Topic 19: Tetrapod Evolution

Question 1

Internal nostrils (the opening from the __ __ into the roof of the mouth) were the first component of the tetrapod body plan to ___

Answer 1

nasal sac

evolve (well before the origin of limbs!!)

Question 2

What’s the origin of internal nostrils?

They evolved ____ in 2 lineages (__ and ____)

Answer 2

Origin: displacement of posterior external nostrils
independently: (lungfish and tetrapods)

Question 3

T/F

Fish-tetrapod transition is an example of decent with modification

Answer 3

true

Question 4

____ are limbs with digits & joints which allowed vertebrates to move onto land

Answer 4

lobe-fins

Question 5

Why transition to life on land?

List and explain 5 reasons

Answer 5

1. Continental drift: coastal regions became land-locked
2. Plants beginning to colonize land= forests
3. Arthropods & other vertebrates colonizing land = lots of food!
4. Most predators still aquatic, fewer competitors on land
5. New niches!

Question 6

List 6 challenges of terrestrial life for organisms adapted to aquatic life

Answer 6

1. gravity
2. desiccation
3. respiration
4. reproduction
5. locomotion
6. temperature

Gravy Does Require Reversing Low Times

Question 7

Why was gravity a challenge of terrestrial life for organisms adapted to aquatic life?

Answer 7

aquatic life is buoyed by water, air is not buoyant!

-so, terrestrial animals need some sort of supporting tissue

Question 8

Why was desiccation a challenge of terrestrial life for organisms adapted to aquatic life?

Answer 8

air is dryer than water, so terrestrial organisms need some form of skin/ coat to keep all their bodily fluids from leaking out ad to protect the embryo

Question 9

Why was respiration a challenge of terrestrial life for organisms adapted to aquatic life?

Answer 9

aquatic organisms exchange oxygen & CO2 dissolved in water
-In air, these substances are gases, so new structures are needed to breathe

Question 10

Why was reproduction a challenge of terrestrial life for organisms adapted to aquatic life?

Answer 10

aquatic organisms often release their eggs/ sperm into the water directly.
This is much less effective in air, so other solutions evolve

Question 11

Why was gravity a locomotion of terrestrial life for organisms adapted to aquatic life?

Answer 11

aquatic animals can swim/ otherwise move through the water

- these motions had to be modified to live on land

Question 12

Why was gravity a temperature of terrestrial life for organisms adapted to aquatic life?

Answer 12

• temp fluctuates more in air than water

- terrestrial animals have to evolve adaptations to deal with these fluctuations –> HOMEOSTASIS

Question 13

The _____ is an intermediate between fishes and tetrapods.

• what are its fishy features?
• what are its tetrapod features?

Answer 13

tiktaalik

• scales, fins without digits, gills + lungs
• neck, ribs, fins w/ skeleton, eyes on top of head

Question 14

Evolution of the pelvic girdle:

Explain the difference between early tetrapod vs. lob-finned fish pelvis

Answer 14

• Tetrapod: pelvis consists of 3 bones, attached to the vertebrae (provides structural support through whole body)
• Fish: single, small pelvis, not attached to vertebrae

note: Tiktaalik pelvis still fish-like

Question 15

Terrestrial vertebrates descended from ancestors with ___ digits

Answer 15

5+

Question 16

List the primitve and derived traits of early amphibians (ichthyostega)

Answer 16

primitive: gills, lateral lines
derived: limbs attached to vertebrae, weight bearing joints (eg elbow, wrist, knee, ankle)

Question 17

List primary & derived traits of the early tetrapod (acanthostega)

Answer 17

primitive: gills, lateral lines, long fin rays around tail
- no true joints like knees (not weight-bearing)

derived: 4 limbs with bony digits, pelvis weakly attached to vertebrae

Question 18

Order of evolution of tetrapods

Answer 18

1. lobe-finned fish
2. tiktaalik
3. acanthostega (early amphibian/ tetrapod)
4. ichthyostega (early amphibian/ tetrapod)

Question 19

T/F

Class amphibia are a paraphyletic group

Answer 19

False

Amphibia are monophyletic

Question 20

Amphibians have thin, ___ skin (site of ___ _____)

-How do amphibians inflate their lungs?

Answer 20

permeable, gas exchange

- Buccal pump (not very efficient)

Question 21

What challenges of terrestrial life have amphibia solved/ not solved?

Answer 21

solved: gravity, respiration, locomotion

not solved: desiccation, reproduction, temp regulation

Question 22

Amphibians use external/ internal fertilization

Answer 22

external –> aquatic feature retained, they need water!

- the eggs lack shells and are subject to desiccation

Question 23

In amphibians, order ____ includes frogs and toads, which have hind legs modified for ____
- They lack a tail in their ___stage, and they lack legs in early ___stage

Answer 23

Anura, jumping

adult, larval

Question 24

• Order Urodela includes ___ and ____
• They are ___ of invertebrates
• Some Urodela remain ____, some become ____ but need a damp environment to keep skin moist
• Urodela walk side-to-side, meaning their legs are set ___.

Answer 24

salamanders and newts
predators
aquatic, terrestrial
laterally

Question 25

Order Apoda (caecilians) have no ___(secondary adaptation); they are ___

Answer 25

legs

burrowers