Origin of LifeBiogenesis – Principle that says all living things come from other living things

We know this now… but it hasn’t always been that way

Spontaneous Generation – Theory from the early 1600’s stating that living things could also arise from nonliving things

(Example: Maggots appear on rotting meat)

The debate was solved by several great experimenters!

Biogenesis vs. Spontaneous Generation

Francesco Redi (1626-1697)• Noticed adult flies producing

‘oval cases’ from which new flies eventually arose

• 1668 controlled experiment (supports biogenesis)

Louis Pasteur (1822-1895)• Different experiment,

but same conclusion• Modification of Lazzaro

Spallanzani’s experiment (monitors microorganismal growth)

The FIRST ORGANIC COMPOUNDS

• Miller and Urey created an apparatus (1953) to mimic the early atmosphere of Earth as proposed by Oparin (1923)

• A mixture of methane, ammonia, hydrogen, and water vapor was energized, then condensed

• A ‘scum’ was extracted and found to contain AMINO ACIDS

Life comes from life, comes from life, comes from… ?

Change over Time• FACT: The planet Earth is extremely old4.6 billion years ago – our planet was formed3.9 billion years ago – oceans formed 3.5 billion years ago – we have evidence of life!

• FACT: The organisms that existed then are different from those that live today

EVOLUTION – A scientific theory that says species change over time

QUESTION: In science, when do we say that a hypothesis is proven?

• DEFINITION: Theory – the status of a hypothesis when

it has been supported by a large amount of evidence

EVIDENCE for EVOLUTION

• The Fossil Record

• Structural Similarities

• Vestigial Structures

• Embryonic Development

THE FOSSIL RECORD• A fossil is an imprint/trace of a long-dead

organism (usually found in sedimentary rock)

FOSSILS CAN BE DATED:

• Relative – Molds found in lower layers of rock are older

• Absolute – Radiometric dating (example: carbon-dating)

THE FOSSIL RECORD (a time scale for the entire history of life on our planet) indicates that over time, organisms of increasing complexity appeared on earth

Radiocarbon Dating

Laboratory

Structural Similarities

HOMOLOGOUS STRUCTURES• Anatomical features found in different species

that show the same relative structure, indicating common ancestry

• EXAMPLE: Forearms in the bat, penguin, human, and alligator

ANALOGOUS STRUCTURES• Anatomical features found in different species

that serve similar functions but have different structures

• EXAMPLE: Wings of moths and wings of birds

VESTIGIAL STRUCTURES

• An anatomical feature that is present in an organism, but (now) serves no useful purpose

EXAMPLES: - Human tailbone

- Pelvic bones in whales

EMBRYONIC DEVELOPMENT• Showing physical similarities during

embryonic development (between conception and birth)

• These similarities usually disappear before birth

EXAMPLE:

• All vertebrates possess a tail and gill slits at some time during development

Theories of EVOLUTION• Jean Baptiste de Lamarck

(1774-1829)• French Scientist• 1809 – “the inheritance of

acquired characteristics”* NO EVIDENCE *

• Lamarck put forward the idea that traits would be changed/modified based on a conscious use or disuse, and that this modified trait would be passed on

- Slithering salamander - Neck stretching giraffes

Theories of EVOLUTION• Charles Darwin (1809-1882)• British Scientist • Theory of NATURAL

SELECTION• Explained in his 1859 book…

THE ORIGIN OF SPECIES* Independently proposed at the same time by Alfred Wallace (1823-1913)*

• 1831-1836 H.M.S. Beagle voyage• Mapping and collecting expedition• Studied finches of the Galapagos

Islands (off the coast of South America)

The Finches of the Galapagos• Darwin saw 13 separate, yet similar species of finches

• The species only differed in their beak shapes and the types of food they ate

• Darwin believed that a single finch species coming from South America could have inhabited the islands, diverging into the 13 different species

NATURAL SELECTION• Resources are limited• A struggle/competition for survival results• There is variation within a species

(some individuals have traits better suited for survival)• Those individuals most FIT are able to…

survive and reproduce • SURVIVAL OF THE FITTEST• Favorable traits are passed down

through the generations• Over time, a population

adapts to the environment