Things To Know About DNA and Genetics
DNA, the molecule that codes for genetic instructions, is found in all forms of life. It is made up of four nucleotide bases: adenine (A), thymine (T), guanine (G) and cytosine (C). These bases pair up with one another, but have to follow certain restrictions: adenine can only pair up with thymine, and guanine can only pair with cytosine. DNA replication occurs when the base pairs are split up and paired with another corresponding nucleotide base, creating two identical strands (as long as no mutations (mispaired bases) occurred).
The traits of an organism are often predetermined by its DNA sequence (some are, of course, attained over time and due to environmental exposure or simply time). When organisms reproduce, only traits in its DNA can be passed on to the offspring. Attained traits cannot be passed on. Thus, it is important to consider the genetics of dinosaurs when asking whether they will resurface on the earth. It is also important to understand the evolution of dinosaurs in the first place to understand if they will come back.
The traits of an organism are often predetermined by its DNA sequence (some are, of course, attained over time and due to environmental exposure or simply time). When organisms reproduce, only traits in its DNA can be passed on to the offspring. Attained traits cannot be passed on. Thus, it is important to consider the genetics of dinosaurs when asking whether they will resurface on the earth. It is also important to understand the evolution of dinosaurs in the first place to understand if they will come back.
The Beginning of the Dinosaurs
Evidence in the change of genetics and evolution with the dinosaurs first occurred when a type of fish, called the Eusthenopteron, evolved to form limb bones in its fins, which helped it navigate and find food on land. Then, the aminiotes began laying shelled eggs-- the first organisms to reproduce out of the water. From here, terrestrial animals evolved.
The first landmark is when the Permian mass extinction occurred. The end of the Permian period also marked the end of the Paleozoic era, and it caused the archosaurs, the direct ancestors of the dinosaur, to evolve and take over the habitats of the carnivores and herbivores that died after the Permain period. Then, about midway through the Triassic period, the archosaurs branched and evolved into two major groups: one branch would eventually lead to crocodiles and such, and the other, dinosaurs and birds. The evolution occurred because of the different ways the different archosaurs held themselves: some walked in a more slithery type way (like lizards-- these branched off to form crocodiles), while other held themselves more upright (which ended up becoming tall-standing dinosaurs and birds). By the late Triassic period, theropods rapidly diversified. However, these carnivores were still quite rare at the time.
Dinosaurs finally came into play after the Triassic period (which included another extinction although not as drastic as the Permian extinction because the end of the Triassic period only marked the ending of a period, not an entire era). The prominence of dinosaurs took place when the early dinosaurs took over the habitats of the archosaurs of the Triassic period, very similar to what the archosaurs did themselves. Dinosaurs then dominated the world, as the reptiles were greatly affected by the environmental changes after the mass extinction.
It can be hypothesized that dinosaurs had gene mutations that aided them through the survival of the environmental change. because of this beneficial mutation, the dinosaurs prospered when the reptiles did not. Further adaptations occurred to dinosaurs, such as natural selection selecting some herbivores with longer necks to stretch into the trees where they could reach food others could not. Sauropods adapted to browsing on lower vegetation, and ornithischian herbivores evolved to form turtle-like beaks for the nipping and close-cropping of low plants.
During the Jurassic period, saurischians were very popular. The diversifying species of dinosaurs was occurring due to the different ways the dinosaurs lived, and by several variables in their separate lifestyles, like where they ate, where they lived, what they ate, who was their predator, etc.
Then, by the Crestaceous period, land masses were beginning to drift apart and small streams were forming between continents, which isolated certain groups of dinosaurs. These groups evolved separately and were unable to breed and exchange genes, and their gene pool was greatly reduced. This also isolated the mutations and adaptions, and allowed for great diversity, and a chance for many Cretaceous dinosaurs to evolve. Quickly, ornithischian dinosaurs replaced many saurischian dinosaurs. Nodosaurs replaced (were the descendant of) the stegosauruses.
Many mutations and evolutions were occurring. The Deinonychus, a 3-metre long tetrapod, evolved to have many specialized structures which aided them in the carnivorous way of life. They had an extremely long, retractable claw on the second two (12-metres longs!) which was for swiping at prey. The late Cretaceous period brought the evolution of the largest terrestrial carnivores, such as the Tyrannosaurus (up to 14 metres long). Their arms, another example of the evolution of dinosaurs through mutations, were tiny, but extremely strong. Their purpose, agreed to be specialized, still remains debated.
Also at the time, the "duck-billed" dinosaurs became prominent. They were low-level grazers and became very diverse: their skull began developing "ornamental" crests. These crests were used as a visual signal, similar to the peacock and his tail. Some even developed "hollow" crests, which provided a sound signal, which sounded a bit like a trombone. Moreover, the well known horned dinosaurs (such as the Triceratops which evolved from the beaked, early Cretaceous Psittacosaurus) had their elaborate horn display serve as a defensive weapon, a signalling device, and perhaps also a regular rutting device (similar to the bucks and their horns today).
The first landmark is when the Permian mass extinction occurred. The end of the Permian period also marked the end of the Paleozoic era, and it caused the archosaurs, the direct ancestors of the dinosaur, to evolve and take over the habitats of the carnivores and herbivores that died after the Permain period. Then, about midway through the Triassic period, the archosaurs branched and evolved into two major groups: one branch would eventually lead to crocodiles and such, and the other, dinosaurs and birds. The evolution occurred because of the different ways the different archosaurs held themselves: some walked in a more slithery type way (like lizards-- these branched off to form crocodiles), while other held themselves more upright (which ended up becoming tall-standing dinosaurs and birds). By the late Triassic period, theropods rapidly diversified. However, these carnivores were still quite rare at the time.
Dinosaurs finally came into play after the Triassic period (which included another extinction although not as drastic as the Permian extinction because the end of the Triassic period only marked the ending of a period, not an entire era). The prominence of dinosaurs took place when the early dinosaurs took over the habitats of the archosaurs of the Triassic period, very similar to what the archosaurs did themselves. Dinosaurs then dominated the world, as the reptiles were greatly affected by the environmental changes after the mass extinction.
It can be hypothesized that dinosaurs had gene mutations that aided them through the survival of the environmental change. because of this beneficial mutation, the dinosaurs prospered when the reptiles did not. Further adaptations occurred to dinosaurs, such as natural selection selecting some herbivores with longer necks to stretch into the trees where they could reach food others could not. Sauropods adapted to browsing on lower vegetation, and ornithischian herbivores evolved to form turtle-like beaks for the nipping and close-cropping of low plants.
During the Jurassic period, saurischians were very popular. The diversifying species of dinosaurs was occurring due to the different ways the dinosaurs lived, and by several variables in their separate lifestyles, like where they ate, where they lived, what they ate, who was their predator, etc.
Then, by the Crestaceous period, land masses were beginning to drift apart and small streams were forming between continents, which isolated certain groups of dinosaurs. These groups evolved separately and were unable to breed and exchange genes, and their gene pool was greatly reduced. This also isolated the mutations and adaptions, and allowed for great diversity, and a chance for many Cretaceous dinosaurs to evolve. Quickly, ornithischian dinosaurs replaced many saurischian dinosaurs. Nodosaurs replaced (were the descendant of) the stegosauruses.
Many mutations and evolutions were occurring. The Deinonychus, a 3-metre long tetrapod, evolved to have many specialized structures which aided them in the carnivorous way of life. They had an extremely long, retractable claw on the second two (12-metres longs!) which was for swiping at prey. The late Cretaceous period brought the evolution of the largest terrestrial carnivores, such as the Tyrannosaurus (up to 14 metres long). Their arms, another example of the evolution of dinosaurs through mutations, were tiny, but extremely strong. Their purpose, agreed to be specialized, still remains debated.
Also at the time, the "duck-billed" dinosaurs became prominent. They were low-level grazers and became very diverse: their skull began developing "ornamental" crests. These crests were used as a visual signal, similar to the peacock and his tail. Some even developed "hollow" crests, which provided a sound signal, which sounded a bit like a trombone. Moreover, the well known horned dinosaurs (such as the Triceratops which evolved from the beaked, early Cretaceous Psittacosaurus) had their elaborate horn display serve as a defensive weapon, a signalling device, and perhaps also a regular rutting device (similar to the bucks and their horns today).