Zygote to neurulation

Question 1

____ which creates new cells through mitosis;

Answer 1

cell division

Question 2

___, which causes groups of cells to organize

and move, to create an animal’s body shape

Answer 2

cell migration

Question 3

___,which causes cells to develop different morphological features for specialization toward specific tasks.

Answer 3

cell differentiation

Question 4

____, the entrance of more than one sperm

Answer 4

Polyspermy

Question 5

as a sperm cell bonds to the surface of the egg,
receptor proteins on the plasma membrane of the egg
recognize the sperm cell (if it is of the same species as
the egg) and erect a _____ to draw the head
of the sperm inside the egg’s plasma membrane.

Answer 5

fertilization cone

Question 6

The mechanism which the electrical potential of the egg’s plasma
membrane changes polarity to block any other sperm
from penetrating.

Answer 6

fast block

Question 7

cortical granules just beneath the egg’s plasma membrane release their contents into the membrane, causing a ______ to form around the entire surface of the egg, creating a more permanent boundary to polyspermy

Answer 7

fertilization membrane

Question 8

Fusion of the nuclear material of the sperm and egg follows and the
fertilized egg, now referred to as a ______, becomes activated to undergo cleavage.

Answer 8

zygote

Question 9

All fertilized eggs contain an embryo and a food reserve,

called _____, to nourish the developing embryo.

Answer 9

yolk

Question 10

the ____ of cell division can more
easily penetrate regions of the egg with very little, evenly
distributed yolk.

Answer 10

cleavage furrows

Question 11

name the four main types based on the amount and distribution of yolk

Answer 11

isolecithal, mesolecithal, telolecithal, centrolecithal

Question 12

______ have very little yolk evenly distributed throughout the egg; Humans and ___ both possess these eggs.

Answer 12

Isolecithal eggs; sea stars

Question 13

Eggs of this type generally undergo ____, meaning that the
cleavage furrow extends completely through the egg
and completely separates daughter cells.

Answer 13

isolecithal eggs ;holoblastic cleavage

Question 14

____ have a moderate amount of
yolk concentrated at one end of the egg, referred
to as the ______. _______
possess these eggs.

Answer 14

Mesolecithal eggs; vegetal hemisphere, or pole; Amphibians

Question 15

______ have a large amount ofyolk,

which occupies most of the cell volume

Answer 15

Telolecithal eggs

Question 16

The embryo is confined to a small disc at the opposite

pole of the cell, the animal pole

Answer 16

Telolecithal eggs

Question 17

___ and ___

possess telolecithal eggs

Answer 17

Birds and reptiles

Question 18

Because of the large, heavily concentrated yolk, cleavage is only partial,
stopping at the border between the embryo and
the yolk, and daughter cells remain connected to
each other. This type of cleavage is referred to as __

Answer 18

meroblastic cleavage, or incomplete cleavage.

Question 19

___ also have a large amount of
yolk, but the embryo forms a thin layer around
the outside of the large, central yolk mass. Most
____ have centrolecithal eggs.

Answer 19

Centrolecithal eggs; arthropods

Question 20

The pattern of cleavage is also dictated by the ____ within the developing embryo

Answer 20

plane of division

Question 21

When cleavage planes occur perpendicular or parallel

to each other, it is referred to as

Answer 21

radial cleavage.

Question 22

When cleavage planes occur at oblique angles, it is referred to
as ____

Answer 22

spiral cleavage.

Question 23

When cleavage planes are restricted to
a dome of cytoplasm at one end of the yolk laden cell, it
is referred to as _____

Answer 23

discoidal cleavage.

Question 24

Because of the unique distribution of yolk in centrolecithal eggs, cleavage occurs
only in the cell’s periphery. This pattern is known as _____

Answer 24

superficial cleavage.

Question 25

The sea star and frog are both ___meaning that the

mouth develops from the second embryonic opening.

Answer 25

deuterostomes

Question 26

Sea stars of the genus ___are familiar marine invertebrates we commonly refer to
as “starfish” (though they are not fish), and are members of the phylum ____

Answer 26

Asterias; Echinodermata

Question 27

State the embryonic development stages in sea star

Answer 27

Unfertilized Egg; fertilized Egg; Two Cell through Eight Cell Stages; Morula(16–32Cell Stages); Blastula (64+ Cell Stages); Early Gastrula; Late Gastrula; Bipinnaria Larva

Question 28

In this stage, the egg appears as a large, nearly spherical cell with a distinct nucleus and nucleolus. Tiny granules are visible within the cytoplasm of the cell. Notice how these granules are ____ distributed throughout the cytoplasm.

Answer 28

Unfertilized egg; uniformly

Question 29

What type of egg does sea stars have?

Answer 29

isolecithal eggs

Question 30

What stage??

After the sperm penetrates the egg, a thin fertilization membrane is erected by the egg, ensphering it to prevent multiple fertilizations by the many nearby sperm (polyspermy).A distinct nucleus is not visible while the nuclear material from
sperm and egg fuse to restore the zygote to the diploid chromosome number.

Answer 30

fertilized eggs

Question 31

What stage???

Shortly after fertilization, the zygote begins to divide through mitosis. At this early stage of development, it is still possible for nearby sperm to penetrate these cells consequently upsetting the genetic balance of the zygote. The persistence of the fertilization membrane prevents this from occurring. Finally, notice that as these cells divide, they do not get bigger. The existing cytoplasm is partitioned equally among the new cells with very little growth during these early stages of embryonic development.

Answer 31

Two Cell through Eight Cell Stages

Question 32

This pattern of cleavage (cell division) completely separates the cells into roughly equal sized, but distinct, cells. This is common in isolecithal eggs with a small amount of evenly distributed yolk.

Answer 32

radial holoblastic cleavage

Question 33

At the ____ stage the embryo is represented by a solid mass of tiny cells, called ____, that continue to divide at a furious pace. Still, the overall size of the embryo has not increased; rather, the size of the individual blastomeres has de
creased to accommodate the fixed amount of cytoplasm being divided among cells. The fertilization membrane is still usually visible throughout this stage

Answer 33

morula; blastomeres

Question 34

The _____ stage is characterized by a migration of cells toward the periphery of the embryonic sphere, creating a hollow cavity deep within the spheroid of cells

Answer 34

blastula

Question 35

During this stage the blastula breaks free from the envelopment of the
fertilization membrane and is able to swim about freely using ciliary movements of blastomeres on the embryo’s surface.

Answer 35

blastula stage

Question 36

The hollow, fluid filled cavity within the blastula is referred to as the ___

Answer 36

blastocoel

Question 37

Several hours after the formation of the blastula, a small depression begins to appear at one end of the embryo, and cells begin to organize, move, and start to create the geometry of the animal’s body

Answer 37

Early gastrula

Question 38

This invagination and migration of cells toward the

center of the blastocoel marks the onset of _____

Answer 38

gastrulation.

Question 39

The opening to the outside of the embryo, marking the site of the inward migration of cells, is called the____

Answer 39

blastopore

Question 40

The hollow tube that is created by the arrangement of invaginated cells is
called the _____(meaning primitive gut).

Answer 40

gastrocoel, or archenteron

Question 41

By now, the individual cells are so small as to be indistinguishable from each other under normal magnification. At most, they appear as a flecking on the surface of the embryo. The archenteron has folded inward to the point of nearly connecting with the opposite end of the gastrula, and the shape of the gastrula has become markedly elongated

Answer 41

late gastrula

Question 42

During late gastrulation ____ begins, and the primary tissue layers of the embryo start to form.

Answer 42

cell differentiation

Question 43

The outer layer begins to develop into ____, while the inner layer differentiates into __. The third embryonic layer, __, will develop later between these two existing layers from cells that disassociate from the endodermal layer

Answer 43

ectoderm; endoderm; mesoderm

Question 44

By the larval stage, morphogenesis and organogenesis
have begun. The larval sea star has a complete digestive tract, including an anus and a functional mouth lined with cilia for sweeping in organic particles

Answer 44

Bipinnaria larva

Question 45

______ (the development of body shape)

______ (the differentiation of organ tissues)

Answer 45

morphogenesis

organogenesis

Question 46

Frogs belong to the vertebrate class ___ within the phylum ___

Answer 46

Amphibia; Chordata

Question 47

Frog eggs are ____, meaning that they contain a
moderate amount of yolk. This yolk is segregated toward
one pole of the egg known as the ___

Answer 47

mesolecithal; vegetal pole

Question 48

_____, which appears lighter in coloration.
The darker pole, or _____, represents the portion of the egg where the embryo
will develop

Answer 48

vegetal pole; animal pole

Question 49

What stage???

the fertilization membrane lifts away from the surface of the egg and the egg rotates so that the heavier, yolk filled vegetal pole is downward. Later, a ____ appears along the margin of the animal vegetal axis on the opposite side of the egg from the entry point of the sperm

Answer 49

Fertilized egg stage; gray crescent

Question 50

What stage??

Cleavage in the frog embryo is ____, similar to that in the sea star. The first two cleavage planes are perpendicular to one another, producing four cells of roughly equal size. The third cleavage occurs parallel to, but slightly above, the equator that separates the animal and vegetal poles. From this point forward, the division of cells will follow this unequal pattern with cells in the animal pole dividing at a faster rate than cells in the vegetal pole, which are laden with yolk.

Answer 50

early cleavage; radial and holoblastic

Question 51

What stage???

the appearance of the two poles differs markedly. The ____ pole is composed of
considerably smaller, more numerous cells while the ____ pole contains relatively few, large cells containing yolk
granules

Answer 51

Late cleavage; animal; vegetal

Question 52

the blastula in frog is much larger than the fertilized egg. True or false??

Answer 52

FALSE. the blastula is NOT much larger than the fertilized egg because
the cells become smaller with each successive division

Question 53

In frog, gastrulation is characterize by the formation of a crescent
shaped line along the surface of the blastula known as the ____, which marks the opening of the blastopore

Answer 53

dorsal lip

Question 54

By the late gastrula stage the
vegetal pole cells have become
almost completely enveloped by
migrating surface cells from the
animal pole and only a small,
circular \_\_\_\_ remains visible
at the opening to the blastopore

Answer 54

yolk plug

Question 55

What stage???

Several hours after gastrulation, the first visible elements of the nervous system begin to appear as a result of ectodermal cells along the middorsal region of the embryo thickening to form two enlarged ridges on the surface, the _____,
which border a depression, the ____

Answer 55

neural folds; neural groove

Question 56

the neural folds will meet and fuse together, forming the enclosed ____ that will develop into the brain and spinal cord

Answer 56

neural tube

Question 57

Beneath the developing neural tube a long, cylindrical section of mesodermal cells is differentiating to form the ____, which later
will develop into vertebrae

Answer 57

notochord

Question 58

What stage???

Several days after fertilization the embryo begins to elongate and takes on the more familiar tadpole shape (morphogenesis). The ___ develops a pronounced tail, and gills and a ___develop at the anterior end. What is left of the yolk mass remains as a slight bulge in the abdomen of the developing tadpole

Answer 58

larva stage; posterior end; mouth