Topic 3 Flashcards
What were the reasons for extinction hypothesized during “pre-Darwin” times?
natural disasters
apparent disappearance of species was actually one species changing slowly into another
supernatural disasters
not actually extinct, just hiding
What is Cuvier hypothesize?
species do not change over time (fixed) = no evolution
the succession of life forms in the Earth’s strata due to: catastrophe –> local extinction –> presence of fossils in the stratum
after catastrophe, new species moved into area –> new fossils in new stratum following another catastrophe
What did Lamarck hypothesize?
species changed over time (evolution) due to: inheritance of acquired characteristics
traits acquired by an individual (during a single lifetime) can be passed on to their offspring
but no experimental evidence, logic greatly flawed
What is uniformitarianism?
present is the key to the past
What is gradualism?
features of the Earth result from slow accumulation of events such as those we see occurring now: catastrophes are rare
What were the five observations that lead to the theory of natural selection?
- Organisms produce many more offspring than survive to reproduce themselves
- Most populations are relatively stable
- Resources (food, land) are limited, not enough for all offspring of all individuals
- Variation among individuals within species
- Some variation is heritable
What are the three inferences of natural selection?
- Organisms must compete for these limited resources, and not all succeed
- Some heritable variations are likely to provide individuals with a competitive advantage
- Individuals with advantageous variations are likely to leave more offspring than individuals without these variations
What is descent with modification?
the process of natural selection gives rise to adaptations
as individuals adapt to different environments, new species may arise over time (over many generations)
populations evolve, not individuals
natural selection acts on existing variations
natural selection is context dependent (no innate tendency towards perfection)
What is heritable variation?
for natural selection to act on variation, it must be “seen” by the environment (expressed in the phenotype) and be heritable (caused by genotype)
variation is random, but not natural selection
What are sources of variation?
mutation: random changes to DNA
recombination: crossing-over
independent assortment: of chromosomes
fertilization: sexual reproduction
What is a selective agent?
component of natural environment that consistently cause differential survival and/or reproduction
the intensity with which the selective agent acts on a population to evolve = selection pressure
biotic (predator, disease, competitor) or abiotic factors (temperature, rainfall)
What are the four types of data that document the pattern of evolution?
- The Fossil Record
- Homology
- Direct Observations
- Biogepgraphy
How is the fossil record evidence for evolution?
dating of sedimentary rock layers (strata) allows fossils to be placed in time
consistent forms occur in the same aged sediment (stratum)
intermediate forms can be identified that appear to be ancestors of current species
extinction is seen in the record
How is homologous characteristic evidence for evolution?
similarity due to common ancestry
embryos and evolutionary history: the common structure is evidence that all evolved from a common ancestor
vestigial structures and embryology
molecular evidence
How is direct observation evidence of evolution?
artificial selection: breeding selects for desirable phenotypes
antibiotic resistance in bacteria
development of pesticide resistance
