Download Evolution by Natural Selection

Evolution by Natural
Selection
Evolution = Adaptation Over Time
For our purposes, we are going to
begin by talking about macroevolution, or the phenomenon in
which species of organisms come
into existence and change across
what is usually a long span of
time.
What is Natural Selection?
What we are going to learn about today is the
process of evolution – otherwise known as Natural
Selection.
Evolution answers the question
What is happening?
Natural Selection answers the question
How is it happening?
Natural Selection: A process that allows the most
successful trait in a species to be passed on.
Who is Charles Darwin?
Charles Darwin is
usually credited with
being the “Father of
Evolution”
He was a naturalist born
in England in 1809
He first published his
theory in “The Origin of
Species” in 1859
Charles Darwin and the HMS Beagle
Charles Darwin left on his
famous voyage to the
Galapagos Islands in
1831, when he was 22.
There he noticed the
“Galapagos Finches”
among many other diverse
species.
He was fascinated by their
feeding structures (beaks)
and by how the differences
in these structures related
to each sub-species of
finch’s specific diet.
Naturals Selection Example
Birds v. Dogs
These finches, just like our example of
domestic dogs, began as the same
bird. Overtime, differences in beaks
lead to varied success in feeding.
Certain beaks were better suited to
eating foods of differing availability.
Birds whose beaks were well suited to
eating the food source in their area
were highly successful. Therefore they
were able to live to reproductive age,
and pass on their traits. Over time,
many different “sub species” of
Galapagos Finches evolved.
What factors make Natural Selection
important?
If all of the organisms in a species are
the same, how can some be more
successful than others in competition?
Variation
Variation in characteristics: For
natural selection to occur, different
individuals in a population must have
different characteristics.
Competition
In order for competition to occur, there
must be a limited amount of resources,
that all of the organisms need.
Competition
Not this kind of
fitness!!!!!!!
Variation and Competition
lead to differences in fitness.
Fitness
Fitness = the ability to survive
and reproduce
Heritability
In order for Natural Selection to occur, traits must
be heritable – or able to be passed on from
parent to offspring.
So What About our Finches?
Variation – Differences in Beaks
Competition for food produces a
difference in fitness
Beak size and shape are passed
down from parent to offspring
Questions?
Does anybody have any
questions about how Natural
Selection works?