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5.1 darwin´s theory
 

5.1 darwin´s theory

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  • https://www.youtube.com/watch?v=6GNUlZhE_jE
  • http://www.youtube.com/watch?annotation_id=annotation_813739&feature=iv&src_vid=dZF4YIQBfAg&v=kjgNT0rBy_8http://www.pbs.org/wgbh/evolution/library/11/2/quicktime/e_s_4_56.html

5.1 darwin´s theory 5.1 darwin´s theory Presentation Transcript

  • CHAPTER 5: CHANGES OVER TIMEMiss Luzma Fabre
  • SECTION 1: DARWIN´S THEORY Charles Darwin sailed on the Beagle to the Galápagos islands. He saw many unusual organisms on the islands, such as giant tortoises.
  • THE VOYAGE OF THE BEAGLE
  • DARWIN´S OBSERVATIONS Darwin´s important observations included the diversity of living things, the remains of ancient organisms, and the characteristics of organisms on the Galápagos islands
  • DIVERSITY Scientists have identified more than 1.7 million species of organisms on Earth. A species is a group of similar organisms that can mate with each other and produce fertile offspring
  • FOSSILS A fossil is the preserved remains or traces of an organism that lived in the past.
  • ADAPTATIONS An adaptation is a trait that helps an organism survive and reproduce. Some plants, such as milkweed, are poisonous or have a bad taste. This prevents them from being eaten.
  • EVOLUTION Darwin reasoned that plants or animals that arrived on the Galápagos Islands faced conditions that were different from those on the mainland. Perhaps, Darwin hypothesized, the species gradually changed over many generations and became better adapted to the new conditions.
  •  The gradual change in a species over time is called evolution. A scientific theory is a well-tested concept that explains a wide range of observations.
  • NATURAL SELECTION In his book called The Origin of Species, Darwin proposed that evolution occurs by means of natural selection. Natural selection is the process by which individuals that are better adapted to their environment are more likely to survive and reproduce than other members of the same species.
  • FACTORS THAT AFFECT NATURAL SELECTION: Overproduction: Most species produce far more offspring that can possibly survive. Variations: Are differences between individuals of the same species Competition: Since food and other resources are limited, the members of a species must compete with each other to survive.
  •  Darwin proposed that, over a long time, natural selection can lead to change. Helpful variations may gradually accumulate in a species, while unfavorable ones may disappear.
  •  A change in the environment can affect an organism´s ability to survive Ex: moths and industrial revolution
  •  Variations can result from mutation and the shuffling of alleles during meiosis. Because of this, only traits that are inherited, or controlled by genes, can be acted upon by natural selection.