1. The Theory of Evolution

2. What is Evolution? Change over time
Fossil evidence shows that living things have not always been the same as today

3. History of the theory… James Hutton (1785)
Earth formed very slowly, earth is old
Forces beneath the earth’s surface act to form mountains, rocks, and valleys

4. History of the theory… Thomas Malthus (1798)
Predicted that the human population would grow faster and larger than the space and food supplies will allow
Predicted there would be a great struggle for survival, leading to wars and famine

5. History of the theory… Jean-Baptiste de Lamarck (1809)
Was the first to propose a mechanism for evolution
Hypothesized that the environment influenced the development of traits
Inheritance of acquired traits

6. Lamarck’s Theory Acquired traits are developed as needed Example:
long neck of giraffe
Fins and tail of a dolphin

7. Lamarck’s Theory-problems…
Acquired traits are passed on to offspring
We know that only traits that are controlled by genes can be passed down to future generations
A trait that is not needed will be lost
We know that an organism cannot “lose” a trait it had at the start of its life, because traits are controlled by its genes

8. History of the theory… Charles Lyell
His book, Principles of Geology, explained that earth continues to change just as it has for millions of years
And processes that have shaped (and continue to shape) the earth are very slow

9. History of the theory… Charles Darwin (1832)
Set sail as ship’s naturalist on the HMS Beagle
Read the works of Malthus, Hutton, and Lyell while sailing around the world
Collected evidence that would be used to support his developing theory

10. History of the theory… Alfred Wallace (1858)
Wrote to Darwin speculating on evolution by natural selection

11. Darwin’s Theory On the Origin of Species (1859)
Individuals differ and some of the variation is inheritable
Many more offspring are born than can survive
There is competition for resources
Each individual has advantages and disadvantages in the struggle to survive
Those most adapted to the environment will survive and pass their traits on

12. Evidence to support Darwin’s Theory
Fossil record

13. Evidence to support Darwin’s Theory
Fossil record
Geographic distribution of living species

14. Evidence to support Darwin’s Theory
Fossil record
Geographic distribution of living species
Homologous body structures

15. Evidence to support Darwin’s Theory
Fossil record
Geographic distribution of living species
Homologous body structures
Embryological similarities

16. Weaknesses of the theory…
Cannot explain how the first life began
First single cell
First multi-cellular organism

17. Weaknesses of the theory…
Relies on random mutation as the explanation for change
Most mutations are harmful

18. Weaknesses of the theory…
A “missing link” is not known for any two species
All species seem to have come into being independently of any other

19. More like a lizard or a bird?
Theory changes as more evidence is found
Dinosaur theory