Transcript Darwin`s Observations

EVOLUTION
Darwin’s Observations
What did Darwin observe?
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Darwin saw huge amounts of biodiversity.
He collected fossils, which are the remains
of once-living organisms.
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Fossils prove that there are lots of living things
that have gone extinct.
This shows that life has changed over time.
Scientists estimate that 99.9% of the species
that have ever existed have already gone
extinct
What did Darwin observe?
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He saw that each organism was uniquely
suited to the life it lead
Adaptations are combinations of physical
characteristics and behaviors that enable an
organism to survive in its environment
They are the traits of survival – from the
cellular level to the behavioral level
Fitness and Adaptations
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Darwin used the term fitness to describe the
ability of an organism to survive and
reproduce
An organism’s evolutionary fitness is its
success in passing genes to the next
generation.
It is not just about survival, but also passing
on your genes
Fitness and Adaptations
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The more offspring an organism has, the
more fit it is
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An adaptation is any genetically controlled
trait that increases an individual’s ability to
pass along of copies its genes.
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Adaptations increase fitness.
The Galapagos Islands
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Darwin learned the most from the Beagle’s
visit to the Galapagos Islands, a group of
islands off the coast of South America
The islands are small, but very different from
each other – even have drastically different
climates
Unique animal and plant life are found there
The Galapagos Islands
Species of the Galapagos
Species of the Galapagos
Peculiar Creatures
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Tortoises vary in a predictable way from
island to island – shells are distinct
Each island had unique bird life that looked
similar but were actually different species –
Darwin’s finches
http://people.rit.edu/rhrsbi/GalapagosPages/
DarwinFinch.html
What did Darwin observe?
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Darwin saw that plants and animals
reproduce much faster than humans
There had to be something limiting the
animal and plant populations
This meant that the majority of offspring of
each species die, and only a few that survive
succeed in reproducing
What is the solution?
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Darwin theorized that in nature, organisms
struggle for survival.
Only the fittest organisms can survive and
reproduce (survival of the fittest)
This is called natural selection – only the
organisms with the best adaptations (best
suited to their environment) will pass on their
genes.