Lecture 21 Amphibians

Question 1

Describe Coelacanth (Actinistia) “a living fossil”

Answer 1

• thought to be extinct (65 mya)
• 1938 – found on South African trawler
• 1998 – 2nd species found in Indonesian fish market

Question 2

Describe Lungfish (Dipnoi)

Answer 2

• 6 species (Africa, SA, Aust)
• “walk” on lobe-fins
• tetrapod motion
• breathe through gills & primitive lungs
• estivate in mud during droughts

Question 3

Describe why tetrapoda move on land

Answer 3

• Devonian droughts (~400 mya)
• shallow inland seas, swamps, ponds
• low dissolved O2
• increased competition in water
• crowding in small pools
• new food resources on land (e.g., arthropods, plants)
• no vertebrate predators on land

Question 4

Describe differences btw living on land and water

Answer 4

• availability of water/moisture
• density of medium
• amount of oxygen
• stability of temperature
• amount of UV radiation

Question 5

Advantages of terrestrial respiration

Answer 5

• Air has higher concentration of oxygen than water.
• Gases diffuse faster in air than water

Question 6

Describe lung evolution

Answer 6

• Lobe-finned fishes
  – 2 ventral pockets formed off esophagus
  – used as a supplemental respiratory device

Question 7

4 problems on land

Answer 7

1. water needed to prevent desiccation
   * need to stay moist
   * most require water for fertilization & larval development
2. air is less dense than water
   * require stronger skeletal support, muscles
   * require more energy, more O2 brought in & distributed
3. air temperature is more variable
   * body temperature will fluctuate more
   * need to modify behavior or physiology
4. UV radiation more intense on land
   * need physical protection or change behavior

Question 8

What’s tetrapod solutions to air less dense than water

Answer 8

1. stronger limbs, vertebral column, ribs
2. more efficient circulatory system
   * 3+ chambered heart
   * double circuit of blood flow

Question 9

Describe early tetrapods (Icthyostega)

Answer 9

• Stronger limbs and girdles, vertebral column, ribs
• Tail used for balance, not swimming
• Lungs were primary respiratory organ
• External & internal nostrils (nares)

Question 10

Comparison of CS (circulatory system) in fish and amphibians

Answer 10

Question 11

Describe difference btw human and amphibian breathing mechanisms

Answer 11

1. Human uses negative pressure breathing
2. Amphibians use positive pressure

Question 12

Describe Amphibians

Answer 12

~ 6000 species
* first tetrapods
* freshwater & terrestrial
* dependent on water
* smooth, moist skin
* no scales
* glands
* carnivores
* teeth

Question 13

Describe two life stages of amphibians

Answer 13

• larvae
  – gills
  – 2-chambered heart
  – herbivorous
  – most undergo metamorphosis
• adults
  – lungs
  – 3-chambered heart
  – carnivores

Question 14

Describe Amphibian diversity (3)

Answer 14

• Salamanders (Urodela)
  – some have internal fertilization
  – some never leave water
• Frogs and toads (Anura)
  – has the most species
  – typically have loud courtship calls to females
• Caecilians
  – have lost appendages
  – internal fertilization

Question 15

Describe parental investment strategies

Answer 15

• 2 extreme strategies:
• produce billions of offspring, provide no care, hope some will survive
• produce 1 offspring, care for it until maturity (ex: humans)
• Most amphibians provide little parental care to their young. Depends on reproductive oddities