EvolutionIntroduction

To believe or not to believe

• BBT Video

• Discussion

Evolution: Just a theory?

• A theory is a set of statements that explains a group of facts or phenomena.

• These statements have been tested repeatedly and are supported by evidence.

• A theory can be used to make predictions about natural phenomena

• E.g. the theory of gravity explains why objects fall to the ground

Evolution

• The process of cumulative change in the heritable characteristics of a population

• Evolution is the idea that all species are descendents of ancient species that were different from modern day species. Evolution is the biological history of life on Earth, from the earliest micro-organisms to the diversity of modern day organisms.

So that settles it then?

• F.R.I.E.N.D.S video

• Discussion

Changing Nature of Science

• Scientists make both the initial identification and the later revision. [Opponents try to focus on the errors alone without mentioning the correction made]

• Laws of physical sciences are typically deterministic while laws of biology usually have a probability factor associated e.g. Mendel’s laws of inheritance work only work with single gene pairs and not even with all such pairs.

• So we must say, “From what we know till now…” while stating scientific “fact”. That fact exists until somebody proves it otherwise.

Our Dear Old Planet• James Hutton (Scottish) studied

the rates of erosion and sedimentation and the thickness of bands of sedimentary rock.

• Uniformitarianism: Earth was formed entirely by slow moving processes like erosion and that these slow forces continue to shape the landscape.

• 1830, Charles Lyell (English) found further evidence to support this and he popularized this idea via his book Principles of Geology

Change in Life• George Cuvier (French) compared

Mammoth skeletons to Elephant ones

• He noticed that they were different enough to say that they were a separate species which had gone extinct.

• In early 1800s Jean-Baptiste Lamark (French) proposed that species evolve (change) over time

• He explained it as a process of Adaptation

Adaptation: Tendency towards Perfection?

• Adaptation is an inherited characteristic that improves an organism’s ability to survive and reproduce in a particular environment.

• He explained this by saying that:• By using/not using certain body parts, an organism

develops certain characteristics. e.g. Giraffes and their long necks

• These enhanced characteristics were then passed down to their offspring

• All organisms have a tendency towards perfection• But…acquired characteristics don’t change DNA