Lecture 2 Flashcards
George Cuvier 1726-1832
- Identified basic morphological plans
(bauplans) - Saw history as a series of creation
periods and extinctions through
natural catastrophe: catastrophism - No change: just extinction and
replacement
Jean Baptiste Lamarck 1744-1829
- Variation acquired over an organism’s
lifetime is passed on - Inherent tendency towards complexity
over time - Didn’t believe in extinction
Alfred Russell Wallace
(1823 – 1913)
- Independently developed a
very similar theory to Darwin’s - Corresponded with Darwin to
discuss their ideas - Had work published alongside
one another - This prompted Charles Darwin
to publish his book - Arguably had a greater impact
on evolutionary theory e.g.
‘the father of biogeography’
William ‘strata’ Smith (1769-1839):
- Observed rock layers, ‘strata’ at a mine pit
- Arranged predictably: always in same relative positions
- Each stratum identifiable by the distinctive fossils it
contained - Same succession could be found in many parts of the
UK: older to younger rocks?
Charles Lyell (1797-1875)
- Popularised “uniformitarianism” (the theory that changes in the earth’s crust during geological history have resulted from the action of continuous and uniform processes)
- Geological [and presumably other!] processes seen today are the
same as those seen in the past, i.e. are uniform over time - Slow moving: i.e. vast time depths were needed
Wednesday 27 April 1859
Sir John Evans and Sir Joseph Prestwich (with several other
respected scientists) present at the in situ find of a handaxe at
St Acheul in France
* First use of photography for a scientific purpose
* Caused controversy!
* Sir Charles Lyell went to visit, was convinced, and promoted the
theory back in the UK
* Followed almost immediately by the publication of The Origin of Species
Charles Darwin
(1809 – 1882)
- Ship’s naturalist on HMS Beagle
- Voyage to the Galapagos Islands
1831 – 1836 - Noticed patterns of geography and
variation among animals - Origin of Species 1859
- Influenced by Thomas Malthus’
ideas on population growth at
geometric rates if unchecked - Combined with his observations of
variation in morphology and
behaviour
Darwinian Theory: the basics
- Individual organisms within a population
vary in their traits. - This influences their ability to access finite
natural resources and hence their survival
and reproductive success. - Individuals with traits that enhance chance
of survival and reproduction contribute
disproportionately to the next generation. - The variation is inherited by offspring.
- There is a shift in the frequency of traits in
the population. - If the process continues for long enough,
eventually the group can no longer breed
with others… - … and constitute a separate species.
Genotype
an individual’s genetic code
Phenotype
observable physiological traits
Variation arises through
- Recombination, e.g. combining 2x parents’ DNA in each child
- and mutations, i.e. mistakes in the copying procedure
Not all mutations are heritable
Somatic mutations occur in body cells and are not heritable
Germline mutations in gametes (egg or sperm) are heritable
Not all mutations affect phenotype and those that do may vary in their effects
- ‘silent’ mutations or mutations in non-coding DNA etc.: do not affect amino acid sequence
- ‘missense’ mutation: slightly different amino acid sequence
- Nonsense mutation: amino acid sequence production stops
- Frameshifts: major difference in amino acid sequences because they move large sequences forward or back along
the gene
Natural selection and differential
reproduction
- Individuals compete for limited
resources - Different phenotypic
characteristics result in consistent
differences in rates of survival or
reproduction (on average) - BUT the differences in phenotype
must be at least partly to do with
genotypic variation - i.e. acquired phenotypic differences
are not passed on!
Ecosystems and community
ecology
The other species in your biome
are agents of natural selection
