Unit 7

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

More VocabDivergence – one species changes over time to become 2 different species

Speciation – Process by which new species form