THE TIME LINE OF LIFE
Time line is an intresting thing to know about how our ancestor have crossed the hurdles?how did the evolution took place?only the fittest could survive to pass the next generation from simplest life forms to complex life forms which are equipped with deadly chemical weapons i find this things very intriguing & if you are the same then LET US BEGIN OUR JOURNEY
The above picture shows us about the geographical time from cambrian which is 600 million years to the cretacious period which is 100 million years.There are eras & periods,periods are grouped inder a single era like the paleozoic era which has procambrian,cambrian,ordovician,silurian period,carboniferous,permian periods this era extends from 600 million ears that is after the period of algal form to 200 million years before the birth of dinosaurs.
The next is coenozoic era which has 3 periods called the trriassic,jurrassic & cretacious period extending from 200 million years to 100 million years.
PRECAMBRIAN & CAMBRIAN PERIOD
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| (an artistic image of trilobite) |
The precambrian period is the period where we begin our journey,as you can see the above picture it started during 600 million years where life was defined just a algal forms or bacteria never the less staring from the small is very good we are discussing something which has really happened under the water or Haldane soup ,it is the time of algae where it has gone through evolution from anoxygenic heterotorpic algae which where capable of surviving in the environment where there is was no oxgen as the earth was not consisting of free oxygen or ozone,the formation of first oxygenic algae led to the formation of free oxygen where animals started to emerge as oxygen is a primary thing for a living organisms ,now we have entered a new period called the cambrian period scientists call it the cambrian explosion where the first animal began to form it was an invertebrate arthropod which was giving rise to new heights of population,now we will be using the word population very frequently the invertebrate which was swimming through the oceans where called the trilobites, these are very small creatures probably the size of a wall nut or an inch long it used to feed up on the small creatures even planktons like the modern krill.
Along with trilobites there was an othere creature which was looking jus like the trilobites they are called the anomelocaris which was bigger than the trilobites,even these creatures where living in cambrian period,as i sead the earliest forms where the arthropods which means they have jointed appandages like these creatures.
Though these where small creatures they where predators hunting down small creatures about the size of trilobites,trilobites & anomelaceris are one of the first animals to have eyes,they have having compound eyes just like the modern insects,these eyes are made of calcide crystals that means they are made up of calcium carbonate.This is a very interesting thing that earliest creatures where having eyes made of an organic substance which includes carbon in it,Just like the insects anomelocaris had lens in their eyes in insects like house fly there are around 2000 lens in each eye,in anomelocaris had 16000 lens.These eyes give them an overlapping images a kind to blur in humans
GEOGRAPHICAL MAP
The geographical map of cabrian period had
ORDOVICIAN PERIOD
These are alige little hunters with a shell on their back now that we have an idea of cambrian period let us go for the next it is called the ordovician period in this period trilobites where most common animals,there are even some new species added to the competition of trilobites these sea creatures are called the natiloid shells these are small shells which have completely spiral shell & an opening on one side thought which it's tentacles protrudes out by which it grabs it's food most of the food it was eating is small meat particles because of the earliest digestion system was not developed so well.
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| (a modern natiloid shell) |
along them there are also conodonts (phosphatic fossils with a tooth-like appearance) found in sequences of shale, limestone, dolostone, and sandstone. In addition, blastoids, bryozoans, corals, crinoids, as well as many kinds of brachiopods, snails, clams, and cephalopods appeared for the first time in the geologic record in tropical Ordovician environments. Remains of ostracoderms (jawless, armored fish) from Ordovician rocks comprise some of the oldest vertebrate fossils which where unearthed by the scientists or paleontologists.
SILURIAN PERIOD
Now we are going a head in the time line now we are in the silurian period where natiloid shells became common,apart form that this period is birth period of fishes where new species of ocean creatures where added for the computation,during the silurian period the temperature rose by 50-80 degrees centigrade this is very high temperature for land animals to with stand hence theire where new species added in the ocean itself,there was a continued proliferation and expansion of the brachiopods, and the oldest known fossils of coral reefs,during this period large glaciers where melted into water and large amount of water is added to the oceans along with this there where also moose & few plants on land with xylem & phloem this was given off by algal members ,as it is the golden age of fishes,fihes ruled the oceans as trilobites and other small invertebrates where having hard shells in order to feed on them fishes first produced jaws & teeth doing so they became the first animals to have jaws or teeth and famous of all the a placoderm called dunkleosteus this was a fearsome predator which many use to feed up on the trilobites & other small invertebrates.
As in the picture dunkleosteus(right) had a 'V' shaped sharp dentation just like the modern sharks(left) their dentation is almost silmilar,with those hard jaws dunkleosteus gave devastating bite which had a bite force of collosal 1300 pounds while the bite force of modern shark is about 670-700 pounds.In this period placoderms became very common fishes which where relatively larger & stronger,during this period a fish which had few fins was evolved into a fish with higher organs and few other fins added up like the pectoral,caudal fins etc.The formation of fishes is our first hope of life on land as these fishes where evolved into amphibians.
Now we are going to learn a new term called transition species,this is nothing but a simple animal which holds the link between 2 different species like the fish & the amphibian or dinosaur & bird.But we are more concern with the transition specie between a fish & an amphibian.
DEVONIAN PERIOD (golden age of fishes)
During this period a new species of animals where emerged they are called the amphibians which are godfather of all the land animals,so how did a fish evolved into an amphibian?.We are now speaking only regarding a group under the fishes called placodermi.
As said before silurian period was the golden age of fishes & even said that it was very hot period where even fishes could not stand a chance against the temperature how ever scientists believed that the hot temperature led to the early drought of lakes,rivers etc.Fishes where the primary animals which where suffering during a course of time this droughtification of rivers & lakes where responsible for the formation of lungs in the fishes which was a final & permanent answer for the hot temperature.now a new transition specie was evolved this is called the celacanth which are lobed fin fish showed the signs of formation the limbs like the legs & arms.Since formation of lungs took place there was no place in the water for it a brave amphibian took it's first step on the land this specie is called as ichthyostega picture below
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| ( artistic image of ichthyostega) |
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| (a celacanth) |
Scientists have uneathed a secreat regarding Celacanth as it consist of smll limbs which where growing in size,like the lobes on the fish these where grown so big that it has gone bod modification and gave rose to amphibians which had flippers on their foot which is a common factor in salamanders,this amphibian step it's foot on land as the temperature was very hish it's soft & mucus skin was not subjected for such kind of temperature so what happned evolution took place.
CARBONIFEROUS PERIOD
The most intresting thing about this period is that it the golden age of REPTILES , now this amphibian which has a soft,tender & mucus skin has lot of problems getting on to the land though a promenent legs are formed,it has to replace it's entire skin in such a way that very few percentages of water shall be dehydrated from the body as of the amphibian which had sof t& mucus skin which is more succeptable to the water loss as it used to live in the water,at this stage this amphibian has changed it's bodily skin into scales which minimises the water loss and hence a new animal in the history was born they where called the reptiles.This animal gave rose a new species of reptile called the Proterogyrinus which is a reptile like amphibian,it's body showd signs of sclaes & very few parts with soft skin may be Proterogyrinus is a connecting link between an amphibian & a reptile this is considered as a transition species
As u can see in this picture Proterogyrinus where reptiles showing amphibian behavior some what like a modern crocodile which are hydrophilic species of reptiles.Formation of one of the first animal like reptiles gave us the hope that there where even other animals which is led by this reptiles.Now these reptiles began to dominate the planet earth which gave rose to many small reptiles which where moving on their their four legs just like a lizard,it also gave rose to smaller specie of reptiles which sbegan to stand on their 2 hind limbs and tried to walk these became succesful and gave rose to dinosaurs.
PERMIAN PERIOD(golden age of sail back reptiles)
The reptiles in this period where responsible for giving rise to new species of animals called the mammals & the dinosaurs,as said before reptiles where categorised into a 2 the the reptiles with which where moving on their four legs which are called the tetrapods & the reptiles which began to move on their 2 hind limbs thecodont this name comes from the thecodont dentation which is primary used for the animals with the socket teeth where the teeth are placed in the persistant cavities called the sockets which allows the animal to produce more bite force.The tetrapods which where also called as sail back reptiles like the dimetrodon & pelycosaurs.
Dimetrodons gave rose to a new group of animals called the mammals like us & the thecodonts gave rose to the most brutal animals to ever step on the earth they where the dinosaurs,along with that it also gave rose to the birds & pterosaurs.The real evolution begins now how did a cold blooded reptile like the dimetrodon gave rose to mammals which are warm blooded animals along with hair?
The dimetrodon was not directly linked to the mammals but these indeed gave rose to the another kind of animals called the therapsids this group of animals are advanced synapsids,now what is a synapsids?
All the animals are classified based up on the number of holes in their skulls like as follows
SYNAPSID:- THEY HAVE 1 HOLE IN THEIR SKULL PRESENT ON THE TEMPORAL REGION
eg:- all the living mammals & their ancystors are synapsids a)it is the skull of cyanognath b)homo sapian
DIAPSID:-THESE ANIMALS HAVE 2 HOLES IN THEIR SKULL
eg:-most of the dinosaurs like the giant T-Rex are classified under diapsids.
ANAPSID:-THESE HAVE NO HOLES IN THEIR SKULL
eg:- all testudines(turtles,tortoises,terrapins)
ALMOST A MAMMAL
So the therapsids are advanced synapsids with one hole in their skull,they which are the real ancestors of mammals,these where walking on four legs & where looking just like the dogs & capibaras.
The above picture is a cyanognath called the dog toothed animals which lived in the late permian are mammals,their body is covered by thick hair & the lactation began which me they slowly produed the distinct thing which represents a true mammal like the eutherian(plasentate mammals),they produed milk for the first time in the dinosaurs timeline along with having tooth fixed ready to strike just like a dog enables the ascess to the mammals.
For that we need to move a head in the time line & now we are going to enter a whole new era called the mesozoic era which is where the earliest dinosaur where born & the end of that period was mass exinction of dinosaurs.
MESOZOIC ERA
This era is divided into 3 periods like the triassic which was around 200 million years,the jurassic which was around 150 million years old & the last is the cratecious period or mass extinction period was around 100 million years ago.
In this era north america which was a paridise of dinosaurs was connected to the south america by the volcanic action when the lava became cool it formed a big fertile land which eventually connected north to the south,now the dinosaurs began to move from one continent to another during this migeration very few species rays was extincted due to new climatic chage & the hurdles.
So we came to know that thecodont gave rose to dinosaurs,ptersoaurs where close relatives of dinosaurs as even they have emerged from the thecodont ,these are first animals to take flight.
PTEROSAURS
These are big animals which where close relatives of dinosaurs,they resemble modern bat with 3 fingers & thin sheath of connective tissue running from their legs to their arms,very amazing creatures.These where the largest animals to take flight on the on the earth with around 40-45 feet wingspan & bigger than a giraffe while standing,there are many species of pterosaurs with some spicies gigantic & some species smaller,some of them had big head they are found in wide verities.
Though pterosaurs where gigantic animal which had the power of flight they fed on fishes as you can see the picture most of the time pterosaurs spend catching fishes they directly depect modern fishing birds most of the costal birds like white tailed fish eagle feed on fishes,Pterosaurs are social animals which has to migrate for their reptroduction of all these species quetzalcoatlus was the largest & had a wing span of 45 feet.These animals also walk on land but for a few distance, lifting their body off the ground was not a tough buisness because they have small bone which where built for flight they had strong muscles on their chest or keel to give the power of flight especially the initial lift.
BIRDS
Birds the sky kings ruling skies from cretacious,all modern birds are dinosaurs why they are direct descendeds of dinosaurs,so how did a cold blooded dinosaurs become a ruler of sky!
As wh have learnt that birds fall under theconds & direclt derived from dinosaurs,now you need to know about the new dinosaurs called the feathred dinosaurs.These dinosaurs has feathers on their scales looking just like a modern bird but with out the power of flight,one of the dinosaur used to live in very cool place since dinosaurs are cold blooded they can not regulate their body temperature in regards to their environment .so, it can came up with an idea what is it?,it produced feathers on it's scales for insulation for prevent the exit of body heat & hence it regulated it's body temperature in this way.Dinosaurs never produced feathers for flight in the first place,velociraptor was considered to be the first feathred dinosaurs.
So as you can see in this picture velociraptor never had the power of flight it's bones where non pnumatized without hallow spaces in the bones unlike the modern birds which have the hollow bones,this velociraptor desperatly wanted the power of flight because of the natural calamaities like volcano & earthquacks there shold be some way to escape from these things so it took advantage of it feathers & started glind from tree to tree,slowly evolution took place & then a new transition specie was born called the archaeopteryx which is the intermideat form between a feathered dinosaurs like the velociraptor & the modern bird with power of flight like the falcon,archaeoptryx had the power of flight so the dream of velociraptor has come true the real power to fly.
ALMOST A BIRD
Archaeoptryx fossil created revolution in the history of paleontology,the fossil was found in germany,after many keen check ups this was considered as the missing link between a dinosaur & a bird.As you can see the picture almost all feathers are very well devoluped like in the modernbirds,their primary feathers streatched longer for the inital lift like in eagles in the right u will be finding similarities like the hight to weight ratio of archaeoptryx is almost to that of an eagle.There may be many feathered dinosaurs but archaeoptryx was the only one to fly this is a 2 feet bird,mostly tree dwelling & became extinct in the same way as the dinosaurs got.There may be very few transition species but with out them evolution would not be continued.
DINOSAURS
A new animal was born during triassic peroid which was the begining of the brutality on earth,in this perod birth of dinosar took place from it's ancistor thecodonts,They lived in 3 different periods.the trissic is the birth of dinosaurs which is around 200 million years,jurrassic is the period where dinosaurs ruled the earth which is around 150 million years & the last is cretacios period where mass extinction of dinosaurs took place.
Dinosaurs got so giangitic that no animal can match its lenght even in the moder era.there are dinosaurs which had grown up to 175 -200 feet in length like the
amphicoelias fragillimus
The above picture of an
amphicoelias fragillimus a very huge dinosaurs what made this dinosars so huge?why have the carnivorus dinosaurs where small with lng teeth? let us focus on it.
All the dinosaurs are divided into 2 major types namly a)Theropod b)saurapod
THEROPOD
(beast footed)
These are the group of carnivorus dinosaurs which live in cenozoic period where responsible for the brutality on the earth,the largest theropod was the spinosaurs which is around 45-50 feet in legth or even bigger accourding to few scientists.
As the picture above spinosaurs where very huge theropods i mailny live near oceans & sea just like a water dewller the main question is how did the animal become so large if it where a water dweller,many scientists even think now that a big creature like the spinosaurs fed on the fishs how ever this questions is a mistry one but moving on to the other species of theropods like the T-Rex which is the most famous of all,even few scientists believe that these creatures are scavengers though they are the secong largest theropods around 40 feet in legth .
As far as theropods are concerned these are large carnivorus animals with largest claws to ever have on the earth,Their exoskeleton cosist of very hard oseoderms which are bony plates,large dinosaurs have developed from its smaller species,as said before theropods are diapsids with two holes in their temporal region of their skull.
Several characters that typify a theropod: hollow, thin-walled bones are diagnostic of theropod dinosaurs. A jumbled box containing theropod bones (from the UCMP collections) is shown at right. The hollow nature of the bones is certainly more obvious in 3D, but you should at least be able to make out the general tubular structure of the bones. Other theropod characters include modifications of the hands and feet: three main fingers on the manus (hand); the fourth and fifth digits are reduced; and three main (weight-bearing) toes on the pes (foot); the first and fifth digits are reduced. Most theropods had sharp, recurved teeth useful for eating flesh, and claws were present on the ends of all of the fingers and toes. Note that some of these characters are lost or changed later in theropod evolution, depending on the group in question.
To be a climax(apex) predator you need to be either large like saurapods or have teeth & claws so big that they are virtualy not created like the theropods even,theropods where very small dinosaurs during triassic period to compete with others it had to become larger & larger until they excel their competators some smaller species like the
Deinonychus antirrhopus though this dinosaurs where small they have developed such a brutal killng mechines,they grew their claws big & killed animals without mercy.so we have come to know that a dinosaurs had to excel in some or the other way to be in top of the food chain.
As the picture abouve
Deinonychus is a featheres dinosaurs paleontologists believe that these feathers are not grown for flight but grown for isulation.
SAUROPODS
All the herbevorus long necked dinosaurs are classified under the group sauropods,They never had limit for their growth might be these dinosaurs where twice their length if they where still living.These first appeared in the late triassic period they become more common & wide spread during jurrassic period of 150 million years,the earliest Sauropods of triassic period where smaller to the sauropods in the jurrassic period,as the carnivours became more aggrassiv & brutal killing mechines they have no choise to exced in one of the other way or get their rays extinct,so these sauropods grew their body size so tremendusly that they are climax herbevorus animals which means they have no predators in wild which is now not possible because all herbivorous are been eaten by carnivours animals as a part of food chain.
If we think of sauropods the first aniamls that strike is the brachiosaurs,diplodocus, & even more,they have their knee joint just above their foot just like the modern elephant.As we go further into classification most of the dinosaurs of triassic period where classified under the family titanosaurs which includes even argentinosaurs.
These creature are very massive their neck alone can grow up to 30-40 feet or even more.Even though these creature are very big but still they hatch from an egg bery small their growth rate is almost 15-20 times greater to elephants,
Sauropods had small teeth that could only feed on the leaves of the tall trees,the creatures cannot sit & sleep hence they sleep in standing position,their stomachs are one of the biggest on earth with many bacteria & small colony of fungai,this is because animals cannot digest a starch compound called cellulose,hence they are in symbiont associate with the cellulase bacteris which diests cellulose of leaves just like moder herbevorous.
As abouve picture of a saropod skull their all teeth are similar like it is monodentation that means they have similar kind to teeth,these where very poor when compared to theropods.As said before even these are diapsids we can see 2 distinct holes on their temporal region which occured in late cretecious period.
Sauropods where social creatures just like the modern elephants which live in groups,how ever these creatures geans where not passed to next generation due to mass extinction.Their jaw muscles gave them minimum bite force to crush leaves just like the modern herbevorous.It is a very remarkable thing that such a large creature but it's muscles & skeletol system is weaker than theropods.
Crocodiles
Crocodile are remarkable creatures which where born during jurrassic period of coenozoic era,very interesting thing about them is that they have survived the mass extionction & passed on their geanus to moder living crocodiles,there are around 23 species of crocodiles living in this world all from a common acistor which is the direct descended of thecodont,It clearly observed that crocodiles have such huge bite force because they have come from thecodont(socket tooth) a persistant socket is present for each tooth.Crocodiles where smaller lizards during their birth they where small & crawling on the land just like modern lizards,their skin was not covered by ostoderms unlike in modern crocodile which is seen in every species,these are the indirectl related to archosaurs which played a major group in permian period along thecodonts,there is a clad called archosauromorpha which includes archosaurs & it's ancestors.
An archosaurs like the above postosuchus is responsible for a new clad in the group.As crocodiles took refuge in lacks,rivers they feed more & increased their size they became very big when compared to their land crocodiles,a super crocodile was born called the sarcosuchus that was a 40 feet giant crocodile living in the late jurassic period,It was so big that is draged sauropods into the water & drained them till their death,there where even more crocodile of this size like the Deinosuchus.It's skull itself was 5 feet in length equiped with sharpest teeth in crocodile history.
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| (sarcasuchus taking dow a sauropod) |
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(a deinosuchus taking town a theropod)
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These above pictures dipect the size & strength of these crocodiles,crocodiles are even cosidered to be living fossiles as they have under goes very little or no change in their body structure for millions of years,there are 2 distinct regions called the dorsal surface & the ventral surface,their dorsal surface is covered by rows of bony plates called the osteoderms this is their primary protection from predatores during jurassic this is so tough that even a knife jap would not penetrate into it's body while the ventral surface is covered by thin layer of muscle when compared to dorsal surface,there are no osetoderms or heavy protection on their ventral surface it is plane & and weak,a crocodile could only be killed by attaking on their ventral surface.
These creautres are eqipped with deadly weapon like the bon ecrushing bite capable of delivering a bite force of 3500-4000 pounds which is the largest bite force of any animal,some time cocodiles even loss their tooth while snapping their jaws so jusge bite force which is provided by the strongest jaw muscles,their main line of defence is their teeth.In order to that they have some sensory organs on the margins of their mouth called the inteumantory resceptors even refered as ampullae of lorenzini in sharks.These are neumerous small holes which are filled with jelly like substance these are mainly useful for recieving of the electronic impulese like the repellings produced by each animal even small repulsions caused when breathing through gills b fishes
