Applied Science

BIO 1100, Non-Majors Biology 1

Course Learning Outcomes for Unit IV Upon completion of this unit, students should be able to:

1. Define the basic concepts of biological sciences. 1.1 Define terms used when discussing evolution. 1.2 Recall the classification of organisms.

2. Apply the scientific method.

2.1 Apply the scientific method to Darwin’s formulation of the theory of common descent with modification.

5. Interpret Darwin’s theory of evolution to include natural selection and common descent.

5.1 Discuss common descent and the evidence that supports it. 5.2 Discuss natural selection and the patterns of selection.

Course/Unit Learning Outcomes

Learning Activity

1.1

Unit Lesson Chapter 11 Chapter 12 Chapter 14 Unit IV Assessment

1.2 Unit Lesson Chapter 14 Unit IV Assessment

2.1 Unit Lesson Chapter 11 Unit IV Assessment

5.1 Unit Lesson Chapter 11 Unit IV Assessment

5.2 Unit Lesson Chapter 12 Unit IV Assessment

Required Unit Resources Chapter 11: Where Did We Come From? Chapter 12: An Evolving Enemy Chapter 14: The Greatest Species on Earth?

Unit Lesson This unit includes materials concerning evolutionary theories, natural selection, and the diversity of life from Chapters 11, 12, and 14. In Chapter 11, “Where Did We Come From?” the authors explain what evolution means and the various theories of evolution. In addition, a detailed explanation of Charles Darwin’s theory of

UNIT IV STUDY GUIDE

Evolution

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evolution is described, including the scientific evidence supporting Darwin’s theory. Linnaean classification is also explained in this chapter. Many people report that they do not believe in evolution. It is not the intent of this course to change anyone’s mind about what he or she believes. This is a biology course, not a theology course. No matter what you believe, we do expect students to come away from the course with an understanding of the basic concepts of Darwin’s theory. Let’s start by understanding what a scientist means when the word theory gets used. Going back to the scientific method, one begins with an observation. For example, Darwin observed on the Galapagos Islands that tortoises were different from island to island. This is step one of the scientific method (Belk & Maier, 2019). Step two is making a hypothesis. It took some time for Darwin to come up with a hypothesis, but eventually he hypothesized common descent with modification. That is, Darwin thought that all the tortoises on the different islands descended from a single species that originally came from the South American mainland. Common descent is the theory that all living organisms on earth are descended from the same ancestor. Step three of the scientific method is to make a prediction based on the hypothesis. For example, Darwin predicted that all the different tortoises would have common characteristics but would also be different depending on the environment on the island on which each tortoise lived. How these differences came to be is explained by natural selection, but we will stick to common descent for now. Step four of the scientific method is to test the prediction. The textbook discusses evidence that supports the prediction on pages 229–230. Consider why a suspect is innocent until proven guilty in criminal investigations. The reason for this is because people cannot prove themselves innocent. Even an alibi could be fabricated. For example, during the Salem witch trials, some people would accuse others of witchcraft. The only proof supporting the accusation was the testimony of the “victim” of the witchcraft. Since one obviously cannot prove that one is not a witch, many people were convicted and hanged (Brooks, 2011). Now, you may ask, what does this have to do with biology? Well, just as innocence cannot be absolutely proved, theories such as the theory of evolution cannot be absolutely proved, either. Einstein, in referring to his theory of relativity, pointed out that while many observations support it, a single observation could disprove it. There may always be something else Einstein or Darwin did not think of to explain the observations. That is why scientists call these ideas theories, even though the scientific evidence is overwhelming.

Common descent—how closely related is human evolution to the evolution of other species? (Pietras, 2017)

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Darwin and the theory of evolution do not address how life began. But once life began, it immediately began to evolve. Organisms must evolve because their environment changes; if the organisms do not also change, they will die out. Just think, every organism on the planet has DNA that directs its life. From the tiniest germ to the largest whales, all living beings have DNA. What a remarkable molecule! This fact supports the hypothesis that all living beings have a common ancestor. Speaking of common ancestors, humans did not descend from the great apes. You may have heard that humans and chimpanzees both derive from a common ancestor that lived about 7 million years ago (Belk & Maier, 2019). That common ancestor has not yet been found. People sometimes ask, “If humans descended from a common ancestor, why are there great apes? Why did we not supplant them?” The answer, of course, is that the various offsprings of the common ancestor moved into different environments and evolved differently. Think back to the Galapagos tortoises. Some offsprings lived in the forest, while others lived in the savannah. The demands placed on each type of offspring by the different environment resulted in different species over time. This is not to say that one species is superior to another—evolution does not strive for superior organisms. Darwin never uttered the well-known phrase

“survival of the fittest.” Evolution involves survival of those who are best suited to the environment in which they find themselves. So, what do species do when the environment changes? Those with traits suited to the new environment do well, while those whose traits do not suit will die out. That is what natural selection is all about. Individuals are naturally selected to survive and reproduce, or they are not. Be aware that individuals cannot adapt or evolve; it is only the population that adapts and evolves, and such evolution occurs over time, not immediately. For most organisms, the male species is the most colorful, can jump the highest, fly the fastest, and so on. The male’s energy is focused on traits that ensure that the fittest female will mate with him. This is known as sexual selection; mating is usually not random. Let’s apply that to a particular scenario. Think about a fish that lives in a pond with predators. Guppies vary in color, just as different traits vary in humans. Some male guppies are very colorful, which attracts a female. If there are no predators in an area, its chances of reproducing are better if the guppy is colorful. However, being colorful also attracts predators. If there are predators in a pond, a guppy’s chances of survival are better if it is not colorful; if it can blend in with its surroundings, a predator will not be able to see it and eat it. Based on that information, if guppies live in a pond with predators, would you expect most of the male guppies to be colorful or to be able to blend in with their surroundings? Evolution and natural selection ensure survival of organisms such as fish and humans; however, these factors also influence diseases that are caused by bacteria, viruses, fungi, and protists. Chapter 12, “An Evolving Enemy,” describes the evolutionary processes of diseases by natural selection. The textbook chapter presents materials by using the example of Tuberculosis to explain the importance of understanding the theory of natural selection and the danger of the evolutionary changes that occur within infectious diseases. Are we overusing antibiotics? Are we forcing the evolution of a superbug? Does the human body become immune to antibiotics?

Statue of Charles Darwin created by Sir Joseph Boehm and unveiled in London’s Natural History Museum in 1885 (Patche99z, 2009)

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Mutations are one way the genetics of a population changes. Depending on the circumstances, most mutations are harmful, some are neutral, and rarely, some are helpful. Do not forget that while mutations are a part of evolution for a population’s gene pool, natural selection also changes genes over time. All humans belong to a species called Homo sapiens. What determines a species? A biological species includes organisms that interbreed naturally and produce offspring that are reproductively viable. Why do different species fail to mate? There are various reasons that keep organisms belonging to one species from attempting to mate with those belonging to another species. These are referred to as pre-fertilization isolation mechanisms. In other words, these isolation measures keep reproduction between species from naturally occurring. Sometimes fertilization occurs; however, offspring are not produced. These are referred to as post-fertilization mechanisms. Fertilization can occur between members of two different species; however, the hybrid offspring is generally not able to reproduce. An example of this would be mules, which are a cross between a horse and a donkey (Belk & Maier, 2019). Both mechanisms prevent gene flow between different species. For specific information about the various types of isolating mechanisms, see page 264 in the course textbook.

Even though genes do not flow from species to species, diversity is vast. Scientists have described over 1.3 million different species (Belk & Maier, 2019). How can scientists keep up with so many different species? They do this by classifying organisms into groups. This type of classification is called taxonomy. The groups have changed some over time due to increased knowledge. Currently, most scientists group all living organisms into one of three domains: Eukarya, Bacteria, and Archae. Eukarya are further divided into four different kingdoms: Plantae, Animalia, Fungi, and Protista. Each kingdom is then divided into phyla, classes, orders, families, genus, and finally, species. The levels start out being very broad or general and result in the specific organisms: genus and species. Where do we fit in?

A billion years is 1,000,000,000 years—a very long time. Scientists think the universe began almost 14 billion years ago (Crew, 2018). Consider that the great pyramids of Egypt, which seem to have been around for such a long time, were built only about 4,000 years ago.

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The Earth formed about 4.5 billion years ago, and after a billion years, life might have made its first appearance (Belk & Maier, 2019). Therefore, prokaryotic cells, such as bacteria and archaea, began the journey of life on this planet around 3.5 billion years ago. Five hundred million years later, cyanobacteria developed photosynthesis. These remarkable organisms can live on water, CO2, and sunlight. Photosynthesis has been on earth 3 billion years. Not much happened after the development of photosynthesis for a billion years, and then the first eukaryotic life forms appeared. It took a billion years for prokaryotic cells to evolve into eukaryotic cells. About 1.5 billion years ago, eukaryotic cells assimilated mitochondria (Crew, 2018). It is thought that single-celled organisms developed sophisticated metabolisms and that eukaryotes took the tiny organisms into their cells as organelles. From this point, things started to move much faster. A billion years ago, the eukaryotic populations became much greater. Five hundred million years ago, multi-celled organisms appeared, and the Cambrian explosion of life occurred (Royal Ontario Museum, 2011). The Cambrian explosion was an important evolutionary event, as many new life forms came into existence at that time. About 700 million years ago, life began to appear on land, and air- breathing animals arrived (University of California Museum of Paleontology, n.d-b.). Around 300 million years ago, the Permian extinction began. By the time it ended 251 million years ago, it had wiped out 90% of all marine species and 70% of the land animals in existence at the time (National Geographic, 2017). While the cause is debated, it might have happened because of planet- wide cooling and the occurrence of glaciation. Nevertheless, life and evolution continued, and about 225 million years ago, the first dinosaurs and mammals appeared. The first birds did not evolve until about 150 million years ago University of California Museum of Paleontology, n.d.-a). Then, 65 million years ago, another disaster occurred—the Cretaceous extinction event that wiped out 75% of the species and gave rise to the first primates. Grass evolved about 35 million years ago (Kellogg, 2001), and great apes appeared about 25 million years ago (Gorillas-World, 2014). The last common ancestor of humans and chimpanzees did not appear until about 6-7 million years ago. The first Homo species arrived 2 million years ago, and finally, modern Homo sapiens arrived about 0.2 million years ago (Pontzer, 2014)—a comparatively short time when considering all the evolution that preceded their arrival. What a journey! As you read chapters 11, 12, and 14, appreciate the great diversity of life and how much work it took for species to get to where they are today.

References At09kg. (2016). Photosynthesis en [Image]. Retrieved from

https://commons.wikimedia.org/wiki/File:Photosynthesis_en.svg Belk, C., & Maier, V. B. (2019). Biology: Science for life with physiology (6th ed.). New York, NY: Pearson Brooks, R. (2011, August 18). History of the Salem witch trials. Retrieved from

http://historyofmassachusetts.org/the-salem-witch-trials/ Crew, B. (2018). This timeline shows the entire history of the universe, and where it's headed. Retrieved from

https://www.sciencealert.com/timeline-shows-the-entire-history-of-the-universe-and-how-it-ends Gorillas-World. (2014). Gorilla evolution. Retrieved from https://www.gorillas-world.com/gorilla-evolution/

Photosynthesis—the process of using sunlight to synthesize foods from carbon dioxide and water—has been occurring on earth for around 3 billion years. (At09kg, 2016)

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Kellogg, E. A. (2001). Evolutionary history of the grasses. Retrieved from http://www.plantphysiol.org/content/125/3/1198

National Geographic. (2017). Permian Period. Retrieved from

https://www.nationalgeographic.com/science/prehistoric-world/permian/ Patche99z. (2009). Charles Darwin statue 5661r [Photograph]. Retrieved from

https://commons.wikimedia.org/wiki/File:Charles_Darwin_statue_5661r.jpg Pietras, D. (2017). ConEvoEyes2jpg [Photograph]. Retrieved from

https://commons.wikimedia.org/wiki/File:ConEvoEyes2jpg.jpg Pontzer, H. (2012). Overview of hominin evolution. Retrieved from

https://www.nature.com/scitable/knowledge/library/overview-of-hominin-evolution-89010983 Royal Ontario Museum (2011). The Cambrian Explosion. Retrieved from https://burgess-

shale.rom.on.ca/en/science/origin/04-cambrian-explosion.php#top-haut University of California Museum of Paleontology. (n.d.-a). The origin of birds. Retrieved from

https://evolution.berkeley.edu/evolibrary/article/evograms_06 University of California Museum of Paleontology. (n.d.-b). The Proterozoic Eon. Retrieved from

http://www.ucmp.berkeley.edu/precambrian/proterozoic.php