Topic 19: Tetrapod Evolution Flashcards
Internal nostrils (the opening from the __ __ into the roof of the mouth) were the first component of the tetrapod body plan to ___
nasal sac
evolve (well before the origin of limbs!!)
What’s the origin of internal nostrils?
They evolved ____ in 2 lineages (__ and ____)
Origin: displacement of posterior external nostrils
independently: (lungfish and tetrapods)
T/F
Fish-tetrapod transition is an example of decent with modification
true
____ are limbs with digits & joints which allowed vertebrates to move onto land
lobe-fins
Why transition to life on land?
List and explain 5 reasons
- Continental drift: coastal regions became land-locked
- Plants beginning to colonize land= forests
- Arthropods & other vertebrates colonizing land = lots of food!
- Most predators still aquatic, fewer competitors on land
- New niches!
List 6 challenges of terrestrial life for organisms adapted to aquatic life
- gravity
- desiccation
- respiration
- reproduction
- locomotion
- temperature
Gravy Does Require Reversing Low Times
Why was gravity a challenge of terrestrial life for organisms adapted to aquatic life?
aquatic life is buoyed by water, air is not buoyant!
-so, terrestrial animals need some sort of supporting tissue
Why was desiccation a challenge of terrestrial life for organisms adapted to aquatic life?
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
Why was respiration a challenge of terrestrial life for organisms adapted to aquatic life?
aquatic organisms exchange oxygen & CO2 dissolved in water
-In air, these substances are gases, so new structures are needed to breathe
Why was reproduction a challenge of terrestrial life for organisms adapted to aquatic life?
aquatic organisms often release their eggs/ sperm into the water directly.
This is much less effective in air, so other solutions evolve
Why was gravity a locomotion of terrestrial life for organisms adapted to aquatic life?
aquatic animals can swim/ otherwise move through the water
- these motions had to be modified to live on land
Why was gravity a temperature of terrestrial life for organisms adapted to aquatic life?
- temp fluctuates more in air than water
- terrestrial animals have to evolve adaptations to deal with these fluctuations –> HOMEOSTASIS
The _____ is an intermediate between fishes and tetrapods.
- what are its fishy features?
- what are its tetrapod features?
tiktaalik
- scales, fins without digits, gills + lungs
- neck, ribs, fins w/ skeleton, eyes on top of head
Evolution of the pelvic girdle:
Explain the difference between early tetrapod vs. lob-finned fish pelvis
- 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
Terrestrial vertebrates descended from ancestors with ___ digits
5+
List the primitve and derived traits of early amphibians (ichthyostega)
primitive: gills, lateral lines
derived: limbs attached to vertebrae, weight bearing joints (eg elbow, wrist, knee, ankle)
List primary & derived traits of the early tetrapod (acanthostega)
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
Order of evolution of tetrapods
- lobe-finned fish
- tiktaalik
- acanthostega (early amphibian/ tetrapod)
- ichthyostega (early amphibian/ tetrapod)
T/F
Class amphibia are a paraphyletic group
False
Amphibia are monophyletic
Amphibians have thin, ___ skin (site of ___ _____)
-How do amphibians inflate their lungs?
permeable, gas exchange
- Buccal pump (not very efficient)
What challenges of terrestrial life have amphibia solved/ not solved?
solved: gravity, respiration, locomotion
not solved: desiccation, reproduction, temp regulation
Amphibians use external/ internal fertilization
external –> aquatic feature retained, they need water!
- the eggs lack shells and are subject to desiccation
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
Anura, jumping
adult, larval
- 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 ___.
salamanders and newts
predators
aquatic, terrestrial
laterally
Order Apoda (caecilians) have no ___(secondary adaptation); they are ___
legs
burrowers
