7th Grade Life Science - Evolution


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7th Grade Life Science - Evolution

  1. 1. Changes Over Time
  2. 2. Warm-up: For the first five minutes of class quick-write about the followingquestion in your notebook. Your answers do not need to be correct, just writewhat you know or think you know.Explain in your own words you understanding so far of the following terms: Artifical Selection Natural Selection Evolution
  3. 3. Pre-Darwin Before Darwin, many scientists had dedicated their lives to categorizing the species of the world. A scientist named Carl Linneaus made numerous travels throughout the globe and noticed that everywhere he went, similar species existed with slighty different changes in each location. This led him to believe that some form of adaptation existed among organisms, and helped him classify many of the species in existence into different categories.
  4. 4. Darwin In 1831 Charles Darwin embarked on a 5 year voyage on the SS Beagle around the globe. After studying thousands of species of organisms on each of the continents he hypothesized that every similar species had a common ancestor. While studying species on the isolated Galapagos Islands the differences between mainland and island species made him reason that plants and animals may have changed gradually over time due to differences in their environments. This gradual change over time is called evolution. Upon returning from his trip, Darwin spent the next decades of his life testing his hypothesis to form a scientific theory. A Scientific Theory is a well tested concept which explains a wide range of observations.
  5. 5. Evolution For many thousands of years humans had used artificial selection to breed plants and animals. Aritificial Selection is when humans use the natural processes of evolution by choosing which species with which specific traits will pass on their genes. Natural Selection is this process as it occurs in nature. Organisms adapt to their surroundings and change over time to better survive and create more offspring. By creating more offspring, the genes which helped one organisms survive will pass on to the children, allowing them to also better survive. All of this is possible because of genetic variation among each individual organism.
  6. 6. Evidence for Evolution Comparative Anatomy shows us the similarities in characteristics of modern and ancient species. Homologous Structures are body characteristics which are similar between two species. This can tell us which species are likely to have a common ancestor.
  7. 7. Also:
  8. 8. Evidence for Evolution Other clues to show the relation between two species are similarities in DNA and in early development.
  9. 9. Fossils Fossils tell us a great deal about how life has developed over time. Finding well preserved fossils is very difficult because so many perfect factors are required to preserve remains. Trace fossils are incomplete fossils which show evidence of life in the past. Because life decomposes fully, there are many gaps in the fossil record, but new discoveries are found every year and the gaps fill in quickly, giving us a clearer picture of how life has changed over time.
  10. 10. New Species Evolution is the change in characteristics of an organismover time. But when can we determine that a new species is born? A new species forms when a group of individuals remains isolated from the rest of its species long enough to evolve different traits. We know something is a new species when it is unable to breed with the species it originally came from.
  11. 11. Common Ancestor A Common Ancestor is the distant relative of any two species. If you go back far enough, every single organism on earth has a distant relative, some are more closely related than others.