Lecture 2

Question 1

Name 6 characteristics that all phylum chordata exhibit

Answer 1

Notochord
Dorsal Nerve tube
Coelom
Post-anal tail
Pharyngeal puches/slits
Endostyle (Thyroid)

Question 2

What is Bilateral Asymmetrical Gynandromorphy?

Answer 2

It is when the sex chromosomes split unevenly early in development leaving half the body having a male phenotype and half the body having a female phenotype.

Question 3

Name 4 developmental differences between Protostomes and Deuterostomes.

Answer 3

D- Blastopore forms anus P-forms mouth
D- Radial cleavage P- Spiral cleavage
D- Enterocoelic coelom P- Schizocoelic coelom
D- Mesodermal skeleton P- Ectodermal skeleton

Question 4

What are Hox genes?

Answer 4

They are genes found across animals which determine what segments along the head-tail axis will eventually become.

Question 5

What is a Morula

Answer 5

It is the human at 4 days of development. It is 32 cells and there is not yet any cavity.

Question 6

What are the 3 parts of the blastocyst?

Answer 6

The outer layer of cells, called the trophobast.
The inner cell mass.
A space filled with fluid called the blastocyst cavity or blastocoel.

Question 7

What will the trophoblast go on to become?

Answer 7

The placenta.

Question 8

What will the inner cell mass go on to become?

Answer 8

The embryo.

Question 9

At what stage of development does the embryo implant?

Answer 9

~1 week

Question 10

What two layers comprise the bilaminar disc?

Answer 10

The epiblast and the hypoblast.

Question 11

What happens to the hypoblast?

Answer 11

It goes on to form part of the yolk sack.

Question 12

What happens to the epiblast?

Answer 12

It goes on to form the 3 germ layers.

Question 13

What are the 2 cavities on either side of the bilaminar disk?

Answer 13

The amniotic cavity is above the epiblast.

The yolk sack is below the hypoblast.

Question 14

What happens during gastrulation?

Answer 14

The primitive streak forms as a grove in the epiblast and cells migrate down from this groove to form the 3rd primary germ layer.

Question 15

When does gastrulation happen?

Answer 15

During the 3rd week of development.

Question 16

What is the trilaminar embryonic disk made up of?

Answer 16

Ectoderm.
Mesoderm.
Endoderm.

Question 17

What do the 3 layers of the trilaminar embryonic disk derive from?

Answer 17

Ectoderm - Epiblast layer
Mesoderm - Epiblast cells through the primitive streak.
Endoderm - Epiblast that displaces hypoblast.

Question 18

Which germ layer does the notochord derive from?

Answer 18

Mesoderm.

Question 19

What does the notochord do in early development?

Answer 19

It plays a role in signalling and coordinating development and defines the primitive axis of the organism.

Question 20

What does the notochord become in most tetrapods, including humans?

Answer 20

They eventually develop into the nucleus pulposus of the intervertebral discs.

Question 21

What is neurulation?

Answer 21

It is the process of developing a neural tube.

Question 22

What is the neural tube a precursor to?

Answer 22

It becomes the CNS.

Question 23

What happens during neurulation?

Answer 23

Part of the ectoderm dorsal to the notochord forms a fold with a neural groove between neural folds which is called the neural plate. This groove deepens and eventually folds back on itself making a hollow neural tube under the epidermis.

Question 24

How is the intra-embryonic body cavity formed?

Answer 24

The trilaminar disc folds on either side and meets in the middle. This causes the endoderm layer to captured within the embryo and begin to form the gut lining and a cavity to form around this which is lined by mesodermal germ layer.

Question 25

What are pharyngeal pouches?

Answer 25

They are pouches that form along the neck of the embryo from invaginations of the endoderm between adjacent arches and parallel to pharyngeal clefts which form in the ectoderm. They later go on to become structures such as the Eustachian tube used to regulate pressure in the ear and the thymus and inferior parathyroids.