Evolution. I. Origins of Life A. General Info 1. Earth is ~4.6 billion years old 2. Primitive oceans were formed and life is hypothesized to have begun.

Evolution

I. Origins of LifeA. General Info

1. Earth is ~4.6 billion years old2. Primitive oceans were formed and life is

hypothesized to have begun ~3.5 billion years ago

B. Oparin-Haldane Model of Life (Abiogenesis)

1. In the 1920’s, Russian scientist Alexandr Oparin and English scientist JBS Haldane independently theorized 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. They randomly bonded to form amino acids, sugars and fatty acids, which accumulated in the oceans

4. Over time these organic compounds combined to form little membranes that produced simple cells, but they could not reproduce and fell apart

5. About 3.5 billion years ago, nucleic acids evolved and cells started to reproduce

6. These simple cells eventually produced chlorophyll To what process would this

eventually lead?

C. Miller and Urey’s Experiment (1953)

1. Demonstrated that organic compounds can be made from inorganic molecules

2. The experiment:

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

b. 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)

D. Origin of Eukaryotic Cells1. Endosymbiotic Theory – summarize pg.

427-428

Aerobic bacteria

Ancient Prokaryotes

Ancient Anaerobic Prokaryote

Primitive Aerobic Eukaryote

Primitive Photosynthetic Eukaryote

Chloroplast

Photosynthetic bacteria

Nuclear envelope evolving

Mitochondrion

Plants and

plantlike protists

Animals, fungi, and non-plantlike protists

Draw Fig. 17-12, pg 427

Primordial Soup Movie

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 world

Just a Theory? MovieD. 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 1000 years old b. Since their creation, neither plants nor

animals had changed

B. Puzzle of Life’s Diversity Read section 15-1 in your textbook and

take notes in your spiral notebook using the given headings:

1. Voyage of the Beagle2. Darwin’s Observations3. The Journey Home

Who Was Charles Darwin? Movie

C. 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 Principles of Population that the human population will grow faster than the space and food needed to sustain it

What happens to populations of organisms that exceed their resource

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 hypothesis?

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

D. Darwin’s Conclusions1. Observations and evidence collected

while traveling on the HMS Beagle led Darwin to hypothesize that organisms evolve over time

a. Diverse plants and animals appeared well suited to their environments1) Galapagos Island tortoises and finches

b. Variety of ways organisms survived and produced offspring

c. Some fossils resembled organisms still alive, but others looked completely different to anything alive

2. On the Origin of Speciesa. 1859, Darwin published his findingsb. Proposed a mechanism for evolution

called natural selection

“I have called this principle, by which each slight variation, if

useful, is preserved, by the term Natural Selection” – Charles

Darwin

E. Evolution by Natural Selection1. Individual organisms of the same

species differ, and some of this variation is inheritable.

a. Today, we know these variations are the result of mutations or changes in DNA.

b. Mutations occur by random chance and are not always bad *Peppered moths, antibiotic resistant bacteria or insecticide resistant insects.

c. Humans use natural variation to improve livestock and crops (e.g. dog breeds, milk cows, fruits and vegetables). This is called artificial selection

Peppered moth

2. Organisms struggle to survive Why?

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

b. “Survival of the fittest”i. Process by which individuals that are better suited to

their environment survive and reproduce most successfully

ii. Fitness = ability of an organism to survive and reproduce in its environment

iii. Adaptation = inherited trait that increases the chance of survival (ex. Giraffe neck)

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

3. Organisms produce more offspring than survive

4. 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. Types of fossils include:

Petrification

Compression/Impression

Amber

Cast/Mold

5,000 year old “Iceman” found

frozen in the Alps, Italy in

1991

Freezing

Baby mammoth found frozen in Russia in 2007

Freezing

How Fossils Form

Sea leve

l

Sedimentary rocks form in horizontal layers.

When part of Earth’s crust is compressed, a bend in a rock forms, tilting the rock layers.

As the surface erodes due to water, wind, waves, or glaciers, the older rock surface is exposed.

New sediment is then deposited above the exposed older rock surface.

Sea leve

l

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 results in the oldest and simplest fossils usually 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. Half-life = length of time required for half of the radioactive atoms in a sample to decay

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

Relative Dating

Can determine

Is performed by

Drawbacks

Absolute Dating

Comparing Relative and Absolute Dating of Fossils

Imprecision and limitations of age data

Difficulty of radioassay laboratory methods

Comparing depth of a fossil’s source stratum to the position of a reference fossil or rock

Determining the relative amounts of a radioactive and nonradioactive isotopes in a specimen

Age of fossil compared to an older or younger rock or fossil

Age of a fossil in years

Radiometric Dating Movie

4. Transitional Formsa. Fossils that show the intermediate states

between an ancestral form and that of its descendants

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

The Aetiocetus nostril placement is an intermediate form between the ancestral form Pakicetus and the

modern beluga

Evolution of Horse Feet

sampling of horse fossils leading to modern horses

the diagram shows transitional stages whereby the four-toed foot became the single-toed foot of Equus

shows the reduction of toes through time

Archaeopteryx

Early transitional form between fish and

amphibians.

How do we know evolution happens? MOVIE

B. Anatomical Evidence

1. Homologous structures – same internal structure but not always same function or external appearance.a. Example: basic bones in the arms of a

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

2. Comparative Embryologya. Closely related organisms pass through

similar stages as embryosb. Shows common ancestry

3. Vestigial Structures- internal structure that once was useful in an animal’s evolutionary past, but is now useless

Top 10 Useless Vestigial Organs

4. 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

Atavism

Atavism

C. Biogeography1. Geological distribution of similar but

genetically unrelated plant and animal species2. Gradual changes in a species as environmental

factors change3. Species living on different continents who

descended from the same ancestor, look slightly different because they were exposed to different ecological conditions

4. Consistent with plate tectonics

D. Molecular biology - compare the biochemical sequences of certain molecules (DNA) common to different species.

1. Closer similarities means more likely to have a common ancestor.

2. Example: a human’s DNA is 97% similar to that of a chimpanzee.

Genetic relatedness

includes

Evidence for Evolution

Physical remains of organisms

Common ancestral species

Similar genes Similar genes

which is composed of which indicates which implies which implies

The fossil record

Geographic distribution of living species

Homologous body

structures

Similaritiesin early

development