EVOLUTION PACKET #2 Davenport/Hass Name: ______

EVOLUTION PACKET #2 Davenport/Hass Name: ______

EVOLUTION PACKET #2 — Davenport/Hass Name: ______

DUE TUESDAY

Use the fossil record below to answer questions 1-3. These fossils are a series of skulls and front leg fossils of organisms believed to be ancestors of the modern-day horse.

  1. Look carefully at the skulls pictured above. Using complete sentences, describe two similarities between each of the skulls that might lead to the conclusion that these are all related species.

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2. What is the biggest change in skull anatomy that occurred from the dawn horse to the modern horse?

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3. What is the biggest change in leg anatomy that occurred from the dawn horse to the modern horse?

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DUE WEDNESDAY:

FOSSIL RECORD

Interpret the fossil record shown to the right, which indicates the evolution of the modern whale. Note specific changes in the structure/characteristics over time.

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Evolution: a change in the inherited traits or characteristics in a population of organisms over time

How can the fossil record be used as evidence to support the theory of evolution??

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DUE THURSDAY: RELATIVE VS. ABSOLUTE DATING OF FOSSILS

The age of fossils intrigues almost everyone. People not only want to know how old a fossil is, but they want to know how that age was determined. Two very straightforward principles are used to determine the age of fossils.

Geologists in the late 18th and early 19th century studied rock layers and the fossils in them. The deeper the fossils were found in layers of earth, the older they were thought to be; the higher they were in Earth’s layers, the younger. We call this relative age dating. Relative dating only provides an estimate of a fossil’s age. For instance, if a fossil lay between a lower layer of fossils that were 50 million years old and an upper layer 35 million years old, scientists would only be able to say the fossil is 35 to 50 million years old.

In the 20th century, scientists began to figure out that certain radioactive (unstable) elements decayed at different rates. Uranium-235, for example, is a radioactive element that slowly changes into lead. In doing so, it loses protons and neutrons from its nucleus at a specific rate— or about half of its unstable protons and neutrons every 704 million years. By measuring the amount of uranium and lead in a fossil sample, scientists can get close to its absolute age.

Using the text above and the diagram at right, answer the following questions:

1.) What is the oldest layer? Why?

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2.) In which layer are the most recent fossils found? How do you know?

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3.) If the fossils in layer D are 220 million years old and the fossils in layer B are 315 million years old, how old are the fossils in layer C. Explain your reasoning.

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4.) How could you figure out the absolute age of the fossils in layer C? Explain.

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DUE FRIDAY: MUTATIONS & EVOLUTION

Natural selection may lead some members of a species with traits best suited to their environment, such as long-necked giraffes, to survive and reproduce, while other members of the same species with less favorable traits (short-necked giraffes) gradually die off. But how do those alleles for short and long necks—or, for that matter, blue eyes or long necks or short beaks or any of billions of other traits—get into the population?

Scientists think that a main cause of different traits in a population is mutation of DNA. Just as you may make mistakes copying your notes, which leads to errors later on a test, your DNA sometimes gets damaged or copied incorrectly during meiosis or mitosis. The mutation might cause a cell to get an extra chromosome or lose a chromosome. Or the mutation might simply affect a single gene, causing an organism’s phenotype to change.

Mutations can be caused by X rays, sunlight, and some chemicals that damage or change DNA. While most mutations are harmful (cancer is often caused by a mutation), some are beneficial. These beneficial mutations add variety to a species when the organism reproduces. In past times, some elephants had a rare mutation that caused them not to grow tusks. However, as elephants are increasingly shot for their tusks, the mutants without tusks have been ignored by hunters. These tusk-less elephants have reproduced and are becoming more common.

Other mutations may give certain plants or animals new defenses against predators, such as a new coloring or poisonous chemical. However, it is rare that a mutation changes an organism or population of species dramatically. Usually mutations take many, many generations to take effect. Meantime, additional mutations enter the population. These mutations, together with natural selection, help a species adapt, change, thrive or sometimes go extinct.

1.) What is a mutation? How does it occur?

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2.) Are mutations good or bad? Explain your answer fully.

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3.) Imagine you’re a farmer who kills the weeds in his corn field with a chemical spray. The spray kills all but a few of the weeds, which aren’t bothered by the poison. Why did these weeds survive? Will their offspring be able to survive the poison? How does this support natural selection? Use extra paper if needed.

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