Lecture 21 - The principles of evolution

Question 1

What is evolution?

Answer 1

Evolution is not a thing/force that can “shape” anything – not a thing but a process

Evolution did not solve any problem/did not find ways to adapt living things

Evolution is the change of living things over time (slow and gradual process)
Evolution is a process that involves a population (occurs at the population level

Question 2

When did simple microscopic unicellular organic microorganisms start to appear on earth?

Answer 2

3.5 billion years ago

Question 3

When did multicellular organisms appear

Answer 3

2.5 billion years ago

Question 4

What are Stromatolites?

Answer 4

Bacteria Colonies

Question 5

When did Jellyfish appear?

Answer 5

2 billion years ago

Question 6

What are the basic principles of evolution?

Answer 6

Everything comes about gradually. Every step has to be advantageous/make sense in its own terms- there is no reference or mechanism for future needs.

There is no such thing as evolving for ‘the good of the species’- only individuals.

Ancestry usually explains similarity
o Analogy vs. ancestry… wings of bats & birds are convergent evolution…

Isolation leads to difference … Galapagos or any isolated place
o Divergence.
o Gives a false impression of progress. If you look at a small subset, you will be mistaken.
o It is not a story of progress

“Progress” is not inevitable, although of course:
o Complex things can only come about after simples ones. But sometimes more simple follows more complex.
 Cave fish, crabs etc. have lost their complex eyes.

New territory or niches opening up tend to draw in new species

Many things have happened again and again.
o Big extinction events.
o Explosions of diversity such as the Cambrian explosion.
o Evolution of carnivores/predators from herbivores- in fish, reptiles, dinosaurs, marsupial mammals, placental mammals… Aldabra tortoises perhaps…

Question 7

What is life anyway?

Answer 7

Living matter is real stuff. Physical stuff. Living cells. Basically, organic compounds.

Life is a very complex chemical reaction. For the last 3.5 billion years, chain chemical reaction has been ongoing in the way we describe as evolution.

Evolution is not a process of progress towards higher complexity

Evolution is a process of diversification