(posted in Evolution)

Leah wrote:

Well I am gonna skip a few years straight to where the first signs of fish were, this is where my question can be found. Ok well after a while one type of fish acquired the first characteristics of landanimals, it had lungs and a ribcage to help its organs against the force of gravity. But what caused them to change? like what caused the fish to change inside it?? like its not just one day they wake up and all of a sudden they have lungs is it?? so what i am really asking is what caused the fish to produce lungs and a ribcage and kidneys and a backbone?? why did the fish get lungs??, do they get it by telling thier body or something?? idk I hope u understand what I am asking cuz we are learning evolution in my biology class but the movie we are watching failed to say how the fish got their charactersitcs of land animals. I was hopping you could help PLEASE!!

I think that's a very fair question Leah.  The process of evolution is often quickly glossed over, particualrly in schools.

The fish did not tell their bodies to grow lungs.  As I'm sure you realise, that is a rather odd idea.

Instead, what happens is all by chance, and occurs over millions of years.  Imagine a pond drying up, located near another pond.  In the same way some people are stronger or taller than others, the fish with the strongest fins, and able to last longest out of water will be able to survive and drag themselves to the other pond.  Here they will survive and have offspring.  In the same way tall parents will often have tall children, and parents with dark hair will often have children with dark hair, these stronger fish, able to last longer out of water will have children able to do the same.  When the time comes that the pond dries out again, only the strongest offspring with the ability to last longer out of water will survive.

This is what we call selection:  A character or 'trait' is selected by the conditions of the environment, and it becomes common and exaggerated in the group of animals, because only those with the trait survive long enough to have children, and then the children inherit these traits.

You can possibly imagine something along these lines happening until we have something resembling a modern day lungfish (http://en.wikipedia.org/wiki/Lungfish) which can breath by passing air over it's gills as opposed to water.

From fish, evolution created amphibians.  Yes they were land animals, but they still need water to keep their skin moist and to breed in.  And this is when we find fossils like Acanthostega (http://en.wikipedia.org/wiki/Acanthostega - note that it's body is still similar to a fish, though it's fins have started to separate into fingers and toes).

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A pretty contrived hypothetical example would be if all the people over 5'6" in the world disapeared.  short parents will usually have short children, so the next generation would mostly be short (there would be a few tall people in there as there are always exceptions).  if all the people over 5'5" then disapeared, the next generation would be slightly shorter.

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So to answer the crux of your question, "what causes fish to grow lungs?" the answer is: chance, variation, and selection by environmental conditions over millions of years.

Adrian wrote:

This is inspired by a documentary I've seen about the hadrasaur mummy fossil, they have found the size of the intervertebral discs to be considerable adding more than expected to the animals length. In museums skeletons are mounted with the vertebrae touching each other, how much would the intervertebral discs add to the lenght of a live dinosaur, 10-15%? As an example what would be the lenght of Sue the T.Rex in life or that of the 27m Diplodocus? And why do estimates of dinosaur size overlook this most of the times?

As I'm from the group that worked on that mummy (Dakota I presume), I'll have a stab at that.

We can only make a really good guess at that percentage (If I recall, 10-15 is about right for Dakota, certainly that is what the program mentions) for hadrosaurs.  Other dinosaurs may not have needed such discs.  A lage sauropod for instance has highly advanced vertebrae that for all intents and purposes interlock.  In this case the intervertebral discs probably won't add much to the length.  Similarly, a smaller dinosaur may only need very small intervertebral discs.

So to sum up:  I think we can take this as an exciting view of palaeobiology we don't normally find with skeletons, but we should be wary of instantly painting the whole of the dinosauria with this discovery.

We should always assume dinosaurs will be a touch longer than their skeletons anyway once soft tissues have been added.  Think of the skeletal measurements as a 'lower bound' on the size of a dinosaur.
  Also, have a good look at the museum specimens, many actually do space the vertebrae out, even if it's only for the steel mounting.

A question often asked by students, and rarely answered adequately by careers advisors - my advisors at school didn't know what palaeontology was!

A-level wise, I would always heartily recommend maths.  Maths is a very useful A-level regardless of what you go into, and that is certainly the case with palaeontology.  New areas involving computer modelling (work I'm nvolved with) are obviously maths orientated, but even if you want to dig up fossils and describe them (a gross simplifaction), you will still need a competency with maths for statistical analysis.
Next up, Biology is always a good option.  Studying life in the past requires an understanding of life today.
Finally, it's a difficult one.  I did geology, because my local A-level college offered it, but to be honest, I think something like physics or chemistry would have been more useful (though also harder).  English doesn't go amis, as you'll be writing plenty as a scientist, and you'll need good writing skills.

Regards Universities, I don't think many people will argue with Bristol being one of the better options, with their 3 year biology and geology course or 4 year palaeontology MSci.  Portsmouth also have a respectable palaeobiology course, and UCL have a palaeontology oriented course as well I believe.  If you want to play it safe with regards to future career prospects, a good geology or biology degree from any other good university will be an entry path into palaeontology, and will give you a wider base for other careers if palaeo turns out not to be for you.

You are right though, the ladder is a difficult one to climb, and I know many people who spend a couple of years between courses whilst they wait for funding.

If you are worried about standing out from the crowd, don't necessarily look at masters in palaeontology once you have an udergraduate degree in the subject.  Instead, look at broadening your fields.  After the geo/bio BSc at Bristol, I then took a Masters in computer science, giving me a skill set much sought after (at the moment) in palaeontology.

shayla wrote:

If a pond freezes solid, and it has fish in it, do the fish freeze, and then in the spring come alive again, or do they die because the have frozen?

Most fish would die.  However, in a climate like ours, few ponds of a size large enough to hold a permernant popultion of fish will freeze entirely.  Water is an odd substance, in that when frozen, it's actually less dense than when liquid.  As such, when water freezes, the ice covers the top first.  This then ges some way to insulating the water below, meaning most large ponds will remain liquid at the bottom, and the fish can survive.

(posted in Evolution)

heh, and more importantly why has the WWF chosen a naturally doomed animal as it's logo rather than something that would be doing fine were it not for us.


In answer to the question though, perhaps we need to think of it the other way around, are there any pressures strong enough to wipe out pandas?  Sure, eating a plant that in many species only flowers on the scale of decades isn't a good idea.  And eating plants when you are in essence a carnivore with a carnivore's dentition and digestion system also isn't a fantastic adaptation, but they do more or less get by.  So without a stronger selective pressure in either direction, they'll linger around just eating bamboo for a while yet (bar human intervention).

Colin Bartlett wrote:

Furthermore, some ornithischians, like the delightful Leallynasaura mentioned in the Subject, were active in times and places (like being a perky nocturnal herbivore near the South Pole) that don’t seem plausible for an ectotherm, and don’t make sense for a naked endotherm either.

remember, the antarctic wouldn't have been over the south pole at the time, AND the climate was generally warmer



Paolo Viscardi wrote:

When it comes to walking bipedally the problems of muscle coordination and control increase vastly.

Which is very interesting, because from a simulation point of view, bipedalism is computationally easier to get walking than quadrupedalism...

Ashton Lee wrote:

Is homosexuality, both orientation and behavior seen as natural and normal, serving some function Naturally, reproductively, evolutionarily, and/or adaptatively?

Remember, something can be natural and normal without having to serve a function.  The way evolution works means that unless there is a relatively strong force against some feature/trait, it will probably stay in the population.

I'm not saying whether homosexuality does or does not, I don't think we know.

Of course, I don't think it's even certain whether homosexuality is genetic (you often hear of the 'gay gene' being found or looked for in news stories), though if someone here is more up on the subject than me perhaps they can say.  Which means it may not just be subject to biological evolution but also social evolution, as Paolo touched on above.

(posted in Birds)

Mike Taylor wrote:

Don't sharks famously smell blood underwater?  It seems off that this aquatic mole has to mess about with air bubbles given the well-known factoids about great whites being able to detect a single molecule of blood in four billion cubic miles of water.  Or is the thing that sharks do not technically "smelling"?

Surely an aquatic mole, being a mammal, would have it's respiritory system which it couldn't flood wth water.  Sharks can smell underwater because they detect the particles straight from the water as e would from air.

(posted in Birds)

Birds are very light, as you note, their bones are almost hollow.

When an object is submerged in water, it submerges to a depth where the mass of the displaced water equals the mass of the object*.

Hence a light bird (and they really are very light) will displace a very small mount of water and so not sink very much at all.  Hence so much of the bird remains above water.


Also, again as you note, the feathers play an important role in your perception of how submerged a bird is.  The submerged part will have feathers pressed down against the body, reducing apparent size, whilst feathers above the water will be at least partially away from the body, increasing apparent size, and thus distorting the proportions of submerged and non-submerged bird.



*edited for accuracy.  Alternatively, James writes:
The upthrust from the liquid depends on the volume displaced - if it's greater than the total mass of the body, then the body will float (mass of displaced volume of liquid = mass of floating body), otherwise it will sink (mass of displaced volume of liquid < mass of immersed body).

90Nz0 wrote:

Hi all,

Since watching Jarrasic park, I have been thinking about what's the best way to deffend one's self against a volocoraptor attacks, esspeicaly if the security doors won't lock.

:D
don't hire an IT support person that is clearly ng to double cross you.  Not only do they shut down the power and prevent the security doors locking, but they spend all day on internet forums asking rather odd questions.


But on a serious note (and why not eh?), think about it in the same way you would avoid a tiger or lion - don't go near them or their habitats in the first place.

Being separeted by a few tens of millions of years helps in this regard.

(posted in Human Biology and Evolution)

In answer to the first part, our lips are a different colour because the skin is much thinner than at other places (note how easy it is to cut your lip and bleed when you bite it by accident!).  This means the blood flows closer to the surface, and the thinner skin doesn't produce the colouration seen elsewhere.

As to your other question, I'm sure there are, as if nothing else hair will stop before the skin enters the mouth, leaving an area of different colour.  Though I fear my answer in this regard may need bolstering by someone else.

I got hold of a reference, but it was french and I couldn't find the actual article anywhere.

Plenty of papers on the tooth morphology, but none mention the composition.

(posted in Birds)

http://news.nationalgeographic.com/news … tools.html

...references a royal society proceedings paper, though it is on /Corvus moneduloides/.

A quick search on google scholar throws up quite a few papers, though again they are all /C. moneduloides/, or the Caledonian Crow from New Zealand and the South Pacific.

I also remember reading about crows in Japan that would sit at traffic lights.  When the lights went red, the crows placed nuts and seeds infront of the tyres of the cars, then flew away.  The cars then obviously drove over and opened the food for the crows to collect the next time the lightsturned red.  Sadly I can't remember the source or the species of crow.

(posted in Mammals)

Professor Gareth Jones at The University of Bristol is another option:

http://www.bio.bris.ac.uk/people/staff.cfm?key=67

Well, complex behaviour doesn't really fossilize too well!  There was an article in Palaeontology in September about a small heard of psittacosaurs, so we may have gregarious behaviour.  As you say, nesting/parental care has been found (Oviraptors, hadrosaurs etc).

Other than that...  I can't really think of any specific behaviours.

With regards birds being intelligent, a larger/more efficient brain may have been either a prerequisite or result of flight.  As such I don't think we can reliably take intelligence of birds as a good indicator of dinosaur intelligence much beyond the dino-bird transition (So, maybe the maniraptorans).

Remember also, that intelligent birds like parrots and crows (crows and ther ilk are astoundingly intelligent, probably more so than parrots in the wild), are not necessarily the norm.  You don't hear about cognitively superior sparrows or flamingos etc.

(posted in Fossils)

It would be useful if you could post a picture.  Whilst the forum can't host pictures itself, if you use something like imageshack (http://imageshack.us/), or a site of your own, you can upload the picture and post a link here.  With a photo I'm sure we can help you identify if it's a fossil.

(posted in Birds)

The Ostrich is the largest living bird.

My collegue Karl Bates, who has worked extensively on Allosaurus fragilis says it weight between 1 and 1.4 tons.  9-13m is probably a bit large for allosaurus, he says a little smaller than that (about 8.5m)