Lecture 2

Question 1

open questions in Darwin’s time

Answer 1

1. where do species come from?
2. how can we explain complex adaptations (ie traits with clear/elaborate function for the survival and reproduction of organisms)?

Question 2

Paley’s argument from Design

Answer 2

• Dominant view in European society - came from Natural Theology (branch of theology)
• on a walk and you find a watch, with perfect hands for minutes and hours
• they clearly have a specific function - somewhere on this planet must exist a ‘watchmaker’.
• trees are adapted to have very specific functions, they are perfectly designed for their life and function
• there has been a designer (ie God)

Question 3

Jean Baptiste de Lamarck, 1744-1829

Answer 3

First to
- use term evolution
- provide a hypothesis for the causal mechanism (inheritance of acquired characters)

Question 4

explain Lamarck’s example for the inheritance of acquired characters

Answer 4

• giraffe feeds on leaves
• will spend its whole life stretching its neck, allowing it to grow and reach further on the tree
• this trait is passed on

Question 5

give a summary of the theory for the inheritance of acquired characteristics

Answer 5

Organisms can change their phenotype within their generation; having changed within the generation, they pass this to offspring

Question 6

draw a diagram for Lamarck’s theory

Question 7

who proved Lamarck wrong?

Answer 7

August Weismann’s Germplasm theory (1889)
- Inheritance only by germ cells (gametes); somatic cells do not function as agents of heredity, information only goes one way
- Thus genetic information cannot pass from soma to gametes and onto the next generation
- Modern interpretation in molecular terms: genetic information flows in one direction only: from DNA to protein but never in reverse

Therefore changes to the body cells would not be able to have an impact on gametes and be passed onto offspring

Question 8

what experiments did Weismann do to prove his Germplasm theory?

Answer 8

got a bunch of mice, chopped off their tails, and bred them together - the offspring still had normal sized tails

Question 9

describe Darwin and Wallace’s roles in developing the theory of evolution?

Answer 9

• Darwin developed first comprehensive theory of evolution
• Darwin and Wallace independently discovered the chief mechanism of evolution, Natural Selection

Question 10

Two major theses of Darwin and Wallace’s theory of evolution

Answer 10

All organisms have descended with modification from a common ancestor: thus, living things changed over time
The process leading to evolution is natural selection operating on variation among individuals

Question 11

describe the contents of Lyell’s book

Answer 11

• argued for uniformitarianism
• the forces and processes that shape the Earth’s surface are uniform through time (ie the forces we see today are the same as previous eons)
• present day geological processes can explain the history of the Earth Gradualism of erosion, earthquakes, volcanoes

Question 12

Give the stages of Darwin’s development of this theory

Answer 12

1. Exploration - voyage on HMS beagle around the world (1831-1836) as ship’s naturalist. Intellectual companion to Capt. Robert Fitzroy
2. Gradualism - reads Lyell’s book ‘Principles of Geology’
3. Species Vary - Variation patterns of Galapagos mockingbirds
4. Struggle for existence - 1838, Darwin reads Malthus’ ‘An Essay on the principle of population’

Question 13

implications of Lyell’s book for Darwin

Answer 13

1. the notion of a dynamic rather than a static world
2. changes build up gradually, by the same mechanisms today as in the past

Question 14

implications of variation patterns of Galapagos mockingbirds for Darwin

Answer 14

• there are 4 similar species endemic to the islands descended from a South American mainland ancestor
• populations had very slightly different traits and were not constant
• Darwin thus began to doubt the fixity of species

Question 15

Malthus’ essay on the principal of the population

Answer 15

there is a constant struggle for existence as populations could grow exponentially nut don’t due to limits on resources

Question 16

two key dates for Darwin and Wallace

Answer 16

July 1858 - Linnean Society presentation of Darwin-Wallace paper
Nov 1859 - publication of 490 pg book on Origin of the Species

Question 17

describe Darwin’s mechanism of Natural Selection (3)

Answer 17

• Variation: individual variation in a population
• Heredity: progeny resemble their parents Moree than unrelated individuals
• fitness: some forms are more successful at (surviving and) reproducing than others in a given environment (i.e. some are more fit than others)

Natural selection is heritable variation in fitness