involution [in voe LOU shun]isolecithal [eye so LESS eh thal]
telolecithal [tel oh LESS eh thal]
centrolecithal [sin trow LESS eh thal]
germ layer
What You Need to Know:
You should be able to:
describe how to obtain sperm and eggs from sea urchins,
demonstrate the ability to effect fertilization of sea urchin eggs with sea urchin sperm,
demonstrate the ability to culture fertilized sea urchin eggs to the two cell stage,
identify in a prepared slide the various stages of development of a sea star, from unfertilized egg to bipinnaria larva,
identify all of the features of a blastula and gastrula,
name the three germ layers and explain what each turns into in the adult,
explain the difference between the three types of eggs according to yolk distribution, and
explain the difference between development in the telolecithal and isolecithal egg.
Exercises: Fill in the Blank.
When a sperm penetrates the egg, other sperm are prevented from entering the egg by the formation of a around the egg.
The cavity or space inside the blastula is called the .
An individual cell of the blastula is called a .
The primitive gut in the embryo is called the and the opening to the outside is called the .
There are three primary germ layers in an embryo. They are a. b. and c. .
The collective term for sperm and eggs is .
In a telolecithal egg, yolk is concentrated in this region of the egg.
Which type of egg has the yolk evenly distributed throughout the egg?
This germ layer gives rise to the brain, the spinal cord, and even the corneas of the eyes of the embryo.
This primary germ layer gives rise to the muscles of the embryo.
The overgrowth of animal cells over the vegetal cells in a telolecithal egg is called and the pushing inward of cells to form the archenteron is called .
This primary germ layer will eventually form the lining of the respiratory system, the lining of the urinary bladder, the lining of the middle ear and even the tyroid and thymus glands in a vertebrate.
Exercises: Multiple Choice. Select the Best Answer.
Which of the following is probably not going to be found in a developing embryo?
(1) 2-cell stage
(2) 4-cell stage
(3) 10-cell stage
(4) blastula
(5) archenteron
Which will form the primitive gut of the embryo?
(1) blastopore
(2) blastomere
(3) archenteron
(4) blastocoel
(5) ectoderm
Which of the following is often pushed out of existence and replaced in the embryo?
(1) blastopore
(2) blastomere
(3) archenteron
(4) blastocoel
(5) ectoderm
Which of the following is an individual cell in an embryo?
