Reproduction and development Part 7

Question 1

After cleavage

Answer 1

the rate of cell division slows

Question 2

The remaining stages of embryonic development are responsible for

Answer 2

morphogenesis

Question 3

What is morphogenesis

Answer 3

the cellular and tissue-based processes by which the animal body takes shape

Question 4

During gastrulation

Answer 4

a set of cells at or near the surface of the blastula moves to an interior location, cell layers are established, and a primitive digestive tube forms

Question 5

two- or three layered embryo

Answer 5

gastrula

Question 6

cell layers produced by gastrulation is called

Answer 6

germ layers

Question 7

ectoderm

Answer 7

outer layer

Question 8

endoderm

Answer 8

inner layer

Question 9

mesoderm

Answer 9

between ecto and endoderm

Question 10

mouth develops from the first opening

Answer 10

blastopore

Question 11

mouth forms in the embryo

Answer 11

protostomes

Question 12

mouth develops in the second opening

Answer 12

deuterostomes

Question 13

Examples of deuterostomes

Answer 13

sea urchins, humans, and other vertebrates

Question 14

Organogenesis

Answer 14

regions of the embryonic germ layers develop into rudiments of body organs

Question 15

Human gestation can be divided into

Answer 15

3 trimesters of about 3 months each

Question 16

First semester

Answer 16

the embryo secretes hormones that signal its presence and regulate the mother’s reproductive system

Question 17

Human chorionic gonadotropin (hCG)

Answer 17

acts to maintain the secretion of progesterone and estrogens by the corpus luteum through the first months of pregnancy

Question 18

occasionally when an embryo splits during the first month of development, it results in

Answer 18

identical or monozygotic twins

Question 19

Fraternal, or dizygotic twins

Answer 19

arise when two eggs are fertilized and implant as two genetically distinct embryos

Question 20

Why can’t some embryos complete development

Answer 20

This is due to chromosomal or other abnormalities. These spontaneously abort and occur in about 1/3 of all pregnancies.