Topic 2 - Darwing and The Theory of Evolution

early greek philosophers: (compatibe or not)

attempted systemic explanation, claimed the world is eternal and unchanging. incompatible with evolution

Artistotle

discussed importance of direction observations, conclusions should be consistent with data

an argument from design is:

a complex sturcture of things and plants were taken as evidence of an intelligent designer

classification in 1600s

systemic classifications were based on similarities among organisms

Carl Linnaeus…

developed a taxanomical system for hierarchy

By the 18th century, what changed?

a radical shift began, a claim that the earth is very old all based on observations.

Charles Lyell

argued that processes must have operated over long periods of time slowly. (uniformitarianism as opposed to catastrophism)

Fossil evidence

there were species in fossil record no longer alive, some were found in deep layers of rock

Lamark’s Theory of Evolution

new, more complex species descended gradually from older, less complex ones

inheritance of acquired characteristics

traits acquired during the liftetime of an individual, due to continued use or disuse of structures are passed on.

how was Lamark special?

he proposed a mechanism for evolution and it explained adaptation

Geological observations (Beagle)

• beds of sedimentary rock upifted volcanically

• land elevated several feet by an earthquake

• continued growth of coral and sinking seabed formed atolls

how did geological observations affect his way of thinking?

after the 5 years, he was in total agreement with Lyell’s uniformitarianism

Fauna of the Islands (Beagle)

• fauna on each island was similar but distinct and resembled a species in S. America

• collected many birds thinkning they were different due to their beaks, they ended up all being FINCHES

Inconsistencies with creationism

• species on diff islands similar in habitat were sometimes distinct

• fauna of continents had relatively few species in common even in similar habitats

• fossil mammals in S. America that no longer exist were simlar to present day species

By the end Darwin was convinced that:

• earth was very old

• current geo patterns were result of slow ongoing processes

• species are not fixed, rather transmute

how were darwin and wallace similar?

Darwin is sure evolution is based on gradual accumulation of slight changes, Wallace had similar theory:species change and that natural selection was the cause

Evolution (darwin and today’s definition)

darwin: a change in charactertistics of a pop over time

today: a change in a allele frequency in a pop across generations

Natural Selection

a process that occurs when certain conditions are met.

individual members must compete for resources, individuals with favoured trait produce better offpsrings and trait becomes more common.

why was natural selection not widely accepted?

earth was not old enough back then, and direct evidence was lacking.

Evidence for common descent from homology

similarity in structure, especially when function differs. comes from darwin’s similar due to inheritance from a common ancestor

vestigial traits

traits that served a function in ancestor but reduced or no long function in focal species.

Evidence for common descent from fossils

fact of extinction, the older the fossils the more old the species and vice versa

evidence for common descent from biogeography

living species tend to be similar to others geographically nearby

experimental evolution

a technique which biotic and or abiotic conditions are manipulated under contorlleed conditions and evolutionary outcome is studied (not necessarily artifical selection)

artifical vs natural selection

systematically breeding those with desired characteristics vs not doing that

misconceptions about evolution

• natural selection is not goal driven

• no organism is higher or lower

• natural selection dies not act for the good of species

mullerian mimicry

Müllerian mimicry is when two or more well-defended, unpalatable species evolve similar warning signals to avoid predation. This mutualistic relationship benefits all involved species because predators only need one negative experience with a Müllerian mimic to learn to avoid similar-looking prey in the future.  

why is creationism not scientific

not scientific cause it can’t be refuted