Photo taken from www.all-creatures.org/hope/
I Introduction
II Evolution
III Global Ecology
IV Population and Resources
V Conclusion
Introduction
I think the origin of life is a fascinating subject. From time to time we all have those moments where we question the origins of life and how our universe, planet, and life in general came about. Evolution is an interesting theory and I appreciated reading more about it. The interactions of species and our ecosystem was even more interesting to me. Looking at how species are linked and serve different roles was thought provoking.
Evolution
According to the text, chemical evolution is a possible source of the origin of life. Around 10-billion years ago our primitive earth included sources of energy like volcanoes, lightning, radioactive isotopes, meteorites, and ultraviolet radiation. The theory is that through this energy primitive gases reacted with each other to form organic compounds like amino acids. An experiment was done by Stanley Miller that simulated this primitive and came out with small organic molecules. It is believed that macromolecules were then formed, possibly RNA from the joining of these organic molecules. A protocell may have been the next link in the chain followed by a true reproducing cell. The earliest cell were probably prokaryotic cells lacking a nucleus.
A graphic showing chemical evolution taken from Human Biology page 468, Sylvia S. Mader
Biological evolution is defined as the process by which a particular species changes over time. There are two components of evolution, adaption and the descent from a common ancestor. Charles Darwin, during his observations in the Galapagos Islands ,began gathering evidence that life-forms change over time. The evidence he found included fossil, anatomical, and biogeographical.
Fossils are the remains or evidence (like footprints or droppings) of lifeforms that lived on earth at least 10,000 pears ago. These are the best evidence of evolution. The fossil record is the history scientists have been able to record by studying fossils.
Biogeographical evidence is the occurrence of unique species in different parts of the world. For example, Darwin noticed there were no rabbits in South America and concluded that this is because rabbits evolved somewhere else. the finches of the Galapagos Islands are an example of biogeographical evidence.
Anatomical evidence is found in the similarities in the skeletons of varying species. When a anatomically similar structures are inherited from a common ancestor they are said to be homologous. Analogous structure may have the same function but are not constructed the same and do not share a common ancestor.
Biochemical evidence is the presence of the same biochemical molecule like DNA and ATP.
Darwin also proposed the idea of natural selection. Natural selection is process by which individuals of a species possessing certain characteristics (like long necks on giraffes) suited to the environment are more likely to thrive and reproduce. The result is that most of the new offspring will possess the original characteristic, for example the long neck of the giraffe.
Humans are primates and therefore probably share a common ancestor with other primates. Humans did not evolve from apes. Primates have mobile limbs and five digits on the hands and feet. An opposable thumb, found in humans and chimpanzees creates a more powerful grip. Having both eyes positioned at the front of the head makes depth perception possible for humans and apes. Humans and apes also have a reduced birth rate and larger more complex brains.
A chart showing the evolution of primates taken from Human Biology page 478, Sylvia S. Mader
Humans are known as hominids, and that is where we branch away from the other primates. Our ability to walk on two feet is one of the traits that separates us from other primates. Our brain size is another feature that separates us.
The earliest hominid fossil was found in Chad and is called Sahelan-thropus tchadensis. Other fossils and evidence of hominids have been found. Homo habilis is believed to be an ancestor tohumans. Homo erectus is another ancestor and has a larger brain and flatter face. Homo erectus is the first hominid to utilize fire and more advanced tools.
Chart showing human evolutions taken from Human Biology page 481, Sylvia S. Mader
Global Ecology
The bioshere is that area of the earth where living organisms are found. An ecosystem is community where species can interact with each other and the physical and chemical environment.There are different terrestrial ecosystems including the tropical rain forest, savanna, prairie, desert, taiga, and temperate forest. Aquatic ecosystems are separated by salt water or fresh water.
Ecosystems are composed of living and nonliving things. Living things are biotic and nonliving are abiotic. Autotrophs need inorganic nutrients along with an outside energy source in order to live. Autotrophs are producers because the produce food for other organisms. Algae and plants are examples of autotrophs. Heterotrophs are consumers and require organic nutrients. Heterotrophs can be herbivores, consuming only plants or algae, or they can be carnivores, meaning they eat other animals. Omnivores eat both plants and animals, like humans. Fungi are examples of decomposers, meaning they break down dead organic matter. All organisms have a niche, that is a role in an ecosystem.
It is important to understand the flow of energy between organisms. When a producer is consumer by a consumer only a portion of the energy possessed is passed on to the consumer. A food web is a diagram that illustrates feeding relationships. The one below is an example of a grazing food web beginning with a tree and grass. A food chain is the order by which a population feeds on one another.
An example of a food web taken from Human Biology page 496, Sylvia S. Mader
Biochemical cycles are pathways by which chemicals circulate through ecosystems. The different biochemical cycles include the water cycle, carbon cycle, nitrogen cycle, and phosphorus cycle. Each of these cycles is important to the various ecosystems and can be altered by human activities.
Graphic of the water cycle, Human Biology page 499, Sylvia S. Mader
Graphic of the Carbon Cycle, Human Biology page 500, Sylvia S. Mader
Carbon dioxide and other gases produced by human activities like the burning of fossil fuels are contributing to global warming. Global warming can lead to serious changes like the melting of the polar ice caps.
Graphic illustrating global warming, Human Biology page 501, Sylvia S. Mader
Population and Resources
The population of earth is currently experiencing exponential growth and is now at about 7 billion people. Less-developed countries have higher growth rates than more-developed countries. Countries with a younger population also have a higher growth rate. As the population grows the need for resource like food, water, and fuel increases. Some resources like food and water are renewable, meaning they can be replenished. However sometimes the need for the resources comes faster than our ability to replenish them. Pollution can contaminate resources, making them unusable. Nonrenewable resource are those that have a limited supply, like fossil fuels. These resources will eventually run out.
It is important for us to find ways to use our resources without squandering them. Conservation is very important. The USA consumes much of the fossil fuels produced but contains only a fraction of the world populations. Alternative energy sources like wind and solar power can be developed to replace non renewable resources.
Pollution, habitat loss, and climate change are effecting biodiversity. Many species are in danger of extinction. This effects ecosystems. The loss of certain organisms can have a direct effect on human life.
Conclusion
Our world is a complex place. What we do has a direct impact on the environment. I think it benefits us to have an understanding of where we came from and where we want to go as a species. These chapters gave me a lot to think about.
Works sited
Human Biology, Sylvia S. Mader
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