EVOLUTION

Charles Darwin

What evolution is NOTAn explanation of how the

universe beganONLY about “monkey to man”Addressing the change in an

individual over its lifetimeA description of how the first

living cell came to beMutually exclusive of faith or

religion

LamarckLaw of Use and Disuse

◦The parts of an organism that are used most frequently become stronger and better developed.

◦This law is observable in natureThe Inheritance of Acquired Characteristics

◦The characteristics of an organism that were developed during the use and disuse (first part of the theory) would be passed on to its offspring

◦Ex: giraffe necks◦This idea is false: using or practicing something

does not change the DNA in an organism’s gametes!

DarwinHe had a strong science background: his father

was a doctorHe started studying medicine but did not care

for it, so began studying to be a minister instead

At age 22, he applied to be the naturalist on board the HMS Beagle that was going to map the coastline of South America and Pacific islands◦ The trip was supposed to be a 2-year break from

school, but it ended up taking 5 years.◦ He would frequently leave the ship and go inland on

the islands to make observations, then rejoin the ship later.

Darwin cont. . .

Darwin had been reading geological theories on the change in the Earth over time, and it got him thinking about whether populations could change over time

He noticed a difference in the organisms as they traveled to various islands.◦ The group of Galapagos Islands were the most

revealing. Each one of the islands had a finch (type of bird) that was similar to another islands’ finch, but a distinct species

◦ Similar observations in comparing insects, plants and other organisms between the islands and the mainland

Darwin’s finches

Darwin cont. . . Darwin began to think that the various

species had originally reached the island from the mainland, then adapted due to the isolation on the islands.

He returned after the voyage and spent years studying others’ research and ideas while trying to make sense of the observations he had made on the voyage.

He eventually published his book On the Origin of the Species by Means of Natural Selection

Six Points of Darwin’s Theory1. Overproduction2. Competition3. Variation4. Adaptations5. Natural selection6. Speciation

Overproduction

◦Most species produce far more offspring than are needed to maintain the population.

◦Not all the offspring will live to reproduce.

Competition

Since living space, food, and resources are limited, offspring of each generation must compete with each other and with other species to survive. Only a small fraction can live long enough to reproduce.

Variation◦The characteristics of individuals

in any species are not exactly alike. These differences are called variations. Many variations occur, and new ones can arise from mutations.

◦Some variations are not important. Other variations may affect the organism’s ability to get food, escape enemies, or find a mate. These type of variations are important.

Adaptations

Because of variations, some individuals will be better adapted to survive than others of the species.An adaptation is any kind of inherited trait that improves an organism’s chances of survival and reproduction in a given environment.

Natural Selection◦ The environment selects organisms with the best

adaptation◦ Individuals with variations that are the most

successful in an environment will be more likely to survive and reproduce than the poorly adapted organisms.

◦ Eventually the genes of the poor adaptations are no longer passed on as frequently in the population

Speciation

Speciation

Speciation◦Over many generations, the results

of natural selection result in a new species because so many of the undesirable characteristics are removed from the gene pool.

◦This is the only controversial point of evolutionary theory today!

◦Don’t discount Darwin’s entire theory just because you don’t agree with the evidence for one point