Animal Reproduction Flashcards
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
C - Bullfrog.
All others can reproduce via parthenogenesis
What is fission/fragmentation? (Type of asexual reproduction)
The separation of a parent into two or more individuals of about the same size.
Ex. Flatworms do this
What is budding? (Type of asexual reproduction)
When new individuals arise from outgrowths of existing ones.
Ex. Jellyfish do this
What is parthenogenesis? (Type of asexual reproduction)
Development of a new individual from an unfertilized egg
Ex. Female komodo dragon
What are eusocial insects?
Only the queen reproduces
Ex. bees, wasps, termites
What is hermaphroditism? (Sequential vs simultaneous)
Individuals can be both male and female. Sequential - changes from one sex to another. Ex. Clownfish
Simultaneous - earthworms, sea slugs, hamlet fish
What is parthenogenesis with ‘mating’?
Only females exist, they switch acting like males in order to start parthenogenesis
What is internal fertilization?
Eggs are fertilized by sperm in the female reproductive tract. Requires behavioral interactions.
What is external fertilization?
Eggs are fertilized by sperm in the external environment. Requires an aqueous environment and precise timing.
What is cloaca?
A common opening between the external environment and the digestive, excretory, and reproductive systems.
In non-mammalian vertebrates (fish, amphibians, and reptiles)
Describe the pathway of egg cell production, fertilization, and development. (Start where they are produced)
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
Describe the pathway of sperm and semen cell production
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
In male mammals, excretory and reproductive systems share:
A) the testes.
B) the urethra.
C) the seminal vesicle.
D) the vas deferens.
B - the urethra
What is spermatogenesis? What is oogenesis?
Spermatogenesis - production of small, motile sperm, occurs in seminiferous tubules of testes
Oogenesis - production of large eggs, occurs in ovaries
What are the 3 main differences between oogenesis and spermatogenesis?
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
Describe the process of oogenesis
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)
Describe what phases of meiosis an oocyte is in before fertilization
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
Describe spermatogenesis
Testes have seminiferous tubules with primary spermatocytes (2n)
Secondary spermatocytes produced from meiosis 1 (n)
Spermatid and sperm cells produced from meiosis 2 (n)
HPG axis (hypothalamus, pituitary gland, gonads) - What does the hypothalamus secrete in this cycle?
Hypothalamus secretes gonadotropin-releasing hormone (GnRH)
HPG - What does the anterior pituitary gland secrete?
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
5 steps of female reproductive cycle
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
What is the difference between menstral and estrous cycles?
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
Describe the male reproductive hormone cycle
Hypothalamus secretes GnRH, which triggers the anterior pituitary gland to release LH and FSH, causing testes to produce testosterone which promotes spermatogenesis
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.
B
What process happens directly after fertilization?
Meiosis 2 of the egg cell completes
First trimester: Placenta and Organogenesis
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)
Second trimester: what happens?
The fetus grows and becomes active (mother can feel movement), uterus grows to accommodate body growth
Third trimester: what happens?
At about 38 weeks, labor starts - the process by which childbirth occurs. Mediated by hormones
