Unit 4 Review #2 Human Evolution

Unit 4 Review#2 Human Evolution
Deep Time Evolutionary History
Natural Selection

Human Ecology

Deep time Evolutionary History
The origins of the earth started 4.6 billion years ago and has been evolving slowly ever since. Its believed that a chemical evolution produced the first cells on earth and they have been evolving into the different creatures that have existed and that do exist today. There have been fossil findings of creatures that do not exist today but have distinct characteristics about them that resemble ones that do live today. These findings lead to the idea of a common descent, that everything living today came from common ancestors that evolved into different creatures. Humans and chimpanzee’s genomes are 99% identical to each other. Other fossil findings and research has shown humans to resemble apes as well. This does not mean we evolved from apes or chimpanzee’s but instead its believed that both apes and humans evolved from a common ancestor which makes apes our distant cousin. These findings show how a common ancestor could have evolved into humans, apes, chimpanzee’s and other animals over the years. [Picture of human (left) and ape (right)]



Natural Selection
Darwin’s idea of natural selection was the most significant description of adaptation. Through many years of research he observed animals such as finches that all had unique difference that helped them in daily life. He believed that they all came from a common “ancestor whose offspring had spread out among the islands and become adapted to different environments.”(Mader 474) This research lead to natural selection that over time a species becomes suited for their environment in order to survive. Giraffes for example Darwin believed neck lengths varied and that competition for food and resources lead to giraffes with long necks having more offspring slowly eliminating those with short. Over time due to natural selection most giraffes now have long necks. Just like with other creatures over time they adapt to their environment and if certain traits and need more for survival then those traits would be passed on to future generations. Darwin believed this is why there are so many different types of one creature. That depending on its environment it adapted making it different from creatures living in different environments.



Human Ecology
Scientists are continuously studying the environment and the effects we have on it. Everything on this plant contributes from and to the environment. There is a natural occurring cycle in the ecosystem and each component relies on each other in order to keep functioning properly. The picture below is a simple demonstration of the ecosystem.



This diagram though simple shows how everything works in a continuous cycle. Trees use carbon dioxide and let off oxygen while we need oxygen and let off carbon dioxide. When animals die and decompose they release organic carbon and replenish the soil. Everything effects the ecosystem for good and bad. As humans we tend to do more harm to the ecosystem from our factories, cars, streets, buildings and waste. Our environment is slowly becoming polluted by our luxuries. The abundance of burning fossil fuels in factories has lead to acid deposition that has dramatically effected forest and lakes. It also reduces agricultural yields and corrodes marble, metal, and stonework. The burning of fossil fuels has lead to a thermal inversion where warm air gets trapped not being able to escape into the atmosphere causing pollutants to be trapped. This is what give phoenix or any large city its dirty orange sky. (picture of inversion layer)


Along with fossil fuels human are also damaging the ecosystem with daily chemicals and products like; Freon a coolant found in refrigerators and air conditioners, cleaning agents and foaming agents. These all contain chlorine atoms that are breaking down the ozone layer which maintains earths temperature and protects us from the suns harmful rays. As the ozone layer depletes the earths temperature rises and the glaciers will melt causing flooding. Also as the “earth’s surface warms due to global warming, less heat reradiates into the stratosphere.”(Mader506) Stratospheric cloud are lasting longer and are expected to increase causing colder winters. Cloud cover also contributes to the breakdown of the ozone layer. Scientist are continuously trying to find new ways of protecting our atmosphere but it is up to everyone to do there part in preserving our world.
(picture of ozone layer)




Work Cited:
Madder, Sylvia S. “Human Biology” 10th ed. New York: McGraw-Hill, 2007
http://www.visitandlearn.co.uk/factfiles/images/eco4.gif (ecosystem)