Darwin notes

1. Darwin notes CP Biology Ms. Morrison

2. Evolution • Change over time, process by which modern organisms have descended from ancient organisms

3. Theory • Well-supported testable explanation of phenomena that have occurred in the natural world

4. Charles Darwin • Traveled around world on HMS Beagle (1831) • Made numerous observations and collected evidence that lead to theory of evolution • Saw great diversity in plant and animal life • Collected fossils on his trip • Questioned fossils relationships to living organisms and wondered why they had disappeared

5. Galapagos Islands • Influenced Darwin the most • Group of small islands off west coast of South America • Although close – had very different climates • Observed that the characteristics of many animals and plants varied noticeably among the different islands

6. Ancient Earth • Until 19th century – thought world was only a few thousand years old and life was like it had always been • Studies of fossils lead to idea that several periods of creation • Two geologists – James Hutton and Charles Lyell – recognized Earth was many million years old and processes that changed Earth in the past were still working now

7. James Hutton • Published theory about geological forces that shaped Earth • Said layers of rock form very slowly – pushed up or buried, shaped by natural forces such as rain, heat, and cold • Proposed Earth to be much more than a few thousand years old

8. Charles Lyell • Principles of Geology • Scientists must explain past events in terms of processes that they actually observe since those processes that shaped Earth in past continue in present • Explained geological features could be built up or torn down over long periods of time

9. Geology and Darwin • Hutton and Lyell influenced Darwin two ways: • If Earth could change, might life also change? • Would have taken many, many years for life to change – Earth would have to be extremely old

10. Lamarck’s Theory of Evolution • Jean-Baptiste Lamarck – recognized living things changed over time and all species descended from other species • Realized that organisms somehow adapted to their environments • Published theory in 1809 • Proposed that selective use or disuse of organs – caused organisms to acquire or lose certain traits over their lifetimes – these could be passed to offspring and over time lead to change in the species • Incorrect – acquired behaviors NOT passed to offspring

11. Population Growth • Thomas Malthus – economist who observed in 1798 that babies were being born faster then people were dying • Reasoned that if human population grows unchecked, that sooner or later there would be insufficient living space and food for everyone • War, famine, and disease – work against population growth • Concept lead Darwin to realize this was true for plants and animals too • Darwin wondered what factors determine which organisms survive and reproduce and which do not

12. On the Origin of Species • Published in 1859 • Proposed mechanism for evolution was natural selection and proposed evidence for evolution • Said natural variation found in all types of organisms • Humans used selective breeding for particular natural variations found useful = artificial selection • Darwin felt a process like artificial selection occurred in nature

13. Darwin’s Theory • Struggle for existence = each member of a species completed to obtain food, living space, and other necessities of life • Fitness = ability of an individual to survive and reproduce in its environment • Said fitness result of adaptations (inherited characteristics) that increase an organisms’ chance of survival • Successful adaptations – enable organisms to become better suited to environment and better able to survive and reproduce

14. Darwin’s Theory, pg 2 • Survival of the fittest = individuals better suited to the environment (high fitness) would survive and reproduce most successfully = natural selection • Over time natural selection results in changes in inherited characteristics of a population which increases a species’ fitness in its environment

15. Descent with Modification • Living species descended with changes from other species over long periods due to natural selection • Means all living organisms related to one another • Principle = common descent = all species, living and extinct, are derived from common ancestors

16. Evidence for Evolution • Fossil Record – shows living things evolving for millions of years • Geographic distribution of living species • Some species become different when adapt to different local environments • Different species living in similar environments may evolve common features

17. Evidence for Evolution, pg 2 • Homologous body structures = structures which have different mature forms but develop from same embryonic tissues • Ex. 4 limbed animals with backbones have common ancestor • Some homologous structures do not serve important functions – vestigial organs – have become very reduced in size and not used in survival • Embryonic similarities – embryos of many animals with backbones look so similar it is hard to tell them apart • Same groups of embryonic cells develop in same order and in same patterns • Help produce homologous structures