1. Evolution & Homeostasis 2011
The Origin of Species
Evolution & Homeostasis
2011

2. In the beginning…
God created the heaven and the earth. And the earth was without form, and void; and darkness was upon the face of the earth. (Genesis)

4. Throughout history, people have tried to explain how the earth was created, and how the great diversity of life came about.
Judaic-Christian belief in Genesis
In the 17th century, it was calculated that the earth was created on Oct 23rd, 4004BC, at 9am
Celtic belief in Yggdrasil, the tree of life
Hindu belief that earth came from the tears of the god Prajapati, or in some beliefs, from the cosmic egg created by Brahma

5. What is faith?
Faith is belief without evidence
What is a scientific theory?
An explanation or model which explains natural phenomena, supported by evidence

6. However, various evidence made people doubt these beliefs
Egyptian civilisation was found to pre-date the supposed creation date
Why would God bury fossils of giant animals now extinct?
Rocks that showed evidence of being below the sea (fossils etc…) had worked their way up to the tops of mountains, obviously taking longer than 6000 years

7. People finding fossils tried to find an explanation
Remains of prehistoric whales found in China led to the shape of Chinese dragons
Ammonites were thought to be stone snakes

8. But there were several important questions that they couldn’t answer:
How old were these fossil remains?
Why were fossils of sea creatures found in high mountains?
Why were there fossils of creatures no longer in existence?
Why were different types of fossilised organisms found in different areas or layers of rocks?
Why were there no fossils of some modern day species?

9. Lamarck’s theory of evolution
Lamarck ( ) theorised that
individuals pass on acquired
characteristics to their offspring
Example: a blacksmith has greater muscle development due to his occupation. This characteristic is passed on to his offspring, who will also have larger muscles.
First to propose that change over time was the result of natural phenomena and not divine intervention.

10. Early Contributions to Evolutionary Thought
Thomas Malthus ( )
Believed that populations increased in size until checked by the environment, called the ‘struggle for existence’.
Charles Lyell ( )
The physical features of the earth were the result of slow geological processes that still occur today.

11. Darwin-Wallace theory of evolution
Charles Darwin worked on the theory for over 15 years, but was hesitant about publishing because of the social & religious opposition
He was prompted to publish “On the Origin of Species by means of Natural Selection” when Alfred Russel Wallace came up with a similar theory of natural selection & published it

14. Darwin’s finches
Darwin traveled on the “Beagle” in & visited the Galapagos Islands
He noted that different islands had different species of finches, and that the beaks were particularly suited to the food available on each island

15. From studying the finches, Darwin concluded that all of the different finches were descended from a common ancestor
The finches were isolated on different islands
On each island there were different foods
In each isolated group of finches, those with the best beak shape for the available food were more likely to survive
They reproduced & passed on their favourable beak to offspring
Over many generations, each island had its own species of finches adapted for the local food

16. Natural selection
From this, he derived the theory of evolution based on natural selection
All species produce more offspring than the resources can support
There is natural variation between individuals of a species
Individuals with advantageous genotypes will be more likely to survive & produce offspring
Over subsequent generations, the frequency of the advantageous genotype increases, leading eventually to evolution of the species

17. Natural Selection Overproduction Variation Natural Selection
Individuals show variation: some variationsare more favorable than others
Overproduction
Populations produce too many young: many must die
Natural Selection
Natural selection favors the best suited at the time
Inheritance
Variations are inherited. The best suited variants leave more offspring.

18. Lamarck v’s Darwin-Wallace

19. Evolution refers to the permanent genetic change (change in gene frequencies) in population of individuals.
It does not refer to changes occurring to individuals within their own lifetimes. Populations evolve, not individuals.