SCIENCE Grade / Name: Date: Cohort: CATALYST 1.) 2.) 3.) OBJECTIVE SWBAT define extinction and describe how meteorite impacts can cause mass extinction events and have altered the evolutionary history of life on Earth (evolution) Criteria For Success (CFS) Students will receive a minimum score of an 80% on the exit ticket 1
SCIENCE Evolution: The oldest fossils are remains of tiny single-celled organisms. These life-forms were so primitive that their cells did not contain a nucleus. They reproduced by splitting into two or more new cells. The first critical advance in the development of more complex life-forms is found in rocks about 1.4 billion years old. Cells with a nucleus appeared. These cells could reproduce sexually and inherit characteristics from two parent cells. Colonies of single-celled organisms developed into simple multi-cellular organisms, such as jellyfish and worms, less than a billion years ago. The first organisms with shells and internal hard parts appeared about 545 million years ago. These organisms eventually gave rise to the complex life-forms that exist today. The gradual change in living organisms from generation to generation is known as evolution. Although it is called a theory, organic evolution is one of the most fundamental ideas of science. What appeared 545 million years ago that caused fossils to start appearing the rock record? Quick Check: Organic evolution is based on four principles. 1. First, variations exist among individuals within a species. Besides differences in size and shape, individual organisms have different abilities to find food, resist disease, and reproduce effectively. 2. Second, organisms usually produce more offspring than the environment can support. Think of the thousands of seeds many trees produce or the number of eggs one salmon can lay. If all these offspring survived, the world would be overrun with just trees and salmon. 2
SCIENCE 3. The third principle is the effect of competition among individuals of a given generation. Organisms die for a variety of reasons, but those best suited to their environment are most likely to survive. 4. Fourth, the individuals best suited to the environment will live long enough to reproduce and pass their traits to following generations. This is what is meant by the term natural selection. 3
SCIENCE Example: In the world of peacocks, peahens (female peacocks) choose their mates based on the size and shape of the plumage, or tail, of the male peacock. Generally, peahens are attracted to, and mate with, the males with the largest and most colorful tails. The peacock above has a large plumage, while the one below has little to no plumage. Is this an example of natural selection? Are peacocks with larger tails more likely to survive or not? 9TH GRADE 4
SCIENCE Note: You can see evidence of evolution in looking at page 8 and 9 of your ESRT. Over time, more complex organisms appear after simpler ones, often in the same species. You can also use the Life on Earth column to see how life has appeared and evolved in the fossil record, and over time. Practice: 1.) 2.) 3.) 5
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SCIENCE Extinction: Competition is not restricted to individuals of a single species. Different species also compete to survive. When one species is better adapted to live in a particular environment than another, the better-adapted group may take food, shelter, or other natural resources needed by the less welladapted species. Predation, or hunting, of one species by another can also eliminate whole species. The American bison, or buffalo, once roamed the prairies of North American in great numbers. Hunting, especially by European settlers with rifles, nearly eliminated the American bison. A much smaller number of bison survive today on farms and game reserves. When all the individuals of a particular species die, extinction has taken place. A number of species including the marsupial Tasmanian tiger and the passenger pigeon have become extinct in the past few centuries. Most of the life-forms found as fossils have, in fact, become extinct. How might we know that organisms in the past became extinct? ACTIVITY 18- The geologic record includes times when large numbers of species became extinct. Recent discoveries have shown that at least one of these mass extinctions occurred about the time that a giant meteorite or other object from space collided with Earth. The impact of this object threw great amounts of dust into the atmosphere causing global changes in climate. The dust-laden atmosphere prevented much of the sunlight from reaching Earth s surface. This killed plants and the animals that depended on them. Most dinosaurs became extinct at that time. How is it that an asteroid impact can cause a mass extinction? Catastrophic events can create very distinct time markers in rock layers. A large volcanic eruption can eject great quantities of ash into the atmosphere. When Mount St. Helens exploded in 1980, a cubic kilometer of ash and rock debris was thrown as high as 18,000 m into the atmosphere. While this is a major event in modern American history, Tambora, a volcano in Indonesia, ejected an estimated 30 cubic kilometers in 1815. Most of the debris from these explosions settled near the volcano. However, fine volcanic ash carried into the strong winds of the stratosphere can be deposited over a large area in a matter or days or weeks, a mere instant of geological time. If such a layer of ash is found in the rock strata over a broad area, it represents a very precise time marker 9
SCIENCE that can be found in almost any environment of deposition. These precise time horizons can be very useful in the regional correlation of rock layers. How can volcanic eruptions be used in correlating rock layers? Scientists also know that the impact of large asteroids, meteorites, or comets results in similar time markers. The impact event that marks the end of the Mesozoic Era was caused by an object estimated to be 10 km across. It created a crater more than 100 km in diameter on the Yucatan Peninsula of Mexico. An unknown quantity of rock from the crater and the remains of the flying object formed a dense cloud of dust. The dust was so widespread it blocked the sun and led to dramatic climatic changes over the whole planet. This event also deposited a distinctive layer of ash that can be found in sedimentary rocks on all the continents and in places on the floor of the ocean. This layer of ash very precisely marks the top boundary of rocks of Mesozoic age. Geologists often say that ash layers from volcanoes and meteorite impacts are very similar to the characteristics of index fossils. What properties do these ash layers share with index fossils? Sample I: 10
SCIENCE Sample II: VERY SPICY! Practice: 1.) 2.) 3.) 11
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SCIENCE Exit Ticket Grade / Name: Date: Cohort: Exit Ticket 1.) 2.) 3.) 14
SCIENCE 4.) 4.) Explain below why a volcanic eruption or meteorite impact makes a good geologic date indicator. 15
SCIENCE Homework: 1.) 2.) 16
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