Darwin’s Theory of Evolution Darwin Presents his Case Chapter 15-3.
EVOLUTION Darwin’s Observations. What did Darwin observe? Darwin saw huge amounts of biodiversity....
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Transcript of EVOLUTION Darwin’s Observations. What did Darwin observe? Darwin saw huge amounts of biodiversity....
![Page 1: EVOLUTION Darwin’s Observations. What did Darwin observe? Darwin saw huge amounts of biodiversity. He collected fossils, which are the remains of once-living.](https://reader036.fdocuments.in/reader036/viewer/2022082518/56649e7b5503460f94b7b93a/html5/thumbnails/1.jpg)
EVOLUTION
Darwin’s Observations
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What did Darwin observe?
Darwin saw huge amounts of biodiversity. He collected fossils, which are the remains
of once-living organisms. – 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
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What did Darwin observe?
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
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Fitness and Adaptations
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
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Fitness and Adaptations
The more offspring an organism has, the more fit it is
An adaptation is any genetically controlled trait that increases an individual’s ability to pass along of copies its genes.
Adaptations increase fitness.
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The Galapagos Islands
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
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The Galapagos Islands
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Species of the Galapagos
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Species of the Galapagos
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Peculiar Creatures
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
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What did Darwin observe?
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
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What is the solution?
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.