Control Of Endocrine Section: The Vertebrate Pituitary

Question 1

What aspects of reproduction do physiologists study?

Answer 1

1) Control of the annual cycle of reproduction.
2) Functions of reproductive cells and organs.
3) Prenatal and postnatal resources.
4) Mate association
5) Control of the reproductive cycle by neural endocrine and neuroendocrine control.
6) Physiology and environmental relations of the young.

Question 2

Sperm+Egg: External Fertilization

Answer 2

▪ Eggs and sperm require a wet environment to survive.
External fertilization:
▪ In aquatic organisms such as fish and amphibians,
▪ Is a chance affair
▪ Odd are increased by:
▪ Releasing large numbers of gametes.
▪ Close contact to improve the chances that the
sperm will fertilize the eggs.

Question 3

Sperm+Egg: Internal Fertilization

Answer 3

• Fertilization that takes place inside the body of the female, is an adaptation for living on land.
• Reptiles, birds, and mammals all use internal fertilization.
• Oddsofconceptionarehigher
• Not exclusive to land dwellers.
• E.g. whales and dolphins
• Evolved from land ancestors

Question 4

Amniotic Eggs have four extraembryonic membranes
1) Amnion

Answer 4

– encloses the embryo in fluid
* Provides cushioning and an aqueous medium for growth

Question 5

Amniotic Eggs have four extraembryonic membranes
2) Allantois

Answer 5

– serves as a respiratory surface and a chamber to store nitrogenous (metabolic) wastes

Question 6

Amniotic Eggs have four extraembryonic membranes
3) Chorion

Answer 6

• surrounds entire contents of egg beneath shell

Question 7

Amniotic Eggs have four extraembryonic membranes
4) Yolk sac

Answer 7

– nutrient storage
* Forms a yolk-sac placenta in some species

Question 8

Amniota

Answer 8

• is the linage with this reproduction pattern (Donavan, reptiles, birds, mammals)

Question 9

Does the embryo develop internally or externally?

Answer 9

• Animals that are internally fertilized can lay eggs, called oviparity (“egg birth”).
• fish and amphibians, reptiles, birds, and most insects.
• nutrients for the developing embryo come from the yolk.

Question 10

Viviparity

Answer 10

• Other animals give birth to live young

Question 11

Oviparity

Answer 11

• The embryo develops inside the mother, and nutrients are obtained directly from the mother.

Question 12

Ovoviviparous

Answer 12

• Eggs hatch internally and then are born live

Question 13

R-Strategists (External)

Answer 13

• Organisms that produce large numbers of offspring without a lot of parental investment.

Question 14

K-Strategists (Internal)

Answer 14

• Those that produce few offspring but put in a lot of parental investment.

Question 15

Mammalian

Answer 15

Mammalia has 29 orders –
1 of monotremes (Prototheria) 7 of marsupials (Methatheria) 21 of placentals (Eutheria)

Question 16

Monotremes

Answer 16

*Oviparous (lay eggs)
* Embryos develop for 10 to 12 days in the uterus
* Thin, leathery shell is secreted around the embryo before the eggs are laid
* Eggs are laid in burrow and incubated for 12 days
* After hatching, young nourished by milk lapped off mother’s fur near mammary glands (no nipples in monotremes)

Question 17

Marsupials

Answer 17

• Pouched, viviparous mammals
• Embryo is encapsulated by shell membranes
  and floats free in uterine fluid for several days
• Embryo “hatches” from shell membranes and erodes shallow depression in uterine wall; here absorbs nutrient secretions from yolk sac
• Gestation is brief; give birth to tiny young that are still embryos
• Prolonged lactation period with maternal care

Question 18

Placentals

Answer 18

• Placentals (eutherians – “true” “wild animals”) are viviparous
• Long gestation period
  Gestation tends to be longer with larger size
• Condition at birth varies
• Precocial young (furred and ready to run) to altricial (blind naked and helpless) young