocolate and vanilla filling. When you cut the pie up, you
notice that some slices have more chocolate than vanilla and that other slices have more vanilla than chocolate.
This uneven distribution of chocolate and vanilla is most like the uneven distribution of
A) nuclei in a zygote.
B) nuclei in an early embryo.
C) nuclei in an egg.
D) cytoplasmic determinants in a zygote.
E) cytoplasmic determinants in an early embryo.

cytoplasmic determinants in a zygote.

A puppy is born with a malformed right leg. A veterinarian studies the animal and determines that all of the
correct types of cells are present, but that the leg simply took on the wrong shape. This is most likely a problem
of
A) morphogenesis.
B) cell differentiation.
C) histogenesis.
D) preformation.
E) fertilization.

morphogenesis.

Molecular genetic evidence that certain genes shared by both humans and fruit flies initiate eye development in
both species suggest a common
A) complete genome.
B) use of ATP in energy-transfer reactions.
C) genetic toolkit for development.
D) homunculi.
E) duration of pregnancy.

genetic toolkit for development.

As an embryo develops, new cells are produced as the result of
A) differentiation.
B) preformation.
C) cell division.
D) morphogenesis.
E) epigenesis

cell division.

Fertilization of an egg without activation is most like
A) placing the key in the ignition of a car but not starting the engine.
B) resting during halftime of a basketball game.
C) preparing a pie from scratch and baking it in the oven.
D) walking to the cafeteria and eating lunch.
E) dropping a rock off a cliff and watching it land in the valley below.

placing the key in the ignition of a car but not starting the engine.

Assume that successful reproduction in a rare salamander species, wherein all individuals are females, relies on
those females having access to sperm from males of another species but that the resulting embryos show no
signs of a genetic contribution from the sperm. In this case, the sperm appear to be used only for
A) morphogenesis.
B) epigenesis.
C) egg activation.
D) cell differentiation.
E) the creation of a diploid cell.

egg activation.

Contact of a sperm with signal molecules in the coat of an egg causes the sperm to undergo
A) mitosis.
B) depolarization.
C) apoptosis.
D) vitellogenesis.
E) the acrosomal reaction.

the acrosomal reaction.

Contact of an egg with signal molecules on sperm causes the egg to undergo a brief
A) mitosis.
B) membrane depolarization.
C) apoptosis.
D) vitellogenesis.
E) the acrosomal reaction.

membrane depolarization.

During fertilization, the acrosomal contents
A) block polyspermy.
B) help propel more sperm toward the egg.
C) digest the protective coat on the surface of the egg.
D) nourish the mitochondria of the sperm.
E) trigger the completion of meiosis by the sperm.

digest the protective coat on the surface of the egg.

The vitelline layer of the sea urchin egg
A) is outside of the fertilization membrane.
B) releases calcium, which initiates the cortical reaction.
C) has receptor molecules that are specific for binding acrosomal proteins.
D) is first visible only when organogenesis is nearly completed.
E) is a mesh of proteins crossing through the cytosol of the egg.

has receptor molecules that are specific for binding acrosomal proteins.

From earliest to latest, the overall sequence of early development proceeds as follows:
A) gastrulation → organogenesis → cleavage
B) ovulation → gastrulation → fertilization
C) cleavage → gastrulation → organogenesis
D) gastrulation → blastulation → neurulation
E) preformation → morphogenesis → neurulation

cleavage → gastrulation → organogenesis

From earliest to latest, the overall sequence of early development proceeds as follows:
A) first cell division → synthesis of embryoʹs DNA begins → acrosomal reaction → cortical reaction
B) cortical reaction → synthesis of embryoʹs DNA begins → acrosomal reaction → first cell division
C) cortical reaction → acrosomal reaction → first cell division → synthesis of embryoʹs DNA begins
D) first cell division → synthesis of embryoʹs DNA begins → acrosomal reaction → cortical reaction
E) acrosomal reaction → cortical reaction → synthesis of embryoʹs DNA begins → first cell division

acrosomal reaction → cortical reaction → synthesis of embryoʹs DNA begins → first cell division

The cortical reaction functions directly in the
A) formation of a fertilization envelope.
B) production of a fast block to polyspermy.
C) release of hydrolytic enzymes from the sperm cell.
D) generation of a nerve-like impulse by the egg cell.
E) fusion of egg and sperm nuclei.

formation of a fertilization envelope.

The ʺslow blockʺ to polyspermy is due to
A) a transient voltage change across the membrane.
B) the consumption of yolk protein.
C) the jelly coat blocking sperm penetration.
D) formation of the fertilization envelope.
E) inactivation of the sperm acrosome.

formation of the fertilization envelope.

In an egg cell treated with EDTA, a chemical that binds calcium and magnesium ions, the
A) acrosomal reaction would be blocked.
B) fusion of sperm and egg nuclei would be blocked.
C) fast block to polyspermy would not occur.
D) fertilization envelope would not be formed.
E) zygote would not contain maternal and paternal chromosomes.

fertilization envelope would not be formed.

In mammals, the nuclei resulting from the union of the sperm and the egg are first truly diploid at the end of
the
A) acrosomal reaction.
B) completion of spermatogenesis.
C) initial cleavage.
D) activation of the egg.
E) completion of gastrulation.

initial cleavage.

Fertilization normally
A) reinstates diploidy.
B) follows gastrulation.
C) is required for parthenogenesis.
D) merges two dipoloid cells into one haploid cell.
E) precedes ovulation.

reinstates diploidy.

In mammalian eggs, the receptors for sperm are found in the
A) fertilization membrane.
B) zona pellucida.
C) cytosol of the egg.
D) nucleus of the egg.
E) mitochondria of the egg.

zona pellucida.

Compared to sea urchin eggs, those of mammals
A) complete the fertilization process more rapidly.
B) have not already completed meiosis at the time of ovulation.
C) have a more distinct animal pole.
D) have a more distinct vegetal pole.
E) have no requirement for the cortical reaction.

have not already completed meiosis at the time of ovulation.

As cleavage continues during frog development, the size of the blastomeres
A) increases as the number of the blastomeres decreases.
B) increases as the number of the blastomeres increases.
C) decreases as the number of the blastomeres increases.
D) decreases as the number of the blastomeres decreases.
E) increases as the number of the blastomeres stays the same.

decreases as the number of the blastomeres increases.

During the early part of the cleavage stage in frog development, the rapidly developing cells
A) skip the mitosis phase of the cell cycle.
B) skip the S phase of the cell cycle.
C) skip the G1 and G2 phases of the cell cycle.
D) rapidly increase the volume and mass of the embryo.
E) skip the cytokinesis phase of the cell cycle.

skip the G1 and G2 phases of the cell cycle.

The vegetal pole of the zygote differs from the animal pole in that
A) the vegetal pole has a higher concentration of yolk.
B) the blastomeres originate only in the vegetal pole.
C) the posterior end of the embryo forms at the vegetal pole.
D) the vegetal pole cells undergo mitosis but not cytokinesis.
E) the polar bodies bud from this region.

the vegetal pole has a higher concentration of yolk.

The small portion of the embryo that will become its dorsal side develops from the
A) morula.
B) primitive streak.
C) archenteron.
D) gray crescent.
E) blastocoel.

gray crescent.

The yolk of the frog egg
A) prevents gastrulation.
B) is concentrated at the animal pole.
C) is homogeneously arranged in the egg.
D) impedes the formation of a primitive streak.
E) supports the higher rate of cleavage at the animal pole compared to the vegetal pole.

supports the higher rate of cleavage at the animal pole compared to the vegetal pole.

An embryo with meroblastic cleavage, extra-embryonic membranes, and a primitive streak must be that of
A) an insect.
B) a fish.
C) an amphibian.
D) a bird.
E) a sea urchin.

a bird.

Meroblastic cleavage occurs in
A) sea urchins, but not humans or birds.
B) humans, but not sea urchins or birds.
C) birds, but not sea urchins or humans.
D) both sea urchins and birds, but not humans.
E) both humans and birds, but not sea urchins.

birds, but not sea urchins or humans.

The sequence of developmental milestones proceeds as follows:
A) cleavage → blastula → gastrula → morula
B) cleavage → gastrula → morula → blastula
C) cleavage → morula → blastula → gastrula
D) gastrula → morula → blastula → cleavage
E) morula → cleavage → gastrula → blastula

cleavage → morula → blastula → gastrula

Cells move to new positions as an embryo establishes its three germ tissue layers during
A) determination.
B) cleavage.
C) fertilization.
D) induction.
E) gastrulation

gastrulation.

The outer-to-inner sequence of tissue layers in a post-gastrulation vertebrate embryo is
A) endoderm → ectoderm → mesoderm.
B) mesoderm → endoderm → ectoderm.
C) ectoderm → mesoderm → endoderm.
D) ectoderm → endoderm → mesoderm.
E) endoderm → mesoderm → ectoderm.

ectoderm → mesoderm → endoderm.

If gastrulation was blocked by an environmental toxin, then
A) cleavage would not occur in the zygote.
B) embryonic germ layers would not form.
C) fertilization would be blocked.
D) the blastula would not be formed.
E) the blastopore would form above the gray crescent in the animal pole.

embryonic germ layers would not form.

The archenteron of the developing frog eventually develops into the
A) reproductive organs.
B) the blastocoel.
C) heart and lungs.
D) digestive tract.
E) brain and spinal cord.

digestive tract.

The vertebrate ectoderm is the origin of the
A) nervous system.
B) liver.
C) pancreas.
D) heart.
E) kidneys

nervous system.

In frog embryos, the blastopore becomes the
A) anus.
B) ears.
C) eyes.
D) nose.
E) mouth

anus.

In a frog embryo, gastrulation
A) produces a blastocoel displaced into the animal hemisphere.
B) occurs along the primitive streak in the animal hemisphere.
C) is impossible because of the large amount of yolk in the ovum.
D) proceeds by involution as cells roll over the lip of the blastopore.
E) occurs within the inner cell mass that is embedded in the large amount of yolk.

proceeds by involution as cells roll over the lip of the blastopore.

The earliest developmental stage among these choices is
A) germ layers.
B) morula.
C) blastopore.
D) gastrulation.
E) invagination.

morula.

A correct statement is:
A) The mesoderm gives rise to the notochord.
B) The endoderm gives rise to the hair follicles.
C) The ectoderm gives rise to the liver.
D) The mesoderm gives rise to the lungs.
E) The ectoderm gives rise to the liver.

The mesoderm gives rise to the notochord.

An open space within the gastrula is the
A) ectoderm.
B) mesoderm.
C) archenteron.
D) endoderm.
E) neural crest cells.

archenteron.

Although it contributes no cells to the embryo, this structure guides the formation of the primitive streak:
A) endoderm
B) mesoderm
C) ectoderm
D) neural crest
E) hypoblast

hypoblast

The primitive streak in a bird is the functional equivalent of
A) the lip of the blastopore in the frog.
B) the archenteron in a frog.
C) polar bodies in a sea urchin.
D) the notochord in a mammal.
E) neural crest cells in a mammal.

the lip of the blastopore in the frog.

In all vertebrate animals, development requires
A) a large supply of yolk.
B) an aqueous environment.
C) extraembryonic membranes.
D) an amnion.
E) a primitive streak.

an aqueous environment.

The least amount of yolk would be found in the egg of a
A) bird.
B) fish.
C) frog.
D) eutherian (placental) mammal.
E) reptile.

eutherian (placental) mammal

A primitive streak forms during the early embryonic development of
A) birds, but not frogs or humans.
B) frogs, but not birds or humans.
C) humans, but not birds or frogs.
D) birds and frogs, but not humans.
E) humans and birds, but not frogs.

humans and birds, but not frogs

Extraembryonic membranes develop in
A) mammals, but not birds or lizards.
B) birds, but not mammals or lizards.
C) lizards, but not mammals or birds.
D) mammals and birds, but not lizards.
E) mammals, birds, and lizards.

mammals, birds, and lizards

At the time of implantation, the human embryo is called a
A) blastocyst.
B) gastrula.
C) fetus.
D) somite.
E) zygote.

blastocyst.

Uterine implantation due to enzymatic digestion of the endometrium is initiated by
A) the inner cell mass.
B) the endoderm.
C) the chorion.
D) the mesoderm.
E) the trophoblast.

the trophoblast.

In placental mammals, the yolk sac
A) transfers nutrients from the yolk to the embryo.
B) differentiates into the placenta.
C) becomes a fluid-filled sac that surrounds and protects the embryo.
D) produces blood cells that then migrate into the embryo.
E) stores waste products from the embryo until the placenta develops.

produces blood cells that then migrate into the embryo

Gases are exchanged in a mammalian embryo in the
A) amnion.
B) hypoblast.
C) chorion.
D) trophoblast.
E) yolk sac.

chorion

Thalidomide, now banned for use as a sedative in pregnancy, was used in the early 1960s by many women in
their first trimester of pregnancy. Some of these women gave birth to children with arm and leg deformities,
suggesting that the drug most likely influenced
A) early cleavage divisions.
B) determination of the polarity of the zygote.
C) differentiation of bone tissue.
D) morphogenesis.
E) organogenesis

morphogenesis.

The migratory neural crest cells
A) form most of the central nervous system.
B) serve as precursor cells for the notochord.
C) form the spinal cord in the frog.
D) form neural and non-neural structures in the periphery.
E) form the lining of the lungs and of the digestive tract.

form neural and non-neural structures in the periphery

Changes in both cell shape and cell position occur extensively during
A) gastrulation, but not organogenesis or cleavage.
B) organogenesis, but not gastrulation or cleavage.
C) cleavage, but not gastrulation or organogenesis.
D) gastrulation and organogenesis but not cleavage.
E) gastrulation, organogenesis, and cleavage.

gastrulation, organogenesis, and cleavage

Changes in the shape of a cell usually involve a reorganization of the
A) nucleus.
B) cytoskeleton.
C) extracellular matrix.
D) transport proteins.
E) nucleolus.

cytoskeleton.

Animal development compares to plant development in that
A) plant cells, but not animal cells, migrate during morphogenesis.
B) animal cells, but not plant cells, migrate during morphogenesis.
C) plant cells and animal cells migrate extensively during morphogenesis.
D) neither plant cells nor animal cells migrate during morphogenesis.
E) plant cells, but not animal cells, migrate undergo convergent extension.

animal cells, but not plant cells, migrate during morphogenesis.

Cadherins and other cell-adhesion molecules that guide cell migration are
A) steroid hormones.
B) glycoproteins.
C) fatty acids.
D) prostacyclins.
E) ribonucleic acids.

glycoproteins.

The term applied to a morphogenetic process whereby cells extend themselves, making the mass of the cells
narrower and longer, is
A) convergent extension.
B) induction.
C) elongational streaming.
D) bi-axial elongation.
E) blastomere formation.

convergent extension.

During gastrulation in frog embryos, fibronectin provides
A) an extracellular anchorage for migrating cells.
B) regulates actin-myosin interactions in the cytosol of migrating cells.
C) reduces the entry of calcium ions into migrating cells.
D) regulates mRNA movement out of the nucleus of a moving cell.
E) the pigment that accumulates in the primitive streak

an extracellular anchorage for migrating cells.

If an amphibian zygote is manipulated so that the first cleavage plane fails to divide the gray crescent, then
A) the daughter cell with the entire gray crescent will die.
B) both daughter cells will develop normally because amphibians are totipotent at this stage.
C) only the daughter cell with the gray crescent will develop normally.
D) both daughter cells will develop abnormally.
E) both daughter cells will die immediately

only the daughter cell with the gray crescent will develop normally

In humans, identical twins are possible because
A) of the heterogeneous distribution of cytoplasmic determinants in unfertilized eggs.
B) of interactions between extraembryonic cells and the zygote nucleus.
C) of convergent extension.
D) early blastomeres can form a complete embryo if isolated.
E) the gray crescent divides the dorsal-ventral axis into new cells.

early blastomeres can form a complete embryo if isolated.

Hans Spemann and colleagues developed the concept of the primary organizer in amphibian embryos while
studying the
A) medial cells between the optic cups.
B) anterior terminus of the notochord.
C) lateral margins of the neural tube.
D) posterior edge of the dorsal ectoderm.
E) dorsal lip of the blastopore.

dorsal lip of the blastopore.

In frogs, formation of the eye lens is induced by chemical signals from
A) cells that will become the neural plate.
B) cells that are forming the inner ear.
C) an outgrowth of the developing brain.
D) both A and B
E) both A and C

cells that will become the neural plate & an outgrowth of the developing brain.

Two primary factors in shaping the polarity of the body axes in chick embryos are
A) light and temperature.
B) salt gradients and membrane potentials.
C) gravity and pH.
D) moisture and mucus.
E) location of sperm penetration and cortical reaction.

gravity and pH

The arrangement of organs and tissues in their characteristic places in three-dimensional space defines
A) pattern formation.
B) induction.
C) differentiation.
D) determination.
E) organogenesis.

pattern formation

If the apical ectodermal ridge is surgically removed from an embryo, it will lose
A) positional information for limb-bud pattern formation.
B) guidance signals needed for correct gastrulation.
C) unequal cytokinesis of blastomeres.
D) the developmental substrate for the gonads.
E) the developmental substrate for the kidneys

positional information for limb-bud pattern formation.

The nematode Caenorhabditis elegans
A) is composed of a single cell, in which the developmental origin of each protein has been mapped.
B) is composed of about 1,000 cells, in which the developmental origin of each cell has been mapped.
C) has only a single chromosome, which has been fully sequenced.
D) has about 1,000 genes, each of which has been fully sequenced.
E) uniquely, among animals, utilizes programmed cell death during normal development.

is composed of about 1,000 cells, in which the developmental origin of each cell has been mapped.

Ectoderm (5)

 Epidermis of the skin and derivatives
 Nevus and sensory system
 Purity glans, adrenal system
 Jaws and teeth
 Germ cells

Mesoderm (5)

o Skeletal and muscular system and
o Circulatory lymphatic system
o Excretory and reproductive systems
o Dermis of skin
o Adrenal cortex

Endoderm (3)

o Epithelial lining of the digestive tract and associated organs
o Epithelial lining of repertory, excretory, and reproduction tracts and ducts
o Thymus, thyroid, and parathyroid glands

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