On your piece of paper

1. Write out your definition of evolution.2. Explain whether you accept this idea or not,

and provide an explanation

Introduction to Evolution

Chapter 15.1

What is evolution?

• Evolution is defined as descent with modification– The change in the genetic makeup of populations

of organisms over time• The processes that we will discuss related to

evolution explain how the organisms present on earth today descended from those that were present here in the path.

Small Changes can create big ones

What we are not talking about…

• Nothing that we will cover in this unit should be at odds with you personal beliefs.

• We are simply discussing how the genetics of living organism’s change over time.

What do we know?• There are many different creatures on Earth• How do we know this? Through OBSERVATION!!

What accounts for all this biological diversity?

What do we know?• All creatures have common characteristics• How do we know this?

DNAcells

Unity of Life on Earth

How could all of life have the same basic features?

Through OBSERVATIONS!!!

What do we know?• Creatures have changed over time• How do we know this?

Fossil Record

OBSERVATION

DNA

Evolution explains Unity & Diversity• Only evolution explains both – unity of life• similarities between all living things

– diversity of life• wide variety of different creatures on Earth

Addressing Important Misconceptions

• Evolution happens to a population, not to an individual.

• Evolution does not result in a “better” form of a life.

• Evolution does not necessarily occur slowly.• A “species” is not distinct from all other

organisms.

Ideas that shaped the theory of evolution

• 1795- James Hutton published a book that detailed how geologic processes might shape the surface of the earth– Discussed forces that both created and eroded the

earths surface.– Acknowledged that these processes happen very

slowly in most cases (erosion)– Proposed that the Earth was more than a few

thousand years old.

Lyell’s Principles of Geology• 1830’s- Charles Lyell explained how geologic features

could be built up or torn down over time.• Once again emphasized how the earth changes over

long periods of time.– Why shouldn’t organism’s also change?

Lamarck’s Theory of Evolution

• 1809- Jean-Baptiste Lamarck was one of the first scientists to recognize that species changed over time– All species descended from other species– Organisms are adapted to their environment

Lamarck’s Theory• “By selective use or disuse of organs,

organisms acquired or lost certain traits during their lifetimes. These traits could then be passed on to their offspring. Over time, this process led to change in a species.”

Components of Lamarck’s Theory

• Tendency Towards Perfection– All organisms are attempting to become more complex

and acquire features that make them better suited to the environment.

• Use and Disuse– Organisms can alter the size/shape of their bodies by

using them in new ways.• Inheritance of Acquired Traits– The new traits, created by behavior are passed on to

offspring

Issues with Lamarck

• If you lift a lot of weights, your children won’t be born with big muscles.

• No matter how much I flap my arms, they won’t become wings.

• Mr. Johnsons isn’t tall because his parents were always reaching for things on high shelves.

• While traits are heritable, an organism lacks the ability to evolve in its lifetime.