Darwin & Evolution

Change Happens…

Evolution• History and prehistory are full of creation stories• People have always guessed at how they “got

here”

Evolution• Greeks

o Hypothesized that form of the organism was related to its function

Evolution• Charles Bonnet

o Because fossils rarely looked like modern organisms, there must have been catastrophes after which new life arose

o First to use the word “evolution”

Evolution• Jean Baptiste Lamarck

o Believed :“fossils are ancestors”o Wrote: “Inheritance of Acquired Characteristics”o His work later influenced Darwin.

Evolution- Lamarko Organisms strive to improve themselveso Most used structures develop & others waste

awayo Once a structure is modified it is inherited

Evolution• Weismann

o Disproved inheritance of acquired characteristics with tests on mice

o Change in an individual’s life time does not get passed on

Charles Darwin

• 1831 HMS Beagle sailed around the world• Arrived at the Galapagos Islands

Charles Darwin• Intrigued by the variety of finches and their

adaptations to different islands

Charles Darwin• Used Lyell’s geologic theory of slow and gradual

change.• Used the ideas of selective breeding for

domesticated animals

Charles Darwin• Thought these processes of change must happen in

wild populations naturally

Charles Darwin• Used Malthus’ Economic Principles:

o (Human) populations that exceed their resources will decline due to war, famine, disease, etc. this must also happen in the wild.

Charles Darwin• Reasoned not all offspring would survive because it

would lead to overpopulation• The ones who were best able to access limited

resources would surviveCheck for errors

Charles Darwin• The survivors would be the ones to reproduce and

pass down the traits that enabled it to survive• This ability is as important as survival itself!

Darwin’s Theory of Evolution

• Challenged the popular belief at the time (creation/church)

• He held off on publishing it• Alfred Russell Wallace came up with a similar theory

after working in the Amazon and the Malaysia & Indonesia

• They published them together• Wallace gave Darwin all the credit• “Origin of Species by Means of Natural Selection”

Darwin’s Theory of Evolution

1. Overproduction: Not all young in each generation can survive (disease, starvation, predation, etc)

2. Genetic variation: There are variations in all populations that are passed on genetically

3. Struggle to Survive: Some variations are

Remember!• Variation does not happen because of the

environment; it is independent and happens:o During genetic recombinationo Through random pairing of gameteso Because of genetic mutations

• A variation only becomes an adaptation when it is favorable in the current environment.

• When adaptation happens to all or some of a population, it can lead to speciation

Speciation• When a population changes enough so that fertile

offspring are no longer produced with other members of the original specieso Pre – zygotic – when the species don’t mate to begin with:

• Wrong timing• Not attractive (looks, behavior, smell)• Wrong area

o Post – zygotic – when the two species mate, but offspring is not viable• Offspring does not come to full term• Offspring is sterile

Divergent evolution• Descendants of a single ancestor diversify because

of changes geographic barriers.

Adaptive Radiation• One species spreads

out to fill different available nicheso Hawaiian Honey Creepers

Convergent Evolution• Analogous adaptations

occur in response to similar niches

Coevolution• The adaptation of closely dependant organisms

over time

Evolution• Can result in speciation – the formation of a new

species from an existing one