Termionology

Population

The general definition of population is all the inhabitants of a particular place, however, in terms of biology it is a name given to a group of individuals of organisms which can be interbred. It is important to understand what is population in order to understand how genetic population works and what organisms are a population.

Population Genetics Introduction

Population genetics contains the study of the factors which contribute and cause changes in allele frequencies. Allele frequency is how often a certain alleles appear within a population. There are five main elements which contribute to change in allele frequency; natural selection, sexual selection, mutation, genetic drift and gene flow.

Natural Selection

Natural selection is highly linked to the theory of evolution. As organisms evolve their alleles evolve with them, alleles that produce new traits within the organism that enables it to survive better than other organisms in the population. They are then able to pass on their new more successful alleles to be passed onto the next generation. This therefore means that alleles for fitter organisms become more frequent. This can also be done in a none natural manner using genetic manipulation.

Sexual Selection

Sexual selection occurs when the organism decides who to breed with for example an organism which appears to be stronger is more likely to be desired than an organism that isn’t. This means that alleles for more sexually attractive organisms become more frequent.

Mutation

Genetic mutation occurs during meiosis, a cell alleles is damaged during the transfer process. People often associate mutation as a bad thing which hinders an organism and its chance for survival; however, genetic mutations can be highly helpful and aid survival.

For example an artic fox was originally brown, but a mutation occurred which caused a selected few to be born with white fur. The white fur made it more difficult for predators to spot the fox, making the white furred fox a better survivor compared to the original coloured fox and the white furred fox went on to reproduce and the gene carried on to next generations.

Genetic Drift

Genetic drift, also known as allelic drift is the changes in allele frequency due to random chance. Genetic drift usually occurs within small populations as the chance is a lot higher and it happens a lot quicker due to the smaller amount of organisms in the population, random fluctuations appear in the gene pool, and it is assumed that it is purely chance rather than natural selection. Those genes are then passed on causing the gene pool to drift away from the original genes. Genetic drift does not cause organisms to become fitter or weaker but simply different.

Gene Flow

Gene flow also known as gene migration causes changes in the allele frequency due to the exchange of genes between to interbreeding populations. This happens when organisms interbreed with other organisms which are from a different population who have their own allele frequencies which differ.

An example of when gene flow occurs is when organisms are forced to migrate into a different area due lack of vegetation or changes in the environment and are forced/ able to breed with other animals outside of their population.

Gregor Mendal

Gregor Johann Mendel, an Austrian monk, discovered the laws of inheritance. Mendel was born the 22^nd July 1822 in Hynice, Czechia. He was a scientist, teacher and monk. Gregor Mendel’s parents were farmers and growing up on a farm Mendel became highly interested in gardening.

Seeing Mendel’s obvious talent his parents struggled to pay his tuition to high school and, later, the Olmutz Philosophical Institute. Unfortunately, they were unable to pay his university fees so instead he joined Augustinian monastery teaching part time at a high school. In order to teach full time Mendel was required to sit exams which he failed on two occasions. Gregor Mendel was also assigned to work as a chaplain for a hospital; he found it infuriating and far too difficult and later decided to resign to the monastery where he had taken to tending the garden.

Another reason he chose to join the monastery is due to his financial troubles, joining meant that he could carry on his studies without having to worry about cost. He later proceeded to the University of Vienna where he chose to study physics, botany and chemistry. After finishing university he returned to the monastery and became a teacher of natural sciences at the Technical School at Brno.

In the 1856 Gregor Mendel, began to experiment with peas, his main purpose of his investigation was to develop an understanding of how any organism passes physical characteristics or traits from one generation to the next.

Gregor Mendel’s Experiments

Mendel focused on certain traits of the pea plant, such as height, colour of seeds and the shape of the pea seeds. He carefully organised which plants cross pollinated in order to track which characteristics were passed between generations. To cross pollinate Gregor Mendel took the pollen from one pea plant and placed it onto another which he had selected.

For Mendel’s first experiment he took the pollen from one short stemmed pea plant and placed it on another selected short stemmed plant; the outcome was as expected, the offspring were all short stemmed pea plants. Mendel called these “true breeders”; the term was given because all of the offspring were the same as the previous generation.

For his second experiment, he completed the same experiment but with long stemmed pea plants. Taking the pollination of one long stemmed plant and placing it on another, like most people Mendel believed the result would be long stemmed pea plant offspring, but, he was wrong. Some of the offspring were tall, however some of the offspring were short stemmed.

After completing more experiments Gregor Mendel eventually discovered some tall stemmed are “true breeders” producing only tall offspring, while others were not “true breeders” as they produced mixed height offspring.

To develop his understanding further Mendel began more experiments taking pollen from tall stemmed pea plants (true breeds) and pollinating short stemmed plants (also true breeds). He did this in order to find out which trait would be passed onto the next generation. Surprisingly thought he result of the offspring were all tall stemmed pea plants, he called this generation the F1 generation.

The short stem trait appeared to have disappeared. Mendel then proceeded to cross pollinate the F1 generation with other pea plants in the same F1 generation, by doing this the short stemmed pea plant trait reappeared creating some short offspring.

Gregor Mendel’s Discovery

By doing this Gregor Mendel discovered that every plant has two genes for each trait not one. This meant that “true breed” short stem plants have two short genes where as a “true breed” long stem plant has two long genes and cross pollinated short and long stem pea plants produce offspring with one long and one short gene.

Later Mendel discovered that some genes are more dominant than others. When there are two mixed genes (long and short) the most dominant gene will determine how the plant will grow. The gene which is not dominant is known as recessive. In pea plants the dominant gene is the tall gene or trait, while the short gene is recessive. Although the offspring may have been a tall stemmed pea plant it can still carry the short recessive gene which may appear in future offspring.

Gregor Mendel’s Hypothesis

            Gregor Mendel then later went on to develop a hypothesis about inheritance and how genes are passed from one generation to the next. The hypothesis which is still used today by scientist states that a pea plant or any other organism has two genes for each trait, creating a gene pair.

            During any reproduction process, each parent can only pass on one gene from each trait or gene pair to their offspring. This therefore means that the offspring will inherit one gene from each parent creating a new gene pair.

Gregor Mendel’s Gene Codes

When writing gene pairs scientists use a mixture of uppercase and lowercase letters (TT), (Tt), (tt). Capital letters represent the dominant genes while the lowercase letters represent the recessive gene.

In Mendel’s experiments with pea plants he coded the “true breed” tall stem pea plants as (TT), this indicates that the gene pair for the height trait are both dominant tall genes, while the code for “true breed” short stem plants is (tt) indicating that the height trait is composed of two recessive short genes.

When cross pollinating a short and a tall stem plant; the result would be (Tt); one tall dominant gene with one short recessive gene. He then later cross pollinated two (Tt) plants, this produced mixed results, and some plants received both (TT) and both (tt) genes, while others still came out with (Tt). All plants with combinations (TT), (Tt) or (tT) were tall as (T) (the tall gene) is the most dominant gene.

From this Mendel was able to work out the chances of having a small stemmed plant when cross pollinating two (Tt) pea plants. The results were three out of four or 75% chance that the offspring will be tall and one out of four chances or 25% chance of the offspring being short.

Dominant and Recessive

            Nearly all gene pairs have a dominant gene and a recessive gene; however this is not always the case. Instead of one gene dominating another, it is highly possible for genes to produce mixed result. For example Four o'clock flower. When you mix a red (RR) flower with a white (WW) flower, the result is (RW), however, the flower is neither the red or white, there is no dominant gene. The result is a mixed pink flower.

            Before passing away on January the 6^Th 1884, wrote “I am convinced that it will not be long before the whole world acknowledges the results of my work”; which as he predicted was true, his discovery was rediscovered thirty-five years later creating a foundation for modern genetics.

Charles Darwin

Charles Darwin was born on February the 12^th 1809, Shrewsbury England and passed away on April the 19 1882at the Down House in Kent. His parents were Robert and Susannah Darwin. Charles Darwin’s father (Erasmus Darwin) had also been a doctor/ physician. Erasmus made his real name by being a poet of the natural world. Susannah Wedgewood (Darwin’s mother) family were potters which is how her father (Josiah Wedgewood) made his fortune. Although their professions may be different both sides of Darwin’s family had liberal politics and felt indifferent about their religion.

            Charles Darwin was home schooled with his sister (Caroline) up until the age of eight when his mother died. He spent the next year attending day school until he was transferred to boarding school. His academic ability was acceptable but highly average. At the age of sixteen his father sent him to the University of Edinburgh where he was to study medicine.

He spent a lot of time hunting and collecting instead of completing his medicine study, this is when he began to learn how to study and collect beetles. During this time he was taken under the wing of biologist Robert Grant. After two years of university Darwin was not to become a doctor. Darwin’s father showed a level of understanding and aided him in his transfer to the University of Cambridge; where he then began his study to be a clergy of the Anglican Church. This is where he met friend and botanist John Henslow.

Not long after his graduation in 1831, Darwin was offered a job on board the HMS Beagle; where he would be mapping the coast of South America. The voyage took five years, according to records and notes Darwin’s most important years were spent at the Galapagos Islands; this is where he found never seen before animals and plants. He took notes and samples which he would send to his friend Henslow in England to be kept safe.

Upon Darwin’s return to England, he was greeted with the excitement and fascination of geologist, zoologist, and botanists as the variety and never before send specimens which had collected. Following this he spent ten years cataloguing and describing all the discoveries he made. By doing this he wrote books upon books about coral reefs, volcanic islands, various papers and a journal about his voyage.

By doing this he encourage himself to think and look deeper into the origin of these new wonderful species. He began his first notebook regarding this topic in 1837; eventually he gained the confidence to share his theory “evolution by natural selection” 20 years later.

In 1839, Darwin married his cousin Emma Wedgewood and moved to London to focus on his work. Unfortunately, they had to relocate again due to Darwin’s health problems. They resided in a village which was quiet, peaceful and the perfect place for Darwin to finish his work.

Upon completing his work on the results of the HMS Beagle Voyage, he was yet to publish his thoughts on his theory of evolution. He chose to focus his theory on a small thing such as the different kinds of barnacles, although the project seemed small at first it grew fast and gradually turned into four volumes of dissection and description. This task took him eight years. Once complete he turned his attention back to his evolutionary theory.

In 1857, Darwin’ theories correlated with a paper regarding the evolution of species, this paper was sent to him by Alfred Russell Wallace (whom shared an extremely similar view). Darwin presented a picture to coincide with Wallace’s paper to the Linnean Society. To prevent someone else taking credit for his extrodinary work Darwin published an abstract from his book which he had been currently working on.

The abstract was published in 1859 as On the Origin of Species, or the Preservation of Favoured Races in the Struggle for Life. It immediately took off and completely sold out of the first prnting of it within a day. It sparked debates across many of its subject area and Darwin decided to isolate himself from it all and made no comments on any of the topics. His theory undergone many critisms and skeptical judges, yet his friends Joseph Hooker (botanist) and Thomas Henry Huxley (zoologist) defended him even though he did not defend himself and continued with his research.

Darwin had five main theories;

1.      Evolution: “Species come and go through time, while they exist they change”

2.      Common Descent: “organisms are descended from one, or several common ancestors and have diversified from his original stock”

3.      Species Multiply: “the diversification of life involves populations of one species diverging until they become two separate species; this has probably occurred billions of times on earth”

4.      Gradualism: “evolutionary change occurs through incremental small changes within populations; new species are not created suddenly”

5.      Natural Selection: “evolutionary change occurs through variation between individuals; some variants give the individual an extra survival probability”

Darwin believed these theories to be part of one big theory which all works together, and all occur together. Scientist took time to see what Darwin did, what Darwin could see then took scientist until the 1930s-1940s to see.

To prove he was correct in his theories he collected evidence and data to support his hypothesis. He researched reports from others to support as well as his own work and observations. Still unable to convince people of what we now know to be the truth he demonstrated it using artificial selection using domestic animals and plants.

Charles Darwin was an enthusiastic with an obsession and rigorous need to research and collect facts. No animal was to escape his notice; domestic animals were dissected ad the drawn highlighting differences. In the picture shown below is a section from his book regarding rabbits.

“I shall in this volume treat, as fully as my materials permit, the whole subject of variation under domestication. We may thus hope to obtain some light, little though it be, on the causes of variability, - on the laws which govern it, such as the direct action of climate and food, the effects of use and disuse, and of correlation of growth, - and on the amount of change to which domesticated organisms are liable. We shall learn something on the laws of inheritance, on the effects of crossing different breeds, and on that sterility which often supervenes when organic beings are removed from their natural conditions of life, and likewise when they are too closely interbred. During this investigation we shall see that the principle of selection is all important. Although man does not cause variability and cannot even prevent it, he can select, preserve, and assimilate the variations given to him by the hand of nature in any way which he chooses.” Charles Darwin, introduction to Variation.

Charles Darwin worked on three during the 1860s, one contained information about variation under domestication, and he saw this as a parallel representation of the wild species. The second was about the evolution of humanity and the roles of sexual selection. The third and final book was about the expression of emotions. His second book which he had worked on was named “The Descent of Man” and was published in 1871.

The book did not do as well as Darwin had planned, he expected it to be in high demand and cause a massive sensation with the public, his claims that humans are descendants should have done as he so wished, however, due to the “Origins” the thunder had been stolen 12 years ago. In 1872, “The Expression of Emotions in Animals and Man” was published. In this he showed the similarity and differences between animals and humans one of his pictures were of an embryo of a human and one of a dog.

Throughout the last ten years of his life, Charles Darwin removed himself from evolution and focused on his gardens. He researched climbing plants and the geological role of earthworms. He proceeded to turn his workshop into a fully functioning greenhouse, which led to him creating several more books. The illness which began at the start of his marriage began to take over making him weaker but no less determined to continue work and enjoying his elderly age.

By the year 1877, his theories still sparked their original controversies; however, he had the respect of the University of Cambridge and did him the honour of giving him a doctorate. In 1882, his condition became even worse and he passed away 19^th April 1882 at home (Down House) and was buried in Westminster Abbey.

Were We Endangered?

According to some research homo sapiens were endangered. A mysterious illness, thought to be tuberculosis, supposable wiped out all but 2,000 if our early ancestors around 70,000BC. This put us on the same level as Black Rhinos and Giant Pandas on the current endangered species list.

We share 70% of our DNA with a slug

Theoretical Timeline from Billions of Years to Thousands of Years

4.6 Billion Years Ago

The Origin of The Earth

3.5 - 3.8 Billion Years Ago

First Life Arises, Simple Celled Bacteria (Prokaryotes)

3 Billion Years Ago

Photosynthesis Began

2 Billion Years Ago

First Complex Cells with Organelles (Eukaryotes)

1 Billion Years Ago

First Multicellular Life Begins, Cells with Multiple Organelles

600 Million Years Ago

Simple Animals Appear, Such as Jellyfish and Worms

570 Million Years Ago

Arthropods (Ancestors of Insects, Arachnids and Crustaceans)

550 Million Years Ago

Complex Animals, Such as Bilaterians

520 Million Years Ago

First Appearance of Trilobites

500 Million Years Ago

First Fish and Proto-Amphibians Begin to Appear

475 Million Years Ago

First Land Plants and Fungi Form

400 Million Years Ago

Insects and Seeds

360 Million Years Ago

Amphibians Evolve, Most of The Land Surface Was Covered in Fern Forest Which Eventually Would Become Coal

300 Million Years Ago

Reptiles Evolve

250 Million Years Ago

First Mass Extinction of Life Forms, Including Trilobites

231 Million Years Ago

Dinosaurs First Appeared

200 Million Years Ago

First Mammals Appear

150 Million Years Ago

First Birds

130 Million Years Ago

First Flowering Plants

120 Million Years Ago

First Appearance of Bees

65 Million Years Ago

Second Mass Extinction, Non-Avian Dinosaurs Die Out

45 Million Years Ago

First Modern Mammals

35 Million Years Ago

First Grasses Form

3 Million Years Ago

First Hominids (Australopithecus)

2.6 Million Years Ago

Start of the Ice Age

2.5 Million Years Ago

Appearance of Homo sapiens

200,000 Years Ago

Appearance of Modern Humans

100,000 Years Ago

Humans Colonise All Habitable Land Masses

25,000 Years Ago

Neanderthals Died Out, Leaving Space For The Homo Sapiens to Become the Only Species of Human

11,500 Years Ago

End of the Ice Age

15,000 Years Ago

Agriculture Began

Theoretical Timeline Over Billions of Years

4.6 - 4 Billion Years Ago

The Origin of Earth

3.8 Billion Years Ago

First Life Appears. Simple celled bacteria producing oxygen, known as Prokaryotes

2.1 Billion Years Ago

Multicellular Life Evolves. First cells with organelles, known as Eukaryotes

2 - 1 Billion Years Ago

Eukaryotes evolved further creating organisms such as algae, seaweeds, sponges, jellyfish and worms

1 - 0 Billion Years Ago

Our species, Homo sapiens evolve

Human Brains are Shrinking

Although as a species we are becoming smarter, our brains are actually shrinking making them more condensed. According to research conducted by John Hawkes at the University of Wisconsin, the size reduction is most likely due to decreased physical size. Less mass = less brain required to control it.

9% of people are missing the muscle in their foot that allows them to grip objects like our primitive ancestors.

Welcome

Hello and welcome to the 'Notion of Evolution', the blog exploring all things evolution, from fact to theory.

Each week I will aim to discuss a new aspect or concept, providing evidence and posing questions, coming up with my own theories by analysing the data available.

From Mysterious to Obvious?

I previously said "evolution in its self is a definition explaining the mysteries of life and its progression throughout its existence" it converts the mysterious into what most evolutionary biologist believe to be now obvious. It does so by equitably analysing ideas and data presented in order to try and achieve a reliable understanding of the available evidence.

It has taken two centuries of rigorous hard work- constant gathering of mass amounts of data, which underwent multiple comparisons of many other interpretations, rejections and controversies from other scientist, religions and philosophers.

In the current age, evolutionary biologist consider the ideas and observations of their data to be reliable. They have survived intense examination and unequivocal considerations of possible alternatives.

Most of society believe that evolution is either fact or theory, but I pose the question to you all, why not both? I accept that some aspects of evolution is fact, but the gaps are filled in with theory, there are still missing answers to which we can only wonder about, whether life was made or occurred being one of the most debated lingering questions. Until we are able to find the missing pieces, it is logical to look at evolution as a mixture of both concepts, fact and theory.

Introducing 'Evolution'

What is Evolution?

Evolution has many different definitions ranging from the basic to the complex intricate details, evolution in its self is a definition explaining the mysteries of life and its progression throughout its existence.

Definition

By definition it means the process in which different kinds of living organisms are believed to have developed from earlier forms beginning from the dawn of life. Or in a more general sense, it is the gradual development of something.

Believed is underlined as there is still a lot of debate as to whether evolution is a theory or fact, this depends on your perspective, religion, research and your personal belief. It is important to remember this in order to keep an open mind regarding the subject. While there is little doubt that things can evolve, to the extent of which is still not confirmed.

Origin

The word evolution stems like most words evolved from Latin. Evolvere -> Evolutio (means unrolling). Resulting in the early 17th century English version Evolve -> Evolution.

Evolution of the Word

First record of the word 'evolve' was used to in describing 'wheeling' in reference to the position and movement of troops or ships. Later it progressed into the notion of 'opening out', giving it the start of its current sense 'development'.

What Even is Evolutionary Biology?

The phrase 'evolutionary biology' or 'evolutionary biologist' has been used a few times and I thought that todays post could take some time to explain what/ who they are, as well as the roles they play within science.

It is a subfield within biology, it aims to understand the diversity of life and the processes that produced the diversity, starting with the origin of life spanning to the present day.

It investigates the evolution of organisms especially in the areas of;

• Molecular and Microbial Evolution
• Behaviour
• Genetics
• Life Histories
• Development
• Systematics
• Morphology

Evolutionary Biology divides into smaller specialised fields;

• Taxonomy
• Palaeontology
• Ethology
• Genetics (population)
• Ecology

Each of these fields investigates evolution on two levels and two scales.

Population & Short Timescale (Microevolution)

How traits become specially adapted to particular survival jobs and reproduction. This process usually occurs quickly and quite short. Also including adaptive and neutral evolution.

Longer Timescale (Macroevolution)

This is the process which is believed to have produced the current diversity  and can been observed throughout the fossil records. It is a longer and slower process, including most of fossil history and systematics.