Module 6 - Sexual Reproduction and Pregnancy

Question 1

Gametes (3)

Answer 1

1) Sex cells containing 23 chromosomes each

2) Males: spermatocytes (sperm)

3) Female: oocytes (egg)

Question 2

Copulation (4)

Answer 2

1) Sexual union facilitating reception of sperm by the female

2) Offspring inherits half its genome from one parent and half from the other

3) Each offspring has a unique genetic combination different from either parent

4) Introduces and maintains genetic variation for environmental changes

Question 3

Diploid cells (3)

Answer 3

1) Human cells throughout the body that contain 46 chromosomes

2) Full number of chromosomes necessary for life (2n)

3) Mitosis
a) Cells grow and divide into identical cells
b) Each daughter cells contains 46 chromosomes

Question 4

Haploid cells (2)

Answer 4

1) Gamete cells in males and females contain 23 chromosomes

2) Half number of chromosomes necessary for life (n)

Question 5

Haploid cells - Meiosis (3)

Answer 5

1) Cells divide into four cells

2) Each daughter cells contain 23 chromosomes

3) Daughter cells are each genetically unique

Question 6

Zygote (3)

Answer 6

1) Gametes combine to form a fertilized egg

2) Has a total of 46 chromosomes
a) Full number required for sustaining life cycle

3) Zygote then grows and divides by mitosis into an embryo and then a fetus

Question 7

Genetic characteristics (3)

Answer 7

1) 46 chromosomes determine all genetic characteristics of the offspring

2) Sex of the offspring
a) Males (XY)
b) Females (XX)

3) Sex is determined by father’s sperm cell

Question 8

Formation of zygote - viability of gametes (3)

Answer 8

1) Sperm are viable for 3-6 days after ejaculation

2) Egg survives for 24 hours after ovulation

3) For fertilization, copulation can occur
a) A few days before ovulation
b) No later than 1 day after ovulation

Question 9

Formation of zygote - fertilization (6)

Answer 9

1) Fertilization usually takes place in the oviducts

2) Egg releases chemicals that attract sperm

3) Sperm release enzymes to break apart corona radiata

4) Many sperm release enzymes to make a hole in the membrane of the egg

5) Allows one sperm to unite with the egg

6) Once union occurs, membrane of the egg instantly alters chemically
a) Prevents other sperm from entering egg

Question 10

Development of zygote - pre-implantation (5)

Answer 10

1) Zygote undergoes mitotic divisions for 3-4 days as it travels through oviducts

2) Forms the morula

3) Morula undergoes mitotic division for 3-4 days while unattached in the uterus

4) Forms the blastocyst

5) Blastocyst secretes HCG
a) Human chorionic gonadotropin
b) Stimulates corpus luteum to secrete progesterone

Question 11

Development of zygote - endometrium (3)

Answer 11

1) Endometrium prepares for implantation
a) Progesterone release from corpus luteum
b) Increased blood supply and secretes glycogen
c) Helps sustain blastocyst before it implants

Question 12

Blastocyst (2)

Answer 12

1) Implants into the endometrium around day 7

2) Begins to develop into three layers which become the embryo
a) Ectoderm
b) Mesoderm
c) Endoderm

Question 13

Blastocyst Supportive Cells (4)

Answer 13

1) Other cells of the blastocyst become supportive cells

2) Amnion: forms a fluid sac to cushion and protect fetus

3) Placenta: temporary organ
a) Carries out nutritive, respiratory, excretory and endocrine functions until delivery

Umbillical cord: Attaches embryo to placenta

Question 14

Ectoderm (2)

Answer 14

1) Outer layer of the embryo

2) Becomes skin and nervous tissue

Question 15

Endoderm (4)

Answer 15

1) Inner layer of the embryo

2) Forms the glands
a) Thyroid, parathyroid, thymus

3) Forms the solid organs
a) Liver, pancreas

4) Forms the lining of the hollow organs of the digestive and respiratory systems

Question 16

Mesoderm (2)

Answer 16

1) Middle layer of the embryo

2) Forms all other tissues
a) Cardiovascular system
b) Red blood cells
c) Muscle tissue