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The Theory of Evolution
Transcript of The Theory of Evolution
How did they arise?
How are they related? The Voyage of the Beagle Darwin's Observations... At this time, the world was very different with scientists really questioning the natural world.
Most of the people at the time believed that the Earth and all of its form of life had been created a few thousand years back. Therefore, it was thought, or never thought about, species changing form over long periods of time.
Many scientists of the time had different theories, including one that stated there were many different periods of creation followed by huge catastrophic events. Jean Baptiste Lamarck He had one of the best known theories preceeding Darwin’s theory
One of the first scientists to recognize that species changed over time and that species all descended from other species. Also, that species were somehow connected to their environments.
Proposed that: “By selective use or disuse of organs, organisms acquired or lost certain traits during their lifetime. These traits could then be passed on to their offspring. Over time, this process led to change in a species.” Darwin FINALLY Presents His Case... The publication of the Origin of Species
Darwin began to fill notebooks full of his findings and his theories, BUT DID NOT want to publish just yet (went against most ideas of that day)
Alfred Russel Wallace, a scientist who was doing work in Malaysia, sent Darwin his essay on the same evolutionary process as he did!
Darwin finally published his book, On the Origin of Species, in 1859. In this book, his theory is based on a process known as Natural Selection Evolution- change over time that has resulted from modern organisms descending from ancient ones
Theory- well supported testable explanation that CAN be proved wrong Charles Darwin
Individual who contributed most to our understanding of evolution
English man who was born on February 12, 1809.
Was a member of the crew of the ship H.M.S. Beagle and set sail in 1831 on the most important trip of all time
He made numerous observations along the way which has become the Theory of Evolution.
Studied his observations and recorded his miraculous findings of the natural world BEFORE AFTER Observed many different species
For example, 68 beetle species in Brazil
He was amazed at how the different species came to survive in these different surroundings and produced offspring.
He came up with some important puzzling questions like:
1. Why were there no rabbits in Australia and Australia seemed to have the perfect conditions for them?
2. Why were there no Kangaroos in England? Darwin collected many fossils
Noticed that many fossils did not resemble living organisms, while some did. Why was this?
The Galapagos Islands
The most important voyage among the Beagle.
Group of small islands west of S. America
He noted that although the islands were very close together, they all had their own distinct climate. For example, higher islands had more rainfall which had different plants and animals than other dry, hotter islands.
He noticed this in different birds as well, in which he collected samples and studied the birds’ different beaks Ideas that Shaped Darwin's Thinking James Hutton Earth is many millions of years old
Process that changed Earth in the past are the same presently
Example- Rock layers Hutton's Theory of Geological Change Charles Lyell 1726-1795 1797-1875 Past event must be explained in term of processes
Example- volcanoes today, erosion
Darwin came to two conclusions:
1) If Earth could change over time, could life also?
2) Earth HAS to be extremely old How does this picture show Lamarck's theory? Thomas Malthus Thomas Malthus, an English economist, observed that babies were being born faster than people were dying
He reasoned that, under perfect conditions, the human population would continue to grow unharmed leaving no space
This helped to shape Darwin’s theory even further by...... 1) How do you think this viewpoint of Thomas Malthus could have influenced Charles Darwin's thoughts?
2) What explanation is there for there not being an overcrowded Earth with absolutely no room to live today? Natural Variation and Artificial Selection He began his book by going against the idea that species were perfect and unchanging, by saying that natural variation accounts for the differences among species
He also said that, a process known as artificial selection accounts for the way farmers select the best naturally diverse animals to breed them. Natural variation supplies choices for humans to artificially select.... Evolution by Natural Selection He compared the processes that naturally occur in nature to artificial selection 1) From what we have covered, what do you think Darwin's theory of natural selection may include? The Struggle for Existence Members of different species compete regularly to obtain food, living space, and other resources to live.
Species that are more “favorable” to compete for food will flourish.
This idea was key to coming to Darwin’ s Theory of Evolution Survival of the Fittest Fitness- the ability of an individual to survive and reproduce in its specific environment.
Fitness comes as a result of Adaptations- any inherited characteristic that increases an organism’s chance of survival. Can either be physical or more complex adaptations, such as behaviors.
Survival of the Fittest- species that inherit favorable adaptations will survive better than those that do not. Natural Selection now came about. How are these polar bears fit for their environment? Descent with Modification Each species has descended from an original ancestor, therefore today’s organisms live in different areas, have different structures, and look different. This is known as descent with modification
All living things are related to one another! This is the idea of common descent
From these ideas, a common family tree of organisms can be drawn What about these giraffes? And these sharks? All living things are connected! The tree of life Now that we know Darwin has developed some strong ideas about evolution, it is time to look at some evidence... Evidence of Evolution Darwin argued that living things have been evolving on Earth for millions of years. Evidence for this process could be found in the:
1) fossil record
2) the geographical distribution of living species 3) homologous structures of living organisms
4) and similarities in early development The Fossil Record Darwin thought of the fossil record as a detailed record of evolution- not just evidence of ancient remains like many others did at the time
He proposed that that fossils provided evidence of gradual change over long periods of time
These changes in fossil findings in the different layers of rock showed evidence for species changed over time Geographical Distribution of Living Species Darwin found entirely different species on different continents with similar structures because of similar environments - Ex. Continent of S. America vs. Australia Homologous Body Structures Structures that develop from the same embryonic tissue but have different mature forms Ex. How can this information about homologous structures contribute to the idea of evolution? Similarities in Early Development Similar embryos in all vertebrates How would this information help? Summary of Darwin's Theory 1. Individual organisms in nature differ from one another. Some of this variation is inherited. 2. Organisms in nature produce more offspring than can survive, and many of those that survive do not reproduce. 3. Because more organisms are produced than can survive, members of each species must compete for limited resources. 4. Because each organism in unique, each has different advantages and disadvantages in the struggle for existence. 5. Survival of the Fittest! 6. Species change over time. Over long periods of time, natural selection causes changes in species. 7. Species alive today have descended with modifications from species that lived in the past 8.All organisms on Earth are united into a single family tree!