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Charles Darwin1831 – Unpaid naturalist - HMS Beagle
Explored coastlines for ~5 yearsNoticed 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 - 1798Every 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
DarwinIndividuals 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
More of Darwin’s ConclusionsOrganisms 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 UpdatesReproductive isolation can lead to populations becoming different species
Rate of evolutionGradualism – Darwin - slow & steady
Punctuated equilibrium – Stephen J. Gould – short bursts followed by nothing
Recent updatesSelective pressure can increase the speed of evolutionBacteria & antibiotic resistance
Natural selection can lead to a change in gene frequency over time
Evidence of Evolution
1. Fossils2. Anatomical comparisons3. Developmental patterns4. Nucleotide sequences
FossilsRelative dating – Location in sedimentary rock
Absolute dating – Radioactive/radiometric dating to determine age
Transitional formsCan infer lifestyle from structures
Anatomical ComparisonsAnalogous structures – similar functions, different origins
Homologous structures – different functions, similar origins
Vestigal structures – no function – remnant of evolutionary past
Nucleotide SequencesDNA 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