BIOL370 Exam 3

the yolk rich region

Vegetal pole

the yolk devoid region

Animal pole

roughly equal distribution of yolk (such as in sea urchins)

Isolecithal

complete cleavage

Holoblastic cleavage

partial cleavage where only some of the cytoplasm is cleaved (insects, fish, reptiles, birds)

Meroblastic cleavage

centrally placed yolk (insects)

Centrolecithal

only one area is free of yolk (birds and fish)

Telolecithal

cleavage in the telolecithal eggs that occurs only in the small disk of cytoplasm

Discoidal cleavage

Holoblastic cleavage subtypes

Radial, Spiral, Bilateral, Rotational

In the urchin for instance, we see the

isolecithal egg

In the insect we see the

centrolecithal egg

In birds, we see the

telolecithal (megalecithal) egg

complete cleavage

holoblastic cleavage

partial cleavage where only some of the cytoplasm is cleaved (insects, fish, reptiles, birds)

meroblastic cleavage

cleavage in the telolecithal eggs that occurs only in the small disk of cytoplasm

Discoidal

The shape of the organism grows much more complex as you move from the

blastula stage to the gastrula

consists of the folding of an area of the exterior sheet of cells towards the inside of the blastula.

invagination

a type of cell movement during gastrulation which involves the in-turning or inward movement of an expanding outer layer so that it spreads over the internal surface of the remaining external cells.

Involution

in an organism using this type, cells detach from the epithelium and become internalized mesenchyme cells that can migrate freely.

ingression

the blastula of the organism utilizing this approach to move to gastrulation will engage in the splitting or migration of one sheet into two sheets

delamination

a monolayer of cells must undergo a physical change in shape in order to spread. Sometimes occurs with multiple layers as the position of cells is changed or the cell layers undergo intercalation.

epiboly

With this increasing complexity due the in-folding of layers of cells, the three dimensional shape of organisms will no longer be

symmetrical in every plane

•mesomeres (animal) equitorially to produce an1 and an2

•macromeres divide meridionally

•micromeres divide unequally producing four small mircomeres and four large micromeres

5th (16 cell stage) cleavage

divide meridionally and vegetal cells divide equatorially.

6th division animal hemisphere cells

divide meriodionally and the animal cells divide equatorially.

7th division vegetal cells

The embryo at about 64 cells is called

a blastula

towards the mouth

oral

away from the mouth

aboral

At the 64 cell stage, the animal pole is where the

ectodermal cells are found

At the 64 cell stage, the vegetal pole s where the

mesodermal and endodermal cells are found

In (B), we see how development proceeds when the ~64 cell urchin has its vegetal pole removed…. The end result is an abnormal larval development of an

animalized larvae that will not fully develop

In (C), we see the same ~64 cell urchin start point with the vegetal pole is also removed….however, the very distal, small micromeres are allowed to remain.   In this experiment, development proceeds

to a recognizable pluteus larva

it appears from the above that some aspects of body plan development (morphology) in the urchin are being controlled/regulated by

micromere cells

late stage blastula will contain roughly

1000 cells

the blastomeric cells are of

different shapes, sizes, and properties

a phase early in the embryonic development of most animals, during which the single-layered blastula is reorganized into a trilaminar ("three-layered") structure

gastrulation

Gastrulation is followed by ____________, when individual organs develop within the newly formed germ layers.

organogenesis

the rudimentary alimentary cavity of an embryo at the gastrula stage.

Archenteron

gives rise to epidermis and also tissues that will later form the nervous system.

ectoderm

gives rise to the muscular system, cartilages, the dermis, the notochord, blood and blood vessels, bone, and connective tissue.

mesoderm

gives rise to the epithelium of the digestive system and respiratory system, and organs associated with the digestive system, such as the liver and pancreas.

endoderm

As cells begin to detach from the vegetal pole in the gastrula and enter the fluid filled cavity in the center (the blastocoel of the former blastula), the remaining cells at the vegetal pole flatten to form

a vegetal plate

In other organisms than urchins, the indentation that is actually formed is called the

lip of the blastopore or dorsal lip

the cells of the archenteron help to form the _________ of the urchin. 

primitive gut

As the urchin transitions from the pleutus larvae into the more recognizable adult form, there is a structure called the ___________that guides morphological development up until the transition point of metamorphosis is reached. 

imaginal rudiment

Snails are molluscs that develop __________ (spiral shaped shells) that can often develop either a right-handed or a left-handed spiral organization.

conchae

If you were to follow the growth from the origin of the shell, left handed growth is in the ________ direction. 

counter-clockwise

A left-handed shell is more technically referred to as a

sinistral shell

A right-handed shell is more technically referred to as a

dextral shell

The chirality of the shell in gastropods appears very in early cleavage (spiral cleavage) and the gene ________ is involved.

NODAL

the NODAL gene which is located on human______________ and it is involved in cell differentiation in early embryogenesis, playing a key role in our early development for mesoderm and endoderm formation and subsequently the organization of left-right axial structures.

chromosome 10

The mussel’s early developmental larval stage is referred to as a

glochidium. 

The glochidum larval form has hooks, which enable it to attach itself to

fish before it detaches and falls to take the form of a juvenile

the larval glochidium is believed to be evolutionarily important in helping to

distribute mussel species to potential areas of habitat

The glochidium forms through _____________ of the some of the early steps of spiral cleavage. 

special modification

a marine invertebrate of a group which includes another well-known species called the sea squirts.

tunicates

a type of cell that synthesizes the extracellular matrix and collagen, the structural framework for animal tissues, and plays a critical role in wound healing.

fibroblast

Endoderm does not produce _____________ and by not doing so, the two types of division into nerve cord (no Macho-1, no FGF) and notochord (no Macho-1, but with FGF) are seen.

Macho-1 factors

___________ does produce Macho-1 factors and by doing so, the two types of division into mesenchyme (Macho-1 ,plus also FGF) and muscle (Macho-1, no FGF) are seen.

Mesoderm

Research into the molecular and developmental biology of C. elegans was begun in 1974 by

Sydney Brenner

Note that earlier meiotic divisions of c. elegans actually involve sperm production and the spermatheca is only for

STORAGE. 

. elegans has been extensively used as a model organism. It was the first multicellular organism to have

its entire genome sequenced and connectome mapped

The _______is the original stem cell in development of c. elegans.

P cell

It is the ____________ and their distribution in the cells prior to cleavage that will shape the differences seen in these very early cleavage events. 

PAR Proteins

the beginning of orientation of cell lineages in an organism.  In C. elegans, this is guided by PAR proteins. 

polarity

The _____________ show in the above has atypical development of the gut musculature. 

SNK-1 Mutation