Animal Reproduction

Question 1

Suppose you wanted to start an animal-breeding business. For most of the following animals, you could start out with just a single animal. Which of the animals below would require that you start with at least two individuals?
A) Whiptail lizards
B) Hammerhead shark
C) Bullfrog
D) Komodo dragons

Answer 1

C - Bullfrog.
All others can reproduce via parthenogenesis

Question 2

What is fission/fragmentation? (Type of asexual reproduction)

Answer 2

The separation of a parent into two or more individuals of about the same size.
Ex. Flatworms do this

Question 3

What is budding? (Type of asexual reproduction)

Answer 3

When new individuals arise from outgrowths of existing ones.
Ex. Jellyfish do this

Question 4

What is parthenogenesis? (Type of asexual reproduction)

Answer 4

Development of a new individual from an unfertilized egg
Ex. Female komodo dragon

Question 5

What are eusocial insects?

Answer 5

Only the queen reproduces
Ex. bees, wasps, termites

Question 6

What is hermaphroditism? (Sequential vs simultaneous)

Answer 6

Individuals can be both male and female. Sequential - changes from one sex to another. Ex. Clownfish
Simultaneous - earthworms, sea slugs, hamlet fish

Question 7

What is parthenogenesis with ‘mating’?

Answer 7

Only females exist, they switch acting like males in order to start parthenogenesis

Question 8

What is internal fertilization?

Answer 8

Eggs are fertilized by sperm in the female reproductive tract. Requires behavioral interactions.

Question 9

What is external fertilization?

Answer 9

Eggs are fertilized by sperm in the external environment. Requires an aqueous environment and precise timing.

Question 10

What is cloaca?

Answer 10

A common opening between the external environment and the digestive, excretory, and reproductive systems.
In non-mammalian vertebrates (fish, amphibians, and reptiles)

Question 11

Describe the pathway of egg cell production, fertilization, and development. (Start where they are produced)

Answer 11

Egg cells are produced in the ovaries, fertilization occurs in the oviducts (fallopian tubes), the embryo develops in the uterus.
Human females have 3 openings

Question 12

Describe the pathway of sperm and semen cell production

Answer 12

Sperm are produced in seminiferous tubules in the testes, they are then propelled via the muscular vas deferens, and combine with additional fluid from the seminal vesicles, prostate, and bulbourethral glands to form semen during ejaculation

Question 13

In male mammals, excretory and reproductive systems share:
A) the testes.
B) the urethra.
C) the seminal vesicle.
D) the vas deferens.

Answer 13

B - the urethra

Question 14

What is spermatogenesis? What is oogenesis?

Answer 14

Spermatogenesis - production of small, motile sperm, occurs in seminiferous tubules of testes
Oogenesis - production of large eggs, occurs in ovaries

Question 15

What are the 3 main differences between oogenesis and spermatogenesis?

Answer 15

1) After meiosis, four cells develop into sperm while only one becomes an egg in oogenesis (polar bodies are discarded)
2) Spermatogenesis occurs throughout adolescence and adulthood; all primary oocytes are present at birth in females
3) Sperm are produced continuously without the prolonged interruptions in oogenesis

Question 16

Describe the process of oogenesis

Answer 16

Every month, a single primary oocyte is released from an egg follicle. One oocyte matures and is released into oviduct (ovulation), the ruptured follicle becomes a temporary corpus luteum (hormone gland)

Question 17

Describe what phases of meiosis an oocyte is in before fertilization

Answer 17

Immediately prior to ovulation, meiosis 1 completes and the secondary oocyte is arrested (paused) and metaphase 2
Only after fertilization, meiosis 2 completes
If no fertilization occurs, no meiosis 2 occurs

Question 18

Describe spermatogenesis

Answer 18

Testes have seminiferous tubules with primary spermatocytes (2n)
Secondary spermatocytes produced from meiosis 1 (n)
Spermatid and sperm cells produced from meiosis 2 (n)

Question 19

HPG axis (hypothalamus, pituitary gland, gonads) - What does the hypothalamus secrete in this cycle?

Answer 19

Hypothalamus secretes gonadotropin-releasing hormone (GnRH)

Question 20

HPG - What does the anterior pituitary gland secrete?

Answer 20

After receiving GnRH, the anterior pituitary gland secretes follicle stimulating hormone (FSH) and luteinizing hormone (LH)
Receptors for FSH and LH in the gonads trigger the release of sex hormones (androgens and estrogens); causes gametogenesis and mediate reproductive behaviors

Question 21

5 steps of female reproductive cycle

Answer 21

1) hypothalamus tells anterior pituitary gland (w/ GnRH) to release LH and FSH
2) LH and FSH increase, estradiol accumulates in bloodstream for about 12 days - tells follicle to mature
3) LH and estradiol spike - causes the secondary oocyte to be released (ovulation)
4) follicle becomes corpus luteum, hormones released from the ruptured site, estradiol and progesterone increases as released
5) causes uterine wall to swell up (endometrium)
If fertilization occurs, embryo will attach itself deep into the uterine wall, many blood vessels to feed it and increase development

Question 22

What is the difference between menstral and estrous cycles?

Answer 22

Menstral (humans and some non-human primates) - endometrium is shed from uterus in bleeding called mestration
Estrous (most mammals) - endometrium is reabsorbed by the uterus. Sexual receptivity is limited to a ‘heat’ period

Question 23

Describe the male reproductive hormone cycle

Answer 23

Hypothalamus secretes GnRH, which triggers the anterior pituitary gland to release LH and FSH, causing testes to produce testosterone which promotes spermatogenesis

Question 24

Which of the following is a true statement?
A) All mammals have menstrual cycles.
B) The endometrial lining is shed in menstrual cycles but reabsorbed in estrous cycles.
C) Estrous cycles are more frequent than menstrual cycles.
D) Estrous cycles are not controlled by hormones.

Answer 24

B

Question 25

What process happens directly after fertilization?

Answer 25

Meiosis 2 of the egg cell completes

Question 26

First trimester: Placenta and Organogenesis

Answer 26

Placenta forms - allows exchange of nutrients, gases, and waste between mother and embryo
Organogenesis - development of body organs, occurs at 8 weeks (then called a fetus)

Question 27

Second trimester: what happens?

Answer 27

The fetus grows and becomes active (mother can feel movement), uterus grows to accommodate body growth

Question 28

Third trimester: what happens?

Answer 28

At about 38 weeks, labor starts - the process by which childbirth occurs. Mediated by hormones