Evolution – The process by which modern organisms have descended from ancient organisms.

Evolution – The process by which modern organisms have descended from ancient organisms.

Adaptation – A trait that helps an organism be better suited to its environment.

ex) a ducks webbed feet

Adaptation – A trait that helps an organism be better suited to its environment.

ex) an arctic fox’s heavy fur coat

Fitness – The physical traits and behaviours that better enable organisms to survive and reproduce in their own environment.

What makes these polar bears fit to live in the arctic?

What makes this fenec fox fit to survive in the extremes of the Sahara Desert?

EXPLANATIONS FOR EVOLUTION

Around 1800, scientists began to realize that living things changed over time.

Jean Baptiste de Lamarck

Lamarck is considered to be the first person to develop a theory of how evolution occurred.

He is credited with encouraging future scientists to examine how evolution occurred.

Lamarck’s Big Ideas

• Desire to change

• Law of use and disuse

• Inheritance of acquired characteristics

Lamarck also believed body parts could change shape or size depending on needs. Lamarck explained the long

neck of a giraffe by saying if it stretched its neck for leaves a “nervous fluid” would flow into its neck and make it longer. Its offspring would inherit the longer neck, and continued stretching would make it longer still over several generations. Meanwhile organs that organisms stopped using would shrink.

Lamarck believed in the inheritance of acquired characteristics.

Consider the ears and tails of Doberman Pinschers.

Charles Darwin• English naturalist • travelled around the world on the

H.M.S. Beagle observing plant and animal life

• the trip took over 5 years

Further Influences on Darwin:

• he argued the Earth was very old while most believed earth to be a few thousand years old

• this meant common descent could have had enough time to occur

Charles Lyell (a rock star - geologist)

Further Influences on Darwin:

• Darwin knew farmers altered their stocks with breeding programs (artificial selection)

• with a.s. humans ensure only animals with desirable traits are allowed to breed

• Darwin felt nature must have a similar process only allowing the best suited to the environment to survive

Farmers

Further Influences on Darwin:

• he realized babies were being born faster than people were dying

• he felt only famine, disease and war would prevent endless human population growth

• Darwin extended this to plants & animals as he realized many individuals of each species die and few raise offspring. The question was what determined who survived and reproduced?

Thomas Malthus

The Beagle’s Journey

Darwin’s time on the Galapagos Islands had a big impact on him developing his theory of evolution.

marine iguana

flightless cormorant Galapagos penguin

Sally Lightfoot crab

frigate bird

Galapagos Tortoises – These were important to Darwin developing his Theory of Evolution.

The islands were once home to 15 different sub-species. 11 of these remain today. One sub-species only has one individual.

Lonesome George – the last of his kind

Five sub-species are found on Isabela and one each on Santiago, Pinzon, Santa Cruz, Española and San Cristobal. Lonesome George is from Pinta but lives on San Cristobal today in a breeding facility.

The main differences between sub-species is the length of their limbs and necks and the shape of their shells.

Galapagos Finches The 13

species of Galapagos Finches were also important to Darwin developing his Theory of Evolution.

• Darwin decided that species change over time

• in 1859, he published his famous book that describes his theory of evolution

• a key part of the theory was the idea of Common Descent. It argued all species have evolved from one common ancestor.

an evolutionary tree, from one of Darwin’s notebooks

Darwin’s Theory of Natural Selection states:• more organisms are born than survive

- the environment can’t support them all

Darwin’s Theory of Natural Selection states:• organisms vary within a species

- no two individuals are exactly alike

Darwin’s Theory of Natural Selection states:• survival of the fittest

organisms with favourable variations survive and reproduce

the individuals with characteristics not well suited to their environment either die or leave fewer offspring

in this way, favourable variations are passed from generation to generation

Darwin’s Theory of Natural Selection states:• a population that is adapted to its

environment will result

Natural Selection

• In 1858 Alfred Wallace wrote to Charles Darwin about his ideas of evolution.

• His work also describes the theory of natural selection.

• Wallace and Darwin co-published a paper on evolutionary theory and are considered the co-discoverers of the Theory of Evolution.

• Each man gave the other as much credit as possible.