Lecture 4 & 5 Evolution I Flashcards
what is the core theme of evolution?
- evolution accounts for the unity and diversity of life all life on earth is related because it evolved from a common ancestor
what did Georges Cuvier hypothesize?
- species DO NOT change over time
- succession of life in Earth’s strata due to: catastrophe –> local extinction –> presence of ew fossils in the stratum
- after catastrophe, new species move into area –> new fossils in stratum
what die Jean-Baptist Lamark hypothesize?
- species change over time (Evolution) due to INHERITANCE OF ACQUIRED CHARACTERISTICS
- use and disuse – heritable change : NO experimental evidence
- philosophically opposed to extinction
what did Darwin hypothesize about the finches?
- species from south america had colonized the Galápagos and speciated on the islands
what is natural selection?
- descent with modification
- process in which individuals with favourable inherited traits are more likely to survive and reproduce because of those traits
- in 1858, Alfred Russell Wallace developed a theory of NS similar to Darwin’s
what did Darwin see on the Galápagos Islands?
- finches were different, but related species
- redundant forms from one place to another – common ancestry
- variation on a basic form within a region (descent with modification)
what were similarities and dissimilarities of Darwin’s finches?
- similar appearance - but slightly different depending on habitat
- varied in use of food sources and way of feeding
what does evolution explain? (patterns…)
- patterns of unity and diversity in living organisms
what does descent with modification mean?
- the view that all organisms are related through descent from an ancestor that lived in the past
what are observations 1&2 + inference 1
O 1: there is existing variation among individuals within populations
O 2: some of this variation is heritable
I 1: individuals whose inherited traits gave them a higher probability of surviving and reproducing in a given environment tend to leave more offspring than other individuals – in the next gen, there will be more ind with that variation than previous
what are observations 3,4,5 + inference 2
O 3: organisms produce many more offspring than are able to survive and reproduce themselves - potential to increase exponentially
O 4: most populations are relatively stable in size
O 5: resources are limited – competition is inevitable
I 2: unequal ability of individuals to survive and reproduce will lead to the accumulation of favourable traits in the population over generations - must compete, not all succeed (Thomas Malthus inspired)
what is observation 6?
- species generally suit their environment
what is a requirement for natural selection to act on variation? (2) (re: geno/phenotype)
- must be seen by enviro - expressed in phenotype (but sometimes phenotype is determined by enviro so it’s not heritable
- be heritable (caused by genotype)
true or false: variation is random
- T
what is a selective agent?
- component of natural environment that consistently causes differential survival or reproduction (ex: a/biotic factors)
what is selective pressure?
- requirement for natural selection
- intensity with which the selective agent acts on a population to evolve
is natural selection context independent or dependent?
is it reversible?
- dependent
- yes, it is reversible
what is fitness?
- ability to survive, find a mate, produce offspring, and leave its genes in the next generation
summarize the five steps of natural selection:
- heritable variation: individuals vary in their characteristics (pheno) due to varied genetic makeup (geno)
- resources are limited; more offspring than enviro can produce
- some phenotypes with favourable traits will be better suited to survive and reproduce
- over time, increase in proportion of favourable traits and genes coding for them in a population
- adaptations to new enviro –> new species
what evolves over time?
populations, NOT individuals
what variation does NS act on?
EXISTING
what is adaptation?
inherited characteristic of an organism that enhances its survival and reproduction in a specific environment
why is increased and survival + reproduction not necessary sometimes?
all that that’s needed is greater reproductive success– ie more offspring produced regardless of it’s adaptive traits
what are five pieces of evidence of evolution?
- observation of pop’n changes in real time - finches, antibiotic resistance
- artificial selection
- fossil record
- similarities b/w organisms
- biogeography
what is homology?
- similarity from common ancestry
- related species have characteristics with similar underlying structures but different fxns
what are homologous structures?
- anatomical resemblances representing variations on STRUCTURAL themes present in a common ancestor
- comparative embryology reveals anatomical homologies are not visible in adult organisms
- look at shared embryonic structures
what are vestigal structures?
- remnants of features that served important functions in organism’s ancestors
what are molecular vestigular structures called?
- pseudogenes
what are intermediate forms?
- forms that can be identified that appear to be ancestors of current species
what are endemic species?
- species that are not found anywhere else in the world
