1. Introduction to Darwin’s Theory of Evolution

2. The Theory of Evolution
Evolution means change over time
A scientific theory is NOT just a belief, it is a well-supported tested explanation of a particular idea or concept.

3. Charles Darwin In 1831 Darwin sets sail on the HMS Beagle.
In 1844 he writes his Theory on the Origin of Species.
In 1858, Darwin and Wallace both publish their theories on evolution.
Evolution means change over time.

4. History of Darwin’s Studies
Darwin went on a trip on the HMS Beagle and ended up traveling to the Galapagos Islands.
He made particularly specific observations of the finches. He also observed the tortoises on different islands.
He observed each different group had its own niche.
He studied 13 different species and saw how they adapted to their environment.

6. Fossils
A fossil is the preserved remains or imprints of ancient organisms.
Someone who studies fossils is called a paleontologist.
Fossils are found in sedimentary rock that formed when sand and silt settle to the bottom of water.
Not all dead plants and animals are fossilized.

7. Determining ages of Fossils
Relative dating
Looks at the layer of the earth they are found in.
The oldest fossils will be deeper within the layers.
Radioactive dating
Determined by remaining radioactive isotopes the fossil contains.

8. Types of Radioactive Dating
Potassium-Argon dating is used for rocks that are suspected billions of years old.
Carbon dating
2 types:
14C Radioactive
12C Non-radioactive, most common

9. Tracking Changes
According to evolutionary theory, all life originated from a common unicellular ancestor through natural selection.
Scientists use radioactive dating to calculate fossil’s age.
The phylogeny (or evolutionary tree), is not linear, it branches and stops and some of it is incomplete.

10. Theory of Evolution Timeline
Explanations of the origin of diversity go back to the Greeks. They theorized that an organisms form is related to its function
In 1769 Charles Bonnet observed that fossils do not resemble modern organisms and theorizes they are from a previous era.

11. An Ancient, Changing Earth
In 1785 James Hutton proposed the Earth is shaped by geological forces that took place over extremely long periods of time. He estimated the earth is millions, not thousands of years old.
Charles Lyell agreed and wrote a book in 1833 the explained the shaping of Earth’s geological features.
He gave his book to Darwin before Darwin set sail.

12. Popular Belief
Prior to the studies of Charles Darwin, the most widespread belief was that all known species were created at the same time and remained unchanged throughout history.
Some scientists at the time believed that features an individual acquired during a lifetime could be passed onto its offspring, and the species could gradually change to fit an environment better.

13. Lamark 3 principles to his theory:
Organisms constantly strive to improve themselves.
Most used body structures develop and unused waste away.
A structure is modified by use or disuse, the modification is inherited to the offspring.
In 1809 Jean-Baptiste Lamarke hypothesized that “simple” organisms emerge spontaneously and evolve to greater “complexity”.
Lamark’s hypothesis about acquired characteristics was disproved by Weisman, who concluded that changes in an individual during a lifetime do not affect its offspring.

14. Darwin’s Arguments
Darwin argued that only biologically inherited characteristics were advantageous in surviving and reproducing.
The offspring would also inherit and pass on those advantages, and over generations the collection of these inherited advantages would lead to new species.

15. Population Growth?
In 1798 Malthus reasoned that if the human population continued to grow unchecked, sooner or later there would be insufficient living space and food for everyone.

16. Population Control and Competition
Darwin read Malthus’ work reasoned that there is always competition for food, water and space in the environment. The individuals that survive the competition can then reproduce.

17. Darwin’s Return Home
When Darwin returned home he studied and read other people’s materials about geological changes.
He also studied the selective breeding of domestic animals and crops.
He found that any domesticated plant or animal bred to accentuate desirable characteristics is the result of artificial selection.

18. Origin of Species
Darwin’s book, published in 1859, was a quick success. It came from the clear and understandable argument that natural selection and selective breeding of animals was in wide use at the time. There was a massive array of biological and fossil evidence to support the argument.
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19. Support From Others
After the publication of Origin of Species, biological evolution was supported by the rediscovery of the genetic experiments of Gregor Mendel, by the identification of genes and how they are sorted in reproduction, and by the discovery that the genetic code found in DNA is the same for all organisms.
Darwin came to his conclusions prior to Mendel’s work.