Amphibians

Question 1

What is an amphibian?

Answer 1

Amphibians are tetrapod vertebrates with a non-scaly, glandular skin, an unshelled
egg, and a life cycle that involves three stages: egg, larva and adult.

The larval stage (represented by
the tadpole in frogs) changes to the adult stage by a process called metamorphosis, which involves
fundamental structural changes to the animal.

Question 2

Why is the larvae stage dependent on aquatic environments?

Answer 2

larval stages are

subject to desiccation and hence are tied to aquatic environments in a variety of ways.

Question 3

The Lissamphibia are represented by three modern sublineages:

Answer 3

1. Order Apoda: caecilians, limbless burrowing or aquatic amphibians that are
   found in the tropics but are not present in Australia.
2. Order Urodela: salamanders and newts. No native Australian species, but the axolotl is
   widely available in the pet trade, and there are established populations of the European smooth
   newt around Melbourne.
3. Order Anura: frogs and toads. The largest order of living amphibians, with 6623
   species, distributed in 56 families.

Question 4

5 families of frogs and toads in Australia

Answer 4

1. 1. Family Bufonidae (true toads): represented by the introduced Cane Toad . An example of attempted biological control gone very wrong
2. Family Ranidae (true frogs): widespread and diverse elsewhere in the world, and the source of
   legs for human consumption, only one species occurs in Australia, the Wood Frog of Cape York and adjacent parts of Arnhem Land.
3. Family Microhylidae: Again, widely distributed outside Australia, but the Australian microhylid
   fauna is limited to 23 species in two genera, confined to northeast Queensland and northeast
   Arnhem Land.
4. Family Pelodryadidae (tree frogs): the Australian
   tree frogs consist of 87 species
5. Families Limnodynastidae:
   ground frogs.

Question 5

How to distinguish between tree frogs and ground frogs?

Answer 5

Most but not all tree frogs have expanded pads on the terminal ends of fingers and toes, which
are absent in the two ground frog families.

Where the digital pads are absent, they can still be differentiated by the persistence of a small cartilage between the last two bones in each digit, which is absent in the ground frog families.

Question 6

Threats to frog populations

Answer 6

Drought, changes in water quality and flow, increased UV irradiation,
introduced predators (particularly fish and aquatic invertebrates of eggs and tadpoles), and disease

Question 7

General anatomy of a frog

Answer 7

The vertebral column is short (8 vertebrae plus a sacrum),
there are consistently four fingers and five toes, and little obvious difference in most of the body
systems across the families.

Question 8

Female reproductive system of frog

Answer 8

the female has paired ovaries which are saccular and contain a central closed cavity containing lymph.

Each mature ovary
produces eggs from its surface.

At greatest development, the ovaries may fill much of the body cavity.

The released eggs are collected by coiled oviducts, and the eggs transported to the cloaca, the common terminal end of the digestive, urinary and reproductive system.