UNIT THREE
Observation :
Are the fossils of fish, reptiles and birds similar to their living counter parts now?
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Are there still dinosaurs in Egypt like those you watched as fossils?
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Conclusion : The fossils in rocks of different areas which are known as the fossil record indicate the extinction of species of once living organisms. Most of them have appeared and become extinct before the creation of man.
Reading in the fossil record
• Since the terrestrial life has appeared 570 million years ago, it witnessed ages when species flourished, and then they suffered from rapid decrease in number of its members until they became extinct. • The known ratio of living organisms now does not exceed 2% of the total species that have appeared since the establishment of planet Earth. Information and enrichment activity (1)
* Most dinosaurs became extinct by the end of the Mesozoic Era (66 million years ago) due to environmental and climatic changes. * Look through scientific magazines and references and check the internet sites for the types of dinosaurs, if they laid eggs or gave birth? How did they become extinct? In addition, write a report supported by pictures about them and add it to your portfolio.
Dinosaur Figure (5)
Factors causing extinction of species:
Scientists postulated many theories to interpret the great extinction phenomenon (mass extinction); theories such as meteorite impacts with Earth, the onset of a long glacial age, or due to the poisonous gases emitted by active volcanoes. Recent extinction that is occurring now caused by different factors. Most of them are due to the interference of man with nature such as:
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Destroying natural habitat Tropical forests include about (one third) of the terrestrial living organisms. Each tree forms a shelter of more than 300 species of living organisms. Removing forests (Fig. 6) destroys the habitat of these species and drive them stray and homeless. Cutting forest trees Scientists estimate that we lose about 68 species of trees every day. Figure (6)
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