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
• Reproductive System Ovaries vs. testes: Development affected by hormones Development influenced by temperature Potential to be male OR female present in most amphibiansFat bodies associated with gonads, supplies energy
Ovaries Produce from 1 to thousands of ocytes at a time under influence of pituitary, squeeze out into peritoneal cavity.TestesLocated near kidneys, produce sperm under pituitary influenceRudimentary ovary often nearby
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
Amphibian Urogenital Tract Mating / fertilization Embryo development Parental investment Sexes of population Breeding seasons and habitats
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
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
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 .
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
Sexes of Population Most are bisexual2. 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
Embryo Development Most reptiles are oviparous Eggs larger and more easily hidden in terrestrial environment so can have fewer eggs than amphibiansSome lizards and snakes are ovoviviparous or viviparous
Length varies by temperature1. Sex of offspring dependent on incubation temperature of clutch in many reptiles.Pivotal temperature= produces 50% of each sexTurtles: males below the PTLizards: females below the PTCrocodilians: two PTs, males in between the two
The three living groups of mammals vary in their methods of reproduction Placental Mammals, like the cat, are viviparousViviparity, 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.
Monotremes – are the most primitive living mammals. They have retained the reptilian oviparous method of reproduction and lay shelled eggs.
Marsupials - undergo a distorted version of viviparity. They give birth to underdeveloped live young. When the young are born, they make their own wayto the permanent brood pouch, or marsupium .Development of the young is completed in the pouch.