Examples of Evolution: Archeopteryx: A transition fossil between reptiles and birds.
A famous example from England that demonstrates natural selection is the Pepper Moth. Two different species of moths, one light colored and one dark. Before the 1850’s the dark one was very rare, after the 1850’s the light color became rare. What happened in the 1850’s? INDUSTRIAL REVOLUTION Coal fired plants produced lots of soot that covered the trees and buildings, making everything dark. So where once the birds preferentially picked off and ate the dark moths, they now saw and ate the light ones instead.
As the use of antibiotics have become widespread many disease-causing bacteria have developed resistance against known antibiotics. Only the resistant bacteria will survive and reproduce
This means that if you become infected with these bacteria, treatment with antibiotics will not cure you and the disease may become fatal.
TThis is more likely to occur when a small dose of antibiotics is used over a short time. IIt will kill some of the bacteria but not all. NNext time antibiotics are used, these bacteria may be less vulnerable and more survive. RRepeated small dosages can produce very resistant strains.
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In the USA, half the livestock is fed antibiotics to increase the growth of the animals. ○ This leads to strains of antibiotic resistant bacteria being discovered in the gut of these animals and then in human guts. ○ The runoff from the waste and feed contains the antibiotic resistant strains that can get out to the rest of the world.
There are numerous examples of humans performing their own type of selection (hence: artificial) on desired, heritable traits belonging to a variety of organisms. Since we seem to like the #3, we have… 3 examples:
#1: The domestication of the wolf (or domestication of any animal) is a good example: Further selection of favored traits resulted in the varied amount of dog breeds we have today. Further selection of favored traits resulted in the varied amount of dog breeds we have today. #1 Dog breeding
Selective breeding transformed teosinte’s few fruitcases into modern corn’s rows of kernels. #2: Selective breeding transformed teosinte’s few fruitcases into modern corn’s rows of kernels.
#3: By selecting various traits of the common wild mustard plant to breed for, we have created many common vegetables we use today such as broccoli, cauliflower and brussels sprouts.
Artificial selection is also important as it acts as an experiment on natural selection. Experimentation is the ultimate test of a scientific hypothesis, without it you can never be sure that a correlation (i.e. the environment selecting for traits) you observe is significant.
In artificial selection, humans are the manipulators (we are the environment)- we choose which individuals get to reproduce. We would expect to see what is found in nature- that the individuals who reproduce pass on their genes/traits, and that is exactly what we see.
Artificial Selection can also be used as evidence of evolution. We will discuss more forms of evidence next.
“Those who cavalierly reject the Theory of Evolution, as not adequately supported by facts, seem quite to forget that their own theory is supported by no facts at all” -Herbert Spencer, Essay Scientific, Political and Speculative, Political and Speculative, 1891.
Fossils do show intermediate stages, despite their rarity. And geological strata (layers) consistently reveal the same sequence of fossils! A quick and simple way to debunk the theory of evolution would be to find a fossil horse in the same stratum as a trilobite.
For example, there are now at least eight intermediate fossil stages identified in the evolution of whales.
An organ present in the organism but either reduced in size or has no use. Ex. Femur in some whales Dewclaw in dogs Eyes in blind mole rats Fake sex in virgin Whiptail lizard Wings on flightless birds
The Appendix
Wisdom Teeth
Human Coccyx (Tailbone)
Body Hair and Erector Pili (Goosebumps)
Ear Muscles
Third Eyelid
Homologous Structures Similar structures in very different organisms is evidence of a common ancestor. An example of this is the similarity of the skeleton between all mammals. Every bone in a bat has is its own identifiable counterpart in a human. Identifiable, because of the order in which they join up. Only the proportions are different.
from Ernst Haeckel's 1904 work Kunstformen der NaturErnst Haeckel Kunstformen der Natur
Embryonic Development Physical similarities between embryos of different species at different stages. In 1866, Ernst Haeckel proposed his theory that the embryonic development of an individual organism followed the same path as the evolutionary history of its species.
Haeckel’s theory has largely been rejected today. Though humans share common ancestors with other animals, stages of human embryonic development are not functionally equivalent to the adults of these shared ancestors. In other words, just because we develop a tail and gill slits embryonically does not mean that they are functional like they are in fish.
Darwin's view: that early embryonic stages are similar to the same embryonic stage of related species but not to the adult stages of these species, has been confirmed by modern evolutionary developmental biology
Similarity of Genetic Code (DNA) All organisms share the same genetic code, based on the series of bases: A, T, G, and C. The more similar two species are the more alike the sequence of bases in their DNA are.
First we need to look at what the word theory means. The Oxford English Dictionary gives two meanings: Theory, Definition 1: Theory, Definition 1: A scheme or system of ideas or statements held as an explanation or account of a group of facts or phenomena; a hypothesis that has been confirmed or established by observation or experiment, and is propounded or accepted as accounting for the known facts; a statement of what are held to be the general laws, principles, or causes of something known or observed. Theory, Definition 2: Theory, Definition 2: A hypothesis proposed as an explanation; hence, a mere hypothesis, speculation, conjecture; an idea or set of ideas about something; an individual view or notion.
Darwin’s Theory, as with all scientific theories follow the first definition. Having your explanation for a group of observations being called a theory is an honor in the scientific field; it means that it is the best explanation we have for why something happens. Does being a scientific law mean you have more evidence to support your explanation than a theory? Not at all… laws and theories are used to describe different things in science. In general, Scientific Laws describe what is happening. Examples include: Newton’s Laws of Gravity, Kepler’s Laws of Planetary Motion, Law of Conservation of Energy, Laws of Thermodynamics…. Scientific Theories explain why something happens. Examples include: The Big Bang Theory, Cell Theory, Theory of Relativity, String Theory… Scientific Theories explain why something happens. Examples include: The Big Bang Theory, Cell Theory, Theory of Relativity, String Theory…
NO! Evolution points to humans sharing a common ancestor with chimpanzees and other great apes around 7-8 million years ago. Chimps have continued to evolved alongside us since then. The ancestor you share between yourself and the chimpanzee at the zoo probably did look something like this though: Sahelanthropus tchadensis
We even shared the Earth at the same time with other hominid species such as Homo Neanderthalensis. And this recent find: Homo Floresiensis, the hobbit people on the island of Flores in Indonesia. In fact we have shared the Earth with many other human like species (called hominids). Courtesy of Smithsonian, 03/10
Though the eye is incredibly complex, even Darwin back in his day saw that the Theory of Evolution could account for it: “...if numerous gradations from a perfect and complex eye to one very imperfect and simple, each grade being useful to its possessor, can be shown to exist; if further, the eye does vary ever so slightly, and the variations be inherited, which is certainly the case; and if any variation or modification in the organ be ever useful to an animal under changing conditions of life, then the difficulty of believing that a perfect and complex eye could be formed by natural selection, though insuperable by our imagination, can hardly be considered real” -Charles Darwin, Origin of Species
The first step in the evolution of the eye, would be a set of photoreceptor proteins that sense light called photoreceptors. Photoreceptors can sense ambient brightness, and distinguish light from dark. These allowed unicellular organisms to move toward where they sensed light, probably to use for photosynthesis. Example of a photoreceptor in a Euglena
The next step would be indenting the tissue behind the eye to make a cup behind the photoreceptor cells. This enlarges the area of photoreceptor cells as well, now known as the retina. These primitive eyes are called eyespots. Example of an eyespot in a planarian (flat worm)
The “pinhole camera” eye stage was next. This is where the eyespot hollows out more and reduces the size of the hole where the light comes through. This gave the organism true imaging, allowing for directional and shape sensing. Example of a pinhole eye in a nautilus.
Next came eyes that were fully enclosed, fluid-filled chambers. A refractive lens has also evolved over the pin-hole. Refraction is when light waves change speed as they enter a new medium. This bends the angle of the light, and in the case of an eye (or camera) directs the light into a single beam on one spot. The refractive lens in most animals is known as the cornea. The iris later evolved, which allows the organism to adjust the “pin-hole”, controlling the amount of light that enters the eye.
So if we remember that evolution is an accumulation of heritable changes, the evolution of complex structures like they eye, though remarkable, isn’t all that unrealistic.