Transcript Evolutionary Theory

Unit 7
Charles Darwin
1831 – Unpaid naturalist - HMS Beagle
Explored coastlines for ~5 years
Noticed that many plants & animals
on the Galapagos Islands looked like
those on the South American coast
Also noticed finches in different areas
with different beaks
Malthus - 1798
Every organism has the potential to
produce many offspring
Only a limited number of offspring
survive and reproduce
Population – interbreeding
individuals of a species that live in
the same geographical area
Darwin
Individuals with traits better suited to
ENVIRONMENT more likely to
survive and reproduce
When they reproduce, the number of
individuals in the population with
this trait will increase
This is evolution by natural selection
UNDERSTANDING CHECK
More of Darwin’s Conclusions
Organisms differ from place to place
because habitats present different
challenges
ENVIRONMENT is the driving force
behind evolution
1859 – On the Origin of Species…
Controversial because…
Species change  new species
Apes are close relatives of humans
1859 – On the Origin of Species…
Supported by…
1. Inherited variation exists within
genes of every population or species
2. In a particular environment, some
individuals are better suited to
survive and reproduce
1859 – On the Origin of Species…
Supported by…
3. Over time, traits that make some
individuals better tend to spread in
that population
4. LOTS of fossil evidence that living
species evolved from organisms
that are now extinct
Recent Updates
Reproductive isolation can lead to
populations becoming different
species
Rate of evolution
 Gradualism – Darwin - slow & steady
 Punctuated equilibrium – Stephen J.
Gould – short bursts followed by
nothing
Recent updates
Selective pressure can increase the
speed of evolution
Bacteria & antibiotic resistance
Natural selection can lead to a
change in gene frequency over time
UNDERSTANDING CHECK
Evidence of Evolution
1. Fossils
2. Anatomical comparisons
3. Developmental patterns
4. Nucleotide sequences
Fossils
Relative dating – Location in
sedimentary rock
Absolute dating –
Radioactive/radiometric dating to
determine age
Transitional forms
Can infer lifestyle from structures
Herbivore vs. Carnivore
Land vs aquatic vs aerial
Nocturnal vs diurnal
Anatomical Comparisons
Analogous structures – similar
functions, different origins
Homologous structures – different
functions, similar origins
Vestigal structures – no function –
remnant of evolutionary past
Analogous Structures
Homologous Structures
Development Patterns –
show common ancestry
Nucleotide Sequences
DNA sequence of nucleotides makes
you who you are
So the more alike the DNA sequence
of 2 individuals is, the more closely
related they are
Chimpanzees & human 98.6%
identical
More Vocab
Divergence – one species changes
over time to become 2 different
species
Speciation – Process by which new
species form