Notion of Evolution: 2016

Sunday, 13 March 2016

Crocodile

Lovely hand drawn Crocodile, perfect example of evolution to achieve the specific requirements for this habitat. This species heritage goes back to dinosaurs and is still a surviving strongly.

Thursday, 10 March 2016

The animal kingdom is made up of many components such as mammals, birds etc. but one of the most forgotten animal families is the amphibians, are ectothermic (cold-blooded) family plays a major role in our ecosystems. Amphibians can be separated into three different categories, frogs and toads, newts and salamanders and caecilians.

What makes amphibians so special compared to other animals is their unique ability to live on both land and water, also the process which they take growing up, from aquatic larvae which use gills to breathe to developing into terrestrials which use their lungs to breathe oxygen. There are exceptions to this though; some salamanders such as the golden alpine salamander (Salamandra atra) which live only on land their whole lives, or the axolotl (Ambystoma mexicanum) which only ever live in the water. Amphibians can vary in size dependant on their species, they can be as small as 7.7 millimetres long or be as big as 1.8 metres long.

The global status of our amphibian gets drastically worse every year due to a number of causes. One of the main causes is unknown diseases as well as climate change, habitat loss, invasive species, and pollution and of course human influences. Research carried out on the 5,743 amphibian species shows and highlights decline, extinction and some of the possible causes.

In more recent years the discovery of a particular disease known as Chytridiomycosis, has vastly contributed to our amphibian decline. It has many abilities such as eliminating an entire species of amphibians and its ableness to spread to different locations around the world like wild fire.

The image below highlights where worlds amphibian species can be found, as well as how many different species can be found there. Not too surprisingly, there is a vast amount of blue colours showing no more than six species are in these areas.

The Global Amphibian Assessment (GAA) analysed every known species of amphibian and found that out of 1,856, 32% were threatened with extinction. Then analysing all of the species, a further 43% of the species are currently in decline compared to the less than 1% which had actually increased in population size. Shockingly only 23% of the amphibian species population were stable leaving the last percentage of species as unknown.

Amphibians are vital to our ecology, disturbance in the population dynamics affects everything in that area from big things like other animal population dynamics to smaller things such as plants, trees and rocks.

Amphibians are highly sensitive to any and all environmental changes due to a number of factors such as having sensitive skin (permeable). When things such as disease, climate change, or habitat destruction amphibians are affected not only first but the most.

In this diagram you can see the trend patterns of 936 populations of amphibians and how over the years they have steadily declined and fluctuated.

This is another diagram highlighting declines in more detail for both North America and Western Europe.

Chytrid Fungus

One of the world’s biggest amphibian killers at the moment is a fungal disease known as

Chytridiomycosis. Chytrid fungus is disease caused by a particular type of fungus; often found in places with water or high moisture. Research so far suggests that it only affects amphibians. However, although the fungus only directly affects amphibians it causes a chain reaction between predators, prey that echo throughout the whole ecosystem. One of the worlds most affected amphibians is the critically endangered is the mountain chicken.

The disease affects the outer layers of the skin, which contain keratin, this is the layer of skin which is meant to resistant to damage. Chrtridiomycosis makes the skin become tougher and thicker, this makes it difficult to absorb water and salts through the skin which in turn cause not to receive the required amount of oxygen. The final result is death by suffocation. The disease can be recognised by its symptoms;

· Reddening

· Discoloured skin

· Shedding increase

· Abnormal behaviour

· Seizures

· Nocturnal animal becoming diurnal

One of the problems scientists diagnosing the disease is that the symptoms overlap with other amphibian diseases. Fortunately captive kept amphibians can be treated with antifungal treatments and full enclosure disinfection, so far there are no ways of treating wild none captive populations.

In Montserrat and Dominica a Mountain Chicken Recovery Programme was put in place the restore the population of this particular breed of frog. They work with European conservation institutions the country governments to try and prevent the frogs from extinction. They manage to breed, restore and research the frogs in order to prevent further extinction of damage to the ecosystem.

In 2009 when Montserrat discovered that the area was infected by the disease they launched a rescue mission where they removed 50 healthy samples of the mountain chicken frog and placed them into captivity to begin their research and bio-secure breeding programme.

Nationally our own amphibians are in decline, for example the Natter jack toad which lives in a variety of habitats such as coastal dunes, upper saltmarshes and lowland heaths. The chytrid fungus is one of the main causes yet again for the decline but also habitat destruction and the

naturally changing climate altering out British seasons play a major role.

To preserve the toad action is being taken to preserve the sand dunes by restoring them and creating new habitats such as the yellow-dune habitats. This is when they place new substrates and environmental attributes to replace where the natural habitat has been eroded. They try to prevent beach cleaning operations and prevent the natural process of land formation.

Not only are they maintained and creating the dunes for the Natter jack toads but they are also doing it for the pools. This involves pH maintenance, putting in basins to prevent natural erosions which could remove the pools from the habitat. The creation of pools for the toads encourages breeding and population as they replace the old ones and provide safer and more distribution.

Sunday, 6 March 2016

Natural Selection

Natural Selection is one of the key ingredients of constant evolution, followed by mutation, migration, and genetic drift.

Both Charles Darwin and Jean-Baptiste Lamarck proposed different explanations of what natural selection was and how it occurred.

Jean-Baptiste Lamarck's Theory

The Giraffe stretches their necks to reach the leaves
Eventually the necks of the giraffes grow with use
The Giraffes offspring inherit the long neck

Charles Darwin's Theory

Giraffes with longer necks can reach more leaves
Making them more likely to gain enough nutrition to survive and go onto reproduce
The Giraffes offspring inherit the long neck trait

After data gathering and analysis Lamarck was dismissed, Darwin's theory was concluded true.

Further break down of Darwin's theory;

Observation 1- All members of any population often vary in their inherited traits.

Observation 2- Every species is capable of producing more offspring than the environment can naturally support, therefore meaning that some will fail to survive and reproduce.

Inference 1- Organisms with inherited traits are more likely to survive and go onto reproduce, leaving more offspring in the environment compared to others of their species.

Inference 2- The unbalanced ability of specific organisms to survive and reproduce eventually leads to an accumulation of desirable traits in the population occurring over generations.

Key Points

Wide range in variation
Variation is caused by the significant number of differences in genes
The characteristics which are most suited to the environment are more likely to survive and be passed on
Genes are passed to the offspring

Tuesday, 1 March 2016

Evolution of the Pentadactyl Limb

What is a Pentadactyl Limb?

It is a limb that has 5 limbs on the hand and foot.

All the bones are symmetrical to the other limbs; such as both hands, both feet as other Pentadactyl animals.

Examples of Pentadactyl animals are; Whales, Bats, Pre-evolved Horses and most mammals.

A Brief History

Extinct species; that existed 380-360 million years ago (the first known Tetrapods) developed 8 digits when evolving into land mammals.

Over time, the number of digits reduced to an average of 5 digits.

However, in some cases, some animals are born with extra or missing digits. This is due to a mutation.

Which Animals Have Pentadactyl Limbs?

It is most common with humans and other mammals, except whales and dolphins, as they have evolved, their back limbs have reseeded back into their bodies, as they no longer need them. Also, with no external hind legs, it allows them to move easily through the water.

Other mammals have extra digits, such as Pandas, which have digits.

Mammals, such as Moles appear to have extra digits, however, these are only out-growth bones on their wrist.

Pentadactyl limbs are most common with Tetrapods; 4 limbed creatures.

Other Animals With Pentadactyl Limbs

These are Birds, Dinosaurs, Reptiles and Amphibians. For example, Amphibians such as frogs have 4 digits, and Birds only have 3.

Extinct Tetrapods, Dinosaurs, had 3 toes, and Marine mammals have 5 digits.

Another example is the bat. Their fingers have adapted; elongating to help form the bats wings, while the thumb is used to grip onto trees.

Examples

A) Mammal Foot

B) Seal

C) Mole

D) Camel

E) Horse

F) Cheetah

G) Bat

H) Kangaroo

I) Lemur

J) Sloth

Saturday, 27 February 2016

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.

Friday, 26 February 2016

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.

Thursday, 25 February 2016

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.