Lecture 2 Flashcards
open questions in Darwin’s time
- where do species come from?
- how can we explain complex adaptations (ie traits with clear/elaborate function for the survival and reproduction of organisms)?
Paley’s argument from Design
- 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)
Jean Baptiste de Lamarck, 1744-1829
First to
- use term evolution
- provide a hypothesis for the causal mechanism (inheritance of acquired characters)
explain Lamarck’s example for the inheritance of acquired characters
- 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
give a summary of the theory for the inheritance of acquired characteristics
Organisms can change their phenotype within their generation; having changed within the generation, they pass this to offspring
draw a diagram for Lamarck’s theory
who proved Lamarck wrong?
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
what experiments did Weismann do to prove his Germplasm theory?
got a bunch of mice, chopped off their tails, and bred them together - the offspring still had normal sized tails
describe Darwin and Wallace’s roles in developing the theory of evolution?
- Darwin developed first comprehensive theory of evolution
- Darwin and Wallace independently discovered the chief mechanism of evolution, Natural Selection
Two major theses of Darwin and Wallace’s theory of evolution
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
describe the contents of Lyell’s book
- 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
Give the stages of Darwin’s development of this theory
- Exploration - voyage on HMS beagle around the world (1831-1836) as ship’s naturalist. Intellectual companion to Capt. Robert Fitzroy
- Gradualism - reads Lyell’s book ‘Principles of Geology’
- Species Vary - Variation patterns of Galapagos mockingbirds
- Struggle for existence - 1838, Darwin reads Malthus’ ‘An Essay on the principle of population’
implications of Lyell’s book for Darwin
- the notion of a dynamic rather than a static world
- changes build up gradually, by the same mechanisms today as in the past
implications of variation patterns of Galapagos mockingbirds for Darwin
- 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
Malthus’ essay on the principal of the population
there is a constant struggle for existence as populations could grow exponentially nut don’t due to limits on resources
