Evolution Part 1 The Introduction

Evolutionary Relationships Studying fossils has helped scientists understand evolutionary relationships Fossils are the preserved remains or impressions left by organisms that lived in the past. The fossil record is the ordered arrangement in which fossils appear within sedimentary rocks. These rocks record the passing of geological time and provides an actual record of the Earth’s past life forms

Geological Time Scale = used to represent evolutionary time Developed by studying rock layers and fossils worldwide

DETERMINING FOSSIL AGE

Relative Dating = estimating a fossil’s age compared with that of other fossils Gives an approximate age of fossils Law of Superposition: The fossils in the top rock layers are younger than the fossils in the deeper layers of rock Layer 1 Layer 2 Layer 3 Layer 4

Radiometric Dating = calculating the age of a sample based on the amount of remaining radioactive isotopes it contains Half-life = the length of time required for half of the radioactive atoms in a sample to decay Example Original amount of radioactive material After 1 billion years After 2 billion years

Evolution The processes that has transformed life on earth from its earliest forms to the vast diversity that characterizes it today. Driven by mutations - changes in the genes (DNA) !!!!!!!!

Definitions Evolution is the slow, gradual change in a population of organisms over time Adaptation is any inherited characteristic that increases the survival and reproductive success.

Lamarck’s Theory of Evolution Jean-Baptiste Lamarck, 1809 One Of First Scientists To Understand That Change Occurs Over Time Stated that changes are adaptations to an environment acquired in an organism’s lifetime These acquired changes are passed to offspring

Lamarck’s Theory of Evolution Example: Ducks spreading their toes wide to avoid sinking into mud over time develop webbed feet.

Lamarck’s Theory of Evolution Idea called Law of Use and Disuse If a body part was used, it got stronger If body part was NOT used, it deteriorated

Lamarck’s Theory of Evolution Proposed That By Selective Use Or Disuse Of Organs, Organisms Acquired Or Lost Certain Traits During Their Lifetime These Acquire Traits Could Then Be Passed On To Their Offspring Over Time This Led To New Species

Lamarck’s Mistakes Lamarck Did NOT Know how traits were inherited (Traits are passed through genes) Genes Are NOT Changed By Activities In Life Change Through Mutations Occurs Before An Organism Is Born A mutation is a change in DNA that is the source of new traits that might be an adaptation for an organism

Voyage of the Beagle Charles Darwin Born Feb. 12, 1809 Joined Crew of HMS Beagle, 1831 Naturalist 5 Year Voyage around world Avid Collector of Flora & Fauna Astounded By Variety of Life

The Galapagos Islands Very Different Climates Small Group of Islands 1000 km West of South America Very Different Climates Animals On Islands Unique Tortoises Iguanas Finches

Darwin’s Observations Tortoises - Each island had long or short neck tortoises Finches - More types appeared on the islands where the available food was different (seeds, nuts, berries, insects…) Finches had different types of beaks adapted to their type of food gathering

Charles Darwin In 1859 wrote : “On the Origin of Species by Means of Natural Selection” Two main points: 1. Species were not created in their present form, but evolved from ancestral species. 2. Proposed a mechanism for evolution: NATURAL SELECTION

Natural Selection Natural selection - the overall process by which organisms with better adaptations for their environment survive and reproduce. “Survival of the fittest” Individuals with favorable traits are more likely to leave more offspring better suited for their environment. no two individuals are exactly alike

Natural Selection Developed independently by both Charles Darwin and Alfred Wallace, claims that only organisms with the necessary survival characteristics will be alive long enough to pass on their traits to offspring. In this way, over time the weakest organisms will be weeded out of a population.

Darwin’s Conclusions 1. Individuals in a population have variation. They differ from one another 2. Variations are inherited from parents 3. Populations produce more offspring than can survive. This creates competition 4. Individuals who inherit characteristics most fit for their environment are likely to leave more offspring than less fit individuals

Types of Natural Selection 1. Sexual Selection 2. Disruptive Selection 3. Stabilizing Selection 4. Directional Selection

Sexual Selection Traits are increased or decreased in a population due to mate choice Usually the female does the choosing Males need to Be more attractive Provide shelter for young Fight for feminine approval

Disruptive Selection Natural selection is favoring two extremes of a trait Leads to two new species after a LONG period of time

Stabilizing Selection Natural Selection is favoring the intermediate (heterozygote) trait

Directional Selection Natural selection is favoring one extreme of the trait

Homework Evolution Part 1 Notes - Notes Assignment #4