Evolution Flashcards
Fossils
Law of superpositions
Fossils found at shallower depths are more recent and complex (similar to modern day animals) than fossils found at deeper depths
Biogeography
Study of past and present geographical distribution of organisms
Environments that are different but geographically close are more likely to be populated by related species
Animals on islands evolved from mainland migrants
Anatomy
Homologous structures have similar structure but different functions
Analogous structures have different structures but similar functions
Vestigial structure is a structure that no longer serves a purpose
Embryology
Studies pre birth stages
Embryos of different organisms have similar stages
Vertebrates have bony spines but also have paired bouches in the throat that became gills in fish and amphibians and ears and throat in humans
Points to a common ancestor
DNA
compare DNA between organisms to see how closely related they are
Indicates DNA sequence was inherited by a common ancestor
Mutations
Mutations are random changes in the DNA of an individual
Creates new genes continual supply of new genetic info
Helps with variation of genetics among organisms
A heritable mutation can affect the entire gene pool
More genetic variation - increase in diversity - increase in survival
Types of mutations
Neutral - no benefit or harm
Beneficial - advantageous
Harmful - reduces reproductive success of an individual
Pseudogenes are genes that have gone through a mutation and no longer serve a purpose
Natural selection
Favorable alleles become more frequent in a population
Greater chance of affected individuals surviving and reproducing
Causes change in allele frequency resulting in an evolutionary change
Selective pressures
Disease
Predators
Climate conditions
Food availability
Types of natural selection
Directional selection :environment favours individuals with a more extreme trait
Stabilizing selection: environment favours most common variation (middle trait)
Disruptive selection: environment favours variations at opposite extremes (opposite of stabilizing selection)
Sexual selection: favouring a trait that enhances the mating ability of an individual
Genetic drift
random shifting of genetic makeup of the next generation
Bottleneck effect
the loss of genetic diversity following an extreme reduction in the size of a population
Founder effect
small number of individuals establish a new population
Hardy Weinberg Principle
in large populations in which only random chance is at work, allele frequencies are expected to retain relatively constant from generation to generation
Prezygotic Speciation
Behavioral isolation - different species use different mating cues to attract a mate
Ecological isolation - different habitats
Temporal isolation - mate at different times of the year
Mechanical isolation - morphological features make the two species incompatible
Postzygotic Speciation
Genetic isolation - gametes can’t fertilize
Zygotic mortality - zygote is unable to develop properly
Hybrid inviability - hybrid either dies before birth or cannot survive to maturity
Hybrid infertility - hybrid is healthy but infertiles
Allopatric speciation
population is separated geographically, no longer able to exchange genetic information, mutations are not shared between populations
Sympatric speciation
individuals become genetically isolated from larger population
Example the hawthorn fly
Patterns of evolution
Adaptive radiation - single species evolves into similar but distinct species, each new species fills an ecological niche, occurs when new resources become available that aren’t being used by another species
Divergent evolution - species that were once similar to an ancestral species become increasingly distinct, result of different selective pressures
Convergent evolution - similar traits arise because different species adapted to similar selective pressures, species are less genetically related, appearance becomes more similar
Co-evolution - evolutionary success closely related to another species, evolutionary arms race (counter evolution, taller trees taller giraffes), dependant species (if one goes extinct the other is likely to go extinct.
Aristotle era
believed that the earth and all living things were immutable
Buffon
believed the earth was 6000 years old, and that organisms have been created perfect but still could have changed over time
Erasmus Darwin
evolution occurs in living things and humans. All life evolved from single source.
Lamark (the big boy)
PRINCIPLE 1: use and disuse ; body parts that are not use would disappear, body parts that were used became stronger
PRINCIPLE 2: inheritance of acquired characteristics
Individuals pass onto their offspring the characteristics they acquired during their lives
OVERALL: he believed that species evolve over long times, that the traits are acquired through use and disuse, that species evolve in response to their environments, and that changes are passed from generation to generation.
Cuvier
identified that fossils at higher levels were more complex than those at lower levels. Believed in catastrophism: global catastrophes caused widespread extinction of species
Lyell
believed in uniformation (basically catastrophism but slower), global change is slow and gradual
Malthus
proposed that competition was a big ol thing
CHARLES DARWIN (THE BIG DADDY)
Believed in natural selection (u know what it is but basically that the environment favors the reproductive success of certain individuals with advantageous traits over others. Population changes as advantageous traits become more common)
His four main reasons for evolution were:
- organisms compete for resources
- individuals of a population vary extensively, much of this variation is heritable
- some characteristics are more advantageous than others
- processes of change are slow and gradual
