Transcript Evolution - West Ada

EVOLUTION
Evolution
What does it mean?
• Evolution: This means change over time. This is the process by
which modern organisms have descended from ancient ones.
• Darwin is the scientists credited with the theory of evolution though
many others had similar ideas before him.
• Darwin set sail in 1831 making numerous observations and
collecting evidence that led him to up with his theory.
• His collection and observations in the Galapagos islands made him
think of the origin of species. The species that helped him create
this theory was the tortoise. He observed that three different
tortoises on three different islands were distinct from one another,
but very similar looking.
• Darwin came up with the idea that perhaps they originally were one
species.
What is this species specialty?
• http://www.youtube.com/watch?v=iarsmqA
3dck
Darwin’s trip
Darwin’s Evolution of thought.
• People questioned his theory (and many
still do). They believed the Earth was
only a few thousand years old.
• Darwin began to fill notebooks with his
ideas about this immense amount of
species diversity.
• Eventually he published “The Origin of
Species”.
Natural Variation and Artificial
Selection
• He abandoned past ideas that species were
perfect and unchanging.
• He said the natural variation (differences among
individuals of a species) existed in all organisms.
• He also came up with artificial selection; this is
where nature provides variation in different
organisms, and humans selected the traits that
they found useful. (For Example different
species of dogs).
What do you think this dog breed is
bred for?
Evolution by Natural Selection
• Natural selection – The best traits are selected by
nature. The animals best selected for their environment
survive and reproduce. This later became known as
“Survival of the fittest”.
The Predator and Prey
Grizzly vs. Bison
https://youtu.be/ZXPUTe6jTkk
Darwin’s greatest contribution
(Survival of the fittest)
• Darwin developed a scientific hypothesis
to explain how evolution occurs. He
compared the process in nature to artificial
selection.
• Organisms compete for resources, the
strongest most efficient predator survives.
The prey which has the best camouflage
survives the longest.
Survival of the Fittest
• Darwin explained this as the ability of
an individual to survive and reproduce
in a specific environment.
• Fitness is the result of adaptations.
• Adaptations is an inherited characteristic
that increases an organisms chance of
survival.
Darwin’s definition of Survival
• Darwin explained that individuals with
characteristics that are not well suited to
their environment either die or leave few
offspring.
• Individuals that are better suited survive
and reproduce successfully.
Pizzly Bear: Fact or Fiction
• The Polar Bear is going to have to adapt
to survive in our warming climate. The
speed at which the warming is happening
is quicker and more dramatic than ever in
Earth’s history. Many see the polar bear’s
disappearance in the next 20 or so years
as inevitable.
Grolar Bear
• However, the bear may not agree. In
2007 the first ever documented cross
between a polar bear and a grizzly bear
was observed in the wild.
• As they are pushed farther south their
ranges are overlapping and the bears
have become to interact.
The Future of Bears
First document cross breed in the wild
between a grizzly and a polar bear.
Descent with Modification
Descent of Modification
• Darwin proposed that over long periods,
natural selection causes organisms to
develop different physically, and occupy
different niches .
• Darwin presented that each living species
descended from other species over time.
This theory also said that all living things
are related to one another, this principle is
called “Common Descent”.
Evidence of Evolution
Darwin’s Evidence for his theory of
evolution
(1) The fossil record
(2) Geographic distribution
(3) Homologous structures
(4) Similarities in early development
(5) DNA and RNA sequencing
Fossil Evolution
• Darwin look at detail fossils collected and
proposed the Earth was several million
years old not several thousand.
• He believed that fossils showed evidence
of gradual change over time. This section
of his theory has just as many gaps in it as
pieces of evidence found to support it.
Avian Ancestor
Human Skull Evolution
Geographic Distribution
• Animals that lived on different continents,
but lived under similar ecological
conditions were exposed to similar
pressures of natural selection.
• They evolved to have similar features.
• A modern example would be the lion of
Africa and the mountain lion of the United
States.
American and Asiatic Black
Bears
Homologous Body Structures
• Structures such as flippers, arms, wings
have different mature forms, but develop
from the same embryonic tissue (same
clump of cells in embryos).
• If you study the modern adult bone
structures of very different animals there
are a lot of similarities.
Similarities in Early
Development
• Embryos of many animals, especially
those with backbones is very similar and
makes it hard to tell them apart.
• In the very early stages of development
the fetus of many different species look
very similar.
Classification
• The evidence for evolution (fossil records,
homologous structures, comparative
embryology, and DNA and protein
sequencing) is also the basis of
classification.
• The more similar two organisms are, the
more likely they evolved from one another
Darwin’s Main Points
• Variation in
individuals is
inherited.
• Organisms produce
more offspring than
can survive.
• The same species
competes for
resources.
• Each individual has
advantages and
disadvantages.
• Individuals best suited for
their environment survive
and reproduce.
• Species change over
time.
• Species today came from
species that lived in the
past.
• All organisms have
descended from one
father species.