How Does Evolution How Does Evolution Happen? Happen?

(Natural Selection)

First man to explaino Charles Darwin

o Took a five year voyage around the world after he got out of college

o Served as a naturalist on the British ship HMS Beagle

o Formed a theory of how evolution happened

o Collected plant and animal samples on his travels

o Visited the Galapagos islands just west of Ecuador (South America)

Map of the Galapagos Islands

Galapagos Island Discoveries

o Found that the finches on these islands were similar to Ecuador’s

o Each island was still a little different from the next

o Found that the beaks of the finches had adapted to their food source on the different islands.

Finches

Darwin starts to think..o How did we get these similar species?o He had ideas about the Earth

o He found that Earth has been formed by natural processes over a long period of time

o He had ideas about breedingo Selective breeding- breeding plants/animals

to have desired characteristics

o He had ideas about populationso Realized that any species can produce many

offspring, but they are limited by several factors.

What limits offspring?o Starvationo Diseaseo Competitiono Predation

o He found that really only a limited amount of individuals will survive to reproduce.

o There is something unique about the survivors. They must have stronger genetic traits. Those are the traits that will pass down to their offspring.

Four factors that limit offspring

Darwin’s thinking lead to his theory of Natural Selection

o Once he returned from his voyage, he thought for 20 yrs about the observations he had taken from the world and wrote a book called On the Origin of Species by Means of Natural Selection.

o Darwin’s theory of natural selection is the process by which individuals best adapted to their environments survive and reproduce more successfully than less well adapted individuals

o This theory of natural selection is broken into four parts.

Four Parts of Natural Selectiono 1) Overproduction

oOrganisms will give birth to thousands of offspring realizing that some will become adults and others will not.

o 2) Inherited VariationoEvery individual has its own

combo of traits. (similar to parents)

Continuedo 3) Struggle to Survive

oPredators, starvation, diseases

o 4) Successful ReproductionoThe organisms best

adapted in their environment will produce the most surviving offspring.

Think About it…

Darwin Lackedo When Darwin was introducing

his theory of natural selection he lacked two important things:o 1- He didn’t know how we inherit

traitso 2- He didn’t know how the

variations occurred

o We have learned how both of these occurrences happen, tell me how!

Yes??o 1) We inherit traits from our

parents when they get passed down to the offspring.

o 2) Variations occur because of the different gene combinations that can be made when the mother and father come together to produce offspring.

Natural Selection in Actiono A population

changes in response to its environment.

o Things that can affect an environments population are:o Huntingo Resistanceo Competition

Huntingo A new affect such as hunting

can play a role in how a population level rises or falls.

o In 1930 Uganda’s male elephant population that contained tusks was 99% and only 1% of them were born without them. Today 85% of male elephant population contains tusks.

o Because of this, more of the tusk less elephants are surviving and reproducing. This trait does get passed down.

Resistanceo Some organisms such as insects can

build resistance to certain chemicals.o This can send an increase in a

particular insects population that could be harmful.

o It doesn’t take long for insects to build up this resistance and reproduce.

o Generation time: the period between the birth of one generation and the birth of the next generation.

Competitiono Many species will Many species will

have competitions for have competitions for their matestheir mates

o Some organisms may Some organisms may over time have some over time have some interesting interesting adaptations.adaptations.

o Feather colors, Feather colors, smells, dances, smells, dances, sounds, etc.sounds, etc.

Forming a New Specieso May form if the groups get

separated from the original population.

o The two groups can adapt to their environments and get to a point where they are so different they can’t even mate anymore.

o A new species is a result of evolution. We call this speciation.

o Separation-Adaptation-Division