evolution and natural selection

patterns of life: what are the four key observations of life

unity, diversity, complexity, adaptation

unity

organisms share fundamental similarities: all use proteins, similar pathways,

diversity

life exists in an extraordinary range of forms- endless forms is the most beautiful and wonderful

organisms are well suited to their environment -

what is the theory of evolution?

Evolution is the idea that biological populations change over successive generations due
to changes in heritable characteristics
• Darwin (1859) described it as “descent with modification’

species refined, new species arise from pre-existing, LUCA, evolution generates tree of life

how evolution explains the patterns of life?

Unity – shared traits reflect common ancestry
• Diversity – lineages branch and diverge in different environments
over deep time
• Complexity – complex traits arise by gradual modification of simpler
ones
• Adaptation – heritable traits that improve survival or reproduction
increase over generations via natural selection

how were species viewed?

fixed and unchanging, with life as a linear hierarchy = LADDER OF NATURE/SCALA NATURAE/ GREAT CHAIN OF BEING

what’s special creeation

each species was individually created in a single event- fixed and perfectly adapted and designed by an intelligent creator with the idea of young earth 6000 years ago

what was the geological breakthrough?

geologists showed earth is older, same processes operated in the past (uniformitarism), geological features form via slow, continuous orocesses

earth is 4.54 billion years old

fossil evidence- how did they come to be

sediments eroded, blown into rivers, settles on seabed, settles in layers, layers form rock layer - strata , in addition there’s minerals and organic matter which can be persevered

fossile evidence- what does it show

had no living equivalents- extinction

show succession of life- lower layers are older than new layers- law of superposition

fossils within them were prehistoric and different- older strata- faunal succession

transformism

idea that species aren’t fixed but change, extinction , new forms arise via modification not separate acts of creation, change was gradual, philosophical,no clear mechansism

lamarcks hypothesis (1809)

use and disuse- structures used frequently become stronger; unused weaker

inheritance of acquired characteristics- acquired during an organisms lifetime are passed to offspring (WRONG)

Charles Darwin (1809-1882) key observations

close related differ in ways that match their local environments

species on islands resemble those on nearby mainlands but are distinct

similar ecological roles are filled by different species in different regiions

adapted to local conditions NOT FIXED

Darwins insight- artificial to natural selection

heritable variations exist among individuals within a species, breeders select for desirable traits- choose what to reproduce - those become more common = directional morphological change

natural selection

nature is a selector- heritable variation, more offspring than can survive - competition for food etc, advantageous traits will survive (higher fitness), more common and selected

modification with descent

all related via LUCA, natural selection causes populations to change heritable traits accumulate generations, time led divergence, repeated divergence produces a branching pattern of relationships among species

wallance

had the theory as Darwin and asked him to check and they both did a joint book

gregor mendel- mechanism of inheritance for natural selection

tartars areinherited as discrete units genes

follows predictable patterns

modern synthesis of evolution (Neo- darwinian synthesis)

unification of natural selection and mendelian genetics

explains evolution happens : • Genetic variation arises through random mutation (raw material for evolution)
• Natural selection acts on this variation - Individuals with advantageous traits (due to
certain alleles) are more likely to survive and reproduce, passing those alleles on
• Evolution occurs through changes in allele frequencies within populations over
generations
• Speciation (the formation of new species) happens when populations become
isolated and diverge through selection (or other evolutionary forces)