Life Science Chapter 7- Changes Over Time. Section 1- Darwin s Theory

Transcription

1 Life Science Chapter 7- Changes Over Time Section 1- Darwin s Theory

2 Pg 29 Topic: Darwin s Theory EQ: How did what Darwin observed on his voyage lead to his proposal of natural selection being the mechanism of evolution? Text Pages: Vocab: Species, fossil, adaptation, evolution, scientific theory, selective breeding, natural selection, variation For your Cornell Notes: Define the key terms Read the textbook pages and answer the questions given (not writing your own questions)

3 Pg 29 Topic: Darwin s Theory (7.1) Questions: Describe the important observations Darwin made on his voyage. How are the comparisons the Galapagos organisms examples of adaptations? How did Darwin account for the diversity of species. Describe with examples. How did Darwin account for the differences between similar species? Describe with examples Describe the factors that affect the process of natural selection. How does natural selection lead to evolution? Pg 28 Left Side Options Write a short story of a day in the life of Darwin in the Galapagos Write a news column about the Darwin s discoveries Make a comic strip about Darwin s voyage and discoveries Make sure to include all the elements of a left side assignment! (pictures and connections included!)

4 Darwin s Theory While on his 1831 voyage, Charles Darwin observed many plants and animals he had never seen before. These observations included: the diversity of organisms, many different species the fossil remains of ancient organisms and the characteristics of organisms on the Galapagos Islands Species- a group of similar organisms that can mate with each other to produce offspring that can also have offspring (they are fertile) Fossil- the preserved remains of animals that lived in the distant past

5 Darwin s Voyage on the HMS Beagle

6 Galapagos Organisms Darwin reached the Galapagos in 1835 He observed that many plants and animals on the islands (far off the coasts of S. America) were similar to those found on the mainland in S. America He also observed important differences He concluded: a small number of different species had come to the islands from the main land but eventually their offspring became different from their ancestor mainland species

7 Comparisons of Galapagos Organisms Many examples of adaptation- a trait that helps an organism survive and reproduce Finches: different beaks (size and shape) from one island to another; these differences reflected differences in what the birds were eating. Iguanas: on the islands had large claws to grip slippery rocks where they ate seaweed vs the mainland iguanas that had small claws to climb trees where they ate leaves Darwin reasoned that the organisms that arrived on the islands faced environmental factors that were different from those on the mainland.

8 Evolution Darwin hypothesized that perhaps the species gradually changed over many generations and became better adapted to the new environments Evolution is the gradual change in species over time Darwin s ideas are often referred to the theory of evolution Scientific Theory- a well tested concept that explains a wide range of observations

9 Natural Selection Darwin proposed that evolution occurs by a process called natural selection Natural selection: the process that individuals that are better adapted to their environment are more likely to survive and reproduce than other individuals of that species For example: a black moth against a gray background will more likely get eaten than a gray moth against a gray background Factors affecting natural selection: Overproduction Competition Variations- any difference between individuals of the same species (aka genetic variations) Some variations (sometimes called mutations) make certain individuals better adapted to their environment because of helpful traits they possess (traits that help them survive and reproduce) Helpful variations accumulate (add up) among surviving members of the species over time leading to evolution

10 Natural Selection

11 In conclusion Darwin proposed that over a long time natural selection can lead to change Helpful variations may gradually accumulate in a species, creating a new species Unfavorable traits cause those species to disappear Without variations all members of a species would have the same traits and natural selection would not occur Only traits that are inherited (controlled by genes) can be acted upon by natural selection Summary(Answer EQ in a paragraph, complete sentences, no fluff!)