Chapter 4 Section 1 By: Mrs. Sergent
To Get You Thinking Could a polar bear live comfortably in Hawaii? Could a fish survive in a forest? Why or why not? What are the characteristics of these animals (i.e. physical adaptations) that make these animals well suited for a specific environment?
Differences Between Organisms A characteristic that helps an organism survive and reproduce in its environment is called an adaptation . Some adaptations are physical , other adaptations are behaviors that help an organism find food, protect itself, or reproduce.
Living things that have the same characteristics may be members of the same species . A species is a group of organisms that can mate with one another to produce fertile offspring. Groups of individuals of the same species living in the same place make up a population . *What is the difference between a population and a species?*
Example of Populations vs. Species 1. All domestic cats are the same species. Those that live in different cities are not part of the same population. 2. All of the same kind of lizard that live on an island are a population and may be the only population of a single species. 3. All humans are the same species, with many different populations.
Across Earth, there are millions of different species of organisms. The species that live on Earth today range from single-celled bacteria, which lack cell nuclei, to multicellular fungi, plants, and animals. Since life first appeared on Earth, many species have died out , and many new species have appeared .
Scientists believe that inherited characteristics in populations change over time.
Evidence Of Changes Over Time Evidence that organisms have changed over time is buried within Earth's crust . The layers of Earth's crust are made up of different kinds of rock and soil stacked on top of each other. These layers form when sediments are carried by wind and water and are deposited in an orderly fashion.
The remains or imprints of once-living organisms found in layers of rock are called fossils . Fossils can be: 1. Complete Organisms 2. Parts of Organisms 3. A Set Of Footprints (or imprints) Fossils usually form when a dead organism is covered by a layer of sediment .
Over time, more sediment settles on top of the organism . Minerals in the sediment may seep into the organism and gradually replace the organism with rock . If the organism rots away completely after being covered, it may leave an imprint of itself in the rock.
A historical sequence of life indicated by fossils found in layers of Earth's crust is called the fossil record . The fossil record organizes fossils by their estimated ages an physical similarities . Fossils found in newer layers of Earth's crust tend to be similar to present-day organisms.
This similarity indicated that the fossilized organisms were close relatives of present-day organisms. Fossils from older layers are less similar to present-day organisms than fossils in newer layers are. The older fossils are of earlier life-forms, which may not exist anymore.
Comparing organisms in the fossil record can reveal how organisms have changed over time.
Evidence of Ancestry The fossil record provides evidence about the order in which species have existed. All living organisms have characteristics in common and inherit characteristics in similar ways. Scientists use the fossil record to figure out the relationship between extinct and living organisms.
Scientists think that all mammal species alive today arose from common ancestors. However, their information is not complete due to parts of Earth's history lacking a fossil record . This is because fossils are rare due to the fact that specific conditions are necessary for them to form.
Examining & Comparing Organisms Examining an organism carefully can give scientists clue about its ancestors .
P. 104 Figure 7 Examine each of the skeletons in figure 7 carefully. Describe one similarity and one difference between each successive species.
Evidence that groups of organisms have common ancestry can be found by comparing the groups' DNA . When scientists compare organisms' traits such as skeletal structures , much of the information that they get supports the theory that organisms share a common ancestor .
The greater number of similarities between the data sets for any two species, the more closely the two species are related through a common ancestory.
In Conclusion Fossils can provide information about how the environment has changed over time. Would you expect to find marine fossils on a mountaintop? Why would the presence of marine fossils on a mountaintop be evidence of environmental change?
Exit Questions 1. Fossils are the remains or physical evidence of an organism preserved by geological processes. What are fossils found in newer layers of Earth's crust more similar to: present- day organisms or earlier life forms that may be extinct? 2. True or False: comparing organisms in the Earth's fossil record can reveal how organisms have changed over time.
Homework Section Review P.107 1-6 & 8 Extra Credit Research to find the four main ancestors of the horse known from the fossil record. Make a poster that shows each ancestral horse in order of appearance and write a paragraph about each one, explaining its unique physical characteristics. Conclude your report with an explanation of the origin of wild horses in North America.
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