Download The Theory of Evolution

Evolution
In science, theories are statements or models
that have been tested and confirmed many
times.
Theories have some important properties:
– Explain a wide variety of data and observations
– Used to make predictions
– Not absolute, they serve as a model of
understanding the world and can be changed as
the world view changes
Questions???
Why do so many different animals have the
same structures, the arm bones in a human
are the same bones as a flipper in a whale?
Why do organisms have structures they no
longer use, like the appendix in a human?
Non functioning wings in penguins
Why are there bones and fossil evidence of
creatures that no longer exist? What
happened to these creatures?
Why do the embryos of animals look very
similar at an early stage?
 Lamarke's Theory
Some thought that you would gain or lose
features if you overused or didn't use them,
and you could pass these new traits onto
your offspring.
Known as the Inheritance of Acquired
Characteristics
A lizard that didn't use it legs would
eventually not have legs and its offspring
wouldn't have legs
A giraffe stretched its neck to reach higher
leaves, and this stretched neck would be a
trait inherited by its offspring
Lamarke's Theory
Lamarke's Theory was eventually
discarded - PROVEN TO BE WRONG!
Why? Logically it doesn't work. Imagine if
you were in a car accident and had a leg
amputed. This does not mean that your
children will only have one leg. Features
gained during life are not passed on to
children.
 Darwin's Theory
- Naturalist
– traveled to the Galapagos Islands on the HMS Beagle
– his observations of the finches (and other animals)
– noted that all the finches looked about the same except
for the shape of their beak.
– conclusion that all the finches were descendents of the
same original population
– The shape of the beaks were adaptations for eating a
particular type of food (Ex. long beaks were used for
eating insects, short for seeds)
Darwin’s Finches
 "The Origin of Species”
1. Variation exists among individuals in a species.
2. Individuals of species will compete for
resources (food and space)
3. This competition leads to the death of some
and survival of others - Survival of the Fittest
4. Individuals with advantageous variations - more
likely to survive and reproduce.

This process by which populations change in response to their
environment is known as Natural Selection .
Natural Selection can be said to be a result of Adaptive
Radiation-This is where species all deriving from a common ancestor
have over time successfully adapted to their environment.
Ex: finches- the finches adapted to take advantage of the various food sources
available on the island, which were being used by other species. Over the long
term, the original finch species may have disappeared, but by diversifying,
would stand a better chance of survival.
The favorable variations are called Adaptations-leading to
increased survival rate.
 Evidence of Evolution
Fossil Evidence
– Carbon dating--gives age of a sample based
on the amount of radioactive carbon is in a
sample.
– Fossil record--creates a geologic time scale.
Biochemical Evidence
- Amino acids-Proteins
– Nucleic acids- DNA
 Evidence of Evolution
Anatomy and Development
Homologous Structures- are
embryologically similar, but have different
functions, the wing of a bird and the
forearm of a human
 Evidence of Evolution
Vestigial Organs/structures-seemingly functionless parts, snakestiny pelvic and limb bones
Humans - tail bone; appendix
 Evidence of Evolution
Embryological development-Embryos of different species
develop almost identically
 Evidence of Evolution cont.
Convergent evolution- organisms of different
species evolve similar features independently
usually because they live in the same environment
– Bird wings and insect wings
Divergent evolution- organisms of the same species
adapt differently because they live in different
environments
- shells of Galapagos tortoises; beaks of finches
 Rate of Evolution
Gradualism
– Gradual change over a long period of time
Punctuated equilibrium
– Period of rapid change in species
separated by periods of little or no
change
Examples of Evolution
1.
2.
3.
4.
industrial melanism (Kettlewell's moths)
dog breeds
viruses & vaccines
bacteria & antibiotics