Bio 305 Exam 1

What was Darwin’s phrase of evolution?

descent with modification

What mechanism did Darwin use to explain how evolution occurred?

Natural Selection

Evolution

life appeared as smaller, simpler cells and over time all living things arose from this common ancestor.

Biological evolution

descent with modification

How did early earth go from abiotic to biotic?

Abiotic molecules formed into biological molecules → biological molecules organized into larger/more complicated molecules inside vesicles (protocells) → protocells replicated themselves → led to the beginning of life.

“Nothing in biology makes sense except in the light of evolution” said…

Theodosius Dobzhansky

T. Dobzhansky’s quote can best explain what?

Explains how come organisms are well suited (but not perfectly suited) for their environment, explains both the unity of all life (everything we all share) and the diversity of all life (all our differences), and can all be explained using natural, not supernatural, phenomena.

The theory of evolution unites what?

all aspects of biology (e.g. genetics, behavior, diversity, distribution, etc.)

Example of unity

Flowers: all have similar form, all have, cells with similar organelles, all use DNA/RNA, etc.

Example of Diversity

Flowers: very different colors, different, pollinators, different inorganic requirements, etc.

Natural Theology

Study nature to understand God’s plan.

• species were created by God as they exist today and don’t change

  • earth is only a few thousand years old.

Nicolaus Steno (mid 1600’s)

One of the 1st to recognize that fossils were the remains of dead organisms — Thus species can change.

What did the discovery of fossils suggest?

The history of earth is very different than modern times.

Steno’s Law of Superposition

Younger rocks near the surface, older rocks deeper in the surface.

• Rocks get built at the surface and cover older rocks

• organisms get trapped and form fossils

Aristotle: The Scala Naturae (“Natural Ladder”/ “Great Chain of Being”)

Thought (from 2,500 yrs. ago) that all things can be placed on a scale from “lower” organisms to “higher” organisms. EX: Rocks (lowest) → Plants (low) → Animals (higher) → Humans (highest) → God?

Carolus Linnaeus (mid 1700’s)

In his book Systema Naturae organized living things into a nested hierarchy of taxa.

System from the mid 1700’s that is still used in biology today

Linnaeus system

Why do we still use Linnaeus system?

Works well because it groups things based on common ancestry.

What century did people begin considering the idea that life has changed over time?

18th Century

Georges Buffon (1700’s)

Began to incorporate the ideas of physics and chemistry into biology

• Earth is much older that previously thought (70,000 years)

• populations can change over time

Thomas Malthus

• Late 1700’s - early 1800's

• Human population grows faster than its food supply

  • Thus, humanity will always have struggles for limited resources

Georges Cuvier (late 1700’s - early 1800’s)

• Realized that fossil elephants were different from modern elephants

• Thus, some organisms no longer exist (went extinct)

What did Cuvier believe to cause extinctions?

Catastrophes wiped out species

Catastrophism

belief that periodic catastrophes wipe out large numbers of species

Mary Anning (Early 1800’s)

Found many important fossils (such as dinosaurs). Made fossil hunting popular.

Jean-Baptiste Lamarck (early 1800’s)

• Before Darwin, he felt that slow, gradual change can create new species.

• Hypothesized that species evolve through the use and disuse of body parts and the inheritance of acquired characteristics

• Thought animals changed during their lifetimes, and the changes were passed on to their offspring.

Example of Lamarckian evolution

First giraffes ALL had short necks, so they had to strain to get higher leaves… and their offspring thus had longer necks. “Acquired” the long neck trait and passed it on.

James Hutton (late 1700’s)

Earth changes VERY slowly over a VERY long time

• 50 yrs. before Cuvier

• Processes we see today can explain the changes over a long time

Charles Lyell’s (1830’s) Principle of Uniformitarianism

• extension of Hutton’s ideas

• natural laws are constant in space and time

• scientists should explain past phenomena by processes seen today

• most geological change occurs slowly and gradually, not in big catastrophic events

Gregor Mendel (A monk, 1850’s)

• Did experiments on plant breeding and figured out some of the rules of inheritance

• No one knew about his work until the early 1900s

Charles Darwin

• Born wealthy, began studying medicine

• Switched to studying theology so he could be a naturalist

• Recruited to sail on the Beagle (5 yr. voyage) in 1831 (when he was 22)

What happened on the voyage of the Beagle?

Darwin witnessed an earthquake and subsequent uplifting of rock, read Lyell’s and Malthus’ books (greatly influenced him), and collected a lot of fossils and organisms from all over the world (including the Galapagos Islands)

What was Darwin’s focus on adaptation?

Each Island was unique and each had organisms well suited to that particular island.

• Organisms were similar to those found nearby in South America

Examples of Darwin’s focus on adaptation

• The Galapagos Finches - different beaks, feather color, etc.

• Giant Tortoise - different shell shape, neck size, etc.

What was Darwin’s BIG IDEA?

Realized that organisms DID NOT pass on acquired characteristics.

• Instead, some are born better suited to the environment.

• Those that are better-suited are more likely to survive, reproduce, and pass their well-suited traits to their offspring = Natural Selection.

What prominent scientist attacked Darwin and his big idea?

Lyell attacked him.

How long did it take Darwin to collect evidence and construct his arguments for his big idea?

20 years

Alfred Wallace

Traveled the world collecting specimens, reading, thinking.

• Supposedly figured out the idea of Natural Selection during a fever brought by malaria

What did Wallace notice while traveling?

Noticed that north of the line traveled, organisms are like those in Asia. While south of the line, organisms are like those in Australia. Even though they’re in the same general area and same climate.

Plate tectonics separately evolved organisms in what 2 continents and Why?

Australia and Southeast Asia because they haven’t always been in the same place on the planet.

What did Wallace send to Darwin in 1858?

Wallace sent Darwin a letter describing his idea of Natural selection and asked Darwin to pass it on to Lyell.

What did Darwin do when Darwin told Lyell about Wallace’s idea? What happened after?

Told Lyell Wallace’s idea and his own idea. Both papers were presented to Linnean Society.

What happened after the papers were presented to the Linnean society?

Darwin published On the Origin of Species by Means of Natural Selection, or The Preservations of Favored Races in the Struggle for Life in 1859 (25 yrs or so after sailing on the Beagle).

What explanation did Darwin feel was the best?

Those best suited to a particular environment would survive and reproduce.

• Natural selection is a process in which individuals with favorable inherited traits are more likely to survive and reproduce.

• Survival + reproduction = fitness

What is natural selection?

“Differential reproduction and survival of individuals that results in elimination of maladaptive traits from a population”

• Mechanism that leads to evolution

Difference between evolution and natural selection

Evolution is the change we see in populations (“average” in population changes over time, NOT individuals changing over their lifetime) over time. Natural selection is the most important mechanism for creating these changes.

What were Darwin’s arguments to support idea of natural selection?

Artificial selection, noted that humans have modified other species by selecting and breeding individuals with desired traits.

What organism did Darwin used to argue artificial selection?

Pigeons

What were the observations Darwin made for the case of natural selection?

1. All species can produce more offspring than the environment can support

   • All organisms “over-reproduce”

2. Natural populations remain relatively constant in size

   • Populations don’t grow exponentially even though individuals produce so many offspring

3. Resources are limited

4. Members of a population often vary in their traits

5. Much of this variation is heritable

What were the inferences Darwin made for the case of natural selection?

• All organisms over-reproduce, but populations remain stable, and resources are limited, so… only some of the organisms will get the limited resources and survive.

• Lots of heritable variability in organisms, and in each generation only a few organisms will survive, so… survival is NOT random

• Over a long time, favorable traits will accumulate

  • Can get very different organisms over time

Why was Lamarck wrong?

He thought individuals would change over their lifetime, and then pass these acquired characteristics to their offspring. Also individuals don’t evolve, populations do.

Darwin’s Argument

Natural selection acts like a “sieve”, favors individuals w/ characteristics favorable to a particular environment at a particular time. Natural selection has no goals/objectives, it just happens that some are better adapted than others, and the better adapted tend to leave more offspring who are also well adapted.

Linnaean Classification

Linnaeus developed a naming system for living things and grouped organisms based on shared characteristics.

Darwin realized what that would result from what descent?

Realized the pattern that would result from descent from common ancestors.

Why could Linnaeus organize things that way?

• Common ancestry

  • Organisms w/ many shared characteristics got them from a recent common ancestor. Organisms w/ fewer shared characteristics have a more distant ancestor.

How are all living things related to other living things?

We all descended from earlier life forms.