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Evidence for Change
We have talked about different evidences for changes in
populations over time
➔ Fossil Record
➔ Biogeography
➔ Anatomy
➔ Biochemistry
➔ Artificial Selection
https://www.youtube.com/watch?v=P3GagfbA2vo
Fossil Record
Palaeontology is the study of fossils
Fossils are found all over the world giving insight to what the
Earth once looked like
Fossils are formed when an organism dies and is covered
very quickly by sedimentation to protect it from the full
decomposition process
Fossil Record
Palaeontologists spend their time studying these fossils and
searching for connections between them
With the use of carbon dating and radiometric dating, scientists
are able to see how old these fossils are
Biogeography
This evidence can be linked to the fossil record as well
Scientists believe that the continents on Earth were once one
big super-continent called Pangea
There are many fossils being found today that are found in
multiple continents that are no where near each other
Biogeography
When looking at organisms in different areas of the world,
scientists can see that they may share similarities but also
show many unique differences
Islands or places that are isolated have species that aren’t
found anywhere else which supports the theory that they
evolved separately from their ancestors
Anatomy
This evidence is looking more at what organisms actually look like and what
similarities arise
Analogous Structures: features that are similar in structure and function
but do not have the same origin
ex. wings in birds and butterflies
Homologous Structures: features with similar structures but different
functions
ex. limbs in different organisms
Biochemistry
This evidence goes as deep as you can by looking at the
genetics of different organisms
Science has come a long way in the field of genetics and
especially in mapping out genomes and the genetic code
We can take these genetic sequences and begin to see trends
between different organisms
Biochemistry
Scientists believe that the more differences there are in the
DNA sequence, the farther our relations go but the closer they
are, the more closely related we are
Scientists also look at the different amino acids in organisms
and the same trend seems to be observed - less differences
= closer relations
Artificial Selection
Humans love to stick their noses in things and change it all
around to make their lives better
Artificial selection is the process of humans selecting and
breeding individuals with desired traits
This is commonly found in the farming community
Ex. pigs, corn, wheat, cows, horses, dogs, etc.
Theories of Evolution
A theory is a model that accounts for all the known evidence
as completely as possible
Remember - nothing in science is FACT - there are always
new discoveries being made either supporting theories or
adding doubt to them
Theories of Evolution
Before the 18th century, people thought that living things were
fixed and stayed the way they are
During the 18th century, many people began questioning this
vision
Georges-Louis Leclerc de Buffon proposed that a species
could change over time
Theories of Evolution
Carl Linnaeus and Erasus Darwin put forth similar ideas
Linnaeus thought that the few species created had become
hybrids which led to the formation of new species
Darwin (Charles Darwin’s grandfather) proposed that all life
had developed from a single source
These were both not widely accepted at the time
Lamarck’s Theory
Jean-Baptiste Pierre Antoine de Monet Chevalier de Lamarck
presented the first theory of evolution that included a
mechanism
He thought that simple species were created by spontaneous
generation (living things came from non-living matter) and
became more complex over time
Lamarck’s Theory
He believed that organisms had a force or desire that caused
them to change for the better
He thought that organisms must be able to produce new parts
to adapt to certain environments
He thought that the use and disuse of structures were then
passed on to offspring and that was how changes happened
over time
Lamarck’s Theory
Lamarckism is now used to describe inheritance of acquired
characteristics which is the false concept of inheritance of
features acquired during the life of an individual
Although Lamarck’s theory isn’t true, he was on to something
when he postulated that the environment played a role in
changing organisms
Darwin’s Theory
Charles Darwin came to be known
as the father of evolutionary
biology after sharing his theories
and observations
In 1831, Darwin set sail on the HMS
Beagle to travel around the world
and returned with a large amount
of observations (now evidence)
that aided his inferences later in
his life
Darwin’s Theory
He spent a large amount of time on the Galapagos Islands
and his most famous and well-known evidence for his later
theories are the Galapagos finches.
He noticed that there were many different beak types
among these birds that each had a specific role to aide the
bird - from thick seed crushing beaks to small skinny beaks
good for eating insects
Darwin’s Theory
Darwin’s Theory
Darwin became interested in artificial selection and thought
that if humans could alter the appearance of organisms,
why couldn’t nature?
After years of observations and research, Darwin
developed and published his theory of natural selection in
his book ‘The Origin of Species by Means of Natural
Selection or The Preservation of Favoured Races in the
Struggle for Life’
Darwin’s Theory
He didn’t write this whole book himself, but worked with a
man named Alfred Russell Wallace who had come to many
of the same conclusions as Darwin in his life of research
as well
The theory of natural selection is one of the major
supporting arguments for evolution today
Darwin’s Theory
Darwin’s Theory
Natural selection is the result of differential reproductive
success of individuals caused by variations in their inherited
characteristics
https://www.youtube.com/watch?v=0SCjhI86grU