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model organisms |
species chosen because of their ease to be studied |
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fertilization |
the formation of a diploid zygote from a haploid egg and sperm |
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acrosomal reaction |
begins with the discharge of hydrolytic enzymes from the acrosome a specialized vesicle at the tip of the sperm |
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fast block to polyspermy |
the acrosomal reaction |
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slow block to polyspermy |
the cortical reaction |
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cortical reaction |
protective fertilization envelope is formed |
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a rise in ca2+ causes: |
egg activation |
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zona pellucida |
the extracelluar matrix of the egg |
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cleavage |
After fertilization, the sperm and egg become a zygote, which then begins a number of cell divisions called cleavage |
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the smaller cells that cleavage creates are called: |
blastomeres |
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blastula |
hollow ball of cells |
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blastocoel |
fluid filled cavity in the blastula |
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holoblastic |
A type of cleavage in which there is complete division of the egg, as in eggs having little yolk (sea urchin) or a moderate amount of yolk (frog). |
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meroblastic |
a type of cleavage in which there is incomplete division of yolk-rich egg, characteristic of avian development |
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morphogenesis |
the cellular and tissue based process by which the animal body takes shape |
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gastrulation |
a set of cells at or near the surface of the blastula moves to an interior location, cell layers are established, and a primitive digestive tube is formed |
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organogenesis |
further transformation that occurs and forms organs |
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gastrula |
2 or 3 layered embryo |
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cell layers produced by gastrulation are called: |
germ layers |
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ectoderm |
One of the three primary (embryonic) germ layers formed during gastrulation. Ectoderm ultimately forms external structures such as the skin, hair, nails, and inner linings of the mouth and anus, as well as the entire nervous system. |
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endoderm |
Germ layer that gives rise to the epithelial lining of the gastrointestinal tract and its outgrowths. |
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mesoderm |
between the ectoderm and endoderm, skeletal and muscular systems |
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archenteron |
The endoderm-lined cavity, formed during the gastrulation process, that develops into the digestive tract of an animal. |
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blastopore |
the open end of the archenteron which will become the anus |
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dorsal lip |
The region above the blastopore on the dorsal side of the amphibian embryo. |
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gastrulation in a frog embryo |
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vegetal pole |
yolk is concentrated here |
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animal pole |
yolk is less concentrated here |
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primitive streak |
a thickening produced by the pileup of cells moving inward at the blastoderm’s midline, which runs along what will become the birds anterior-posterior axis; functionally equivalent to the dorsal lip in frogs |
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blastocyst |
the mammalian version of the blastula |
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4 stages in early embryonic development in humans: |
blastocyst is formed with the inner cell mass, then the trophoblast is formed then the extra embryonic membranes are formed, then the 3 germ layers have formed by the end of gastrulation |
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trophoblast |
it initiates implantation by secreting enzymes that break down molecules of the endometrium |
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mammals and reptiles and birds are called: |
amniotes |
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notochord |
A rod of tough, flexible material that runs the length of a creature’s body, providing the majority of its support |
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neural tube |
runs along the anterior-posterior axis of the embryo, it will become the spinal cord and the brain |
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neural crest |
a band of cells that develops along the borders where the neural tube pinches off from the ectoderm |
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somites |
Formed in the mesoderm and appear as a bump on the surface of the embryo on either side of the notochord |
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neural plate formation |
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differentiation |
the resulting specialization in structure and function |
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totipotent |
can each develop into all the different cell types of that species |
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The first stage of embryonic development is _____. This process produces _____. cleavage … a cluster of cells |
cleavage … a cluster of cells |
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Tissue and organ formation begins during the process of organogenesis. The notochord forms from mesoderm and develops into the central nervous system. |
The neural tube forms from ectoderm and develops into the central nervous system. 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. Some somite cells migrate to other locations in the developing embryo. |
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In animal development, which of the following best describes the process of cleavage? Meiosis |
mitosis |
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What are the cells created by cleavage called? Blastopores |
Blastomeres |
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Which of the following are the three germ layers contained in the gastrula? Ectoderm, mesoderm, epidermis |
Ectoderm, mesoderm, endoderm |
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Which of the following stages of development is defined by the three embryonic tissue layers (ectoderm, mesoderm, and endoderm)? Zygote |
Gastrula |
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What happens to a cell during the process of differentiation? Material moves across the cell membrane from a region of higher concentration to a region of lower concentration. |
It undergoes a change toward a more specialized form or function. |
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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 |
Endoderm formation |
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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. True |
false |
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In sea urchins, the process of fertilization produces a(n) _____. archenteron |
zygote |
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What is the cortical reaction? the formation of a fertilization envelope that bars additional sperm from entry into the egg |
the formation of a fertilization envelope that bars additional sperm from entry into the egg |
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As cleavage continues, a zygote forms into a solid multicellular ball called a(n) _____. endometrium |
Morula |
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Several hours after fertilization, cleavage results in the formation of a hollow ball of cells called a _____. blastomere |
Blastula |
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The three-layered embryo is the _____. archenteron |
Gastrula |
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The _____ eventually develops into the sea urchin’s digestive tract. blastocoel |
archenteron |
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During gastrulation, invagination occurs at the _____. archenteron |
blastopore |
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In vertebrates, the ectoderm gives rise to the _____. skeleton |
outer layer of skin |
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During gastrulation in frogs, a rod of mesoderm under the dorsal surface forms the _____. notochord |
notochord |
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During gastrulation in frogs, cells from the animal pole spread over the embryo and form the _____. endoderm |
ectoderm |
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The notochord functions as a core around which mesodermal cells form the frog’s _____. backbone |
Backbone |
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An ectodermal thickening above the frog’s notochord forms a _____. pancreas |
Neural plate |
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The _____ is(are) formed when the neural folds join and a portion of the neural plate sinks beneath the embryo’s surface. archenteron |
neural tube |
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The enlarged anterior portion of the neural tube will develop into a frog’s _____. spinal cord |
brain |
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The posterior portion of the neural tube will develop into the frog’s _____. spinal cord |
spinal cord |
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The mesoderm gives rise to _____. the central nervous system |
skeletal and muscular systems |
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Birds, reptiles, and mammals are called "amniotes" because _____. they digest yolk and form a network of blood vessels to distribute nutrients to the embryo |
they have extra-embryonic membranes that develop an aqueous environment in which development occurs |
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Embryonic cells especially active in assuring nutritional exchange between a pregnant woman and her embryo are found in the _____. epiblast |
Trophoblast |
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An embryonic cell that is "totipotent" is one that can _____. organize the blastula |
by itself, give rise to the entire embryo, as cleavage proceeds |
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Choose the correct developmental sequence of animal development. organogenesis → cleavage → fertilization → gastrulation |
fertilization → cleavage → gastrulation → organogenesis |
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Among the following, the earliest consequence of the acrosomal reaction is _____. the membrane of the egg depolarizing |
the membrane of the egg depolarizing |
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The uneven cleavage of cells early in the development of the yolk-rich embryos of birds is called _____. gastrulation |
meroblastic cleavage |
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Even in the absence of sperm, metabolic activity in an egg can be artificially activated by _____. depletion of its ATP supplies |
injection of calcium ions into the cytosol |
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The formation of the fertilization envelope requires an increase in the availability of _____. sodium ions |
calcium ions |
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Contact of a sea urchin egg with signal molecules on sperm causes the egg to undergo a brief _____. membrane depolarization |
membrane depolarization |
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The plasma membrane of the sea urchin egg _____. releases calcium, which initiates the cortical reaction |
has receptor molecules that are specific for binding acrosomal proteins |
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Fertilization of an egg without activation is most like _____. preparing a pie from scratch and baking it in the oven |
placing the key in the ignition of a car but not starting the engine |
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A reproductive difference between sea urchins and humans is _____. sea urchins, but not humans, have a need to block polyspermy, because only in sea urchins can there be more than one source of sperm to fertilize the eggs |
the sea urchin egg completes meiosis prior to fertilization, but meiosis in humans is completed after fertilization |
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During fertilization, the acrosomal contents _____. block polyspermy |
digest the protective jelly coat on the surface of the egg |
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In a newly fertilized egg, the vitelline layer _____. reduces the loss of water from the egg and prevents desiccation |
lifts away from the egg and hardens to form a fertilization envelope |
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In sea urchins, the "fast block" and the longer lasting "slow block" to polyspermy, respectively, are _____. membrane depolarization and the cortical reaction |
membrane depolarization and the cortical reaction |
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In an egg cell treated with a chemical that binds calcium and magnesium ions, the _____. fertilization envelope would not be formed |
fertilization envelope would not be formed |
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In mammalian eggs, the receptors for sperm are found in the _____. cytosol of the egg |
egg plasma membrane |
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A human blastomere is _____. a cell that contains a (degenerating) second polar body |
an embryonic cell that is smaller than the ovum |
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At the moment of sperm penetration, human eggs _____. are still surrounded by follicular cells |
are still surrounded by follicular cells |
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In a developing frog embryo, most of the yolk is _____. found within the cleavage furrow |
located near the vegetal pole |
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Among these choices, the largest cell involved in frog reproduction is _____. one of the products of the first cleavage |
an egg |
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The pattern of embryonic development in which only the cells lacking yolk subsequently undergo cleavage is called _____. meroblastic development, which is typical of birds |
meroblastic development, which is typical of birds |
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As cleavage continues during frog development, the size of the blastomeres _____. decreases as the number of the blastomeres decreases |
decreases as the number of the blastomeres increases |
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The vegetal pole of a frog zygote differs from the animal pole in that _____. the vegetal pole cells undergo mitosis, but not cytokinesis |
the vegetal pole has a higher concentration of yolk |
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Meroblastic cleavage occurs in _____. humans, but not in sea urchins or birds |
birds, but not in sea urchins or humans |
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h of the following correctly displays the sequence of developmental milestones? cleavage → blastula → gastrula |
cleavage → blastula → gastrula |
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The first cavity formed during frog development is the _____. anus |
Blastocoel |
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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. In this case, the sperm appear to be used only for _____. egg activation |
egg activation |
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The cortical reaction of sea urchin eggs functions directly in _____. the release of hydrolytic enzymes from the sperm |
the formation of a fertilization envelope |
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The structure of the Drosophila gene, called Tinman, is similar to a gene in humans that also _____. specifies the location of the heart |
specifies the location of the heart |
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From earliest to latest, the overall sequence of early development proceeds in which of the following sequences? cortical reaction → acrosomal reaction → first cell division synthesis of embryo’s DNA begins |
acrosomal reaction → cortical reaction → synthesis of embryo’s DNA begins → first cell division |
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During the early development of a human embryo, the _____ eventually forms the _____. epiblast … ectodermal, mesodermal, and endodermal tissues |
epiblast … ectodermal, mesodermal, and endodermal tissues |
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Cells move to new positions as an embryo establishes its three germ-tissue layers during _____. gastrulation |
gastrulation |
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Which of the following is a correct description of the fate of the germ layers? The ectoderm gives rise to the liver. |
The mesoderm gives rise to the notochord. |
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The outer-to-inner sequence of tissue layers in a post-gastrulation vertebrate embryo is _____. ectoderm → mesoderm → endoderm |
ectoderm → mesoderm → endoderm |
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If gastrulation was blocked by an environmental toxin, then _____. cleavage would not occur in the zygote |
embryonic germ layers would not form |
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In a frog embryo, gastrulation _____. proceeds by involution as cells roll over the lip of the blastopore |
proceeds by involution as cells roll over the lip of the blastopore |
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The primitive streak in a bird is the functional equivalent of _____. the notochord in a mammal |
the lip of the blastopore in the frog |
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In all vertebrate animals, development requires _____. extraembryonic membranes |
an aqueous environment |
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At the time of implantation, the human embryo is called a _____. gastrula |
Blastocyst |
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Uterine implantation due to enzymatic digestion of the endometrium is initiated by the _____. endoderm |
trophoblast |
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From earliest to latest, the overall sequence of early development proceeds in which of the following sequences? preformation → morphogenesis → neurulation |
cleavage → gastrulation → organogenesis |
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Changes in cell position occur extensively during _____. cleavage, but not during gastrulation or organogenesis |
gastrulation |
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The embryonic precursor to the human spinal cord is the _____. notochord |
neural tube |
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Which of the following is common to the development of birds and mammals? the formation of an embryonic epiblast and hypoblast |
the formation of an embryonic epiblast and hypoblast |
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The archenteron of a frog develops into the _____. placenta |
lumen of the digestive tract |
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The cortical reaction of sea urchin eggs functions directly in the release of hydrolytic enzymes from the sperm. |
the formation of a fertilization envelope. |
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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. |
The reorganization of cell layers during gastrulation allows the layers to interact with each other in new ways. |
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