Hot and Cold Bloodedness Flashcards
What are Tetrapod’s
4 legged animals - reptiles, amphibians, birds and mammals
Is the the Tiktaalik
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
When did the Tiktaalik exist in time
around 375Ma
Why is the Tiktaalik thought to be an intermediate between fish and tetrapods
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
What is the link between bony fish and their swim bladders in evolution
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
Why it suspected that the Tiktaalik gained these lobe-shaped fins, which evolved into limbs
A hybrid fin allow movement on the floor and in shallow waters
What organism is suggested to be the next evolutionary stage closer to tetrapods, from Tiktaalik
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
After Icthyostega, what was the next evolutionary characteristic that occured
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
During the Paleozoic, which time period came after the Carboniferous
Permian (299-252Mya)
The Edaphosaurus was a herbivore, and one of the earliest tetrapods
What was feature of it, is high controversial
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
Having warm-bloodedness allows the maintenance of a high metabolsim
What is the trade-offs however
To maintain such a high body temperature, it requires a lot of energy
When is warm-bloodedness first known to occur in organsims
After the great oxygenation event
What is the orientation of contients and climate like in the Permain
The Earth is significantly warmer and wetter at this time
The orientation of the continets due to the existence of Pangaea (supercontient)
What is meant by Darwinian travel
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
If we were turn a Lizard into a slightly warm-blooded animal, metabolic rate would significantly increase
What effect would this have
The lizard would have a large increase in its food requirements
Why could insulation allow increased metabolic rates
However what is the issue with this idea
- 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
- 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
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
What is the issue with the theory that as animals became smaller, they evolved into warm-blooded to maintain a higher metabolism
- 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
What is a suggestion on why we became warm-blooded which is unrelated to keeping warm
- 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
What are the assumptions behind becoming warm-blooded for higher metabolic activity
- 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
What are respiratory turbinates (RTs)
- 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
What is the significance of respiratory turbinates
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
Which group of organisms where respiratory turbinates, first found within
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
Where many dinosaurs warm-blooded or cold-blooded
Warm-blooded
