Change through Time

Earth has been home to living things for about 3.8 billion years. Fossil records inform humans about the development of life on Earth. Information from fossils can help scientists reconstruct Earth's history. 250 million years ago 70 million years ago55 million years ago 6.1 VISUALIZATION CLASSZONE.COM Explore how fossils form.

Fossils The remains of organisms preserved in the earth Age of fossils: Absolute age tells you when it was formed, determined by radioactive decay Relative age is determined by a fossils location More complex organisms develop over time

Unicellular organisms 3.8 billion years ago single-celled organisms lived in the ocean and were responsible for creating the oxygen in our atmosphere

Multicellular organisms 1.2 billion years many celled organisms appeared in the ocean

Life on land The first land dwellers were simple plants and fungi

Mass extinctions Huge numbers of species died or became extinct in a very short period of time Permian extinction – 250 million years ago, 90% of the species living in the ocean became extinct and many land dwelling animals disappeared Cretaceous extinction – 65 million years ago, dinosaur fossil record ends. At the same time, more than half of the other species living on Earth became extinct.

Evolution Process through which species change over time

Theories Lamarck – acquired traits are inherited Example: giraffes had to stretch their necks to reach leaves. Passed on the trait to the next generation Darwin – natural selection: members of the same species that are better suited to their environment will survive to pass on their traitsnatural selection Example: tortoises, finchesfinches

Species change over time. SECTION OUTLINE SECTION OUTLINE Darwin's theory of natural selection explains evolution. Four principals of natural selection are overproduction Overproduction adult salmon eggs 6.2 CHAPTER RESOURCES CHAPTER RESOURCES

Species change over time. SECTION OUTLINE SECTION OUTLINE natural selection adaptation evolution speciation Darwin's theory of natural selection explains evolution. Four principals of natural selection are overproduction variation Variation curve 6.2 CHAPTER RESOURCES CHAPTER RESOURCES

Species change over time. SECTION OUTLINE SECTION OUTLINE natural selection adaptation evolution speciation Darwin's theory of natural selection explains evolution. Four principals of natural selection are overproduction variation adaptation Adaptation 6.2 CHAPTER RESOURCES CHAPTER RESOURCES

Species change over time. SECTION OUTLINE SECTION OUTLINE Darwin's theory of natural selection explains evolution. Four principals of natural selection are overproduction variation adaptation selection Selection 6.2 CHAPTER RESOURCES CHAPTER RESOURCES

Speciation Evolution of a new species from an existing species Contributes to a new species Isolation

Salamander evolution What were the two strategies used by the salamanders to adapt to their environment? What was the problem with the hybrid?

Tree of life video Tree of life interactive Simple tree of life

Evidence for evolution Genetic – comparing DNA for similarities Fossil – sharing a common ancestor Biological – similarities in structure, similarities in development

Genetic – Comparison of chimp and human chromosomes

Fossil evidence From Wolf to Whale

Similarities in structure Vestigial organs – structures that at one time had a function but no longer do Homologous structures – structures or organs that are similar from one species to another

Biological evidence Homologous structures

Vestigial organs Top ten

Embryological

Even a caveman can do it! Cave man challenge brainpop Evolution of humans Why Does Evolution Matter Now?