Topic 29 Tetrapods

Question 1

Lobe-fins have

Answer 1

fleshy, muscular pectoral, and pelvic

fins supported by bony elements

Question 2

Tetrapods

Answer 2

• the third surviving lobe-fin lineage.

- vertebrates with two pairs of sturdy, skeleton-supporting limbs with feet and digits

Question 3

One of the most significant events

in vertebrate history

Answer 3

when fins of some lobe-fins evolved into

limbs and feet of tetrapods

Question 4

tetrapods include

Answer 4

amphibians, reptiles, and mammals

Question 5

three-parted tetrapod limbs

Answer 5

1. Upper, single long bone hinged to;
2. A pair of parallel long bones;
3. Terminal hand/foot with jointed digits

Question 6

Why did vertebrates transition to life on land?

Answer 6

Competition and predation in aquatic ecosystems. Escape aquatic predators; few
terrestrial competitors.

Question 7

Tetrapods evolved ___ for life on land

Answer 7

• Waterproofing of skin.
  − Internal gas exchange systems.
  − Reproduction independent of water.
  − Strong endoskeletons to support body weight and enable movement on land

Question 8

Early land problems for moving onto land

Answer 8

gravity, desiccation (need a protective skin from drying out), respiration (before absorbing gases from water using gills), reproduction by throwing gametes into the water, swimming locomotion, senses (water transmits smells differently), temperature fluctuations in air

Question 9

Transitional tetrapods had

Answer 9

legs and both lungs and gills, but were still primarily aquatic and unsuited to life on land because: limbs were too weak to support body weight, ribs too sort and lungs would get crushed under body weight, fishy tail would get damaged from friction on ground

Question 10

Traits critical to the move to land that evolved prior to tetrapods exiting in water

Answer 10

• Vertebral column (backbone) (clade Vertebrata).
  − Mineralization of skeleton; two pairs of lateral appendages (clade Gnathostomes).
  − Simple lungs (clade Osteichthyans): outgrowths of the gut, forming gasfilled cavities above the digestive tract
• Bony, muscular pectoral/pelvic fins (clade lobe-fins).
  − Internal nostrils (early aquatic tetrapods): opening from the nasal sac into the roof of the mouth.

Question 11

Tiktaalik

Answer 11

• shows both fish and tetrapod characteristics
• fish features: scales, lobe fins without digits
• tetrapod features: neck, ribs, limb skeleton, flat skull, eyes on top of the
  head

Question 12

Tiktaalik neck

Answer 12

Shoulder (pectoral girdle) not fused to skull Allows tetrapod to move head independently of body

Question 13

Tiktaalik Loss of the operculum (but gills present) also contributed to

Answer 13

mobility of the neck

Question 14

Tiktaalik fingers

Answer 14

• Shoulder, elbow, proto-wrist joints, but
  fish-like fins instead of digits
• likely could not walk

Question 15

Tiktaalik pelvis

Answer 15

shape and size of the hip socket (pelvis) reveal that fins were capable of a wide range of movements
still fish-like (only one bone and not attached to the vertebral column)

Question 16

Tetrapod limbs evolved for _____, and only later became weight-bearing limbs on land

Answer 16

use in water

Question 17

Two gorups of tetrapods

Answer 17

amphibia and amniota

Question 18

SHared derived traits fo tertapods

Answer 18

1. Four limbs with feet with digits.
2. A neck, which allows separate movement of the head.
3. Fusion of the pelvic girdle to the backbone.
4. Absence of gills (except for some aquatic species).
5. Ears for detecting airborne sounds