Early conditions (~4.6 billion years ago) High temperatures Volcanoes, Earthquakes

Early atmosphere High levels of gases not compatible with life No OXYGEN!

~3.5 billion years ago Ancient prokaryotes, similar to modern

bacteria Found in the ocean

How did they get there in this inhospitable environment? Two different theories: abiogenesis vs.

biogenesis

Simple molecules randomly combined and separated

Larger, more complex molecules formed

When these were able to reproduce, life was formed

Proved in experiment by Miller and Urey (1953) Produced organic

compounds similar to those of early Earth

The idea that life comes from pre-existing life

Redi (1668) observed that maggots (larval fly form) only appeared on meat that was exposed to flies

Further confirmed by Spallanzani and Pasteur, who also showed that life does not arise from nonlife

You simulated this lab back in Week 1!

First organisms were prokaryotic (extremely simple!) heterotrophs

Rely on consuming compounds to obtain energy anaerobic, meaning they did not need oxygen

to survive (a good thing because there was no oxygen in the atmosphere!)

Over the next billion years, atmospheric oxygen increased from 1-21%

O2 important because reactions using oxygen allow organisms to use chemical energy more efficiently

Development of autotrophs appeared (3-3.5 bil yrs) Created organic chemical energy from inorganic

compounds O2 allowed the development of mitochondria, which

use O2 to process energy. These cells would be eukaryotes with membrane-bound organelles

Over millions of years natural selection resulted in the variety of life we see today Organisms with characteristics that favor

survival pass those characteristics to offspring Originally proposed by Charles Darwin

Changes came about in spurts due to environmental changes

• Existing organisms adapt and become new species as they fill niches left by extinct species through evolution• The theory that explains how organisms

change over time

Went around the world in a ship called the Beagle and collected observations of different organisms

Most important work was with the finches of the Galapagos Island

Muskopf, Shannan. Online Images. The Biology Corner. 13 May 2007. http://www.biologycorner.com/bio3/notes-chap16-history.html

Darwin observed that

all of the finches were

similar except for their

beaks.

Organisms adapt to their environment Finches had adapted beaks to eat the available

food in their environments

Some species that do not adapt do not survive

“Survival of the Fittest” Fitness refers to the physical traits and behaviors that

help an organism to survive and reproduce in its environment

Called “Natural Selection” because the environment or nature selects how well the traits of an organism will help it survive; organisms without those traits are less “fit” and may not survive

Online Images. Welcome Trust. 13 May 2007. http://www.wellcome.ac.uk/doc_WTD026025.html

•The “spunk” animals in the figure have different traits.

• The environment or the food selects for tall spunks while the short spunks are at a disadvantage because they can’t reach the food.

•The tall spunks are better suited to their environment and will survive to reproduce more offspring.

•The less “fit” or short spunks will not survive, so their DNA will not be passed on. Over time, the population will be all tall spunks.

1. VARIATION: variety in traits exist2. STRUGGLE FOR EXISTENCE:

members of a species compete for resources (food and living space); Competition leads to the death of those less fit

3. SURVIVAL OF THE FIT: individuals best suited to their environment survive & reproduce

1. Fossils: provide indirect evidence that modern species evolved from ancient organisms that are now extinct

Absolute or radioactive dating uses isotopes to provide a general age of how old a rock might be Isotopes break down over time Remaining amounts can be analyzed to

determine a rock’s age Relative dating uses rock layers to show

which fossils are more recent than others

• 2. Homologous Structures: structures with similar bone arrangements but different functions; the similarity is evidence that they came from a common ancestor– Ex: the forearms of a human, cat, whale, and bat have

similar bone arrangements but are used for different things

Muskopf, Shannan. Online Images. The Biology Corner. 13 May 2007. http://www.biologycorner.com/bio3/notes-chap16-evidence.html

• 3. Analogous Structures: structures that do not have a common ancestor but develop similar structures because they are in similar environments

Online Images. Wikipedia. 13 May 2007. http://en.wikipedia.org/wiki/Analogy_(biology)

Example of Analogous Structures: the wings of pterosaurs, bats, and birds have similar structures but did not come from a common ancestor

4. Vestigial Structures: a body structure that has diminished in size or usefulness

Ex: appendix or the pelvic bone in a whale (these

structures have no function)

Muskopf, Shannan. Online Images. The Biology Corner. 13 May 2007. http://www.biologycorner.com/bio3/notes-chap16-evidence.html

• 5. Embryology: the study of organisms in early stages of development; related organisms will have similar embryos

Online Images. Wikipedia. 13 May 2007. http://en.wikipedia.org/wiki/Embryo_drawing

In the early stages of development (top pictures), the fish, salamander, hog, rabbit, and human look similar, providing evidence that they came from a common ancestor.

• 6. Biochemistry and DNA: similar DNA or amino acid sequences between two organisms is evidence that the two organisms came from a common ancestor

Populations Evolve, Not Individuals An individual organism cannot evolve

but is part of a population that will evolve over time

Each individual has genes that characterize the traits of their species

Evolution occurs as a population’s genes and their frequencies change over time

Muskopf, Shannan. Online Images. The Biology Corner. 13 May 2007. http://www.biologycorner.com/bio3/notes-chap16-history.html

Originally, there was variation in neck length. Over a long time, the population of giraffes evolved to have long necks because long necks are selected for by the environment. An individual giraffe can not stretch his neck and evolve, only a population of giraffes can evolve to have longer necks over many, many generations.

Gene pool: all of the genes in a population For evolution to occur, the percentage of a

gene in the gene pool must change A population in which the frequency of

genes remains the same over generations is in genetic equilibrium and does not evolve

A population in genetic equilibrium is not evolving

One cause of evolution is a mutation (a change in the DNA) A mutation provide the opportunity for an

organism to have a trait that increases its chances of survival (ex: stronger beak to eat seeds). Trait is passed to offspring through its DNA.

Organisms without the mutation may not be able to get food, for example, and will die, not passing along their DNA

“Survival of the Fittest”!

Muskopf, Shannan. Online Images. The Biology Corner. 13 May 2007. http://www.biologycorner.com/bio3/notes-chap16-history.html

Darwin observed thatall of the finches weresimilar except for theirbeaks. The environment (available food) will select the type of beak that will enable a finch to survive and reproduce. Over time, the finches that do not have the “fit” beak will not survive and reproduce.

Cause of speciation: Behavioral Isolation - occurs when two species have

different courtship behaviors (males have courtship songs or dances that will only be recognized by females of the same species)

Geographic Isolation – physical barrier (river, mountain) prevents contact between individuals and leads to speciation

Pesticide or antibiotic resistance: bacteria become resistant to pesticides (sprayed on crops) and antibiotics and survive

Online Images. Wikipedia. 13 May 2007. http://en.wikipedia.org/wiki/Image:Antibiotic_resistance.gif

Originally, there are a variety of bacteria. The pesticide or antibiotic kills all of them but the dark red bacteria. These resistant bacteria survive and reproduce and eventually the population evolves and is made up of resistant dark red bacteria.