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Biology - Principles of Evolution

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    Study Guide Biology – Principles of Evolution 1. History of the Theory of Evolution 1.1 What Is Evolution? Evolution means change over time. In biology, it refers to changes in the characteristics of a population of organisms across many generations. These changes do not happen all at once. Instead, they occur slowly over long periods of time. 1.2 Early Ideas About Evolution The idea of evolution is very old. Ancient Greek philosophers were already thinking about how living things might be connected. Some believed that all organisms were related in some way, even if the connection was distant. One famous Greek philosopher, Aristotle, suggested the idea of a “ladder of life.” According to this view, simple organisms were at the bottom, and more complex organisms were at the top. He believed life moved step by step from simple forms to more advanc ed ones. 1.3 Religious Views and Creationism Not everyone agreed with these ideas. Many religious leaders believed in creationism, which is based on the biblical account of creation in the Book of Genesis. They argued that all living things were created exactly as they are now. One religious scholar, James Ussher, even calculated the exact time of creation. He claimed that Earth was created on October 26, 4004 B.C., at 9 a.m. 1.4 Discoveries in Geology Challenge Old Beliefs As science progressed, geologists began to question the idea that Earth was only a few thousand years old. Their studies suggested that Earth must be much older.

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    Study Guide • In 1785, James Hutton proposed that Earth was shaped by slow, natural processes such as erosion, earthquakes, and uplift. • In the early 1800s, Georges Cuvier estimated that Earth was about 6,000 years old. • By 1830, Charles Lyell presented strong evidence showing that Earth was several million years old. These discoveries made scientists more open to the idea that life could also change over long periods of time. 1.5 Lamarck’s Early Theory of Evolution During this period, French zoologist Jean - Baptiste Lamarck proposed an early theory of evolution. He believed organisms developed new traits in response to changes in their environment. Lamarck suggested the idea of “use and disuse.” He argued that body parts used often became stronger, while unused parts became weaker. For example, he believed giraffes developed long necks because they stretched their necks to reach high leaves. Lamarck also believed in “acquired characteristics,” meaning traits gained during an organism’s lifetime could be passed on to offspring. This idea was widely accepted for many years. 1.6 Charles Darwin and the Voyage of the Beagle Charles Darwin was the son of an English doctor and became a naturalist. He traveled aboard the ship H.M.S. Beagle , visiting South America and other distant regions. During this journey, Darwin carefully observed plants and animals. He was especially fascinated by the finches and tortoises of the Galapagos Islands, located about 200 miles west of Ecuador. He noticed that different islands had different species, even th ough the islands were close together. This made him wonder how new species could develop in such isolated places. 1.7 Influence of Population Growth After returning to England in 1838, Darwin continued thinking about evolution. He was strongly influenced by Thomas Malthus’s Essay on the Principle of Population .

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    Study Guide Malthus explained that populations tend to produce more offspring than can survive. Because resources are limited, individuals must compete to live and reproduce. Darwin realized this idea could apply to plants and animals as well. This insight became a ke y part of his theory. 1.8 Wallace and the Theory of Natural Selection In 1858, another English naturalist, Alfred Russel Wallace, independently developed a theory of evolution very similar to Darwin’s. Wallace shared his ideas with Darwin through letters. The two scientists decided to present their ideas together to the scientific community in London. This joint presentation helped introduce the theory of evolution by natural selection. 1.9 On the Origin of Species In 1859, Darwin published his most famous book, On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life . Today, it is commonly known as The Origin of Species . This book clearly explained Darwin’s theory and provided strong evidence for evolution. It became one of the most important scientific works ever written and permanently changed how people understand life on Earth. 2. Evidence for Evolution In On the Origin of Species , Charles Darwin did more than just propose a theory. He also presented strong evidence to support evolution. His goal was to convince the scientific community that evolution is real and that species change over time. Darwin used observations from many dif ferent areas of science to build his case. 2.1 Paleontology: Evidence from Fossils One major source of evidence for evolution comes from paleontology , the study of fossils. Fossils are preserved remains or traces of ancient organisms, such as bones, shells, teeth, or footprints. By studying fossils, scientists learn about life that existed millions of years ago.

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    Study Guide Paleontology supports evolution because it shows that modern organisms descended from earlier forms. Fossils found in deeper rock layers are usually simpler and less diverse. As scientists examine higher rock layers, they find fossils that look more like o rganisms living today. This pattern suggests that life began with fewer and simpler organisms and gradually became more complex over time. The oldest fossils represent ancestors, while the most recent fossils resemble present - day species. 2.2 Comparative Anatomy: Similar Structures, Shared Origins Another strong line of evidence comes from comparative anatomy , which compares body structures of different organisms. Darwin noticed that the forelimbs of humans, porpoises, bats, and other animals are built in very similar ways, even though they are used for different purposes. For example: • Humans use forelimbs for lifting and grasping • Porpoises use them for swimming • Bats use them for flying Darwin explained that these similar structures likely came from a common ancestor. Over time, they were modified to meet the needs of different organisms. These changes are examples of adaptations.

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    Study Guide 2.3 Vestigial Organs: Structures with No Current Use Darwin also pointed out that some organisms have body parts that no longer serve a useful purpose. These are called vestigial organs . In humans, vestigial structures include: • The appendix • Fused tail vertebrae (the coccyx) • Wisdom teeth • Muscles that move the ears and nose Darwin suggested that these structures were useful to ancestors but became unnecessary after environmental changes. Over time, they shrank or lost their function. For example, the appendix may once have helped digest certain foods, and the coccyx may be th e leftover remnant of a tail. 2.4 Embryology: Similarities in Early Development Darwin also found evidence for evolution by studying embryos. Embryology is the branch of biology that focuses on embryos and their development. He observed that embryos of complex animals — such as humans, chickens, frogs, reptiles, and fish — look very similar during early stages of development. These similarities suggest that these organisms share a common ancestor. In early development, many embryos have: • Gill slits • A two - chambered heart • A tail with muscles As development continues, the embryos become more distinct and take on the unique features of their species. This pattern supports the idea that organisms share inherited developmental pathways that were modified over time.

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    Study Guide 2.5 Comparative Biochemistry: Molecular Similarities Although Darwin did not know much about biochemistry, modern science has revealed powerful evidence at the molecular level. Comparative biochemistry examines similarities in chemical processes among living organisms. Scientists have discovered that: • Nearly all organisms use the same methods to capture and use energy • Proteins are built from the same amino acids • DNA and RNA carry genetic information in all living things • The genetic code is almost identical across species These shared biochemical features strongly suggest that all life forms are related and descended from common ancestors. 2.6 Domestic Breeding: Evolution Guided by Humans Darwin also learned from domestic breeding , where humans selectively breed plants and animals to produce desired traits. For example: • Pigeon breeders created many different pigeon varieties from a single ancestral type • Farmers developed new crop varieties through selective breeding Darwin realized that if humans could cause noticeable changes in species over a short time, nature could do the same over long periods. This idea helped him understand how evolution could occur naturally. 2.7 Geographic Distribution: Location Matters Darwin was especially fascinated by where organisms live, a field known as geographic distribution . While studying the Galapagos Islands, he noticed that many species — especially finches — were found nowhere else in the world. He identified 13 different finch species, all unique to the islands.

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    Study Guide Darwin concluded that these finches likely evolved from a single ancestral group that arrived on the islands long ago. Because the islands were isolated, the finches evolved into different species over many generations. Similar patterns are seen elsewhere: • Alligators are found only in certain regions • Australia and New Zealand have unique animals due to long - term isolation These observations support the idea that isolation and environment play important roles in evolution. 3. Quiz Evidence for Evolution 1. Question Which of the following statements does paleontology NOT support? Answer Choices • Fewer kinds of organisms existed in past eras. • Modern organisms descended from common ancestors. • Organisms were probably more complex during past eras. Correct Answer Organisms were probably more complex during past eras. Why This Is Correct Paleontology studies fossils to understand life in the past. Fossil evidence shows that early organisms were generally simpler , and complexity increased over time through evolution. Paleontology does support that fewer kinds of organisms existed in the past and that modern organisms descended from common ancestors. However, it does not support the idea that organisms were more complex in earlier eras. 2. Question Which of the following statements about fossils is FALSE?

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    Study Guide Answer Choices • Fossils from the deeper layers are the ancestors of current forms. • Fossils from the upper layers are the ancestors of modern forms. • Fossils from the uppermost rock are most like current forms. Correct Answer Fossils from the upper layers are the ancestors of modern forms. Why This Is Correct In rock layers, deeper layers are older and contain earlier organisms that can be ancestors of modern species. Upper layers are younger and usually contain organisms that are more similar to present - day forms. Therefore, fossils in the upper layers are not ancestors of modern organisms — they are closer in time and represent later or more recent forms. 3. Question Which comparative anatomy example does NOT support the theory of evolution? Answer Choices • Bats, humans, and cats have similarly constructed forelimbs and thus suggest a common ancestor. • The genus of legless lizards are no longer considered lizards and are now part of the snake genus. • Vestigial organs are structures that are no longer necessary for survival and are thus gradually becoming nonfunctional and reduced in size. Correct Answer The genus of legless lizards are no longer considered lizards and are now part of the snake genus.

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    Study Guide Why This Is Correct Comparative anatomy focuses on structural similarities and differences between organisms to show evolutionary relationships. • Similar forelimb structures in bats, humans, and cats are homologous structures , which support common ancestry. • Vestigial organs show evidence of evolutionary change over time , supporting evolution. However, reclassifying legless lizards into the snake genus is based on taxonomic classification , not direct anatomical comparisons used as evidence in comparative anatomy. Therefore, this example does not support the theory of evolution through comparative anatomy. 4. Question Embryology does NOT suggest which of the following? Answer Choices • Developmental mechanisms are evolutionarily modified in a way that is unique to an organism’s way of life. • Developmental mechanisms are unique for every different type of life and share no commonalities. • Human embryos pass through embryonic stages inherited from their ancestors. Correct Answer Developmental mechanisms are unique for every different type of life and share no commonalities. Why This Is Correct Embryology shows that many organisms share similar early developmental stages , which suggests common ancestry . These shared patterns indicate that developmental mechanisms are not completely unique , but are modified over time to suit different lifestyles. Therefore, the statement claiming that developmental mechanisms share no commonalities is false and is not supported by embryological evidence.

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