Lecture 8: Tetrapods

Question 1

What was the huge leap that allowed vertebrates to move to terrestrial habitats ?

Answer 1

walking on land

Question 2

What are the clades in the phylum vertebrata?

Question 3

What two key features of tetrapods allowed them to move onto land ?

Answer 3

1. Lungs (evolved from air sacs)
2. Limbs for supporting body and moving on land

Question 4

What clades are tetrapods included in?

Answer 4

gnathostome, Osteichthyes, lobe fin

Question 5

In a lineage of lobe-fins, the fins became progressively

Answer 5

limb-like

Question 6

One of the most significant events in vertebrate history was when?

Answer 6

fins of some lobe-fins evolved into the limbs and feet of tetrapods

Question 7

4 derived characteristics of tetrapods

Answer 7

1. four limbs, feet with digits
2. ears
3. neck
4. pelvic bones fused to vertebrate

Question 8

Two Major Clades of Tetrapods

Answer 8

amphibians and amniotes

Question 9

Amphibians

Answer 9

• frogs, salamanders, etc.
• strongly dependent on water
• moist, unprotected skin
• eggs without shells
• survived all 5 planet wide mass extinction events up to now

Question 10

Amniotes

Answer 10

• reptiles and mammals
• evolution of amniotic egg
• extra embryonic membranes (amnion, chorion, yolk sac, allantois)
• water impermeable skin
• rib cage to help ventilate the lungs for better respiration
• differentiated by skull structure

Question 11

what is the significance of the amniotic egg?

Answer 11

• it contains membranes that protect the embryo
• allowed total departure from an aquatic/wet environment

Question 12

Why do amniotes have better respiration?

Answer 12

• their lungs have greater surface area
• ribs have sturdy structure
• ability to develop negative pressure in thoracic cavity
• crocodiles and mammals have greater control on breathing due to muscular diaphragm

Question 13

different types of amniote eye characteristics

Answer 13

anapsid: no hole behind eye socket (turtles)
diapsids: 2 holes behind eye socket (remaining reptiles)
synapsids: 1 hole behind eye socket (mammals)

Question 14

Amniotes: Reptiles

Answer 14

• tuaturas, lizards, snakes, turtles, crocs, birds, extinct dinosaurs
• scales that create a waterproof barrier
• lay shelled eggs
• ectothermic: heat comes from external environment
• birds are the only exception

Question 15

Origin of birds

Answer 15

• feathered theropods evolved into birds
• Archaeopteryx is oldest bird known

Question 16

Birds (reptiles)

Answer 16

• archosaurs
• derived changes (feathers, light skeleton) facilitate flight
• don’t have lungs, instead have air sacs: this helps with airflow through parabronchi

Question 17

Amniotes: Mammals and their 4 derived characteristics

Answer 17

1. Mammary glands
2. hair
3. larger brain
4. differentiated teeth

Question 18

three clades of mammals

Answer 18

1. monotremes
2. marsupials
3. eutherians

Question 19

Monotremes

Answer 19

• small group of egg-laying mammals consisting of echidnas and platypus

Question 20

Marsupials

Answer 20

• opossums, kangaroos, and koalas
• embryo develops within a placenta
• marsupial is born very early into development
• completes embryonic development while nursing in a pouch called marsupium

Question 21

Eutherians

Answer 21

• longer period of pregnancy
• complete embryonic development within a uterus, joined to mother by placenta
• elephants, humans, tree sloth, whale