Amphibia

Question 1

Where do Amphibia lie in the Sarcopterygians?

Answer 1

Question 2

What are sauropsids?

Answer 2

Reptiles and Birds

Question 3

What are synapsids?

Answer 3

Mammals and extinct reptiles

Question 4

What are the Sarcopterygians?

Answer 4

Lobe finned fish

Question 5

What are the Lissamphibia?

Answer 5

Extant amphibia

Question 6

Lissamphibia features?

Answer 6

• Permeable skin:
  Extensive vascularisation used in gas exchange. Smooth muscus covers the thick skin which has dermal glands. Water and active salt uptake through the skin.
• Wide variety of body forms
• Diverse reproductive strategies
• Carnivorous feeding
• Many habitats but never back in the sea

Question 7

Development in Lissamphibia?

Answer 7

Many have an aquatic early development stage - tadpole. Thought to be the original pattern.

Eggs are laid in water by the female and fertilised by the attending male as they are being laid.

Tadpoles feed on algae, then insects. Grows and develops gills, hind legs, lungs, forelegs. The tail regresses.

The froglet becomes terrestrial, but returns to water to breed several years later.

Complete metamorphis - controlled by thyroid glands.

Question 8

Describe the skin in lissamphibians?

Answer 8

Epidermis is soft with local horny regions. The dermis contains numerous glands.

Chromatophores expand to change the skin colour. Epidermal cells may contain keratin as a horny protection.

Question 9

What can chromatophores be used for?

Answer 9

Camouflage - Peron’s tree frog

OR

Highly conspicuous warnings - Dendrobates azureus

Question 10

What glands are there in Lissamphibia?

Answer 10

1. Mucus glands secrete mucus to cover the skin
2. Poison glands secrete alkaloids under active control. Includes batrachotoxin (fatal to humans). Powerful poisons are often associated with special colours and defensive behaviours.

Question 11

How does gas exchange occur in Lissamphibia?

Answer 11

Amphibian lungs are relatively small - made of simple sacs with a few septa to increase the blood to air exchange area.

Aquatic salamanders have external gills as well.

Skin is richly vascularised and important in gas exchange.

Exchange through the lungs and skin of a toad in air depends on the temperature. At low temperatures, more exchange occurs via skin than via lungs. At higher temperatures, the lungs become more important for O2, but skin remains most important for CO2. In winter, a toad relies almost completely on exchange through the skin.

Question 12

What must an amphibian eye accomodate?

Answer 12

Both air and water. Both have different refractive indexes.

Question 13

What are the three Lissamphibia orders?

Answer 13

1. Urodela/Salamanders
2. Anura/ Frogs + Toads
3. Caecilians

Question 14

Describe Urodela?

Answer 14

All have long tails - used for swimming and walking. Least derived. Northern hemisphere. Range from 50mm to 1.5m
Most are only aquatic for breeding season.
Walking is accompanied by considerable bending of the body, which increases the effective arc swing of the legs.
Courtship - male directly transfers pheremones to female. Fertilisation in oviduct and zygotes/embryos may be retained.

Question 15

Describe Anura?

Answer 15

Lack tails. 10mm-30cm. Hind legs are long with shock absorbing shoulders. Less acceleration is needed in legs for jumps due to the zig zag shape which extends.

Frogsicles - can cope with sub zero conditions by producing specialised glycoproteins.

Acoustic communication. Shows male fitness as takes lots of energy to produce the noises. Songs are species specific.

External fertilisation with parental care. Males protect eggs.

Adhesive toe pads for climbing.

Question 16

Describe Caecilians?

Answer 16

Lack legs and are specialised burrowers. Inhabit soil and water in wet tropics.

Small weak eyes and no ears.

Long cylindrical trunk with concertina burrowing.

Internal reproduction.

Question 17

Advantages of amphibians having aquatic larvae?

Answer 17

Gives a terrestrial species access to resources that would not otherwise be available to it. Avoids competition between parent and offspring for resources.

Question 18

Costs of Anuran vocalisation?

Answer 18

Costs:

1. Risk of predation
   (Male tungara frog only produces certain noises when lots of competition with males as the risk of predation by bats is higher. The females prefer these noises but no point making them when there’s no competition)
2. Energy that goes into call production is large