Evolution Mechanisms of Evolution Change in the heredity

Evolution

Mechanisms of Evolution • Change in the heredity features of a species over time is evolution. • In the mid-1800 s, Charles Darwin developed theory of evolution still accepted today.

Principles of Natural Selection • Natural Selection means that organisms with traits best suited to their environments are more likely to survive. • Examples: vision, hearing, speed, color, etc…

Factors that Govern Natural Selection • Organisms produce more offspring than can survive. • Variations are found among individuals of a species. • Some variations enable members of a population to survive and reproduce better than others. • Over time, offspring of individuals with helpful variations make up more and more of a population.

Variations • A variation is the appearance of an inherited trait that makes an individual different from other members of the same species. • Camouflage is a protective adaptation that lets an organism blend into its environment.

Camouflage

Variations Variations

Variations

Gradualism • The evolution model that describes evolution as a slow change of one species to another species. • Example: horses appear to have evolved gradually over millions of years.

Punctuated Equilibrium • This model shows that rapid evolution of species can come about by the mutation of just a few genes. As quickly as every few million years. Example: elephants.

Evidence for Evolution 1. 2. 3. 4. 5. Examples of fossils include: The imprint of a leaf, feather, or organism in rock A cast made of minerals that filled in the hollows of an animal track, mollusk shell, or other parts of an organism A piece of wood or bone replaced by minerals An organism frozen in ice An insect or other organism trapped in plant resin

Fossil Imprint on Rock

Fossil of wood or bone replaced by minerals

Fossil in Ice

Fossil in Plant Resin

Geologic Time Scale

Geologic Time Scale

Geologic Time Scale

Fossil Records • Unique rock layers and fossils give information about the geology, weather, and life-forms of each time period. • There are two basic methods for reading the record of past life. Relative Dating and Radioactive Dating

Relative Dating • One method often used to determine the approximate age of a rock layer, or fossils within the layer, is to look at where the particular rock layer is. • Older rock layers lie below successively younger rock layers. • Fossils found in the lower layers of rock are older than those in upper layers. • Relative dating can only estimate the age of a fossil.

Rock Layers

The 4 -foot gray-and-brown baby Woolly Mammoth carcass, believed to be between 40, 000 and 10, 000 years old, was discovered in May 2007 by a reindeer herder in the subarctic Northern Siberia region

Radioactive Dating • Radioactive elements give off radiation, a form of atomic energy. • Radioactive elements change to more stable products as they give off radiation. • Radiation is given off at a constant rate. • Scientists can measure how much of a radioactive element has changed.

Radioactive Dating • Uranium ( a radioactive element) changes to lead as it ages. • Scientists can determine how old a fossil in a rock sample is by measuring the amounts of uranium and lead in the rock. • The more lead, the older the rock, therefore the older the fossil.

Uranium Lead

Radioactive Animation

Other Evidence of Evolution • Body parts that are similar in origin and structure are called homologous.

Homologous Structures

Vestigial Structures • A vestigial structure is a body part that is reduced in size and doesn’t seem to have a function.

Vestigial Structures Hind Leg Bones in Whales Human Appendix

Vestigial Structures

Evolution 26: 24