Science Starter #1 – 11/28/17What is evolution? What are some forms of

evidence that support evolution?

NEW GREEN SHEET

Chapter 15-2

Evolution defined Change of heritable

traits within a population over time

Evolution is a process of gradual modifications over generations

Darwin called this descent with modification

Common Ancestor All organisms share a

common ancestor

Organisms today deviated from that common ancestor over time

Evidence for Evolution – 1. Fossils

Fossils provide geologic evidence of evolution

Relative age: fossils are older in lower layers than those in the upper layers

Law of Superposition

Fossils - Transitional Species Descent with

modification states that newer species are modified versions of older species

Fossil record contains the intermediates

2. Vestigial structures Vestigial structures- remnants of organs or

structures that had a function in an early ancestor

Shows that these organisms are descendants from organisms that used them

Ex: (tailbone coccyx or hip bones in whales)

3. Homologous Structures

Homologous Structures: body parts that are similar in structure may have different functions

Indicating at in the past they did the same job and came from a common ancestor

4. Analogous Structures

Analogous Structures: same functions but different development

Indicates that different populations evolved to be better suited to the same environment

Evidence for Evolution –5. Biogeography Geographical distribution of

living things

Similar species are found in similar places showing common ancestry

Continental Drift The continents have not always been in the position

they are now

Fossils of the same ancient species have been found on different continents

Providing evidence that they were once connected

Evidence for Evolution –6. Embryology Same stages of embryo

development of different organism are similar

Shared ancestry accounts for shared development

Evidence for Evolution –7. Biological Molecules

DNA RNA Proteins

Similar proteins means similar DNA

The longer it has been since they shared a common ancestor the more differences in protein