Evolution
Evolution is the process of which new species of organisms develop from earlier life forms. The groundbreaking idea of evolution was made famous and technically introduced by Charles Darwin. Before this concept, people believed in other theories such as God creating humans, the two famous ones being 'Adam and Eve', which is still commonly believed today. There are other theories some taken so seriously in some parts of America that there is still a debate to teach the theory of evolution whatsoever.
Evolution is about change and almost all modern animals that we see everyday have undergone evolution. Amphibians are not an exception, once amphibians started to live on dry land they adapted to this environment by growing other limbs such as arms and legs. The driving force of
evolution are changes in allele frequency. Allele frequency is a measure of the
relative frequency of an allele on a genetic locus in a population. [1] Evolution also changes allele frequency, there are four reasons why allele frequency might change: mutation,
migration, genetic drift, and natural selection.
4 Methods of Allele Frequency Change
Lets start with genetic drift. Genetic drift is a random change in allele frequency. [2] Genetic drift comes in two forms, the bottleneck effect and the founders effect. The bottleneck effect occurs when a population is reduced by at least one generation, this decreases variation throughout the population. [3] For example, Northern elephant seals have reduced genetic variation
probably because of a population bottleneck effect. Hunting reduced their population size to as few as only 20 seals at the
end of the 19th century. Obviously, their population has grown (up to 30,000 now)—but their genes were still effected by the bottleneck: they have much less genetic variation than a population of
southern elephant seals that was not so intensely hunted. [4]
The founders effect is a little different. "A founder effect occurs when a new colony is started by a few members of the original population."[5] With few members in the colony, the chances of genetic variation is reduced and non-random sample of the genes in the original population is increased. I like to think of the original population as a city- a variety of people, but after the founders effect takes place it turns into something more suburban. For example, the Afrikaner population of Dutch settlers in South Africa is descended mainly from a few colonists. Today, the Afrikaner population has an unusually high frequency of the gene that causes Huntington’s disease, because those original Dutch colonists just happened to carry that gene with unusually high frequency. This effect is easy to recognize in genetic diseases, but of course, the frequencies of all sorts of genes are affected by founder events. [5]
Mutation by definition is a change in the DNA or addition of new alleles into DNA. Mutation in evolution is based a lot on the environment that organisms were put in and how they adapted to it. This change or adaptation is set into the organisms sex cells and gametes, which is how future generations of the organisms would inherit this feature. If the organism is lucky, it would inherit new alleles that are beneficial for survival. If organism is unlucky, it might inherit harmful new alleles that would bring diseases or physical disadvantages for organisms in future generations. [6]
Migration is the movement from one population to another. That also means that new population moves
or integrates their genes to a new population. For example, some individuals
from a population of brown beetles might have joined a population of green
beetles. That would make the genes for brown beetles more frequent in the green
beetle population. [7]
Natural Selection
“It is not the strongest of the species that survives, nor the most intelligent that survives. It is the one that is the most adaptable to change.” Charles Darwin. This quote provides a definition for the Natural selection. The changes can come in any possible form (climate changes, food shortage, predators) and organisms have to learn how to adopt in order to survive. [8]
Natural selection can come in three forms: stabilizing selection, directional selection, and disruptive selection.
Stabilizing selection - Stabilizing selection is when natural selection supports the intermediate states of organisms. For example, very dark and very light col ored oysters are easier for birds to spot and prey on. Oysters with mingled colors have better possibility for survival. This is an example of predator impact on Natural Selection process. [9]
Stabilizing selection - Stabilizing selection is when natural selection supports the intermediate states of organisms. For example, very dark and very light col ored oysters are easier for birds to spot and prey on. Oysters with mingled colors have better possibility for survival. This is an example of predator impact on Natural Selection process. [9]
Disruptive selection - disruptive selection is when natural selection supports both extremes in organisms features. An example would be when the light colored oysters match the color of the rocks and dark ones blend in with the shade of the rocks. This is an example of environmental impact on Natural Selection process. [10]
Lastly, there is directional selection - directional supports only one extreme in organism’s features. In this situation, thicker shelled oysters would be preyed on by crabs and other predators less than thinner shelled oysters because of this factor. This is an example of food shortage impact on Natural Selection process. [10]
Evidence Of Evolution
1. The fossil record. Darwin’s research and discoveries of old fossils proved that the simplest fossils were found in the oldest rocks, and more advance organism fossils were found in top layers of the rocks. Investigation of the different layers of rocks showed a smooth and gradual transition from one form of life to another. [11]
2. Genetic commonalities. Human DNA research showed similarities with many organisms on the planet. For example, human beings have approximately 96% of genes in common with chimpanzees, about 90% of genes in common with cats 80% with cows 75% with mice, and so on. This research gives an idea about common ancestors for many living organisms on this planet. [12]
3. Common traits in embryos. Research of embryos of humans, dogs, snakes, fish, monkeys, eels (and many more life forms) showed striking similarities in its development. As embryos, all these life forms have gill slits, tails, and structures involving the spine. That evidence is also an indication of the same ancestor for many organisms.[13]
4. Bacterial resistance to
antibiotics. Bacteria
colonies can only build up a resistance to antibiotics through evolution.
It is important to note that in every colony of bacteria, there are a tiny few
individuals which are naturally resistant to certain antibiotics. This is
because of the random nature of mutations. [14]
Evolution of Amphibians
Red Spotted Newts are amphibians and are in the family of Salamanders.
The evolution of amphibians is quite interesting when they evolved from
Protists to Vertebra's, then fishes and finally to Amphibians. The main
amphibian branch came from the first vertebrates ever to climb out of the water
onto land, almost 370 million years ago which is about 140 million years before
the earliest dinosaurs. The closest
relatives of the first amphibians were lobe-finned fish in which the fins were
supported by bone instead of thin cartilage strips, and which also had a bony
girdle to support their forelimbs. These allowed them to drag themselves along
the muddy shallows of freshwater swamps. Eventually, amphibians ancestors had
to develop qualities to survive on the land. The oldest and most primitive
known amphibian, Acanthostega, had gills and could not use its new limbs
to support its body weight. Later on they developed abilities to live in the
water and move on land. The amphibians have already survived several mass
extinction events. ‘Modern’ amphibians evolved from some of the large ancestral
amphibians at about the same time as the dinosaurs first appeared, over 200
million years ago, but they survived the end-Cretaceous mass extinction that
wiped out the dinosaurs and many other groups. However, amphibians may now be
facing the worst threat of their long evolutionary history – and we have to
work harder than ever to try and prevent them from finally disappearing from
the earth forever. [15]
Example of Amphibian Fossil Record
This is a fossil of a large Sclerocephalus haeuseri that died while eating a small Sclerocephalus haeuseri about 300 million years ago.[16]
Where It All Began
Special Adaptations of a Newt
1. Newts have the ability to regenerate limbs, eyes, spinal cords, hearts, intestines, and upper and lower jaws.
2. Newts produce toxins through their skin to scare away enemies.
3. The skin is slimy so it doesn't dry up.
4. The eyes are horizontal so it can see in the daylight.
5. Newts have a dorsal fin, which is used for swimming in water.
2. Newts produce toxins through their skin to scare away enemies.
3. The skin is slimy so it doesn't dry up.
4. The eyes are horizontal so it can see in the daylight.
5. Newts have a dorsal fin, which is used for swimming in water.