Fossils and the History of Life : Part Three

Fossils and the History of Life: Part Three

Okay, I’d better crack on with my round up of S193, Fossils and the History of Life’.

Part Three: Common Phyla in the fossil record

As I mentioned last time, the animal kindom is split into groups called phyla. These are represented in the fossil record and the following is a brief summary of the main points concerning the most important animal phyla represented:-
Porifera:

• Sponges

• Cambrian to Recent
• Mainly marine though some freshwater
• Simple multicellular organisms – no nervous system
• Filter feeders
• Locally abundant fossils especially in Cretaceous rocks
• Found in flint nodules

Cnidaria:

Above: Coral fossil, Favosites turbinatus (Devonian)

• Corals
• Late Precambrian (Ediacaran) to Recent
• Almost entirely marine
• Colonial or solitary
• 3 groups: 1) rugose (solitary or colonial) Ordovician to Permian; 2) tabulate (colonial) Ordovician to Permian; 3) scleractinian (solitary and colonial) Triassic to Recent.
• Have central mouth and stinging tentacles

Note that Sea anemones and jellyfish are also cnidarians, but being soft bodied are rarely found in the fossil record.

Bryozoans:
• Also known as ‘Moss animals’.
• Ordovician to Recent
• Normally marine but also freshwater (uncommon)
• Very small colonial creatures living in groups of several to thousands of individuals
• Feed through tentacles
• Fossils can resemble corals and graptolites (see later)

Brachiopods:
• Cambrian to Recent
• Entirely marine and benthic (sea floor dwelling)
• Consist of 2 parts or valves and shells made up of calcium carbonate mainly though some of calcium phosphate.
• Filter feeders
• Are common fossil in Palaeozoic limestones and shales.

Molluscs:
• Cambrian to Recent
• Mainly marine.
• Very diverse phylum and most abundant large invertebrates in the fossil record.
• Phylum includes: bivalves; gastropods and cephalopods

Brachiopods seem rather similar to bivalves in many ways, but differ in that their ‘plane of symmetry’ passes through both valves rather than between them. Invariably, one valve is larger than the other in a brachiopod hence the common name of ‘lamp shells’.

Gastropods are aquatic, living in shallow marine and freshwater environments.

Cephalopods are entirely marine; have chambered shells and include ammonites, belemnites and nautiloids.

Echinoderms:

Above: Echinoderm fossil, Orophocrinus stelliformis (Lower Mississippian - 345ma)

• Cambrian to Recent
• Entirely marine are benthic, sessile (fixed to rocks) or vagrant (move around sea floor).
• Feed, respire and move using extendible tentacles called ‘tube feet’.
• Echinoids commonly has 5 rayed arrangement of plates and tube feet.• The phylum includes sea urchins, starfish (asteroids) and brittle stars (ophiuroids) and sea lillies (crinoids, see below).

Above: Crinoid fossil, Macrocrinus mundulus (Lower Mississippian - 345 ma)

Arthropods:
• Cambrian to Recent
• The largest animal phylum
• Found in land and water habitats.
• Includes: crustaceans, insects, spiders, and now extinct groups such as trilobites
• Have hard outer segmented exoskeleton which is periodically shed to allow growth

Above: Trilobite fossil, Greenops boothi (Middle Devonian)

• Exoskeleton comprises chitin and possibly strengthened by calcium carbonate or phosphate.

Hemichordates:
• Cambrian to Recent
• The most important group of hemichordates are the extinct and entirely marine graptolites. These are confined to the palaeozoic era and are therefore an important zone fossil. (see later) These look strangely like ‘saw blades’ where the ‘teeth’ are actually small recesses that house individuals that make up a colony.

Chordata:

•  Cambrian to Recent
•  Possess a notochord through the length of the body
• Include the 5 classes of vertebrates i.e. fish; amphibians; reptiles; mammals and birds.

Above: Dinosaur fossil, a juvenile Tyrannosaurus rex, (Cretaceous) located at the Burpee Museum of Natural History, Rockford Illinois, USA.

• Extinct groups include the land dwelling dinosaurs (see above); marine ichthyosaurs and plesiosaurs; and the flying pterosaurs.
• Vertebrate fossils are rare and usually comprise only fragments.

So that's a brief and way too rapid round up of the common phyla in the fossil record. The phylum 'Chordata' itself could warrant an entire blog on its own - as indeed any of them could. But I'll maybe do that at a later date if time permits. Next time I wil start that journey through time, starting with a look at the mysterious Ediacaran fossils, examples of which were found close to my hoome in the East Midlands, at Bradgate Park. Then I'll get down to the nitty-gritty of the 'Cambrian Explosion'.


All photographs included above were courtesy of 'The Virtual Fossil Museum' web site. This is an excellent resource, providing photographic galleries of the fossil groups and a lot of other information besides. For a closer look click here.

Cheers for now,
 Alyn.

Course Result!

Greetings Folks!

I interrupt the series of S193 summaries to bring you the long awaited result of the fossil course, just announced by the Open University . . .

Well, I PASSED. Hoorah!

Mind you, I would be pretty devastated to have failed it. A pass mark of 40% shouldn't be beyond anyone with a modicum of interest in palaeontology to be honest, but I did surprise myself by achieving a whopping

97%

If I had got anything around 80% I would've been quite happy, but getting 97% just makes me wonder how I managed to lose those 3%!?! Anyway, detailed feedback will arrive by post soon I believe, so I'll let you know!

Next up in a day or two will be Part 3 of my S193 summary.

See ya then!

Cheers,
Alyn.

Fossils and the History of Life: Part Two

Here is the second part of my summary of Open University course “S193: Fossils and the History of Life’.

 

Part Two: Fossil Classification and Evolution

Before anyone can get really stuck into palaeontology, an understanding of how fossils are named and classified is a useful starter. Immediately one is confronted with Latin which to many is the stuff of nightmares, but is actually really pretty straightforward in its use in science. Basically, fossils are classified according to the binomial system developed in the 1800s. Here, living things are classified according to a series of groupings in what is called the taxonomic hierarchy.

Firstly, we have the category ‘Kingdom’ and any organism can be classified as either ‘animal’, ‘plant’ or ‘fungi’. Within each Kingdom, organisms fall into broad groups according to their body arrangement or ‘bodyplan’ and these groups are called ‘Phyla’, (singular ‘Phylum’), an example of which is ‘Chordata’ which includes all vertebrates. Phyla are then subdivided into ‘Class’ such as ‘Mammalia’ that is mammals, obviously. The next subdivision is ‘Order’, for example ‘Carnivora’ , e.g. dogs, cats and these then constitute the next division, called ‘Family’. Cats are from the family ‘Felidae’ and include lions, tigers and the domestic cat.

Now, to get to the important bit – two final subdivisions serve to identify a specific species and make up the two parts of the specie’s binomial name. Below ‘family’ lies the category ‘Genus’, e.g. Felis which includes all wild and domestic cats. Finally, individual species are given a (not surprisingly) ‘Species’ name, e.g. catus for the domestic cat. So, the domestic cat is given the name Felis catus while us humans are called Homo sapiens. The observant amongst you will have noticed that the genus name must start with a capital letter while the species name does not and the whole name is written in italics. If you are hand writing an essay (does anyone hand write anything anymore?) then the whole name must be underlined.

Additionally, sometimes one may see what appears to be a surname after the species name. This in fact denotes the name of the person who first described the species in that particular genus. This is generally restricted to formal scientific journals though.

Giving any fossil a species name isn’t as simple as it might first seem. For instance, a ‘species’ is a group of organisms, the members of which can all interbreed. If one discovers a group of fossils, it is unfortunately not possible to determine if they could interbreed! So fossils are invariably categorised on their morphology alone.

Evolution and the fossil record:

A common definition for evolution, taken from the S190 course book is:-

“Evolution is any cumulative change in the heritable characteristics of species or populations from generation to generation or over longer periods”.

Or, more simply, it can be said to be ‘descent from an ancestor and modification of biological features with time’.

Charles Darwin and others had the nerve to suggest in the mid 1800’s that species were not fixed at all but actually changed with time. Darwin and Alfred Wallace were the first to actually come up with a mechanism for this to occur – by way of ‘Natural Selection’. Darwin of course published his ground breaking book ‘On the Origin of Species by Way of Natural Selection’ in 1859 and the whole idea of nayural selection can be summarised in 3 points:

 

• Members of any population will vary and such variations will be inherited by their offspring.

• A population will produce more offspring than can possiblys urvive and reproduce.

• Every population will experience a ‘struggle for existence’ and the offspring that vary in the ways most suited to their own environment will survive and breed again, causing the favourable variations to accumulate in these populations by ‘natural selection’.

A nice quote from the course book is “variation is the raw material on which selection acts”. So natural selection brings about biological change in a gradual and accumulative way.

Now this seems okay until one wonders, as I do, how did say, a birds wings gradually develop? At what point did this part-developed creature suddenly flap its new feathery arms and say, “well what d’ya know? I can fly!” Darwin, needless to say, had an answer – The Principle of Preadaption.

Feathers it is believed began firstly, merely as insulation and were in fact modified fish scales, a chance modification that just happened to help with insulation. Further gradual changes ultimately allowed flight – a radically different function to the original.

S193 has given tantalising introduction to the subject of evolution and so enrolling on another OU short science course, ‘S170: Darwin and Evolution’ will be a natural progression. Roll on May 15th! So many questions await, such as:-

• If evolution is gradual, why aren’t there examples of a line of fossils of a creature that highlight how it has changes over millions of years? Or are there?

• Did the Ediacaran fauna really become extinct or are they in some way related to modern life forms. I currently find it hard to believe that they just disappeared to be ultimately replaced by totally unrelated creatures.

• Did the ‘Cambrian Explosion' really happen? How can all categories of modern animal phyla ‘suddenly’ appear as if overnight (geologically speaking)? Surely they too gradually evolved but if so, why does the fossil record not reflect this?

I will try to delve into the Cambrian Explosion issue at a later date, but I think it warrants a bit more reading first.

By the way, if anyone out there (a post graduate perhaps?) has any thoughts on this subject or anything to contribute, drop me a line. Remember, I’m just an Open University mature student, delving into something that has fascinated me for ages but hasn't done anything about it, until now!

Next time I will look at the common phyla in the fossil record and start a journey through time.

See you then!

Cheers,

Alyn.

Fossils and the History of Life: Part One

So that’s that! S193 done and dusted. I’ve submitted my end of course online assessment and now await the result! I’m quietly confident of a comfortable pass, though I should never underestimate my ability to fall into the clever little traps the OU like to set for you! After doing the first 10 questions early and then going back over them towards the end, I did manage to spot one little mistake of mine, but hopefully there won’t be too many others – we’ll see!

As the Open University’s short, 10 point science courses don’t require any written assignments like the epic S104 foundation course, I thought it would be a good idea for me to summarise the course content here in ‘Holey Schist’. This will help consolidate my knowledge and maybe with a little help from you lot out there, help spot some glaring misconceptions that I may have picked up along the way? So here goes . . .

 

Part One: A Brief introduction to fossils

Firstly, let’s answer the obvious question: what is a fossil? Well, to quote the S193 course book, “a fossil is simply any evidence of ancient life, naturally preserved within the materials that make up the earth”. Such ‘materials’ are invariably rocks, formed from mud, silt and volcanic ash, but can also include other substances like natural resins (producing for example amber) and even ice.

Prior to doing this course I did wonder what the dividing line was between ‘dead animal’ and ‘fossil’ and the truth is that there is no strict dividing line between the two. Generally speaking though, palaeontologists would only really consider remains over 10,000 years old to be fossils.

The development of life on earth through time is recorded in successive layers of sedimentary rock – their strata. As time passed, the deposition on sediments layer upon layer effectively form ‘pages’ of the earth’s history ‘book’ and present evidence of environmental conditions at the time of deposition and a sample of life around at that time in the form of fossils.

Unfortunately, things are complicated by the fact that many pages of the ‘book’ are often missing. Periods of time when deposition didn’t occur in an area thus creates a time gap. Similarly, when layers are eroded, evidence of the time that that particular eroded rock was deposited is lost. When new deposition occurs on top, the gap in time created between the resulting strata is called an unconformity.

The study of strata and their relationships in time and space goes by the name of stratigraphy. Studying successive sequences of strata and their fossil content has enabled geologists to firstly place events in a geological perspective by dating strata relative to each other. That is, Rock ‘A’ is above Rock ‘B’ and is therefore younger. The arrival of radiometric dating enabled geologists to establish ‘absolute’ dates to rocks, subject to certain levels of uncertainty e.g. +/- 3 million years. Prior to this, dating was, with the benefit of hindsight, wildly inaccurate, but one must also bear in mind that new discoveries and advances in scientific techniques could easily spark a hasty redraft of the currently accepted stratigraphic column.

The British Geological Survey website has an excellent example of the latest Stratigraphic columm. Take a look here.

How to become fossilised:

For all of you who share my somewhat misguided ambition to be dug up ‘x’ million years from now as a beautifully preserved fossil by a future earth creature/alien visitor, just what does one have to do to become a fossil? Well, alas, it ain’t that easy! For instance, when we look at the fossil record it is important to realise that it only represents a tiny fraction of the likely total population of past life and that record is heavily biased towards creatures that lived in shallow marine environments.

The reason for that is simply due to the fact that such environments provide the best conditions for preservation to take place. As well as environmental conditions, other factors have a bearing on an organism’s ‘preservation potential’. For example, whether it has any ‘hard parts’, whether and how quickly it becomes buried in sediment and whether that sediment ultimately becomes a part of the rock record. So, if I am aiming for the best possible chance of preservation I will need to aim to be buried in suitably fine grained, oxygen starved sediment, either in a shallow marine or lake/river environment. Alternatively, I could aim for entombment in sticky tree resin as per insect fossils in Amber. Somehow this latter option doesn’t appeal quite so much – don’t ask me why!?!

It might seem odd that seemingly hard, solid substances like shell and bone can be converted into rock, but both contain miniscule pore spaces which can in the right situation, become filled with mineral rich water. In time the minerals may crystallise out thus filling the pore spaces with those minerals. This process is called ‘permineralisation’. Additionally, original bone can be replaced by minerals completely in a process called (rather unimaginatively) ‘replacement’. Together, these two processes are called ‘petrifaction’, but neither of these processes have to occur for remains of an organism to be termed a fossil. Some fossils can indeed be composed of barely altered bone or shell!

I think that will do for now.

In Part 2 we’ll look at the way that fossils are named and classified and how palaeontology fits in with evolution’. Any comments? Feel free to contribute!

Until next time!

Cheers,

Alyn.

The Holey Schist 'Review of 2009

Greetings Everyone!

And a slightly belated 'Happy New Year' to one and all!

So that was it - 2009! What a year that was!?! Some good, some bad and definitely, some downright UGLY! So here goes. Brace yourself - it's The Holey Schist Review of 2009 from my own personal vantage point!

January:- Okay, so 2009 got off to an optimistic start with Ruth being offered a job at Nottingham Trent Uni opening the way for our longed for relocation to the East Midlands! Then I received an unconditional offer of a place at Leicester Uni to study Geology! Exciting times ahead . . .

February:- Ruth and Amy move to Loughborough in readiness for their starts at NTU and Robert Bakewell Primary School respectively! Both settle in really well, but boy is it tough being separated from me and Anna back in Bolton. What sounded a straight forward idea in principle wasn't to prove as easy as all that!

March:- Meanwhile, my Open University course - S104 starts to get tougher, more so when weekend study time is swallowed up by trips to Loughborough in order to reunite the family!

April:- Quantum Physics! The subject that I feared most in S104 turns out to be my greatest triumph! It just showed that with grit and determination great things can be achieved! 90-odd percent? Extraordinary! The 'End of Course Assessment beckons!

May:- My 49th Birthday arrives and gifts of money were used to purchase several books of a geology persuasion, including Wayne Ranney's 'Ancient Landscapes of the Colorado Plateau' - definitely my 'Book of the Year - 2009'. Simply, a GEM!

June:- After Anna completes her GCSEs we both move down to Loughborough to be reunited with Ruth and Amy! Hoorah! Meanwhile, S104 Exploring Science is finished, done and dusted. Just a 2 month wait for the result! Left my job with Jacobs and endured possibly the most farcical and stressful job change of my life!

July:- Had offer on the house in Bolton! Hoorah! Buyer later pulls out! Boo! Meanwhile, now working for Balfour Beatty - kind of, err sort of jumped ship as it were!?!  Don't ask!!!

August:- Passed S104 with 'flying colours' (whatever that means!?!). Just 8 tantalising percent short of a distinction! Getting that close was something of a miracle in itself, given the mega-stressful year we've all had! Anna also got her GCSE results - umpteen passes as expected! We're VERY proud of her!!!

September:- Can't remember much happening in September other than too much work and stress, Work proving to be fun though - actually involved in building a road - 28 kilometres of it to be precise. Okay, it means turning green fields into tarmac and concrete, but it wil actually improve peoples lives in the long run and help stop lots from getting killed! Yes, really!

October:- Enrolled on S193 - Fossils and the History of life with the OU. Starts in December and is just a short 2 month, 10 pointer. Should be very interesting! Went to sister-in-law Caroline and Charlie's Wedding in Sileby, Leicestershire.  Fantastic day! Lovely couple! Got a tad drunk, myself!

Here's a few photos of the great day....

Caroline, Charles and  his parents.

My gorgeous wife Ruth, with me looking rather like Mr Fezziwigg from Scrooge. I mean me, not Ruth!

Amy Claire and  Anna-Ruth looking beautiful!

November:- NOT a good month! Ruth not well. Details are rather personal, but suffice to say, our 'work/life balance' is a bloody mess and needs addressing as soon as poss! The sooner that damned house is sold in Bolton the better!!! On a positive note, both the girls took to the stage, with Anna singing in a choir called 'Enchanted' while Amy made her first public perfomance with 'Stagecoach'. Step-dad (yours truly) blubbed through every performance! Bless!

December:- Christmas comes and with it snow and weather, the like of which I aint seen for decades! The fossil course is now underway and fascinating it all is!

Above: Gryphaea arcurata, also known as 'Devils toenail' a fossil from  the Triassic/Jurassic. (Source: Wikipedia - 2009).

Regular reference to the 'Geological Timescale' means that it is at long last sinking in! Had a great Christmas break well and truly recharged the batteries in readiness for the NEW YEAR!!!



So there you have it. A 'funny old year' and not one I'll look back on with much pleasure in truth. BUT, at least the family has relocated to Loughborough at last and there's so much to be positive about as we get stuck into 2010.

I fully intend to blog a bit more this year and I'll start with a review on S193 once I finish it off in a couple of weeks time. As there are no written assignments required on this one, I think it would be a good idea to summarise the whole thing in a series of blogs right here!


So Happy New Year and stay tuned for some palaeontology! Nice!

Cheers,
Alyn.