The Theory of Evolution

In science, theories are statements or models that have been tested and confirmed many times

Some important properties of theories : They explain a wide variety of data and observations They explain a wide variety of data and observations They can be used to make predictions They can be used to make predictions They are not absolute, they serve as a model of understanding the world and can be changed as the world view changes They are not absolute, they serve as a model of understanding the world and can be changed as the world view changes In science, the term “Theory” does not express doubt In science, the term “Theory” does not express doubt

T he Theory of Evolution is considered a Unifying Theory of Biology because it answers many questions and explains many observations. T he Theory of Evolution is considered a Unifying Theory of Biology because it answers many questions and explains many observations.

Lamarck's Theory of Acquired Characteristics According to Lamarck, organisms altered their behavior in response to environmental change. Their changed behavior, in turn, modified their organs, and their offspring inherited those "improved" structures. According to Lamarck, organisms altered their behavior in response to environmental change. Their changed behavior, in turn, modified their organs, and their offspring inherited those "improved" structures.

Examples Giraffes developed their elongated necks and front legs by generations of browsing on high tree leaves. The exercise of stretching up to the leaves altered the neck and legs, and their offspring inherited these acquired characteristics. Giraffes developed their elongated necks and front legs by generations of browsing on high tree leaves. The exercise of stretching up to the leaves altered the neck and legs, and their offspring inherited these acquired characteristics.

Examples A lizard that didn’t use its legs would eventually evolve into a snake without legs. A lizard that didn’t use its legs would eventually evolve into a snake without legs.

Lamarck’s Theory was proven to be wrong! We now know that features gained during life are not passed onto children.

Darwin's Theory of Evolution by Natural Selection 1. Variation exists among individuals in a species. 2. Individuals of species will compete for resources (food and space) 3. Some competition would lead to the death of some individuals while others would survive 4. Individuals that had advantageous variations are more likely to survive and reproduce. This process he describes came to be known as Natural Selection The favorable variations are called Adaptations

Darwin’s observations of the finches on the Galapagos island led to the conclusion that all the finches had a common ancestor. The shape of the beaks were adaptations for eating a particular type of food.

Evidence for Evolution 1. Evidence from fossils If today's species came from ancient species, the we should be able to find remains of those species that no longer exist. If today's species came from ancient species, the we should be able to find remains of those species that no longer exist. We have tons of fossils of creatures that no longer exist but bear striking resemblance to creatures that do exist today. We have tons of fossils of creatures that no longer exist but bear striking resemblance to creatures that do exist today. Carbon dating--gives an age of a sample based on the amount of radioactive carbon in a sample. Carbon dating--gives an age of a sample based on the amount of radioactive carbon in a sample. Fossil record--creates a geologic time scale. Fossil record--creates a geologic time scale.

2. Evidence from Living Organisms Evidence of Common Ancestry Evidence of Common Ancestry Homologous Structures Homologous Structures Vestigial Organs Vestigial Organs Cell and DNA Cell and DNA Embryonic development Embryonic development Observation of species change Observation of species change

Evidence of Common Ancestry -- Hawaiian Honeycreeper

Homologous Structures-A body part with the same basic structure and embryonic origin as that of another organism, though not necessarily sharing the same function

Vestigial Organs--seemingly functionless parts

Closely related species are more similar in their DNA sequences than distantly related species. Closely related species are more similar in their DNA sequences than distantly related species. Cell and DNA evidence All living things are made of cells which have similar organelles. All living things are made of cells which have similar organelles.

Embryonic development--Embryos of different species develop almost identically

Observation of species change (wolves/dogs, peppered moths)

Examples of Evolution 1. Industrial Melanism (Kettlewell's moths) 2. Dog breeds 3. Viruses & Vaccines 4. Bacteria & Antibiotics 5. Elephant Tusks

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