Chapter 47 HW
Suppose that during gastrulation in humans, a protease (an enzyme that degrades proteins) is present such that the enzymes released by the trophoblast cannot function. What is the most likely immediate outcome of this situation?
The embryo will not implant into the endometrium.
Researchers were investigating the effects of bicoid in fruit fly development. The gene bicoid controls normal development of anterior structures in flies. In one experiment, they took a normally developing embryo and injected bicoid mRNA into the posterior end of the embryo. What result would they most likely observe?
The embryo would develop with a normal anterior end and anterior structures on the posterior end.
The allantois stores nitrogenous wastes in a reptile egg. What is the function of the allantois in human development?
The allantois helps form the umbilical cord in human development.
In a multicellular organism, it is cell-to-cell communication that allows the trillions of cells to coordinate activities, including during development and regeneration. The three stages of cellular communication include: reception, transduction, and response. This study determined the key steps of a cell communication pathway involved in salamander limb regeneration. After amputation of a front salamander limb, the severed axons retract within the stump and grow back along the nerve sheath. To elucidate the molecular mechanisms, the researchers set up a series of controlled experiments to determine the events in salamander limb regeneration. Drag the general cell communication steps of the regeneration experiment into the correct order.
1. Schwann cells along the axon sheath express the nAG gene, resulting in the production and secretion of the nAG protein. 2. The protein-ligand nAG binds to the Prod 1 surface receptor of the blastemal cells. 3. Blastemal cells start to enter the S-phase of the cell cycle. 4. Blastemal cells proliferate.
1. Gastrulation is a dramatic reorganization of the hollow _____ into a two-layered or three-layered embryo called a _____. 2. Invagination of cells into the blastocoel forms a tube called the _____. 3. The open end of the archenteron is called the _____.
1. blastula, gastrula 2. archenteron 3. blastopore
1. _____ is an anatomical term that refers to a point situated away from the center of the body or point of attachment. 2. _____ is an anatomical term that refers to a point situated close to the center of the body or point of attachment. 3. A _____ is a mass of undifferentiated cells with the ability to develop into an organ or body part. 4. _____ is the increase in the number of cells due to cell growth and division via the cell cycle. 5. A _____ is an undifferentiated cell that can be a source of differentiated cells. 6. _____ is the process by which some organisms replace lost or amputated body parts.
1. distal 2. proximal 3. blastema 4. cell proliferation 5. stem cell 6. regeneration
Which of the following is true?
A population with fewer women in poverty will have fewer stillbirths and miscarriages.
Which of the following is true?
About half of miscarriages are due to chromosomal abnormalities.
What are the cells created by cleavage called?
Blastomeres
Determine which terms, phrases, and images describe each phase of development. Drag each item to the appropriate bin.
Cleavage: blastula, cytoplasm partitioned into many cells, (yellow ball of cells) Gastrulation: embryonic germ layers form, gastrula, blastopore, (ball of cells with three layers yellow, red and blue) organogenesis: organs begin to develop from germ layers, neural tube, somites
Which of the following are the three germ layers contained in the gastrula?
Ectoderm, mesoderm, endoderm
True or false? Early animal development progresses through distinct stages: first the production of the zygote through fertilization, then cleavage, then the formation of the gastrula, and then the formation of the blastula.
False
Suppose you wanted to start an animal-breeding business. For most of the following animals you could start out with just a single animal, but for which of the animals below would you need to start with at least two individuals?
Frogs
Which of the following stages of development is defined by the three embryonic tissue layers (ectoderm, mesoderm, and endoderm)?
Gastrula
Which of the following is a result of gastrulation in animals? I) The archenteron is formed. II) The body axes are established. III) The germ layers are formed.
I and III only
Which of the following answers best describes a feature of the plasma membrane of a sea urchin egg that is required for fertilization?
It has receptor molecules that specifically bind to acrosomal proteins.
Which of the following statements best describes the function of the vitelline layer in a newly fertilized sea urchin egg?
It lifts away from the egg and hardens to form a fertilization envelope.
In animal development, which of the following best describes the process of cleavage?
Mitosis
Time point 5 corresponds to the 12th cell division, except in the presence of the toxin, which blocks cell division. Do the data support the hypothesis that the timing of the end of cleavage depends on counting cell divisions?
No, because the toxin's blockage of cell division does not affect the timing of the end of cleavage.
Retinoic acid (a metabolite of vitamin A) plays a key role in vertebrate development, differentiation, and organogenesis. Retinoic acid is produced in cells via redox reactions catalyzed by enzymes. The structure of retinoic acid is shown below. What statement regarding retinoic acid is TRUE?
Retinoic acid is a morphogen and it likely binds to intracellular receptors.
In an embryonic vertebrate, the zone of polarizing activity (ZPA) is a block of tissue located on the posterior side of a limb bud. The ZPA provides information about the anterior-posterior axis of the limb. Cells nearest the ZPA form the most posterior of digits (like our little finger); cells farthest from the ZPA form the most anterior digits (like our thumb) How would a vertebrate forelimb bud develop if it had two zones of polarizing activities, one on the posterior side and one on the anterior side of the bud?
The forelimb bud would develop with extra digits, in a mirror image arrangement to the normal digits.
Which of the following correctly matches a structure with the germ layer from which it is derived?
The mesoderm gives rise to the notochord.
Select Figure 2 from the dropdown menu at left (Figure 2). The graph shows DNA synthesis and RNA synthesis with and without the toxin that prevents cell division. For the DNA data, one straight line represents the general trend for time points 1-5, and another straight line for time points 5-11. What changes in synthesis occur at the end of cleavage, at time point 5?
The rate of DNA synthesis decreases, and RNA synthesis begins.
Select the correct statement about embryonic development in a frog.
The reorganization of cell layers during gastrulation allows the layers to interact with each other in new ways.
What would happen if stem cells divided like spermatogonia?
The supply of stem cells would be used up, and spermatogenesis would not be able to continue.
Embryonic induction, the influence of one group of cells on another group of cells, plays a critical role in embryonic development. In 1924, Hans Spemann and Hilde Mangold transplanted a piece of tissue from the dorsal lip of an amphibian embryo to the ventral side of another amphibian embryo. The transplanted piece of tissue influences the formation of the notochord and neural tube. If embryonic induction occurred, which of the following observations justifies the claim of embryonic induction?
The transplanted tissue induced the formation of a second notochord and neural tube on the ventral side of the developing embryo.
Which of the following correctly describes a difference between the vegetal pole of a frog zygote and the animal pole?
The vegetal pole has a higher concentration of yolk.
How were the researchers able to independently measure DNA synthesis and RNA synthesis?
Thymidine is a nucleoside building block for DNA, but not RNA, whereas uridine is a nucleoside building block for RNA, but not DNA.
Occasionally, two-headed animals are born. Thinking about the occurrence of identical twins and the property of totipotency, how might this happen?
Totipotent cells of the early embryo are split into two almost separate masses.
The anterior pituitary
acts as a relay in hormone cascades.
Actin microfilaments are required for
amoeboid movement.
Which of the following is required for development in all vertebrate animals?
an aqueous environment
Which of the following is the largest cell involved in frog reproduction?
an egg
In addition to maternal effect genes, paternal effect genes are important for fruit fly development. One such paternal effect gene codes for Sneaky, a protein required for breakdown of the fruit fly sperm plasma membrane that is a critical step for normal embryo development. Suppose that a female fruit fly's oocyte (egg) with a mutation in the bicoid gene is fertilized by a male fruit fly's sperm with a mutation in the Sneaky gene. Both mutations yield nonfunctional proteins. What would be the most likely outcome of this fertilization?
an embryo would not be able to develop
Which of the following processes reduces the size of a tadpole's tail during metamorphosis?
apoptosis
The notochord functions as a core around which mesodermal cells form the frog's _____.
backbone
Hormones and pheromones both
bind to specific receptors
Contact between signaling molecules on a sperm membrane with receptor molecules on an oocyte membrane will most directly result in which of the following responses?
membrane depolarization
In sea urchins, which of the following pairs of events most directly results in the short-lasting "fast block" and the longer-lasting "slow block" to polyspermy, respectively?
membrane depolarization and the cortical reaction
The uneven cleavage of cells early in the development of the yolk-rich embryos of birds is called __________.
meroblastic cleavage
As cleavage continues, a zygote forms into a solid multicellular ball called a(n) _____.
morula
Which of the following is an adult organism that has fewer than 1,000 cells?
nematodes, Caenorhabditis elegans
An ectodermal thickening above the frog's notochord forms a _____.
neural plate
The _____ is(are) formed when the neural folds join and a portion of the neural plate sinks beneath the embryo's surface.
neural tube
Which of the following structures is the embryonic precursor to the human spinal cord?
neural tube
During gastrulation in frogs, a rod of mesoderm under the dorsal surface forms the _____.
notochord
In human reproduction, the anatomical location for the typical union of a sperm and an egg (conception) is the __________.
oviducts
Which of the following correctly describes gastrulation in frog embryos?
proceeds by involution as cells roll over the lip of the blastopore
If current research proves correct, which of the following hormones is most likely to help prevent miscarriage?
progesterone
In which of the following pairs of organisms does holoblastic cleavage typically occur?
sea urchins and humans
Some lizard species consist of genetically identical females and lack males because __________.
sperm do not fuse with eggs during reproduction, but the eggs develop into embryos anyway
Reptiles (including birds) and mammals are called amniotes because __________.
they have extraembryonic membranes that develop an aqueous environment in which development occurs
The direct regulators of differential gene expression are typically
transcription factors
How do the emergent properties of the cells of the gastrula direct embryonic development? Rank the stages from earliest to latest.
Earliest stage -The cells of the gastrula arise from a single parental cell, and all are initially undifferentiated. -Differences in composition and environment affect the behavior of individual cells. -Whole sets of cells change shape, move, or migrate, resulting in the gastrula. -The changes in individual cells guide organogenesis. -An ordered and functional form emerges. Latest stage
In an embryonic vertebrate, the apical ectodermal ridge (AER) is a thickened area at the tip of the bud. The cells of the AER secrete protein signals that promote limb-bud outgrowth, and removing the AER blocks growth of the limb along the proximal-distal axis. How would the forelimb of an embryo develop if the AER was removed early or late in limb development?
Early removal of the AER would prevent the formation of many distal structures, whereas late removal of the AER would prevent the formation of a few distal structures.
In both mitosis and meiosis,
chromosome duplication precedes cell division.
Which of the following is a primary external factor in determining the polarity of the body axes in chick embryos?
gravity
Sexual reproduction includes a reproductive pattern called __________.
hermaphroditism
The mesoderm gives rise to __________.
skeletal and muscular systems
In sea urchins, the process of fertilization produces a(n) _____.
zygote
Which of the following are found in developmental precursors to the gonadal tissues of Caenorhabditis elegans?
P granules of mRNA and protein
The G1 and G2 phases of the cell cycle are required for
RNA and protein synthesis.
In an investigation into sperm-oocyte binding, researchers isolated the egg receptor protein, ERB1, from the sea urchin Strongylocentrotus purpuratus. ERB1 binds to the sperm acrosomal protein, bindin, during fertilization. The researchers coupled the ERB1 receptor from S. purpuratus to plastic microbeads and then mixed the ERB1-coupled beads with sperm from S. purpuratus or from the related species, S. franciscanus. A summary of the treatment mixtures and a graph of the results are shown. A: S. purpuratus sperm mixed with S. purpuratus ERB1-coupled beads B: S. purpuratus sperm mixed with beads with no coupled ERB1 protein C: S. franciscanus sperm mixed with S. purpuratus ERB1 beads D: S. franciscanus sperm mixed with beads with no coupled ERB1 protein Which of the following conclusions is most consistent with the data?
Sperm from S. purpuratus bind to beads more if ERB1 is present than if ERB1 is not present.
In some rare salamander species, all individuals are females. Reproduction relies on those females having access to sperm from males of another species. However, the resulting embryos receive no genetic contribution from the males. Given this information, what is the role of sperm in reproduction in this species?
Sperm trigger egg activation.
Which of the following were Hans Spemann and colleagues studying when they developed the concept of the "organizer" in amphibian embryos?
dorsal lip of the blastopore
Identical twins are possible in humans because ________.
early blastomeres can form a complete embryo if isolated
In humans, identical twins are possible because
early blastomeres can form a complete embryo if isolated.
During gastrulation in frogs, cells from the animal pole spread over the embryo and form the _____.
ectoderm
Which of the following options describes the correct outer-to-inner sequence of tissue layers in a post-gastrulation vertebrate embryo?
ectoderm → mesoderm → endoderm
Which of the following outcomes would most likely occur if gastrulation was blocked?
embryonic germ layers would not form
Which of the following is common to the development of both birds and mammals?
epiblast and hypoblast
During the early development of a human embryo, the __________ eventually forms the __________.
epiblast; ectodermal, mesodermal, and endodermal tissues
The eggs of which of the following organisms contains the least amount of yolk?
eutherian mammal
What structural adaptation in chickens allows them to lay their eggs in arid environments rather than in water?
extraembryonic membranes
Which of the following contributions of the extra embryonic membranes was crucial for the colonization of land by vertebrate organisms?
extraembryonic membranes provide an aqueous environment for embryo development
Choose the correct developmental sequence of animal development.
fertilization, cleavage, gastrulation, organogenesis
Treating an oocyte with a chemical that binds calcium and magnesium ions will block ________.
formation of the fertilization envelope
The cortical reaction of sea urchin eggs is required for which of the following events in fertilization?
forming a fertilization envelope
The three-layered embryo is the _____.
gastrula
During which stage of development do cells in a triploblastic embryo move to new positions to establish the three germ tissue layers?
gastrulation
Cell migration occurs extensively as part of which of the following processes?
gastrulation and organogenesis
An embryonic cell that is totipotent is one that can __________.
give rise to the entire embryo, by itself, as cleavage proceeds
Which of the following is a similarity between a mature human sperm and an ovum that has completed meiosis? Both gametes ________.
have the same number of chromosomes
Which of the following is a similarity between spermatogenesis and oogenesis in vertebrate animals? Both spermatogenesis and oogenesis ________.
lead to the production of gametes from germ cells
Thalidomide, now banned for use as a sedative during 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 limb and organ deformities. Which of the following processes did the drug most likely influence?
morphogenesis
Cells transplanted from the neural tube of a frog embryo to the ventral part of another embryo develop into nervous system tissues. This result indicates that the transplanted cells were
determined.
Release of the acrosomal contents during fertilization most directly results in which of the following events?
digesting the protective jelly coat on the surface of the egg
What does the archenteron of the developing sea urchin eventually develop into?
digestive tract
Which of the following is most likely to occur if an amphibian zygote is manipulated so that the first cleavage plane fails to divide the gray crescent?
only the daughter cell with the gray crescent will develop normally
In vertebrates, the ectoderm gives rise to the _____.
outer layer of skin
Which of the following processes determines the arrangement of organs and tissues in their characteristic places in 3-D space?
pattern formation
In mammalian eggs, the receptors for sperm are found in which of the following locations?
plasma membrane
Which of the following processes will be disrupted if the apical ectodermal ridge is surgically removed from an embryo?
positional information for limb-bud pattern formation
Reversal of left-right asymmetries in humans can arise in response to a genetic condition that __________.
renders cilia immobile
In the process of spermatogenesis, each _________ cell undergoes meiosis II, resulting in the production of two __________ cells.
secondary spermatocyte, early spermatid
Evolution in insects and vertebrates has involved the repeated duplication of body segments, followed by fusion of some segments and specialization of their structure and function. In vertebrates, what anatomical features reflect segmentation?
segmented muscles associated with the vertebral column and the ribs
Which of the following correctly traces the path of sperm from their site of production to their exit from a man's body?
seminiferous tubule, epididymis, vas deferens, urethra
The posterior portion of the neural tube will develop into the frog's _____.
spinal cord
Cells transplanted from the neural tube of a frog embryo to the ventral part of another embryo develop into nervous system tissues. Which of the following claims about the transplanted cells is most consistent with the results?
the cells were determined
If an egg cell treated with EDTA, a chemical that binds calcium and magnesium ions,
the fertilization envelope would not form.
What is the cortical reaction?
the formation of a fertilization envelope that bars additional sperm from entry into the egg
The cortical reaction of sea urchin eggs functions directly in
the formation of a fertilization envelope.
Which of the following is common to the development of birds and mammals?
the formation of an embryonic epiblast and hypoblast
The primitive streak in a bird embryo is the functional equivalent to which of the following structures?
the lip of the blastopore in the frog
The archenteron develops into
the lumen of the digestive tract
For which of the following is the number the same in spermatogenesis and oogenesis in animals?
the number of meiotic divisions required to produce each gamete
Which of the following cellular structures is usually reorganized when a cell changes shape?
cytoskeleton
Scientists can now make identical copies, or clones, of animals ranging from dairy cows to pet cats. What are a few arguments for and against this application of discoveries about embryonic development to pet cats? Select the two correct statements.
-Having clones of a pet cat would mean than an owner could in effect have the same animal companion throughout the rest of the owner's life. -Resources spent on cloning could be better used to help abandoned pets than to circumvent the natural cycle of aging and death.
Scientists can now make identical copies, or clones, of animals ranging from dairy cows to pet cats. What are a few arguments for and against this application of discoveries about embryonic development to dairy cows? Select the two correct statements.
-Having many identical cows in a herd might make it more susceptible to a disease epidemic. -Making copies of a particularly productive dairy cow could provide a better nutrition for a community lacking in resources.
This study illustrates an example of how scientists progress from one experiment to the next. The results from one experiment served as a springboard to ask the next experimental question and set up the next experiment. Select all the statements that represent key conclusions from this study.
-Homologous proteins to nAG are found in a variety of vertebrate species. -In animals with denervated limbs, nAG expression is not present. -nAG is a secreted protein that binds to the receptor protein Prod1. -Expression of nAG in the denervated limb rescues limb regeneration.
Identify the correct statement(s) about Spemann's organizer. Select all that apply.
-Spemann's organizer is the dorsal lip of the blastopore in frog gastrulation. -Spemann's organizer initiates a chain of inductive interactions in frog development.
Tissue and organ formation begins during the process of organogenesis. Which five of the following statements are true about organogenesis in a frog embryo?
-The neural tube forms from ectoderm and develops into the central nervous system. -Some somite cells migrate to other locations in the developing embryo. -The endoderm gives rise to the lining of the frog's digestive tract. -Somites form along the length of the notochord and neural tube. -The notochord does not persist in adult frogs.
What happens to cells that fold inside the blastula during gastrulation in a triploblast? Select the three that apply.
-They are in contact with the mesoderm. -They become endoderm. -They form the lining of the gut cavity.
Among the following, the earliest consequence of the acrosomal reaction is __________.
depolarization of the egg plasma membrane
A child is born without a fully developed pancreas. He is normal in all other respects, and thus doctors believe that the problem most likely began early in development. During which of the following processes did the original error most likely occur?
Endoderm formation
One of the most important science practices is designing controlled experiments. Controlled experiments include control groups, experimental groups, and independent and dependent variables. The experiment presented in Figure 4 of this study illustrates a unique experimental design. Review Figure 4D in the online paper to see an illustration of the setup. In this experiment, the researchers manipulated two groups of salamanders. In both groups, they denervated one front limb but left the nerve of the other front limb intact. Then they amputated both front limbs. In one group, the researchers electroporated the denervated side with a nAG plasmid. In the other group, they electroporated the denervated side with a control plasmid. Can you identify which groups are experimental and which are controls? Sort each item to the appropriate bin.
Experimental group(s): Limb that is denervated, amputated, and electroporated with a nAG plasmid Control group(s): Limb that is denervated, amputated, and electroporated with a non-nAG plasmid. Limb that is only amputated. Neither: A regenerated limb
Just prior to the onset of gastrulation in an embryo, the "organizer" cells are specified. What would you expect in the developing embryo if the specification of these cells were experimentally blocked?
Gastrulation would not occur, and normal development would cease.
In an investigation into sperm-oocyte binding, researchers isolated the egg receptor protein, ERB1, from the sea urchin Strongylocentrotus purpuratus. ERB1 binds to the sperm acrosomal protein, bindin, during fertilization. The researchers coupled the ERB1 receptor from S. purpuratus to plastic microbeads and then mixed the ERB1-coupled beads with sperm from S. purpuratus or from the related species, S. franciscanus. A summary of the treatment mixtures and a graph of the results are shown. A: S. purpuratus sperm mixed with S. purpuratus ERB1-coupled beads B: S. purpuratus sperm mixed with beads with no coupled ERB1 protein C: S. franciscanus sperm mixed with S. purpuratus ERB1 beads D: S. franciscanus sperm mixed with beads with no coupled ERB1 protein Which of the following is a broader implication from the observations of the experiment?
In sea urchins, fertilization of eggs by sperm is dependent upon species-specific protein interactions.
What happens to a cell during the process of differentiation?
It undergoes a change toward a more specialized form or function.
Retinoic acid (a metabolite of vitamin A) plays a key role in vertebrate development, differentiation, and organogenesis. Retinoic acid normally binds to the RAR receptor to initiate changes in gene expression. Researchers have determined that one type of RAR receptor is found at high levels in muscles, but is not found at all in neurons. How can you explain these findings?
The RAR receptor gene is expressed in muscle cells but not neurons.
In C. elegans, P granules act as cytoplasmic determinants to assist with the development of the posterior end of the organism. Suppose that P granules were abnormally found in both the anterior and posterior ends of a developing C. elegans organism. What would you expect to observe?
The embryo would develop with a normal posterior end and posterior structures on the anterior end.
In a separate experiment, researchers disrupted the block to polyspermy, generating embryos with 7 to 10 sperm nuclei. At the end of cleavage, these embryos had the same nucleus-to-cytoplasm ratio as the wild-type embryos, but cleavage ended at the 10th cell division rather than the 12th cell division. What do these results indicate about the timing of the end of cleavage?
The end of cleavage depends on the nucleus-to-cytoplasm ratio.
The researchers hypothesized that the toxin increases diffusion of thymidine into the embryos. What was their reasoning?
The rates of DNA synthesis are the same with and without the toxin, so the likely explanation is that the DNA is labeled more extensively due to a greater uptake of the labeled thymidine.
Which of the following is true about human eggs at the moment of sperm penetration?
They are still surrounded by follicular cells.
Previous research on salamander regeneration demonstrated that the process of regeneration is stopped when the amputated limb or developing blastema (a mass of undifferentiated cells that can develop into a new limb) is denervated (deprived of nerve supply). What remained unclear was what molecules were involved in normal regeneration and what happened to their role once denervation occurred. These researchers set out to answer these questions. Which choice represents the most significant finding from this study?Hint: Turn on the "Results and conclusions" learning lens to highlight this study's significant findings.
This study identified a protein called nAG that can rescue the denervated blastema and induce regeneration of an amputated limb.
In an investigation into sperm-oocyte binding, researchers isolated the egg receptor protein, ERB1, from the sea urchin Strongylocentrotus purpuratus. ERB1 binds to the sperm acrosomal protein, bindin, during fertilization. The researchers coupled the ERB1 receptor from S. purpuratus to plastic microbeads and then mixed the ERB1-coupled beads with sperm from S. purpuratus or from the related species, S. franciscanus. A summary of the treatment mixtures and a graph of the results are shown. A: S. purpuratus sperm mixed with S. purpuratus ERB1-coupled beads B: S. purpuratus sperm mixed with beads with no coupled ERB1 protein C: S. franciscanus sperm mixed with S. purpuratus ERB1 beads D: S. franciscanus sperm mixed with beads with no coupled ERB1 protein Based on the description of the experiment, which of the treatments would be considered a negative-control treatment for S. purpuratus sperm binding?
Treatment B
Which of the following types of embryos displays meroblastic cleavage, extraembryonic membranes, and a primitive streak?
a bird
Researchers wish to better understand miscarriage. Which length of pregnancy should they focus on?
a pregnancy of less than twelve weeks
The migratory neural crest cells give rise to which of the following structures?
a variety of peripheral neural and non-neural structures
Animals utilizing external fertilization are typically __________.
aquatic animals
Which of the following correctly describes the order of events of early development from earliest to latest?
acrosomal reaction → cortical reaction → synthesis of embryo's DNA begins → first cell division
Which of the following correctly matches an extraembryonic membrane with its function?
allantois-waste storage
The _____ eventually develops into the sea urchin's digestive tract.
archenteron
Which of the following structures is formed before the others during frog development?
blastocoel
What is a human embryo called at the time of implantation?
blastocyst
During gastrulation, invagination occurs at the _____.
blastopore
Several hours after fertilization, cleavage results in the formation of a hollow ball of cells called a _____.
blastula
The enlarged anterior portion of the neural tube will develop into a frog's _____.
brain
The formation of the fertilization envelope in a sea urchin egg is most directly stimulated by an increase in the cytosolic concentration of which of the following ions?
calcium ions
Which of the following correctly describes the sequence of developmental milestones in chordates?
cleavage → blastula → gastrula
The first stage of embryonic development is __________. This process produces __________.
cleavage, a cluster of cells
Which of the following terms applies to a morphogenetic process whereby cells extend themselves, making the mass of the cells narrower and wider?
convergent extension
Choose two modified versions of the cell lineage so that each version produces three cells. Apoptosis is marked with an X.
image
Under which condition will the metabolic activity in a sea urchin egg most likely be activated even in the absence of sperm?
injection of calcium ions into the cytosol
Which of the following occurs to the blastocoel during frog development?
is replaced by the expanding archenteron
Which correctly matches the organ with its embryonic source?
kidney-mesoderm
Embryonic cells especially active in assuring nutritional exchange between a pregnant woman and her embryo are found in the _____.
trophoblast
Which of the following structures releases enzymes that initiate implantation of an embryo in the endometrium?
trophoblast
Following an in-depth study, it is discovered that sitagliptin is effective in reducing the chance for miscarriage. Which of the following is this working on?
womb lining