Evolution Changes Over Time

Evolution What have you heard? Facts vs. Myths

Charles Darwin Charles Darwin was a British naturalist. Naturalist: someone who studies nature He sailed around the world on his ship The Beagle and learned about plants and animals from different lands.

Darwin’s Travels

Galapagos Islands A group of islands off the coast of South America Darwin observed great diversity among organisms

Darwin’s Discoveries iguanas finches tortoises He noticed that all of these types of organisms appeared on each of the islands, but they looked and acted very differently from one another. He developed a theory as to why the finches and other organisms looked different…Natural Selection.

Darwin’s Finches Finches ( a small bird) were also very different from island to island. Each finch was specially designed to the food it ate

Variation All individuals are different because of their genetic code Some variations help an individual survive & others do not If they survive they will reproduce more individuals with that trait

Finch Beaks Finches that ate insects had a needlelike beak. seeds had a strong, wide beak. Discovery Education

Adaptations Beak shape is an example of an adaptation. Adaptation- a structure or behavior that helps an organism to survive and reproduce in it’s environment.

Natural Selection Natural Selection: the survival and reproduction of individuals with traits that enable them to better survive in their environment.

Thinker! If a group of birds with thin, long beaks and a group of birds with thick, heavy beaks live on an island where only seeds are available, What type of birds will survive? The birds with thick, heavy beaks. What will happen to the birds with thin, long beaks? That group will eventually die off! = extinction

Mutations Inheritable changes in the DNA Can result in favorable changes that allow species to adapt Those species will live to reproduce Some mutations create unfavorable changes in individuals Those species will become extinct.

Do these changes happen in organisms today??? Adaptations in Action Do these changes happen in organisms today??? Bacteria: becoming resistant to antibiotics Hunting: elephants born without tusks were not valuable to poachers…therefore their numbers increased and the numbers of those with tusks decreased. Insecticide Resistance: insects are adapting to the use of certain chemicals in pesticides

Changes over time Evolution: the gradual change of a species over time. How can a species change over time?

Natural Selection & Evolution Over a long period of time, natural selection can lead to evolution. Helpful variations gradually accumulate in a species, while unfavorable ones disappear. Organisms with those traits become extinct: no longer exist

Evolution Darwin's ideas are often referred to as the theory of evolution. A scientific theory is a well-tested idea to explain observations. (Not just a guess) There is a lot of other evidence for evolution The fossil record Radiometric dating Genetic Information Similarities and differences in anatomy

Fossils A fossil is a preserved record of an organism that lived in the past Bone, teeth, & shells Footprints or burrows Scientists can learn a lot about the Earth’s past by looking at fossils (like a detective!)

How do Fossils Form? When an animal dies the soft parts of the body decay or are eaten The remains get buried in sediment (soil & rock) Over a long time the sediment harden to form a fossil!

Reading the Fossil Records Fossils can show how organisms in the past are different from organisms today! The oldest layer is on the bottom

Determining the Age of Fossils Relative Dating Absolute Dating Used to determine which fossils are older Top layers of rock formed last = youngest Determines actual age by radioactive dating Rocks contain elements that decay over time Age of a fossil can be determined by how much of certain elements are left

Molds & Casts Mold Cast The empty space left in the rock When a mold gets filled with hardened minerals

The Fossil Record Fossils help scientist piece together the Earth’s past The collection of fossils scientists have found is called the fossil record. Still Gaps! Most fossils are of extinct organisms: no longer alive

Evidence for Evolution By studying fossils, scientists have learned how organisms have changed over time! Ex: First organisms lived in water, & after plants produced enough oxygen, animals began to live on Earth!

Homologous Structures Homologous Structure: a similar body part the species may have inherited from a common ancestor. Shows that some organisms may have evolved from a common ancestor

Similar Development During early development organisms go through similar changes Can show how closely related organisms are

Similar DNA Scientists are also studying DNA to see how closely related organisms are. The closer the sequence the more closely related Scientists can now take DNA from fossils

Combining the Evidence Scientists have used evidence to construct evolutionary trees: diagrams that show evolutionary relationships among the different groups of organisms.