ArtsAutosBooksBusinessEducationEntertainmentFamilyFashionFoodGamesGenderHealthHolidaysHomeHubPagesPersonal FinancePetsPoliticsReligionSportsTechnologyTravel

A Guide To Evolution

Updated on March 14, 2013

The Father Of Evolutionary Thought

A photograph of Charles Darwin aged 51. He was the first person to bring evolution by natural selection to the public's attention.
A photograph of Charles Darwin aged 51. He was the first person to bring evolution by natural selection to the public's attention. | Source

Examing The Evidence For Evolution

Peppered Moth Variation

Source
These two moths are members of the same species. The variations originally occurred as a result of genetic mutations. Natural selection led to the darkest moth becoming more abundant, as industrial pollution made them better at blending in.
These two moths are members of the same species. The variations originally occurred as a result of genetic mutations. Natural selection led to the darkest moth becoming more abundant, as industrial pollution made them better at blending in. | Source

Darwin's Finches

Isolated gene pools in islands such as the Galapagos create unique traits. The woodpecker finch has evolved to use tools to catch prey.
Isolated gene pools in islands such as the Galapagos create unique traits. The woodpecker finch has evolved to use tools to catch prey. | Source

Speciation Explained

Co-Evolution And Mutual Dependency

Some flowers rely on hummingbirds for pollination, while some hummingbirds rely on specific flowers for nectar. They have co-evolved in terms of shape and colour to accommodate each other's survival.
Some flowers rely on hummingbirds for pollination, while some hummingbirds rely on specific flowers for nectar. They have co-evolved in terms of shape and colour to accommodate each other's survival. | Source

DNA

The thread like structure is two entwined DNA molecules otherwise known as a chromosome. The other DNA molecules form a spiral shape(double helix) that is linked by four bases.
The thread like structure is two entwined DNA molecules otherwise known as a chromosome. The other DNA molecules form a spiral shape(double helix) that is linked by four bases. | Source

The Basics

Evolution is the process of change in the inherited characteristics of populations of animals over time. The crux of this theory is that all life today has evolved and diverged from simple ancestors that lived in the seas over 3 billion years ago. This means that all animals are related to each other. Accumulated evidence from biology, genetics, and fossils supports evolution as the unifying theory that directs our understanding of life and its history.

Evolution is famously known for its large-scale patterns of change, also known as ‘macroevolution.’ Macroevolution refers to large-scale changes such as the evolution of limbed vertebrates from those with fins. Other examples of macroevolution are the emergence of the shelled egg, freeing some land living, four limbed animals from dependence upon water for reproduction and the divergence of egg laying reptiles into other major groups, including turtles and crocodiles. This occurs as a result of small scale descent with modification, known as ‘microevolution.’ For example, since their introduction to the United States of America, house sparrow populations in the north and south of the continent have developed differences, with the northern variant becoming bigger, probably as an adaptation to climate change.

We often hear animals, including ourselves described as a species. But what is a species exactly? Well, in amongst other meanings a species can be basically defined as a group of similar organisms that can interbreed to produce fully fertile offspring. Speciation is the process whereby new species evolve from a single ancestral species. This occurs for a number of reasons, such as geographical isolation arising from habitat fragmentation. If a small population is isolated from the main group and its members can only share genes with each other, over time they will evolve independently to the point where, if they came back into contact with the original group, they wouldn't be able to interbreed.

Over vast periods of time, repeated speciation has led to evolutionary divergence, where new descendent species become significantly different from their common ancestors. For instance, all life on land has diverged from water living ancestors, and all living species of mammal have diverged from a common ancestral mammal like creature that lived alongside the dinosaurs. These series of changes arise as a product of Earth’s dynamic environments, which vary from place to place and from time to time.

Sometimes though, different organisms will evolve similar characteristics to adapt to the environment that they inhabit. For example, the similarity in body forms of whales, seals, and penguins is the result of similar ways of life. The common factor is the adaptation of a streamlined body shape, with reduced limbs for a more efficient swimming motion. In a similar way, wings have evolved independently in birds and bats for flight. This is often known as convergent evolution.

Before I proceed to describe the different evolutionary processes, I shall briefly summarise the building blocks of life, the tiny molecules that make evolution and our lives possible- DNA and genes.

Every form of life is made up of a specific series of molecules, and the order of molecules is contained in a chemical code. This code is extremely complex and is encased in spiral-shaped molecules of deoxyribonucleic acid (DNA). Chemicals known as bases, link each molecule of DNA. There are four different kinds- adenine, cytosine, guanine and thymine. They are always linked up in pairs, with adenine always fusing with thymine, and cytosine with guanine. The sequence of these bases makes up the cell’s genetic code. The code found in each human cell consists of 20,000-25,000 separate instructions. Each of these instructions is known as a gene, and each gene is responsible for controlling certain characteristics. For example, there is a single gene that is responsible for the colour of eyes. Genetics is the study of how these characteristics are inherited and is one of the central pillars of biology.

Sharing A Common Ancestor

Above is a cladogram- a diagram showing a group of organisms descended from a common ancestor. The insect groups in this diagram are all related to an ancestral form that lived more than 300 million years ago.
Above is a cladogram- a diagram showing a group of organisms descended from a common ancestor. The insect groups in this diagram are all related to an ancestral form that lived more than 300 million years ago. | Source

An Example Of Mutation

A chance mutation has caused this moss rose to produce flowers of a different colour to the others. It's possible that, over time the new colour may become dominant.
A chance mutation has caused this moss rose to produce flowers of a different colour to the others. It's possible that, over time the new colour may become dominant. | Source

Genetic Drift Explained

Gene Flow Made Easy

The Five Basic Processes Of Evolution

I shall now summarise the mechanisms that enable evolutionary change to occur, using a hypothetical species of butterfly as an example. Now, originally this particular species was bright yellow, but a chance mutation in the genetic material of one of the yellows resulted in the birth of a purple butterfly. Over a sufficient amount of time, it’s possible that the populations of the yellows and purples could strike even.

Firstly I shall explain how a population of yellow butterflies produced a purple one. As already mentioned, it occurred through chance mutation. A mutation is brought about by a change in the genetic material of an organism that is subsequently inherited by its offspring. This chance alteration can happen through deletion or insertion of a single base in a DNA molecule. Occasionally, single mutations may produce large effects but generally, evolutionary change is the result of many mutations.

The first and most widely known process is natural selection, which is often described as ‘the survival of the fittest.’ Now imagine another hypothetical species of butterfly that varies in colour (yellow/purple) and reproduces in large numbers, not all of which survive, due to limited resources in the environment. Predators eat more of the purples, as they are less camouflaged than the yellows. The surviving yellows produce more of their own kind. With continued predator preference over time, the yellow butterflies become dominant.

Another evolutionary process occurs through a random change in the genetic makeup of a population over time, which is known as genetic drift. For example, a forest fire wipes out most of the purple butterflies in the population. The next generation contains the genes of the lucky survivors, not necessarily the ‘fitter’ ones. Despite being unlikely, it is even possible for a series of chance events to lead to the total loss of the purple population.

Yet another evolutionary process is gene flow (or migration), which results from the movement of genes from one population to another. For instance, genes are carried from one population and introduced to another by the migration of an adult organism. In this example, a purple butterfly leaves a purple population and joins a yellow population. The migrant interbreeds with members of the yellows and, in doing so, introduces its purple genes into the yellow population.

The most interesting process, at least from our point of view is something called gene shuffling. It’s the reason why every single individual human, and indeed every other sexually reproducing organism is unique; it’s all to do with the reshuffling of parental genes. Offspring are genetically identical to each other (except identical twins), nor to one or other parent, but show various combinations of their parents’ genes. New gene combinations, and hence genetic variation, are introduced into a population through the mechanism of sex.

Highly Recommended Literature

The Origin of Species: 150th Anniversary Edition
The Origin of Species: 150th Anniversary Edition

Charles Darwin's groundbreaking book that finally explained how we, and every other living thing came to be.

 
The Voyage of the Beagle
The Voyage of the Beagle

Follow Darwin's exploits on the Beagle and find out how he stumbled across his marvelous discovery.

 
The Ancestor's Tale: A Pilgrimage to the Dawn of Evolution
The Ancestor's Tale: A Pilgrimage to the Dawn of Evolution

Richard Dawkins takes us on a journey through the history of life from the present, right back to the beginning using 'The Canterbury Tales' as inspiration.

 
The Greatest Show on Earth: The Evidence for Evolution
The Greatest Show on Earth: The Evidence for Evolution

Richard Dawkins presenting indisputable evidence of evolution's presence, showing how it continues to operate today.

 
The Last Human: A Guide to Twenty-Two Species of Extinct Humans
The Last Human: A Guide to Twenty-Two Species of Extinct Humans

This excellent book explores our own evolution and how we came to be the sole surviving human species. Whereas previously we had shared the planet with at least four other species.

 

Comments

    0 of 8192 characters used
    Post Comment

    • Dan Barfield profile image

      Dan Barfield 4 years ago from Gloucestershire, England, UK

      This is a very clear explanation of evolutionary theory that covers all the bases! Very impressive sir! Voted up, shared and all of that jazz :)

    • JKenny profile image
      Author

      James Kenny 4 years ago from Birmingham, England

      Thank you very much Dan. Very much appreciate you taking the time to pop by.

    Click to Rate This Article