THEORIES OF EVOLUTION

BUT FIRST…• DNA test Make-up – Friday March 6 • Work for your retest! • All test corrections shown, complete with explanation

where you went wrong, how you can improve. • MINIMUM of ONE Lunch time tutorial session

• If you were ABSENT for the test, a note must be provided to excuse absence before you can write the test

• No Note, No test.

LAST TIME

•We looked at some of the evidence of Evolution • In the form of fossils

• Introduction to Evolution Research Project

TODAY• Intro to research project

•Some of the great minds who started to piece together the theory of evolution

• Jean Baptiste Lamarck

•Charles Darwin

•A look at some more evidence of Evolution

•Homologous, Analogous and Vestigial Structure

•Patterns of Evolution

TERMS TO REMEMBER FOR TODAY

•Phenotype – A physical characteristic of an organism •Species – largest group of organisms capable of interbreeding and producing fertile offspring. •Population – All the organisms of the same species that live in the same geographical area

ALTHOUGH THERE ARE SEVERAL SCIENTISTS WHO WORKED ON THIS THEORY…

•We will focus today on •Jean Baptiste-Lamarck

•Charles Darwin

!

•This is not a history course, but it is also important to understand the ideas that lead behind to the theory

JEAN BAPTISTE LAMARCK

• French Scientist (18th Century) • First to propose that similar species

descended from a common ancestor • Living species were descended

from similar extinct species • Evident in the fossil record (As

we can recall)

• Related fossil forms to modern living animals

JBL CONT’D.

• In order to explain how species changed over time he hypothesized that ACQUIRED TRAITS were passed on to offspring. •An acquired trait is one that is NOT determined by

genes, but arises during an organisms lifetime

!• For example; the webbed foot of aquatic birds

resulted from repeated stretching of the membrane between the toes, which over time would evolve into the webbed and would be preserved by reproduction.

With your partner, given what we know about Evolution and DNA, would JBL’s hypothesis be proven, or disproven?

JBL

• Lamarcks hypothesis of the passage of acquired traits was disproven, and criticized (by opponents to the idea of evolution) • However, Lamarck was instrumental, in that he was the

first to state that types of organisms change over time, and new types are modified descendants of older types. • Lead to the work of another famous scientist by the

name of…

CHARLES DARWIN

• 19th century British Scientist • Proposed the hypothesis that species were modified by

natural selection •NATURAL SELECTION – Organisms best suited for their

environment reproduce more successfully than other organisms. • Therefore, over GENERATIONS the proportion of

organisms with favorable traits increases in a POPULATION

SO LET’S SEE HOW NATURAL SELECTION WORKS

• I am now the Hill Hawk !!!!!!

• And you are all the Student Birds

TIME TO PICK A TRAIT

•WRITE ONE OF THESE TRAITS LARGE ON A SHEET OF PAPER •ARMOR

• INCREASED SPEED

• POISON SPRAY

•CAMOUFLAGE

• I’M HAPPY JUST THE WAY I AM ☺

SO HERE’S HOW NATURAL SELECTION WORKS…

• The Hill Hawk is hungry, and he is looking for a snack… • He is big, strong, and an excellent hunter •Much stronger than those normal student birds, with

no adaptations… so he eats them all up. !

• Students who were eaten, turn over your paper, and pick a new trait. (Camouflage, increased speed, armor, poison spray)

• A mutation occurs, which develops sharper talons for the Hill hawk, who is now able to penetrate and rip apart the armor of the student birds. !!• The Hill hawks eat up all the Armored Birds (If you

have been eaten, write a new trait on the back or separate sheet of paper)- Camouflage, Poison Spray, Increased speed

• Years pass, and the student birds continue to live happily. Over the years however, another mutation occurs which provides the Hill hawks with an immunity to the Poison spray.

!• Hill Hawks Feast on the poison birds (If eaten, turn

page over, and pick one of last two traits – Increased speed, or camouflage)

•As the years go by, the student birds are still happily living… •OH NO FIRE!

•OHHH all the forest in which the student birds lived in have been destroyed. The green leaves and grasses in which the camouflaged birds would hide, have been destroyed. • The Camouflage birds are now exposed and open to

be snacked upon. • If you are eaten, now put the final trait on your Sheet of

paper (increased speed)

• Now the entire student bird population has the increased speed. • The Hill hawk is a big, not incredibly agile animal, and is unable

to keep up with the speed of the student birds. • Hill Hawks may undergo mutations, which will allow the

population to evolve into a faster population of hawks. • Student birds who undergo mutations which allow them to

evade the Hill hawk will continue to survive in the same way. !• This is also what we call an Evolutionary Arms Race

SO THERE IS OBVIOUSLY MORE TO IT… BUT THAT SHOULD PROVIDE AN IDEA FOR NOW…

•Back to Darwin…

DARWIN’S THEORIES

•Descent with Modification •Newer forms appearing in the fossil records are actually the modified descendant of other species.

DARWIN

•Darwin came up with this theory by, famously, observing the Finches of the Galapagos Islands •Reasoned that even though they exhibited different characteristics, they descended from a recent common ancestor.

DARWIN•Darwin took it one step further, and inferred that ALL

living things likely descended by one, or a few, remote common ancestors that lived many years ago (millions… billions of years).

DARWINS THEORIES•Modification by Natural Selection • Environment limits the growth of populations by increasing

the rate of death, decreasing rate of reproduction or both. • Thomas Malthus - Noticed that human populations have

the potential to double, than redouble their population, but growth of the population was limited by adverse environmental conditions (i.e. war, disease, supply of resources).

•As we saw earlier, environmental conditions may affect different individuals in the population in different ways. • Some organisms cope better than others

• Those organisms tend to leave more offspring than those with less than favorable traits.

•Different degrees of success of organisms= Natural Selection • NOT survival of the fittest… But rather non-survival of

the non-fit.

NATURAL SELECTION CONT’D

•Advantageous traits are passed on to offspring

• The POPULATION of organisms can then adapt to environment as the proportion of favorable genes increases.

•Within the population, a single organisms genetic contribution to the next generation is termed it’s FITNESS

• So what is the difference between what Lamarck and what Darwin were saying? •Organisms don’t select favorable traits (Lamarck),

the environment “selects” them (Darwin)

•A significant change in the environment can cause rapid evolution as populations adapt to the change

• If a change is too extreme, it will lead to an extinction.

SO RIGHT NOW…

•5 minutes of SILENT READING •P284-286

•Get to know background behind Charles Darwin

•Chapter 15.2 Review until break