Download Chapter 47 Worksheet: Animal Development Objectives 1. Compare

Chapter 47 Worksheet: Animal Development
Objectives
1. Compare the concepts of preformation and epigenesis.
Preformation: former belief in a miniature human in the egg or sperm
Epigenesis: current model of gradual development
2. List the two functions of fertilization.
1. Combines the haploid sets of chromosomes from the sperm and egg
2. Activates the egg metabolism, initiates development
3. Describe the acrosomal reaction and explain how it ensures that gametes are
conspecific.
Acrosome reaction is a package of hydrolytic enzymes at the sperm tip. It discharged
upon contact with the egg's jelly coat. It digests through jelly coat. It ensures that gametes are
conspecific because of its process. Acrosomal process elongates. (binds to specific receptors)
The receptors are species-specific.
4. Describe the cortical reaction.
-Membrane fusion releases Ca from egg ER
-Cortical granules (vesicles) fuse with the zygote membrane
-Contents cause swelling of the jelly coat away from the membrane
5. Explain how the acrosomal and cortical reactions function sequentially to prevent
polyspermy.
The acrosomal and cortical reactions function sequentially to prevent polyspermy by
membranes fusing and depolarizing, blocking other sperm. Cortical reaction has two effects:
1. Swelling physically separates the jelly from the zygote
membrane
2. Hardens the inner (vitelline) layer of the jelly
6. Describe the changes that occur in an activated egg and explain the importance of
cytoplasmic materials to egg activation.
The changes that occur in an activated egg is that Ca is released from ER increases
respiration and protein synthesis. The importance of cytoplasm materials to egg activation is that
H+ is pumped out of the cell and DNA replication begins after nuclear fusion.
7. Compare fertilization in a sea urchin and a mammal.
Differences b/w sea urchin and mammalian eggs
1. Follicular cells surround eggs
2. Glycoprotein zona pellucida immediately surrounds egg
membrane
Events
1. Sperm migrate through follicular cells
2. Receptors in zona pellucida initiate acrosome reaction
3. Receptors on egg membrane initiate fusion and cortical
reaction
4. Zona pelliucida doesn't swell, it hardens
8. Describe the general process of cleavage. Explain how the distribution and abundance
of yolk influence this process.
Cleavage is the first stage of embryological development and is the division of the zygote
immediately following fertilization. The distribution and abundance of yolk influence in this
process is that cytokinesis divides the zygote cytoplasm in place forming blastomeric.
9. Explain the importance of embryo polarity during cleavage. Compare the
characteristics of the animal hemisphere, vegetal hemisphere, and gray crescent in
amphibian embryos.
The importance of embryo polarity during cleavage is because most animals have both
eggs and zygotes with a definite polarity.
1.Vegetal pole has much more yolk, less protein and stored mRNAs.
2.Animal pole is much darker in frogs with less yolk
In frogs all three embryo directions are present in the zygote
1. First cleavage forms right-left, bisecting the gray crescent
2. Anterior is toward the animal pole
3. Dorsal is the side with the gray crescent
10. Describe the formation of a morula and blastula in sea urchin, amphibian, and insect
embyros. Distinguish between meroblastic cleavage and holoblastic cleavage.
Morula (early solid ball) and blastula (fluid-filled)
1.Sea urchin: holoblastic cleavage; central blastocoel
2. Amphibian: holoblastic cleavage; blastocoel toward animal pole
3. Insect: nuclear division without cytokinesis
Meroblastic: cytokinesis at animal pole only; holoblastic: whole embryo
11. Descrive the process of gastrulation and explain its importance. Explain how this
process rearranges the embryo. List adult structures derived from each of the primary
tissue layers.
Process and rearrangment
1.movement of outer cells into the embryo
2.Forms germ layers and digestive tract
Germ layers
1. Ectoderm: skin and nervous system
2. Mesoderm: muscle and connective tissue
3. Endoderm: lining of gut and respiratory system
12. Compare gastrulation in a sea urchin and a frog.
Sea urchin
1.Inner vegetal pole cells detach and move inward
2. Help invagination forming the blastopore and primitive gut
Frog
1. Cells at gray crescent invaginate forming dorsal lip of blastopore
2. Involution follows: outer cells migrate over the lip
13. Describe the formation of the notochord, neural tube, and somites in a frog.
Notochord: dorsal mesoderm condenses
Neural tube: ectoderm overlying the notochord folds inward and fuses
Somites: mesoderm lateral to notochord separates into blocks
14. Describe the significance and fate of neural crest cells.
The significance and fate of neural crest cells is that it is derived from ectoderm dorsal to
the forming neural tube and vertebrates migrate to form skull and nerve components.
15. List and explain the functions of the extraembryonic membranes in bird and reptile
eggs.
Amnion: fluid-filled, surrounds and cushions the embryo
Chorion: outer-most; protects and exchanges gases
Allantois: exchanges gases and stores wastes
Yolk sac: stores nutritional supply
16. Compare and contrast embryonic development in birds and mammals.
Chorion: in mammals gives rise to the placenta
Amnion: same
Allantois
1. Extends from the gut as in birds
2. Forms the umbilical cord
3.Yolk sac has blood-forming cells
18. Describe the role of the extracellular matrix in embyronic development.
Extracellular Matrix is glycoprotein fabric outside of cells and the role is to guide
migrating cells, provide positional information.
19. Describe the locations and functions of cell adhesion molecules.
Cell adhesion is the binding of a cell to a surface, extracellular matrix or another cell
using cell adhesion molecules such asselectins, integrins, and cadherins. Cell adhesion
molecules involved in the process are first hydrolyzed by extracellular enzymes.
20. Describe the two general principles that integrate our knowledge of the genetic and
cellular mechanisms underlying differentiation.
1. Proteins and mRNAs stored are in eggs in position to guide development
2. Interactions among cells induce changes in gene expression
21. Describe the process of fate mapping and the significance of fate maps.
The process of fate mapping is that it marks on early embryos that are followed through
development. The significance of fate maps is that the marking embryos reveals the fates of the
the parts.
22. Describe the two important conclusions that have resulted from the experimental
manipulation of parts of embryos and the use of fate maps.
1. Founder cells generate specific tissues
2. Developmental potential becomes restricted
23. Explain the relationships between polarity, cytoplasmic determinants, and embryonic
development.
24. Explain the process of induction and its significance in embryonic development.
Explain the significance of the dorsal lip of the blastopore in the early amphibian
gastrula.
The process of induction and its significance in embryonic development is that one group
of cells influences the development of another. The significance of the dorsal lip of the blast pore
in the early amphibian gastrula is that transplanting the dorsal lip sets up a second head-to-tail
axis.
25. Describe the molecular interactions associated with induction events.
The molecular interactions associate with induction events is the physical contact
between cells and the activation or inactivation of morphogens.
26. Explain how pattern formation occurs in a developing chick limb. Explain the roles of
the apical ectodermal ridge and the zone of polarizing activity.
Apical ectodermal ridge: secretes growth factor that stimulates elongation; sets
dorsal-ventral axis
Zone of polarizing activity: secretes sonic hedgehog; sets anterior- posterior axis
27. Explain how a limb bud is directed to develop into either a forelimb or hind limb.
A limb bud is directed to develop into either a forelimb or hind limb because cells
respond according to their developmental histories and genes are activated in hierarchies.
Key Terms
preformation: the idea that the egg or sperm contains an embryo that simply becomes
larger during development
epigenesis: the idea that the form of an animal emerges gradually from a relatively
formless egg
acrosomal reaction: the discharge of hydrolytic enzymes from the acrosome, a vesicle in
the tip of a sperm, when the sperm approaches or contacts an egg
fast block to polyspermy: The depolarization of the egg plasma membrane that begins
within 1-3 seconds after a sperm binds to an egg membrane protein. The depolarization
lasts about 1 minute and prevents additional sperm from fusing with the egg during that
time.
cortical reaction: exocytosis of enzymes and other macromolecules from cortical
granules in the egg cytoplasm during fertilization, leading to the formation of a
fertilization envelope.
cortical granules: A vesicle containing enzymes and other macromolecules located in
the cortex (the region just under the plasma membrane) of an egg. Cortical granules
undergo exocytosis during the cortical reaction.
fertilization envelope: The protective layer formed when the vitelline layer if an egg is
pushed away from the plasma membrane and hardened after fertilization by molecules
exocytosed during the cortical reaction.
slow block to polyspermy: The formation of the fertilization envelope and other changes
in an egg's surface that prevent fusion of the egg with more than one sperm. The slow
block begins about 1 minute after fertilization.
zona pellucida: The extracellular matrix surrounding a mammalian egg.
cleavage: (1) The process of cytokinesis in animal cells, characterized by pinching of the
plasma membrane.(2) The succession of rapid cell divisions without significant growth
during early embryonic development that converts the zygote to a ball of cells.
blastomeres: An early embryonic cell arising during the cleavage stage of an early
embryo.
yolk: Nutrients stored in an egg.
vegetal pole: The point at the end of an egg in the hemisphere where most yolk is
concentrated; opposite of animal pole.
animal pole: The point at the end of an egg in the hemisphere where the least yolk is
concentrated; opposite of vegetal pole.
gray crescent: A light gray, crescent-shaped region of cytoplasm that becomes exposed
after cortical rotation, located near the equator of an egg on the side opposite sperm entry,
marking the future dorsal side of the embryo.
morula: A solid ball of cells resulting from division of a fertilized ovum, and from which
a blastula is formed.
blastocoel: The fluid-filled cavity that forms in the center of a blastula
blastula: An animal embryo at the early stage of development when it is a hollow ball of
cells
meroblastic cleavage: incomplete cleavage of the zygote, restricted to the blastodisc, the
non-yolky cytoplasm at one end of the egg; typical of teloblastic eggs
Holoblastic cleavage: A type of cleavage in which there is complete division of the egg:
occurs in eggs that have little yolk (such as those of the sea urchin) or a moderate amount
of yolk (such as those of the frog).
gastrulation: the process in which a gastrula develops from a blastula by the inward
migration of cells.
gastrula: An embryo at the stage following the blastula, when it is a hollow cup-shaped
structure having three layers of cells
ectoderm: The outermost layer of cells or tissue of an embryo in early development, or
the parts derived from this, which include the epidermis and nerve tissue
endoderm: The innermost layer of cells or tissue of an embryo in early development, or
the parts derived from this, which include the lining of the gut and associated structures
mesoderm: The middle layer of an embryo in early development, between the endoderm
and ectoderm
invagination: The action or process of being turned inside out or folded back on itself to
form a cavity or pouch
archenteron: The rudimentary alimentary cavity of an embryo at the gastrula stage
blastopore: The opening of the central cavity of an embryo in the early stage of
development
dorsal lip: The upper edge of the blastopore produced by invagination during gastrula
formation in amphibian embryos; the site toward which surface cells of the gastrula
converge and migrate inward along the roof of the blastocoel in the process of involution.
involution: A function, transformation, or operator that is equal to its inverse, i.e., which
gives the identity when applied to itself
yolk plug: Yolk plug is the remaining patch of endodermal cells that is created during the
formation of the ventral lip of the blastopore. It is a patch of large endodermal cells
which remains exposed on the vegetal surface of the amphibian blastula that will
eventually be internalized by epiboly.
organogenesis: The production and development of the organs of an animal or plant
notochord: A cartilaginous skeletal rod supporting the body in all embryonic and some
adult chordate animals
neural tube: (in an embryo) A hollow structure from which the brain and spinal cord
form. Defects in its development can result in congenital abnormalities such as spina
bifida
Somite: Each of a number of body segments containing the same internal structures,
clearly visible in invertebrates such as earthworms but also present in the embryonic
stages of vertebrates
amniote: An animal whose embryo develops in an amnion and chorion and has an
allantois; a mammal, bird, or reptile
blastodisc: a layer of cells on the inside of the blastula
primitive streak: The faint streak that is the earliest trace of the embryo in the fertilized
ovum of a higher vertebrate
extraembryonic membranes: Four membranes (yolk sac, amnion, chorion, allantois)
that support the developing embryo in mammals and birds and other reptiles
yolk sac: A membranous sac containing yolk attached to the embryos of reptiles and
birds and the larvae of some fishes
amnion: The innermost membrane that encloses the embryo of a mammal, bird, or reptile
chorion: The outermost membrane surrounding an embryo of a reptile, bird, or mammal.
In mammals (including humans), it contributes to the formation of the placenta
allantois: The fetal membrane lying below the chorion in many vertebrates, formed as an
outgrowth of the embryo's gut. In birds and reptiles it grows to surround the embryo; in
eutherian mammals it forms part of the placenta
blastocyst: A mammalian blastula in which some differentiation of cells has occurred
inner cell mass: The cluster of cells inside the blastocyst. These cells give rise to the
embryo and ultimately the fetus. The ICM cells are used to generate embryonic stem
cells.
trophoblast: A layer of tissue on the outside of a mammalian blastula, supplying the
embryo with nourishment and later forming the major part of the placenta
convergent extension: cell movement resulting in tissue elongation via intercalation of
adjacent cells in an epithelial sheet to form a narrower, longer strip of tissue.
cell adhesion molecules (CAMs): Cell Adhesion Molecules (CAMs) are proteins located
on the cell surface involved with the binding with other cells or with the extracellular
matrix (ECM) in the process called cell adhesion.
cadherins: Cadherins (named for "calcium-dependent adhesion") are a class of type-1
transmembrane proteins. They play important roles in cell adhesion, ensuring that cells
within tissues are bound together. They are dependent on calcium (Ca2+) ions to
function, hence their name.
fate maps: A map of an embryo showing areas that are destined to develop into specific
adult tissues and organs.
pattern formation: The science of pattern formation deals with the visible, (statistically)
orderly outcomes of self-organisation and the common principles behind similar patterns.
positional information: Signals to which genes regulating development respond,
indicating a cell's location relative to other cells in an embryonic structure.
apical ectodermal ridge (AER): The apical ectodermal ridge (AER) is a thickened layer
of ectodermal cells at the distal tip of a developing limb bud. Along with the zone of
polarizing activity, it is a crucial organizing region during limb development.
zone of polarizing activity (ZPA): A limb-bud organizer region consisting of a block of
mesoderm located where the posterior side of the bud is attached to the body.