Early Theories of EvolutionEVOLUTION: change in a population

(DNA) over time

• no scientific explanations of evolution were given until the 18th

Century

1. Lamarck’s Hypothesis of Evolution (Theory of Use and Disuse):

• 1809

• was one of the first to develop a theory of evolution

J.B. Lamarck

Three Main Ideas:i. organisms strive to improve themselves,

to become more advanced

ii. the most used structures develop, while the less used ones waste away. Known as the principle of Use and Disuse

iii. once a modification has occurred it is passed on to the offspring

- disproved by Weisemann• cut off the tails of mice, allowed them to

reproduce and then cut off the offspring’s tails

• he continued this for 20 generations and they continued to produce offspring with tails

2. Charles Darwin’s Theory of Natural Selection(aka: Survival of the Fittest)• 1844(but took him 20 years to publish

his ideas)• 5 main points:

i) there is variation within populationsii) Some variations are favourable. A favourable variation is one that improves the organism’s ability to function and reproduceiii) More young are produced in each generation than can surviveiv) Those with the favourablevariations, survive, reproduce and pass on the favourable trait to their offspring.v) Over enormous spans of time, small changes accumulate and populations change.

Darwin’s Finches

Requirements:

2. those with longer necks

get better/more food, have

more babies

(have an advantage in

the struggle for existence)

1. Variation in a trait

within a population.

(some had longer necks

than rest of population)

3. More individuals are born each

generation than can survive

“struggle for existence”

4. those with longer necks are

more likely to survive, and pass

this trait on to their offspring

(variation is heritable)

5. gradually, over many generations, necks

became longer and longer

Results:

Over time,

average neck

length increases

Homework

•Compare how Lamarck and Darwin would explain the frog’s tongue for capturing food

•Use one paragraph to explain Lamarck’s theory and another paragraph to explain Darwin’s theory.