Evolution

I. Origins of Life on Earth

A. Oparin Model of Life1. In 1924, Russian scientist Aleksander

Oparin proposed that Earth is approximately 4-5 billion years old and that the ancient atmosphere contained:

a. ammonia (NH3)

b. water (H2O) vapor

c. methane (CH4)

d. hydrogen (H2) Which important gas(es) is/are

missing?

2. Energy from the sun, lightning and heat from the earth broke apart these molecules.

3. The atoms randomly bonded together to form amino acids, sugars and fatty acids, which accumulated in the oceans.

What are proteins made of?4. Over millions of years these organic

compounds combined to form simple cells that filled the Earth’s primordial oceans.

B.B. Miller & UreyMiller & Urey’’s s ExperimentExperiment

1. In 1953, Stanley Miller and Harold Urey showed that you can make organic compounds from inorganic molecules.

2. The experiment:

a. Miller electrocuted a mixture of water vapor, methane, ammonia and hydrogen gas.

b. He collected the liquid and found amino acids, simple sugars and simple fats!

c. However, as of today, no one has produced a living cell from nonliving materials.

Miller & Urey’s Experiment (1953)

II. General InfoA. Evolution means “change over time”B. Process by which modern organisms

have descended from Earth’s earliest forms of life

C. It is a scientific theory What is a scientific theory?

It is a well-supported, testable explanation of events that occur in

the natural worldJust a Theory? Movie

D. Foundation of modern biology that unifies many different branches of science

III. Darwin’s Theory of Evolution

A. Background Info1. Most Europeans in the 1700-1800’s

believed:a. Earth was only several thousand years

old b. Since their creation, neither plants nor

animals had changed

Approximately how old is Approximately how old is Earth?Earth?

B.Ideas that Shaped Darwin’s Thinking1. In 1795, James Hutton proposed that

layers of rock form over millions of years; therefore Earth had to be more a few 1000 years old

2. In 1841, Thomas Malthus predicted in his Essay on the Principle of Population that the human population will grow faster than the space and food needed to sustain it

What happens to populations of What happens to populations of organisms that exceed their resource organisms that exceed their resource limits?limits?

3. Hypothesis of Acquired Traitsa. In 1809, Jean Baptiste de Lamarck proposed

that traits developed during a parent’s lifetime are inherited by their offspring

Is this a supported Is this a supported hypothesis?hypothesis?

My, How You’ve Changed!Prior to the 1800s, life scientists knewthat living things changed overgenerations. They just didn’t know howthese changes were brought about.

1.1.Make two columns:Make two columns:

Inherited TraitsInherited Traits Acquired TraitsAcquired Traits

2.2.1st column, list the traits that you believe 1st column, list the traits that you believe you have always had. Ex: brown eyes, curly you have always had. Ex: brown eyes, curly hair hair

3.3.2nd column, list your acquired traits. 2nd column, list your acquired traits. Ex: playing a musical instrument Ex: playing a musical instrument

4.4.Which of the items in your lists do you think Which of the items in your lists do you think you might pass on to your children? you might pass on to your children?

4. In 1830, Charles Lyell explained in his book Principles of Geology how geological events (volcanoes, earthquakes) build up or tear down the Earth over millions of yearsa)a) Explains how marine fossils can end Explains how marine fossils can end

up on mountain topsup on mountain tops

C. Evolution by Natural Selection1. Voyage Around the World

a. In 1831, Charles Darwin set sail from England on the HMS Beagle for a voyage around the world

Voyage of the HMS Beagle

b. As the ship’s naturalist, Darwin recorded observations and collected specimens of the many plant and animals species he saw

c. Galapagos Islandsi. Group of islands 1,000 km off the coast of

Central and S. America that are close together but have very different climates and an amazing variety of species (iguanas, finches, tortoises)

ii. Diverse animals and plants seemed very well suited to their island’s environment

iii. Beak shape of each species of Galapagos finch is related to its eating habit

iv.iv. Based on his observations, Darwin Based on his observations, Darwin hypothesizedhypothesized that the Galapagos plant and that the Galapagos plant and animal species animal species evolved from ancestorsevolved from ancestors from from Central and S. America Central and S. America

2. On the Origin of Species (book)a. 1859, Darwin published his findingsb. Species are not perfect and

unchanging

c. Proposed a mechanism for evolution called natural selection

organisms with traits best suited to their environment are more likely to survive and reproduce (“survival of the fittest”)

d. Survival of the fittest• Fitness = ability of an organism to

survive and reproduce in its environment

• Adaptation = inherited characteristic that increases the chance of survival (write examples)

• Over time, natural selection results in changes in the inherited traits of a population, increasing that species’ fitness.

Natural Selection Movie

3. Summary of Darwin’s Theorya. Organisms produce more offspring that

can survive (think mice, bunnies, etc)b. Individual organisms of the same

species differ, and some of this variation is inheritable.

Homo sapiensHomo sapiens Drosophila Drosophila polymorphapolymorpha

i. Today, we know these variations are the result of mutations.

ii. Mutations occur by random chance and if favorable, it will be inherited by organism’s offspring (e.g. Peppered moths, antibiotic resistant bacteria or insecticide resistant insects)

c. Organisms struggle to survive Why?

i. Individuals of each species compete for resources (food, space, mate, etc)

d. Species alive today have descended with modification from ancestral species of the past. This process unites all organisms on earth into a single tree of life.

IV. Evidence for evolutionA. The Fossil Record – provides evidence

about the history of life on Earth

1. Fossils are preserved impressions or physical remains of an organism that once lived.

PetrificatioPetrificationn

Impression

Cast/Mold

Amber

Cast/Molds

Baby Baby mammoth mammoth found frozen found frozen in Russia in in Russia in 20072007

Iceman found Iceman found frozen in the frozen in the Alps, Italy in Alps, Italy in 19911991

2. Fossils occur in a particular order; simpler forms existed before more complex forms (e.g. the oldest known fossils are prokaryotes)

3. Fossil dating techniques

a. Relative Dating -- layering of sediment layering of sediment results in the oldest and simplest fossils results in the oldest and simplest fossils usually further downusually further down

b. Absolute/Radiometric Datingi. Some rocks contain elements that are

radioactive and will decay (break down) at a constant rate over time

ii.ii. Half-life Half-life = length of time required for = length of time required for half of the radioactive atoms in a half of the radioactive atoms in a sample to decaysample to decay

iii. Scientists can calculate the age of a sample by measuring remaining amount of radioactive isotopes like carbon14

4. Transitional Formsa. Intermediate forms of life appearing in the

fossil record that are "in-between" existing types of organisms found today or in the past

b. Many examples of transitional forms exist in the fossil record

The The AetiocetusAetiocetus nostril placement is an nostril placement is an intermediate form between the ancestral form intermediate form between the ancestral form Pakicetus and the modern beluga.Pakicetus and the modern beluga.

Evolution of Evolution of Horse FeetHorse Feet

sampling of horse sampling of horse fossils leading to fossils leading to modern horsesmodern horses the diagram shows the diagram shows transitional stages transitional stages whereby the four-whereby the four-toed foot became the toed foot became the single-toed foot of single-toed foot of EquusEquus shows the shows the reduction of toes reduction of toes through timethrough time

Archaeoptryx

A model of A model of Tiktaalik Tiktaalik roseaeroseae, a fish in , a fish in transition to becoming transition to becoming a land animal. a land animal.

Early transitional form Early transitional form between fish and between fish and amphibians.amphibians.

Limb EvolutionLimb Evolution

How do we know evolution happens? MOVIE

B. Biogeography1. Geographical distribution of species2. Species living on different continents who

descended from the same ancestor, look slightly different because they were exposed to different ecological conditions (e.g. armadillos and anteaters, lions and tigers)

3. Consistent with plate tectonics

C. Comparative Anatomy

1. Homologous structures – made of the same types of bones, but the function or structure may be differenta. Example: basic bones in the arms of a

human, wings of a bird and fins of a whale.

2.2. Vestigial Vestigial StructuresStructures- internal - internal structures that serve structures that serve no known purpose.no known purpose.

3. Atavism - rare reappearance of a lost characteristic specific to an evolutionary ancestor (gene is turned back on)

a. Ex: whales with legs, human babies with true tails The hind-flippers The hind-flippers

of a bottlenose of a bottlenose dolphin found in dolphin found in Japanese coastal Japanese coastal waters in 2006.waters in 2006. Yellow arrows Yellow arrows indicate the indicate the location of a well-location of a well-formed formed atavisticatavistic set of set of hind limbshind limbs.. (photos from (photos from the Taiji the Taiji Whaling Whaling Museum) Museum)

D.D. Comparative EmbryologyComparative Embryology- closely - closely related organisms pass through similar related organisms pass through similar stages as embryos -> shows common stages as embryos -> shows common ancestryancestry

E.E. DNADNA1.1. Scientists can compare the DNA of different Scientists can compare the DNA of different

species to determine their relatednessspecies to determine their relatedness2.2. Closer similarities means more likely to have a Closer similarities means more likely to have a

common ancestorcommon ancestor

3.3. Example: a humanExample: a human’’s DNA is ~ 97% similar to that s DNA is ~ 97% similar to that of a of a chimpanzeechimpanzee.

Genetic relatedness

Number of Number of amino acid amino acid differences in differences in hemoglobin hemoglobin