science evolution assignment

The theory of evolution Evolution

What is Biological Evolution?

It’s nine o’clock and science class has begun. “Good morning class today we are looking at a very important topic, the evolution of humans, now who can tell me how men and women came onto this earth?” A boy in the front row named Jimmy raised his hand, “a zoo keeper told me that we all evolved from bacteria over millions of years.” Immediately the teacher responded “Jimmy go down to the bathroom and wash your mouth out with soap now!” Jimmy leaves the classroom head bowed and tears running down his cheeks. “Okay we have wasted enough time, every one get your science books and turn to genesis 2, the creation of Adam and Eve and we will learn the real truth about how you were created. … While it may seem absurd this form of teaching about evolution is commonplace all throughout the world. Surveys show that 42% of Americans believe in creationism, which holds that all life on earth was only created several thousand years ago. The actual scientifically accepted theory is simpler than many think but commonly misunderstood. Biological evolution can be put as genetic change in a population that can be inherited from generation to generation. For it to be considered biological evolution there must be a visible change in the phenotype of the population. It also involves the belief that all life on earth can be traced back to common ancestor.

N E W E R S C I E N T I S T

www.interactive-biology.com

www.howitworksdaily.com

www.urchinmovement.com

Deadstate.org

THE LOREM IPSUMS FALL 2016

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The Fossil Record How does it relate to the age of the Earth?

Fossils have played a key part in dating the age of the earth, when an organism has died millions of years ago there is small chance that it’s bone structure can be preserved for millions of years. For this to occur it requires the animals remains to be in an area with no oxygen or microorganisms as they will cause bones to decompose. The bones are then eventually covered over by sedimentary rock and as more rock covers them and more weight is added on the pressure slowly builds. Scientist can tell the age of the rock surrounding the fossil by looking at a cross section of the rock and can judge the age depending on how deep that rock is. Occasionally older rocks can be pushed above younger or vice versa due to a fold or fault pushing a slab of rock up or down through the layers meaning scientists must use extreme care when using this method. The oldest rock on earth was discovered in Hudson bay, Canada and is thought to be 4.5 billion years old “just” 100 million years after the earth was thought to be formed 4.6 billion years ago.

How long has life been evolving on Earth?

The oldest fossil ever was a bacterium found in rocks almost 3.5 billion years old in Western Australia. The bacteria have since been named cyanobacteria and are thought by many scientists to have made life on earth, as we know it today. These small bacteria actually produced oxygen and over almost a billion years they increased the amount of oxygen in the atmosphere drastically. As these are one of the first known life forms then we were all once in a microscopic bacteria colony 3.5 billion years ago making cyanobacteria the building blocks for the more advanced multicellular begins that we see today.

www.dailymail.co.uk

www.prehistoricplanet.com

www.ucmp.berkeley.edu Diagram of cyanobacteria

www.seas.ucla.edu


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Fossil Dating Methods (Radio Metric Dating, Dendrochronology and the molecular Clock)

What is Speciation

For scientist to unravel this evolutionary mystery they had to come up with methods to date fossils. There are three main ways for scientists to date them; they are radiometric dating, dendrochronology and the molecular clock. Radio metric dating is a method that gets the absolute age of fossils. (an estimate of it’s age) All life on earth contains carbon, most is carbon twelve but a small percentage is carbon 14. Over time carbon decays and turns into nitrogen so therefore scientists judge how old a fossil is by how much carbon 14 is left. This technique can also be used on rocks but rather than testing for carbon it tests for the amount of uranium in a rock. As every rock contains a small amount of uranium and uranium slowly turns into lead over a period of 4.47 billion years paleontologist can determine an age of a rock by analyzing the uranium to lead ratio. Dendrochronology commonly referred to as tree-ring dating can get an accurate reading of the age of the tree by counting the visible rings in a tree’s cross section. The colour and thickness of the ring directly relates to the climate of that year and therefore when wood fossils are found we can get a general idea of the climate during that time period. Finally the molecular clock method can find out when two species had a common ancestor. It does this by looking at a strand of DNA and as one base will mutate every 25 million years we know that if two strands differ by 2 bases then the two species had a common ancestor 50 million years ago. This procedure has been vital in working out our own lineage and discovering our origins.

www.visualisingdata.com

Speciation according to Berkeley is “a lineage splitting event that produces two or more separate species.” For it to be speciation the species must no longer be able to produce fertile offspring. The most common form is known as allopatric speciation, this is when a physical barrier such as a river, mountain or a continent splitting cuts a population in half and prevents gene flow each populace. Over a period of time they will gain unique traits and if the two species are ever reunited they will no longer be able to have offspring. A prime example of this was the squirrel population at the Grand Canyon. When the canyon formed the squirrels could no longer reach those on the other side while bird species could still move across freely the squirrels were now completely cut off. Eventually the linages split and now two different squirrel species occupy the north and south sides of the canyon.

Biology-forums.com

www.mun.ca

people.highline.edu


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How do genes and environmental factors interact to affect the survival of organisms? Speciation according to Berkeley is “a lineage splitting event that produces two or more separate species.” For it to be speciation the species must no longer be able to produce fertile offspring. The most common form is known as allopatric speciation, this is when a physical barrier such as a river, mountain or a continent splitting cuts a population in half and prevents gene flow each populace. Over a period of time they will gain unique traits and if the two species are ever reunited they will no longer be able to have offspring. A prime example of this was the squirrel population at the Grand Canyon. When the canyon formed the squirrels could no longer reach those on the other side while bird species could still move across freely the squirrels were now completely cut off. Eventually the linages split and now two different squirrel species occupy the north and south sides of the canyon.

How do we know that the evolutionary theory is accurate

For us to prove the theory of evolution you must separate the facts into categories. Firstly by looking at the fossil records we can see when species had common ancestors and as Charles Darwin once said, “the further we go back the less distinguishable the two species will become.” For example if we look at the fossil of a basilosaurid whale we can see that this 40 million year old ancestor of the modern day whale has small little feet suggesting that the whale was once a land mammal. Additionally the nostrils are half way between were a land mammals nose would be and a whales blowhole. If we go back almost 50 million years then the fossil of Maiacetus Innus while having four defined legs have been found among fossilized sea creatures and is also said to be a relative of the hippopotamus. Secondly if use comparative anatomy for whales and hippos we can see that they both have very similar ankle bones, both animals give birth and nurse their young underwater, they both have multiple stomach chambers, they both have no fur and lastly both have internal testicles. Furthermore by comparing the embryo development we can clearly see that the hippopotamus and the whale’s embryo’s look extremely similar. Finally by looking at the molecular clock and comparing whale and hippopotamus DNA we can that the molecular clock suggests that

they had a common ancestor almost 50 million years ago. This example of whales and hippo’s can be applied to all animals on earth although many are still being researched, as there are currently 8.7million different species on earth.

www.pinterest.com

Evolution.berkeley.edu


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Evolution of birds case study It has only been in recent years that scientists have discovered the evolution tree for birds. Since Darwin first hypothesized his theory it has long been a mystery as to where birds lineage began. Recent discoveries have now shed light on what was once an unknown branch on the evolutionary tree. The first piece of the puzzle was a well-preserved fossil of an Archaeopteryx found in Germany 1860. At the time scientists did not realize the significance of their findings but this reptile-bird hybrid was latter hailed the missing link between dinosaurs and the modern day birds we see today. Archaeopteryx shares traits to both birds and dinosaurs; unlike birds the Archaeopteryx had teeth opposed to a beak and had a long bony tail. Additionally its bone structure was not fused together and its arm/wing joints did not allow for optimal thrust. It would not be for millions of years till we saw birds have the maneuverability that we see today. In 1970 scientists began to see similarities between small carnivorous dinosaurs known as therapods. With this new groundbreaking information scientists aimed to complete an evolutionary tree and once completed it confirmed their initial suspicions that birds did indeed evolve from two legged dinosaurs. Evidence has shown that some of the first feather bearing dinosaurs were not intended for flight but rather used feathers for warmth in cold climates. It wasn’t till many thousands of generations later were the feathers used to take to the skies. The first feathers on dinosaurs were more reminiscent of fur than the feathers we see today, at first they did not have a

central column and branches were not streamlined together making them ineffective for flight. Scientists now know that the ancestor of all the living birds lived at Late Cretaceous some 65 million years ago and from there it has diversified into the thousands of species of birds we see on earth today.

http://evolution.berkeley.edu/evolibrary/article/

Bibliography


• Understanding Evolution. 2016. Understanding Evolution. [ONLINE] Available at:http://evolution.berkeley.edu/evolibrary. [Accessed 01 June 2016].

• Fossils, Rocks, and Time: Fossil Succession . 2016. Fossils, Rocks, and Time: Fossil Succession . [ONLINE] Available at: http://pubs.usgs.gov/gip/fossils/succession.html. [Accessed 02 June 2016].

• Evolution and the Fossil Record by John Pojeta, Jr. and Dale A. Springer. 2016. Evolution and the Fossil Record by John Pojeta, Jr. and Dale A. Springer. [ONLINE] Available at:http://www.agiweb.org/news/evolution/datingfossilrecord.html. [Accessed 23 May 2016].

• YourDictionary. 2016. Examples of Natural Selection. [ONLINE] Available at:http://examples.yourdictionary.com/examples-of-natural-selection.html. [Accessed 01 June 2016].

• The Life of Birds | Evolution. 2016. The Life of Birds | Evolution. [ONLINE] Available at:http://www.pbs.org/lifeofbirds/evolution/. [Accessed 02 June 2016].

• BBC. 2016. BBC - Earth - How do we know that evolution is really happening?. [ONLINE] Available at:http://www.bbc.com/earth/story/20150803-how-do-we-know-evolution-is-real. [Accessed 29 May 2016].

• Live Science. 2016. Where Are the Oldest Rocks on Earth Found?. [ONLINE] Available at:http://www.livescience.com/32763-where-are-the-oldest-rocks-on-earth-found.html. [Accessed 04 June 2016].

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