Evolution

      The Earth has been around for a very long time. We can learn about its history by studying layers of rocks. Sometimes, remains of organisms are found deep in rocks. These remains are called fossils. Fossils found compared to organisms seen today are very different. Why is it like this? The answer is simple, evolution has taken place. Evolution is the change of the genes of a population of organisms through successive generations. It usually happens when the offspring of an organism has a change in its DNA.  The change is usually small so it isn't noticed at first. However, once many generations go by, they will have more noticeable differences in their DNA. If you notice, evolution is similar to variation and adaptation. This is because evolution works mainly by natural selection.However, all adaptations are good but sometimes bad traits can be gained through evolution. An example can be found in a dinosaur called the spinosaurus. They were different from other dinosaurs because they had a spine in the shape of a fan. Scientists say that this spine helped them cool off. However, it also made this dinosaur very vulnerable because if it is hit, they will be paralyzed for some time.

Evolution of Humans

     Do you ever wonder how humans got here? You should know humans evolved from primates. The oldest primate like animals can be found about 65 million years ago. The oldest known primate is the Plesiadapis. The Plesiadapis was found all over Eurasia and Africa during the tropical conditions of that time. Once climates got more modern, more primates moved to Africa. The remaining population eventually became many primates. They gave rise to lemurs, lorises, bush babies, modern monkeys, and all the great apes and humans. The evolution of these apes eventually led to our genus, Homo.

     The first species of the genus homo is the Homo habilis. It lived about 2.5 to 1.4 million years ago. It had small molars and larger brains than previous ancestors. A man names Louis Leakey discovered the Homo habilis and nicknamed them "handy man" because they used stone tools. Some scientists think that the Homo habilis should be moved out of the Homo genus and into the genus, Australopithecus because the Homo habilis's skeleton wasn't as adapted to living on land but more adapted to living in the trees like a monkey.

http://en.wikipedia.org/wiki/File:Homo_habilis.JPG

     The Homo erectus is the next human-like species to follow the Homo habilis. They were discovered by a Dutch physician, Eugene Dubois. The Homo erectus lived from about 1.8 million years ago to 70,000 years ago. Scientists believe that the Homo erectus arose from a few populations of Homo habilis that had larger brains. The larger brains allowed them to make more elaborate stone tools and to walk upright. These differences were large enough for scientists to consider them a new Homo species. The Homo erectus was the first human ancestor to walk truly upright. This was caused by the evolution of locking knees and the spine entering the skull through a new hole. Another thing the Homo erectus is well known for is to be the first human ancestor to control fire. They made fires for warmth and cooked their meat in it. Some scientists theorize that the Homo erectus went extinct in the Toba catastrophe. The Toba catastrophe was the eruption of a super volcano at Lake Toba, Sumatra.

     The Homo heidelbergensis is another species in the genus, Homo. They lived from 800,000 to 300,000 years ago. It is believed that the Homo heidelbergensis is the direct ancestor of the neanderthals. This species of the genus, Homo isn't well known for many things. However, the Homo heidelbergensis was believed to develop a form of a primitive language. While other human ancestors lived together in hunter-gatherer societies, none of them used a language. They rather used signals. The Homo heidelbergensis had evolved ears and vocal chords allowing them to communicate with different sounds.

http://en.wikipedia.org/wiki/File:Homo_heidelbergensis_(10233446).jpg

     The Homo neanderthalensis, or Neanderthal Man, was another human ancestor. They lived from 400,000 to about 30,000 years ago. The first Neanderthal skulls were found in Belgium. Like other human ancestors, they too used stone tools. Neanderthals had wider shoulders, barrel shaped ribcages, large kneecaps, round finger tips, and a more muscular build than modern humans. Currently, there is an argument over Neanderthals. Scientists are arguing about whether Neanderthals should be a subspecies of Homo sapiens and be called Homo sapiens neanderthalensis, or remain its own separate species. They currently remain a separate species because of the DNA difference. Neanderthals probably went extinct when Homo sapiens arose and beat the Neanderthals to all the resources due to larger brains.

http://mjmobbs.files.wordpress.com/2010/01/neanderthal.jpg

     Finally, after the Neanderthals, came the Homo sapiens. They arose at about 250,000 years ago and live to the present. They most likely came because of their skull expanding and having more elaborate tools. They migrated all over the world and settled in different places. Humans are a subspecies of Homo sapiens. The scientific name for humans is Homo sapiens sapiens. We have the largest brains of all primates which allowed us to make many technologic and scientific discoveries.

Fast forward to 5:54 for a faster version of this.

http://www.youtube.com/watch?v=-ONwp56pMBE 

Evolution of Other Animals

     The earliest form of whales is the Pakicetus. They are hooved mammals with long feet and thick tails. The Pakicetus looks somewhat like a dog. They are connected to whales because of their ears. The shape of the region where the ear was resembles only the whale and no other animal which is very unusual. Following the Pakicetus is the Ambulocetus. The Ambulocetus was very similar to a crocodile. It was amphibious and it hunted in a similar style a crocodile would. The way it swam was alike to the way otters and seals would. The Rodhocetus followed the Ambulocetus. It was more adapted to the water. It had limbs that could support it on land but it lived mostly in the water. Unlike its past ancestors, its nose was more up its snout showing that it was more adapt to the oceans. Scientists think that like turtles, the Rodhocetus and its cousins gave birth on land. The Rodhocetus also has traces of hooves near the end of its toes. The whale's ancestors were amphibious up until the Basilosaurus and Dorudon. They looked a lot like modern whales but they both lacked the organ that allowed them to locate each other in the oceans through the use of echoes. This organ later developed and can be found in modern whales and dolphins. These two also had remnants of their hind legs. They were starting to shrink and not getting used as much. Early forms of the whale came which had baleen (the filtering structure in the mouth of some whales). These whales then evolved and became modern whales.

http://www.youtube.com/watch?v=8cn0kf8mhS4            http://www.indiana.edu/~ensiweb/images/whal.amb.jpeg

     Spiders are nasty little creatures. Their ancestry however, is very interesting. Scientists think that spider-like organisms have been evolving from up to 400 million years ago. The oldest known spider ancestor is called the Trigonotarbida. They were very much like spiders; they were arachnids (meaning they walked on eight legs), they had two little fang-like structures in front of their mouth, and they breathed in a way spiders now breathed. It is still being argued about whether they could produce silk from their mouths. Currently, they are not being considered spiders but just an early organism in the arachnid class. The oldest true spider was found in the carboniferous period. Unlike modern spiders which have spinnerets (the thing that produces their web) at their bottom end, these spiders had them underneath their abdomen. These spiders also probably used their silk webs for protective covering on their eggs instead of catching food. Only until about 250 million years ago did spiders start using their webs to catch prey and were made of intricate designs. It was thought that the largest spider to ever walk on the earth lived in the carboniferous period, it was about one foot tall and its leg span was about 20 inches long; however, scientists examined it more and found out it was more of a scorpion. By the Jurassic period, spiders began weaving webs in the air and instead of on the ground. They were also round shaped. By this time, the spiders then were much like the spiders now and not much evolution happened since then.

     Ants are really tiny creatures that can be found everywhere; however, they weren't as common in the past. Surprisingly, ants have only been around since the cretaceous period. Ancient ants did not just show characteristics of ants, they also had characteristics of wasps. Ants arose and spread out after flowering plants came. They were very uncommon; they made up about 1% of all insect life at that time. Later, they were living all over the world. This happened at about 60 million years ago. They possibly went through speciation after spreading throughout the world. Most of the fossilized ants found today were found in Baltic amber.

If you have an animal's evolution record you want me to put up here, leave a comment!

Sources

• http://en.wikipedia.org/wiki/Evolution
• http://en.wikipedia.org/wiki/Human_evolution
• http://en.wikipedia.org/wiki/Evolution_of_cetaceans
• http://www.pbs.org/wgbh/evolution/humans/humankind/index.html
• http://en.wikipedia.org/wiki/Evolution_of_spiders
• http://www.sciencedaily.com/releases/2009/08/090804211128.htm
• http://en.wikipedia.org/wiki/Ant