Hot and Cold Bloodedness

Question 1

What are Tetrapod’s

Answer 1

4 legged animals - reptiles, amphibians, birds and mammals

Question 2

Is the the Tiktaalik

Answer 2

It is an intermediate form between fish and tetrapod’s which was found at Ellesmere
It is an extinct genus of lobe-finned fish of the Late Devonian age
It is an example of a missing link

Question 3

When did the Tiktaalik exist in time

Answer 3

around 375Ma

Question 4

Why is the Tiktaalik thought to be an intermediate between fish and tetrapods

Answer 4

Tiktaalik exhibits many features similiar to those of four-legged animals
Tiktaalik, and other lobe-finned fish, developed adaptations to oxgyen-poor, shallow water environments. These stressed settings are therefore thought to have led to the evolution of tetrapods by moving onto land
They are suspected to be the first species which developed lungs

Question 5

What is the link between bony fish and their swim bladders in evolution

Answer 5

Bony fish, which are common within sea today, gained lungs through evolution, then reinvaded the sea and these lungs evolved into swim bladded - allowing for buoyancy

Question 6

Why it suspected that the Tiktaalik gained these lobe-shaped fins, which evolved into limbs

Answer 6

A hybrid fin allow movement on the floor and in shallow waters

Question 7

What organism is suggested to be the next evolutionary stage closer to tetrapods, from Tiktaalik

Answer 7

Icthyostega
An early tetrapod with lungs and libs, eating the early land plants
Though still had a fish like tail - hence suggested to have evolved from Tiktaalik

Question 8

After Icthyostega, what was the next evolutionary characteristic that occured

Answer 8

Anamniotes laied eggs in water and gained 4 proper legs
Now all modern tetrapods lay eggs in water
Towards the end of the carbonferous, these types of creatures started to develop closely to the modern amphibians and reptiles

Question 9

During the Paleozoic, which time period came after the Carboniferous

Answer 9

Permian (299-252Mya)

Question 10

The Edaphosaurus was a herbivore, and one of the earliest tetrapods
What was feature of it, is high controversial

Answer 10

The ‘sail’ on its back - is it either for thermoregulation or a display feature (attract mates)
If it was for thermoregulation, this would suggest they were too large so a large SA would help expose these capiliaries, which would fit with the tropical climate expected at late Carboniferous

Question 10

Having warm-bloodedness allows the maintenance of a high metabolsim
What is the trade-offs however

Answer 10

To maintain such a high body temperature, it requires a lot of energy

Question 11

When is warm-bloodedness first known to occur in organsims

Answer 11

After the great oxygenation event

Question 12

What is the orientation of contients and climate like in the Permain

Answer 12

The Earth is significantly warmer and wetter at this time
The orientation of the continets due to the existence of Pangaea (supercontient)

Question 13

What is meant by Darwinian travel

Answer 13

Evolution is usually in small steps
For this to happen, we need something that would allow a selective advantage
However, the path has to be straight (first scenario) as the dips in the seconds scenario would likely lead to an extinction

Question 14

If we were turn a Lizard into a slightly warm-blooded animal, metabolic rate would significantly increase
What effect would this have

Answer 14

The lizard would have a large increase in its food requirements

Question 15

Why could insulation allow increased metabolic rates
However what is the issue with this idea

Answer 15

• Mammals and birds are insualted but lizards and frogs aren’t
• If Lizards evolved fur coats, they could double their metabolic rate
• However cold-blooded organisms like lizards warm themselves by finding places in warm environments. Insulation however stops heat leaking out, but also stops the sun getting in - hence seems unlikely

Question 16

• From dinosaurs out ancestors have shrank
• These dinosaurs were cold-blooded because their small SA:vol meant less heat is lost at night
• Smaller animals have faster metabolic rates than big animals
  Hence from these facts, what is expected to happens when animals evolved to be smaller

Answer 16

Two options:
1. Going back the the other energy metabolic pathways like lizards - however they would likely be out-competed as they are no-longer as well adapted to the niches the lizards/other organisms
2. Reduce the need to overcome biochemical pathways and keep the high metabolism

Question 17

What is the issue with the theory that as animals became smaller, they evolved into warm-blooded to maintain a higher metabolism

Answer 17

• Assumes the benefit of small size outweighs the cost of revving up
• Assumes that small warm-bloods had advantage over small cold-bloods at least somewhere
• Doubt both is possible

Question 18

What is a suggestion on why we became warm-blooded which is unrelated to keeping warm

Answer 18

• A higher metabolic rate was the key advantage
• The advantage of a higher aerobic metabolic rate for a big animal allows higher activity levels e.g. wolves can run for days, cold-bloods can’t

Question 19

What are the assumptions behind becoming warm-blooded for higher metabolic activity

Answer 19

• Assumes benefits of increased aerobic capacity outweigh costs of revving up
• Assumes that revved up warm-bloods had advantage over cold-bloods at least somewhere in the environment

Question 20

What are respiratory turbinates (RTs)

Answer 20

• RTs (nasal muscosal tissues) allow rapid breathing without the drying out of the nasal passage - prevent loss of water
• Turbinates are responsible for filtration, heating, and humidification of inhaled air
• They keep water and heat in the body

Question 21

What is the significance of respiratory turbinates

Answer 21

Cold-blooded animals do not have them - they are a sign of warm-bloodedness
Respiratory turbinate’s have occured in the fossil record indicating a high level of aerobic activity

Question 22

Which group of organisms where respiratory turbinates, first found within

Answer 22

The Therocephalians
They are the first protomammal genus suspected of having significantly elevated ventilation rates
Hence it is conclused the advantage of a revved up metabolism probably related to activity and stamina

Question 23

Where many dinosaurs warm-blooded or cold-blooded

Answer 23

Warm-blooded