Lecture 18: Amphibians

Question 1

lung fish

Answer 1

lobe finned fish

• “walk” on lobe fins (first tetrapod movement)
• breath thru gills as well as primitive lungs
• estivated in mud during drought

Question 2

Why move on land?

Answer 2

• Devonian drought (low dissolved O2)
• increased competition in water
• new food resources on land
• no vertebrate predators on land

Question 3

Advantages on land

Answer 3

• more O2

- easier for gases to diffuse

Question 4

Lung Evolution

Answer 4

1. Lobe finned fishes

- 2 ventral pockets formed off esophagus

Question 5

Problem on land: air density is less than water

Answer 5

• this created the need for strong skeletal support
Solution:
- tetrapods used tail for balance, not swimming
- lungs were the primary respiratory organ
- has external and internal nostrils
• need more energy brought in
Solution:
- more efficient circulatory system (3 chambered heart, double circuit flow)
- advantage was that the blood was higher in pressure, but disadvantage was that the blood was mixed which reduces the efficiency

Question 6

mechanisms of breathing

Answer 6

involves changes in thoracic cavity

- gases move from high pressure to low pressure

Question 7

Negative breathing

Answer 7

• diaphragm relaxes (curves), volume decreases, pressure increases: EXALE
• diaphragm contracts (flattens), volume increases, pressure decreases: INHALE

Question 8

Positive breathing

Answer 8

• Inhalation is a 2 stroke process

• air enters through the nostrils (mouth and glottis remain closed)
• glottis opens, air is forced into lungs

Question 9

Amphibians

Answer 9

• first tetrapods
• dependent on water
• smooth, moist skin

Question 10

Metamorphosis of Amphibians

Answer 10

• egg and sperm make tadpoles in water, tadpoles form and will appear on land
• little parental care

Question 11

Stages in Life: Amphibians

Answer 11

•Larvae:

• gills
• 2 chambered heart
• herbivores

•Adults:

• lungs
• 3 chambered heart
• carnivores

Question 12

Salamanders

Answer 12

• some have internal fertilization
• never leave the water
• some places they are highly poisonous (depending on how resistant the snakes are)

Question 13

Frogs & Tadpoles

Answer 13

• largest group
• have loud courtship calls to females
• some carry tadpoles on back

Question 14

Cacsilians

Answer 14

• lost appendages due to burrowing in group
• worm like
• eat dead skin off mother for nutrition