Evoloution: The Unifying Theory Of Biology

Evolution: The Unifying Theory of Biology Investigating Darwin’s Theory Of Evolution Flynn Gordon - May 2, 2017

So What Is Evolution?

The theory of Evolution is often misunderstood or thought to be more complicated than it really is due to the skepticism that surrounds it and misleading statements like “Humans evolved from monkeys”. In reality, evolution is simply the changing in characteristics of a species overtime across many generations driven by the process of natural selection. Natural Selection was introduced by Charles Darwin in his book “On the Origin of Species” back in 1859.

Natural selection is a selection mechanism in which plants/ animals/organisms with favorable traits have a higher chance of surviving and then reproducing, therefore passing on there traits to the future generations. Because species with less

THE THEORY OF EVOLUTION

BY FLYNN GORDON

1

favorable traits are less likely to reproduce, the species as whole will become made up of organisms with favorable traits and therefore adapt to their environment. The reason the organisms within a species are not born the same is because of differences in heredity. This means that the offspring inherit traits from both parents and therefore are a combination of genetic traits. This means that every individual within the species is born with different variations based on their genetics. These variations effect whether or not that animal will also survive and reproduce.

Overtime a species can migrate to new environments or be separated from the original population. The new selective pressures will cause it to evolve different to the rest of its species in the old environment and eventually it can change to a point where it becomes a new species. It is considered a new species when it has a reached a point where it can no longer produce fertile offspring with the original species. This is why there is so much biodiversity on earth. 

Let’s take a look at the Fossil Record‌ Through the use of the fossil record we can determine the age of the earth because we can determine how long the fossils have been there for. When we find fossils that date back further and further we know that earth must have been around for at least that length of time because we know the fossil has been on earth since then. Many fossils have been found that show the earth is at least 3.5 billion years old with many believing it is closer to 4.5 billion years old. Not

THE THEORY OF EVOLUTION

BY FLYNN GORDON

2

only do these fossils show the age of the earth, they also so show ho long life has been on earth. Fossils have been found in Australia in 3.4 billion year old rocks. In other parts of the world we have found fossils that are 3.5 billion years old and a recent study has possibly found tube like fossils dating 3.77 billion years old.

Archeologists use different dating techniques in order to determine the age of objects depending on what it is made of and what they are comparing it to. There are two main categories of dating, relative dating and absolute dating. Relative dating, as the name suggests, compares artifacts based on which one is older than the others. It cannot give an exact date or time but instead shows the order in age. Absolute dating on the other hand uses new dating techniques which show the exact age of an object using different techniques.

Absolute dating uses the chemical and physical properties of an object in order to determine the exact age.

Some absolute dating methods include radiometric dating, dendrochronology and the molecular clock. Radiometric dating, sometimes known as radioactive dating is a method used to date objects like rocks or carbon. This is done by tracing the radioactive impurities that are contained in the fossil when it was formed. Dendrochronology, informally known as tree-ring dating is used to determine the age of trees by counting the layers of the tree that form yearly. As well as showing the age of the trees, the tree rings can show changes in the

THE THEORY OF EVOLUTION

BY FLYNN GORDON

3

environment, (especially the climate) that occurred during the tree's lifespan. By demonstrating the climate during certain years, the tree rings can be used to show the conditions fossils from the same time period underwent.

The molecular clock, also known as the gene clock or evolutionary clock, is a measure of evolutionary change that shows the mutation rate or the number of changes and mutations in the gene sequences of a species that have occurred overtime. The fossil record shows different changes of a species overtime therefore we can determine the relative speed at which the species mutates overtime. We can then calculate using the molecular clock the times at which a species has diverged.

Now let’s take a deeper look at Natural Selection…

Natural selection, the driving mechanism of evolution, was first theorized by Charles Darwin along with Alfred Wallace. It is the idea that living things which are more suited to their environment have a higher chance of surviving long enough to reproduce and have large number of offspring. On the other hand, plants and animals that are not suited to their ecosystem are more likely to be outcompeted and preyed on leading to them having less or no offspring. In darwin’s theory there are three main components that affect natural selection.

Firstly, variation among the species can affect it’s ability to survive and reproduce. This could include differences in size and color among the organisms that enable them to blend in better within their environment or bigger animals may be more likely to dominate in a pack and reproduce. Overall organisms with characteristics that are more suited to their environment are more likely to survive and reproduce compared to animals with unfavorable variations.

THE THEORY OF EVOLUTION

BY FLYNN GORDON

4

Secondly, another factor influencing whether or not organisms survive and reproduce is selection. Certain organisms within the species possess traits that make them more likely to survive. Selective agents can range from predators to lack of food or lack of light as well as viruses and disease. For example, if a deadly disease spreads throughout a species only the animals that are naturally resistant to the disease will survive and go on to produce disease resistant offspring. Another example could be that animals which are naturally faster are more likely to escape their predators and therefore survive and reproduce equally fast offspring.

Furthermore, competition influences the survival of an organism. Among a species, or among similar species living in the same environment, there is competition for limited resources. For example if two species share the same prey they compete for food. Another example is how animals within a species may compete to be the alpha and therefore reproduce more. Another example is that similar plants may compete for light in a dense forest and therefore only certain plants survive. Competition leads to survival of the most competitive among species.

So is Natural Selection Occurring around us?

Yes, natural selection is a continuous process that is happening all around us whether we notice it or not. A great example of natural selection is the peppered moth. In Europe, before around 1760, most birch trees where a light brown color. This meant that the peppered moths which were pale, were more likely to survive then the darker variety as they camouflaged on

THE THEORY OF EVOLUTION

BY FLYNN GORDON

5

these trees. The darker moths where easily seen by birds meaning there was less chance of them surviving and reproducing. As the industrial revolution progressed from this time onwards the trees became much darker due to the pollution. This meant that the pale moths no longer blended in and the darker moths where now more likely to survive and reproduce as they could camouflage with the dark bark of the birch trees. In areas that where less urban the light colors still lived on because the trees colors didn’t change as much but among the urban towns and cities the dark variety grew much larger in population.

Survival of the fittest?

Survival of the fittest is a common phrase linked to Darwin’s theory of natural selection but is often misleading. This is because fittest doesn’t necessarily refer to the strongest or fastest among a species but the animal that has a wide range of characteristics and traits that best suit its environment. This leads to the ‘fittest’ animals, surviving and reproducing.

What is speciation?

Speciation is defined as the formation of new species overtime. This can happen in two ways, branching evolution or Phyletic evolution. Phyletic evolution, which is the less common form of evolution, occurs when a species changes slowly over time in a uniform pattern until it reaches the point where it is a new species. Then there is branching evolution

THE THEORY OF EVOLUTION

BY FLYNN GORDON

6

which can be broken down into two main processes, divergent and convergent evolution.

Branching evolution usually occurs when a species is separated to form different populations. This separation whether it be caused by a body of water blocking the path or some other barrier like a mountain range will stop the species interbreeding. The different populations then overtime evolve and develop new characteristics in order to suit their environment.

Divergent evolution is when new species have come from the same ancestors but have changed so much that they are now different species. This is because at some point they were separated as discussed above. They are considered new species when they have evolved to such a point where even if they were reintroduced they would be unable to produce offspring.

Convergent Evolution on the other hand, is when two different species develop similar characteristics because they have undergone similar environmental conditions and pressures overtime. This occurs over a long period of time as two different species adapt to the same environment. Through their adapting they develop similar characteristics.

Speciation in the real world‌ An example of speciation could be sharks and dolphins. We know that sharks and dolphins are not closely related and therefore don’t have the same ancestor.

Although they come from different ancestors they share similar traits such as streamlined bodies, dorsal fins and flippers all caused by Convergent evolution.

THE THEORY OF EVOLUTION

BY FLYNN GORDON

7

Where’s the proof?

There is a lot of evidence to back up the theory of evolution. Firstly, the fossil record contains a great deal of evidence to backup the theory. The fossil record shows how gradual change has occurred overtime as we can see certain organisms changing over millions of years in order for them to adapt to their new environments.

Furthermore we can see where certain organisms have died out along the way as they have not been able to adapt. In addition to this, we can see that animals have become more complex overtime and have adapted and changed depending on their location. As well as this, transitional fossils have been found which show us the progression between different species and how they might have evolved.

We can also look at the anatomy of different species to determine if they have similar structures and therefore possibly similar ancestry. When we find homologous structures we can determine that although these different species have different environment they in fact come from the same ancestor.

As well as all this evidence we can also compare the DNA and proteins of species in order to determine how closely related they are. The more closely related to species is, the closer the match is in their DNA. DNA can also show us how long a species has been separated providing further evidence to the theory of evolution.

Finally, by looking at the animals currently existing we can see how selective pressures have caused similar animal to overtime develop different traits in order to fit in with there environment. An example of this is the differences among birds. Birds that spend time in water have webbed feet whereas land birds do not. Not only this but different birds also have different beaks depending on their diet.

More obvious adaptations include different colors of birds that help them fit in better with their environment.

THE THEORY OF EVOLUTION

BY FLYNN GORDON

8

A Whale Case Study It is believed that the journey to the whales aquatic life began some 50 million years ago when they first started developing an entirely new set of characteristics to suit their changing environment.

It first started with the Indohyus, a type of deer shaped animal about the size of a cat that belonged to the even-toed ungulates family. There greatest link to whales is the thick bone located in the middle ear which was most likely an adaptation to improve underwater hearing, thus providing evidence that whales also originated from the same family. It is believed that these animals entered the water to escape prey or hunt for the wider abundance of food. Several fossils, as seen above, have been found that prove the Indohyus’s existence.

The next link is the ancient whales from the pakicetids family. They looked more like wolves than whales but had more adaptations that made them able to survive in water and on land. This animal had eyes located higher up the skull letting the animal see above the water while still submerged. They also had heavier bones in order to stop them floating above the water and the same thick bone in the middle ear. Fossils of the Pakicetus where first found in Pakistan, hence their name.

After that came the Ambulocetus (the name means ‘walking whale’) which was much larger at around four metres long and thought to have swum like an otter. It had strong front limbs as well as bigger back limbs. It could walk on land but would be slow and most research suggests that it was mainly aquatic. It consumed a diet of fish and possibly hunted animals venturing to close to the water. It had more adaptations to improve hearing then any of the other animals discussed including a large cavity in the jaw used to transmit

THE THEORY OF EVOLUTION

BY FLYNN GORDON

9

sound to the ear better. This transitional fossil provides a strong link showing that whales evolved from land mammals. There has been less than 10 Ambulocetus fossils found, with the majority of them in Pakistan and only one complete fossil.

Next where the Protocetids which existed about 40-49 million years ago and were slightly similar to the Ambulocetus in size and shape. It is believed they spent all most all there time in the water but came on land to mate and give birth. They had more adaptations like modified jaws and ears in order to improve their hearing in the water. As well as this they had more adaptations connecting them to whales such as their loosely connected pelvis and the nasal openings positioned halfway up the snout. Multiple Protocetids fossils have been found including a pregnant Protocetid and the unborn calf, which has provided evidence for the idea that they gave birth on land as well as providing an example of a female skeleton.

Continuing on, around 40 million years ago the Basilosaurus and Dorudon were alive.

The Basilosaurus was unusual in shape measuring up to 18m long and over 2m wide. The Dorudon was a smaller whale with a similar shape to that of the Basilosaurus. Both animals had webbed like hands and lived only in water. They both consumed a diet of fish but is believed that Basilosaurus often killed and ate young Dorudon’s when they came in contact.

After this the fossil record ends but is thought to be more likely that the Dorudon evolved into the modern whales of today. Many Basilosaurus and Dorudon skeletons have been found including Dorudon fossils with Basilosaurus bite marks in the skull. These fossils show how the evolution continues as they have become fully aquatic.

THE THEORY OF EVOLUTION

BY FLYNN GORDON

10

About 34 million years ago Mysticeti and Odontoceti whales appeared. At the time the environment was changing rapidly and new food sources such as krill appeared. These early Mysticeti ate krill by consuming the water and kirill before trapping them with its teeth and forcing the water back out. As it evolved further it grew teeth and baleen in order to consume large amounts of krill before eventually evolving into the different types of baleen whales present today. In most species the teeth disappeared and simply Baleen was present in the mouth. The Odontoceti whales on the other hand became whales with teeth like the beaked whale and sperm whale.

In conclusion, it is thought that these animals are not direct ancestors of the whale but a more likely to belong to the family tree in which the whale evolved from.

THE THEORY OF EVOLUTION

BY FLYNN GORDON

11

Bibliography "Evolution, Biological." Encyclopedia of Science and Religion. . Retrieved March 28, 2017 from Encyclopedia.com: http://www.encyclopedia.com/education/encyclopediasalmanacs-transcripts-and-maps/evolution-biological http://evolution.berkeley.edu/evolibrary/article/evo_02 Article by: Berkeley University Website name: understanding evolution Launched in 2004 Link to list of authors: http://evolution.berkeley.edu/evolibrary/credits.php perkins, roger. "Fossil Record". Fossilmuseum.net. N.p., 2017. Web. 10 Apr. 2017. http://www.fossilmuseum.net/fossilrecord.htm Source: Boundless. "The Fossil Record as Evidence for Evolution." Boundless Biology Boundless, 9 Aug. 2016. Retrieved 10 Apr. 2017 from https://www.boundless.com/biology/ textbooks/boundless-biology-textbook/evolution-and-the-origin-of-species-18/evidence-ofevolution-129/the-fossil-record-as-evidence-for-evolution-521-13099/ "Dating | The Smithsonian Institution's Human Origins Program". Humanorigins.si.edu.

N.p., 2016. Web. 12 Apr. 2017. http://humanorigins.si.edu/evidence/dating Barazesh, Solmaz. "Probing Question: What Is A Molecular Clock? | Penn State University".

News.psu.edu. N.p., 2008. Web. 12 Apr. 2017. http://news.psu.edu/story/141281/2008/11/17/research/probing-question-whatmolecular-clock http://www.actionbioscience.org/evolution/futuyma.html published: December 2004, Website: Action Bioscience N.p., 2017. Web. 14 Apr. 2017 "Evolution And Natural Selection". Globalchange.umich.edu. N.p., 2017. Web. 14 Apr. 2017.

(University of michigan) http://www.globalchange.umich.edu/globalchange1/current/ lectures/selection/selection.html Society, National. "Speciation". National Geographic Society. N.p., 2010. Web. 18 Apr. 2017. http://www.nationalgeographic.org/encyclopedia/speciation/ “Core Science Stage 5 NSW Australian Curriculum edition� (textbook) 12.6 speciation, N.p., 2010. Web. 18 Apr. 2017

THE THEORY OF EVOLUTION

BY FLYNN GORDON

12