Macroevolution
Evolutionary changes the create new species
Microevolution
Evolution as it relates to allele frequencies
Drawbacks of Morphological Traits
How many traits to consider, traits my very continuously, what degree of dissimilarity, members of the same species can look different, members of different species can look similar
Biological Species Concept
Group of individuals whose members have the potential to interbreed with one another and produce fertile offspring
Evolutionary Lineage Concept
New species are the result of speciation from immediate ancestral species - Individual
ecological species concept
Each species occupy an ecological niche with a unique set of habitat resources, species also influences ecosystem
General Species Concept
Each species is a population of individually evolving lineages
Phylogenetic Species Concept
Monophyletic groups identified by synapomorphies
Morpholocal Species Concept
Evolutionary independent lineages vary by size, shape, and other features
Reproductive isolation
Mechanism that prevents interbreeding between species
Interspecies hybrid
When species produce hybrid
Prezygotic isolation
Mechanism that prevents the formation of a zygote. Includes: Habitat: Different habitats Temporal: different breeding times Behavioral: different species have different mating rituals Mechanical: reproductive organs don't fit Gamete: the sperm is unable to fertilize the eggs
Postzygotic isolation
After the zygote has formed Hybrid Inviability: Prevents the offspring from reaching a reproductive age Hybrid sterility: Offspring can't reproduce Hybrid breakdown: subsequent generations become weaker until line dies out
2 explanations for speciation
abrupt events that cause chromosome number to change
consequence of adaptation to different ecological niches
Allopatric speciation
Members of a species become geographically separated Dispersal: the species move Vicariance: event splits population
sympatric speciation
Occurs when members of a species that are within the same range diverge into 2+ species with no physical barriers
mechanisms of sympatric speciation
Polyploidy, adaption to local environment, sexual selection
Taxonomy
Science of describing, naming, and classifying living/extinct organisms
Systematics
the study of biodiversity and the evolutionary relationships among organisms
Binomial Nomenclature
Latin names - Genus species (italicize) Established by international organizations
Phylogeny
Evolutionary history of a species or group of species.
Anagenesis
Single species evolves into a different species over time
Cladogenesis
single species diverges into 2+ species
Clades
Group of species (taxon) consisting of an ancestor and descendants
Monophyletic Group:
group that consists of a single ancestral species and all its descendants; includes individual clades
Paraphyletic
Not all descendants are included in the grouping
Polyphyletic
Specific traits evolve separately in different species (homoplasies /convergent evolution)
Synapomorphy
Trait found in 2+ taxa that are present in recent common ancestors but missing in more distant ones
Shared Primitive Character
Shared by 2+ taxa and is inherited from an ancestor older than the last known common ancestor
Shared Derived Character
Shared by 2+ taxa, originated from the most common ancestor
Outgroup
The most primitive ancestor, diverged before the rest of the species
Parsimony
Simplest way to organize characters and states
Neutral Theory of Evolution
Favorable mutations are rare, detrimental mutations are quickly eliminated, neutral mutations occur at a constant rate
Horizontal Gene Transfer
Any process in which an organism incorporates genetic material from another organism without producing offspring
Vertical Gene Transfer
Sexual reproduction, changes in groups due to descent from common ancestor
Habitat Bias
Fossils are only found in areas where sediment is distributed
Tissue Bias
Hard-bodied organisms are more likely to be preserved
Temporal Bias
Recent organisms are more common than ancient fossils
Abundance Bias
Common, widespread, long lasting species are more likely to be fossilized
Life's Timeline
Precambrian - unicellular organisms, no oxygen
Panerozoic Era - Paleozoic: most lineages Mesozoic: Dinosaurs, gymnosperms Cenozoic: mammals, angiosperms
Gymnosperm
Cone bearing plant
Angiosperm
Flowering plant
Adaptive Radiation
A single lineage produces many descendants with a wide range of adaptive forms
HOX Genes
series of genes that controls the differentiation of cells and tissues in an embryo
What lead to the explosion of life?
High oxygen levels and aerobic respiration
Predation, drilling through sea shells
New niches form on the sea floor
New genes lead to new bodies
Permian Extinction
90% of life disappeared, extensive flood basalts added CO2 to the atmosphere, leading to coal fires
High levels of SO2 lead to acid rain, oxygen in the ocean disappears and bacteria thrives
Impact Hypothesis
Extinction event caused by an asteroid - left high levels of iridium, shocked quartz, and leaolinite
Evolution
The change of alleles in a population over time
Aristotle
Life is perfect, there are no changes or variations - Scala naturae
George Buffon
Proposed that living things change through time
Catastrophism
Each boundary between strata correspond to a catastrophe
Hutton/Levy
Geologists, studied the rocks in the grand canyon, proposed that Earth's forces pushed the rock layers upward
Uniformitarianism
Processes stay the same over the course of Earth's history
John Baptiste Lamarck
Theory of acquired traits, heritable experience
Thomas Malthus
Economist, humans are born faster than they are dying, leading to overpopulation
Alfred Wallace
Darwin's mentor, came up with the theory of evolution by natural selection using biogeography
Charles Darwin
All organisms are descended from an ancestral species, proposed descent with modification (Galapagos tortoises, finches)
Tested via artificial selection with pigeons
Species diverge from common ancestor
Evidence of Evolution: Fossils
Fossil record, show history of life and how different groups of organisms change over time
When animals die, tissue decays, and hard parts are replaced with silica/pyrites
Evidence of Evolution: Relative/Absolute Dating
Relative= based on sediment layers Absolute = carbon dating (percentage of N14 compared to C14, as is broken down through beta decay)
Transitional Forms
Intermediate states between ancestral and current forms Ex: Fishapods, or Tiktaalik, explains land vertebrate, missing link between aquatic and land organisms
Evidence of Evolution: Biogeography
Species with a common ancestor are found in different geographic locations
Convergent Evolution
2 species with different lineages develop similar characteristics
Analogous Structures
Similar adaptive characteristics - species from different linages develop similar traits due to a shared environment Ex: birds and bats
Artificial Selection
Reduces genetic variation, can be harmful to species Ex: bulldogs
Homologous Structures
Similar structures with different functions Ex: a human hand v the flippers of marine mammals
Vestigial Structures
Have no apparent function in one species, is homologous in another Ex: hip bone in whales
Embryonic Development
More closely related species have similar embryonic development
Genetic Homology
Similarities in DNA sequences or amino acid sequences that are due to inheritance from a common ancestor.
Developmental Homology
seen in embryos of different species
Divergent Evolution:
Traits held by common ancestor evolves into different variations over time
Coevolution
Close interacting species exert selective pressures on one another, and they evolve together Ex: flowers and bees
Gene Pool
All of the alleles for every gene in a given population
Polymorphism
Presence of 2+ variants or traits for a given character
Hardy Weinberg Equation
p2 + 2pq + q2 = 1 p + q = 1
4 Mechanisms that shift allele frequencies
Natural Selection: increase in the frequency of alleles that contribute to reproductive success
Genetic Drift: causes allele frequency to change randomly
Gene flow: occurs when individuals leave a population and join another
Mutation: modifies allele frequencies
Hardy-Weinberg equilibrium
-No mutation -No gene flow -Random mating -Large populations -No natural/sexual selection
Genetic Variation
Relative frequency of alleles present in a particular population
Adaptations
Changes in population of living organisms that increase the ability to reproduce
Two categories of reproductive success
Adaptation - survive to reproductive age Reproductive traits - Traits that help organisms find mates
Fitness
The measure of reproductive success
Directional Selection
Average phenotype changes in one direction - favorable allele will approach a frequency of 1.0. Ends in purifying selection Ex: Cacti with more spines have greater reproductive success
Stabilizing Selection
Average value of a trait doesn't change, reduces extremes, frequencies approach 0.5 Ex: average birth weight of human babies
Disruptive Selection
Favors extreme phenotypes at both ends of the range, increases variation of a trait Ex: black bellied seed crackers develop large or short beaks depending on seed size
Speciation
Product of disruptive selection, formation of new species
Balancing Selection
Maintains variation, balance among alleles, favors heterozygotes Ex: sickle cell anemia
Balanced polymorphism
2+ alleles are kept in balance, maintained in population over the course of a generation
Sexual selection
Form of natural selection directed at certain traits of sexually reproducing species
Intrasexual selection
Occurs between members of the same sex, results in competition for mating opportunities and territory
Intersexual selection
Occurs between opposite members, results in female choice and showy characteristics
Fundamental Asymmetry of Sex
Females invest more in offspring: Female fitness is limited by ability to gain resources Male fitness is limited by number of mates
Bateman-Trivers Theory
When certain alleles increase male attractiveness to females, the frequency of those alleles will increase
Female Choice
Females prefer healthy males - In birds, their brightly colored feathers are the result of carotenoids, which also protect tissue and help to improve the immune system
Sexual dimorphism
any trait that differs between males and females
Genetic Drift
A change in the allele frequency of a population as a result of chance events rather than natural selection, frequency of allele is 0 or 100
Genetic Drift - Bottleneck
population size dramatically decreases for at least 1 generation, then rebuilds, surviving members have different allele frequencies from the original population Ex: the American bison after being hunted to near-extinction
Genetic Drift - Founder Effect
Small group of individuals separate from larger population, form a new colony
Neutral Theory of Evolution
Do not affect phenotype, most genetic variation is due to the accumulation of neutral mutations that have attained high frequency
Nonrandom mating - Assortative Mating
Individuals with similar phenotypes are more likely to mate
Nonrandom mating - disassortative mating
Dissimilar phenotypes mate, resulting in heterozygosity
Mutations
Restore genetic diversity, random with respect to fitness, can change frequency of allele over time