Sheri - Animal Reproduction

Question 1

What are Androgens and the most important 2 Androgens.

Answer 1

Androgens: Masculinising compounds
* Most important natural androgens are
testosterone (T) and dihydrotestosterone
(DHT)

Question 2

What is the main natural oestrogen and how is it produced?

Answer 2

Main natural estrogen is estradiol-17b
* Produced from testosterone in presence
of aromatase

Question 3

What does Oviparous mean and give examples?

Answer 3

Oviparous – animals that lay eggs.
* Most invertebrates, most amphibians, reptiles, birds
and monotremes.

Question 4

What does Ovoviviparous mean and give examples?

Answer 4

Ovoviviparous – animals that retain the eggs within their bodies. Nourishment comes from the yolk sac.
* Some annelids, some insects, some fishes, some
reptiles.

Question 5

What does viviparous mean and give examples?

Answer 5

Viviparous – eggs develop in oviduct or uterus, nourishment from mother.
* Mammals, some sharks, few invertebrates, few
reptiles and few amphibians

Question 6

Define and describe the process of vitellogenesis, including its hormonal regulation in amniotic vertebrates. In which sex, and in what type of
amniotes is vitellogenesis normally seen?

Answer 6

Vitellogenesis is a process typically seen in female amniotes, specifically in oviparous species such as reptiles and birds.
The oocyte through the help of the granulosa and thecal cells are producing estradiol-17B which goes out into the bloodstream and is absorbed by the liver which signals the liver to produce vitellogenin (the yolk precursor) that is absorbed into the bloodstream and back into the oocyte to be transformed into yolk. It starts as yolk globules then eventually all runs into each other til it is full of yolk.