This document summarizes amphibian and reptile reproduction. It discusses that amphibians lay anamniotic eggs that require moisture, while reptiles lay amniotic eggs with shells that are resistant to drying. It also describes that amphibians can be influenced by temperature to develop as male or female, and may use internal or external fertilization depending on the species. For reptiles, it notes they generally have internal fertilization and produce shelled eggs with specific embryonic structures. It also discusses sex determination and various reproductive strategies among different groups of mammals.

1. Amphibian Reproduction

2.  Anamniotic eggs – no shell, require moisture,
produce larval form – amphibians
 Amniotic eggs – have shell and embryonic
membranes, resistant to drying out, protect
embryo, stores wastes, produce adult form -
reptiles

3. •
Reproductive System
 Ovaries vs. testes:
 Development affected by hormones
 Development influenced by temperature
Potential to be male OR female present in most
amphibians
Fat bodies associated with gonads, supplies energy

4.  Ovaries
Produce from 1 to thousands of ocytes at a time under
influence of pituitary, squeeze out into peritoneal
cavity.
Testes
Located near kidneys, produce sperm under pituitary
influence
Rudimentary ovary often nearby

5.  Female ducts –
 Oviduct covers egg with jellylike material
 Oviduct and ureter may be united through much of
length
 Male ducts
 Mesonephric ducts carry both sperm and excretory
wastes

6. Amphibian Urogenital Tract
 Mating / fertilization
 Embryo development
 Parental investment
 Sexes of population
 Breeding seasons and habitats

7. Amphibian Mating/Fertilization
 External fertilization
 Sperm fertilizes egg outside of female’s body
 Eggs / sperm laid at same time
 Amplexus used in anurans
 Found in all anurans except tailed frog
 Found in primitive salamander families

8. Amphibian Mating/Fertilization
 Internal fertilization - Spermatophore = packet
with pedestal and sperm bubble deposited by male,
picked up by female – advanced salamanders
Cloacal kiss = press cloacas together for sperm
transfer – some salamanders

9. Egg laying
 Oviparous species
 1 to 25,000 laid – species dependent
 Laid singly, in clusters, in strands –
species dependent
Laid in a variety of moist environments –
species dependent .

10. Reptile Reproductive
System

11.  Gonads -
 Paired, in abdominal cavity
 Snakes/legless lizards: one gonad anterior,
one posterior
 Snakes/lizards: gonads are sacs with lymph
cavities
 Turtles/crocs/tuatara: gonads are solid structures
Fewer Graafian follicles at a time than in amphibians

12. Reptile Egg Structure
1. Embryo
2. Amnion= cushion membrane
3. Yolk sac= nutrition
4. Allantois= waste sac
5. Chorion= membrane immediately inside
shell

13. Sexes of Population
 Most are bisexual
2. A number of lizard species have parthenogenetic
populations or whole species.
 Some parthonogenetic females mate with males of
related species, result is triploid sterile offspring

14. Embryo Development
Most reptiles are oviparous
Eggs larger and more easily hidden in
terrestrial environment so can have
fewer eggs than amphibians
Some lizards and snakes are ovoviviparous
or viviparous

15. Length varies by temperature
1. Sex of offspring dependent on incubation
temperature of clutch in many reptiles.
Pivotal temperature= produces 50% of each
sex
Turtles: males below the PT
Lizards: females below the PT
Crocodilians: two PTs, males in between the
two

16. Methods of Reproduction
in Mammals

17. The three living groups of
mammals vary in their methods of
reproduction
 Placental Mammals, like the cat, are viviparous
Viviparity, or birth of live young, has independently evolved
more than one hundred times in vertebrates However,
many vertebrates retain the shelled egg laying method of
giving birth due to the nutrients provided by the shell and
passed to the embyo.

18.  Monotremes –
 are the most primitive living mammals.
They have retained the reptilian oviparous
method of reproduction and lay shelled
eggs.

19.  Marsupials - undergo a distorted
version of viviparity. They give birth to
underdeveloped live young. When the
young are born, they make their own way
to the permanent brood pouch, or
marsupium .Development of the young is
completed in the pouch.