Study #4: Test 3: Amphibians

Question 1

Major challenges to colonizing land:

Answer 1

1. O2 higher in concentration but not easy to diffuse solved by lungs with moist surface;
2. Locomotion in higher gravity solved by lobe-fins or limbs with muscles
3. Temperature regulation harder
4. Dessication
5. Habitat diversity

Question 2

Alfred Romer Hypothesis

Answer 2

1. Unstable environment 400 MYA led to freshwater habitats alternating between floods and droughts
2. Freshwater fish had to adapt by finding new places to live, which led to evolution of limbs and lungs
3. Fish that could “walk” and “breathe” survived to reproduce

Question 3

New Fossil evidence

Answer 3

Tetrapods already had limbs, for underwater locomotion, and then moved to land

Question 4

Tetrapods (4 feet)

Answer 4

amphibians
reptiles
birds
mammals

Question 5

Sarcopterygians (lobe-finned fishes)

Answer 5

Early in transition stages between fish and tetrapods

Question 6

Tiktaalik (fossil freshwater fish) (considered missing link bet fish and walking land creatures)

Answer 6

Canadian Arctic

Had fins, gills, scales but also had tetrapod forelimb skeletal homologies

Question 7

Homeotic genes or Hox genes

Answer 7

Role in determining identity and location of body structures.
Small gene changes have large effects

Question 8

Fin to Limb Transition

Answer 8

LOOK AT SLIDE 6

Question 9

Fin: Limb #1

Answer 9

Skull/Clavicle/Cleithrum connect to humerus in fish: humerus in land animals

Question 10

Fin: Limb #2

Answer 10

Ulna/radius in fish: ulna/radius in land animals

Question 11

Fin: Limb #3

Answer 11

Ulnare/Intermedium in fish: carpals in land animals

Question 12

Fin: Limb #4

Answer 12

Dermal fin rays in fish: phalanges in land animals

Question 13

Traits of Early Tetrapods (based upon fossil record)

Answer 13

1. Polydactylous
2. Double circulation: systemic & pulmonary
3. Fleshy fins used as paddles to navigate land; evolved into jointed appendages
4. Stronger backbones
5. pectoral and pelvic girdle
6. muscles to hold up head
7. Internal nostrils

Question 14

Amphibian ancestral condition

Answer 14

1. Eggs hatch in water
2. Water larval stage uses gills to breathe
3. Larvae metamorphasize: lose gills and grow lungs
4. adult form adapted to land

Question 15

Traits of Modern Amphibians

Answer 15

1. Adapt to be able to live in and out of water
2. No scales, moist skin for gas exchange
3. Small, light skull, vertebral column, and pelvic girdle for support
4. muscular jaws
5. Seperate pulmonary (lung) and systemic circuits.
6. Osmotic like fishes
7. Ectotherms
   8 Senses: chemoreception, vision to find food, auditory to find mate all well developed

Question 16

Order Gymnophiona: Caecilians

Answer 16

Most burrow
Feed on Worms
Retractile tentacle bet eyes and nose for smelling
Almost blind, with skin over eyes
Internal fertilization

Question 17

Order Caudata: Salamanders

Answer 17

Tail
Unspecialized legs
Live in Moist forest floor litter
Internal fertilization, aquatic larvae
complete or incomplete metamorphasis

Question 18

Order Anura: Frogs & Toads

Answer 18

No tails or caudal vertebrae in adults
Long, muscular back legs
external fertilization
Moist habitats

Question 19

Amphibians in Peril

Answer 19

Highly threatened w/ extinction
Think skin so vulnerable to pollution
Dessication due to loss of habitat, climate change
Major culprit: chytrid fungus (infects and ulcerates skin)