Chapter 18- Developmental Biology

Question 1

what does cleavage result in

Answer 1

progressively smaller cells with an increasing ratio of nuclei to cytoplasm and the surface area to volume of each cell

Question 2

how long after fertilization is the first cleavage completed

Answer 2

32 hours

Question 3

how long after fertilization is the second cleavage completed

Answer 3

72 hours

Question 4

what is the result after the second cleavage

Answer 4

a morula

Question 5

what is blastulation

Answer 5

when the morula develops a fluid-filled cavity called the blastocoel

Question 6

what does the blastocoel become

Answer 6

the blastula

Question 7

what is the order of “embryonic development”?

Answer 7

morula-> blastocoel-> blastula-> gastrula

Question 8

what is the outer layer of cells of the blastula called

Answer 8

the trophoblast

Question 9

what does the trophoblast do

Answer 9

• plays a role in the implantation of the blastula in the uterus
• provides nutrients to the embryo and develops into part of the placenta

Question 10

what is the amnion

Answer 10

a thin, tough membrane containing a watery fluid called amniotic fluid

Question 11

what is the purpose of the amnion

Answer 11

is acts as a shock absorber of external pressure during gestation and localized pressure from uterine contractions during labor

Question 12

what does placenta formation begin with

Answer 12

the chorion

Question 13

what is the chorion

Answer 13

a membrane that completely surrounds the amnion

Question 14

what does the chorion do

Answer 14

assists with transfer of nutrients from the mother to the fetus

Question 15

what is the allantois

Answer 15

an outpocketing of the gut

Question 16

what is the purpose of the allantois

Answer 16

the blood vessels of the allantoic wall enlarge and become the umbilical vessels, which will connect the fetus to the placenta

Question 17

what does the yolk sac do

Answer 17

comes associated with the umbilical vessels

Question 18

when is the gastrula formed

Answer 18

after week two

Question 19

what does the ectoderm differentiate into

Answer 19

integumentary system, lens of the eye, the retina, the nervous system

Question 20

what does the mesoderm differentiate into

Answer 20

musculoskeletal system, circulatory system, excretory system, gonads, connective tissue throughout the body, and portions of digestive and respiratory systems

Question 21

what does the endoderm differentiate into

Answer 21

epithelial linings of the digestive and respiratory tracts and parts of the liver, pancreas, thyroids, and bladder lining

Question 22

what is neurulation

Answer 22

regions of the germ layer begin to develop into rudimentary nervous system at the end of gastrulation

Question 23

what do neural crest cells give rise to

Answer 23

sensory ganglia, autonomic ganglia, adrenal medulla, and schwann cells

Question 24

what are the three final stages of development

Answer 24

organogenesis, growth, gametogenesis

Question 25

what happens in organogenesis

Answer 25

the body organs begin to form

Question 26

what happens in growth phase

Answer 26

organs increase in size which is a continual process from infancy to adulthood

Question 27

what happens in gametogenesis

Answer 27

eggs develop in women and sperm develop in men which permits reproduction to occur

Question 28

what happens during the first weeks of fertilization

Answer 28

major organs begin to develop, the heart starts to beat at 22 days

Question 29

describe the embryo at the end of the first trimester

Answer 29

most of the organs have developed, the embryo is referred to as a fetus, it is 9 cm long

Question 30

describe the fetus at the end of the second trimester

Answer 30

its face appears human, its toes and fingers elongate, the fetus is 30-36 cm long

Question 31

what happens during the ninth month of pregnancy

Answer 31

antibodies are transported from the mother to the fetus

Question 32

what occurs in the first phase of labor

Answer 32

cervix thins and dilates, the amniotic sac ruptures and contractions are relatively mild

Question 33

what occurs in the second phase of labor

Answer 33

rapid contractions, resulting in the birth of the baby

Question 34

what occurs in the third phase of labor

Answer 34

uterus contracts, expelling the placenta and the umbilical chord

Question 35

what are teratogens

Answer 35

congenital disorders from chemical and biological agents

Question 36

what is vertical transmission

Answer 36

when a mother passes on an infection directly to her developing offspring

Question 37

what process occurs in angiosperms

Answer 37

double fertilization

Question 38

what are the components in a seed embryo

Answer 38

epicotyl, cotyledons, hypocotyl, endosperm, seed coat

Question 39

what is the epicotyl

Answer 39

precursor of the upper stem and leaves

Question 40

what is the cotyledons

Answer 40

seed leaves, dicots have two seed leaves, while monocots have only one

Question 41

what is the hypocotyl

Answer 41

the lower stem and root

Question 42

what is the endosperm

Answer 42

feeds the embryo in angiosperms. in dicots the cotyledon absorbs the endosperm

Question 43

what is the seed coat

Answer 43

develops from the outer covering of the ovule, the embryo and its seed coat together comprise the seed

Question 44

what is seed germination

Answer 44

the process of a seed sprouting into a seedling

Question 45

what are meristem cells

Answer 45

they determine how tall a plant can grow

Question 46

where is the apical meristem found and what occurs here

Answer 46

found at the tips of roots and stems and growth in length only occurs at these points

Question 47

where is the lateral meristem located

Answer 47

between the xylem and phloem

Question 48

what is the purpose of the lateral meristem

Answer 48

permits growth in diameter and can differentiate into new xylem and phloem cells