College Bio 2 Unit 1

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Macroevolution

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Macroevolution

Evolutionary changes the create new species

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Microevolution

Evolution as it relates to allele frequencies

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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

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Biological Species Concept

Group of individuals whose members have the potential to interbreed with one another and produce fertile offspring

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Evolutionary Lineage Concept

New species are the result of speciation from immediate ancestral species - Individual

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ecological species concept

Each species occupy an ecological niche with a unique set of habitat resources, species also influences ecosystem

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General Species Concept

Each species is a population of individually evolving lineages

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Phylogenetic Species Concept

Monophyletic groups identified by synapomorphies

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Morpholocal Species Concept

Evolutionary independent lineages vary by size, shape, and other features

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Reproductive isolation

Mechanism that prevents interbreeding between species

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Interspecies hybrid

When species produce hybrid

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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

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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

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2 explanations for speciation

  1. abrupt events that cause chromosome number to change

  2. consequence of adaptation to different ecological niches

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Allopatric speciation

Members of a species become geographically separated Dispersal: the species move Vicariance: event splits population

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sympatric speciation

Occurs when members of a species that are within the same range diverge into 2+ species with no physical barriers

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mechanisms of sympatric speciation

Polyploidy, adaption to local environment, sexual selection

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Taxonomy

Science of describing, naming, and classifying living/extinct organisms

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Systematics

the study of biodiversity and the evolutionary relationships among organisms

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Binomial Nomenclature

Latin names - Genus species (italicize) Established by international organizations

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Phylogeny

Evolutionary history of a species or group of species.

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Anagenesis

Single species evolves into a different species over time

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Cladogenesis

single species diverges into 2+ species

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Clades

Group of species (taxon) consisting of an ancestor and descendants

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Monophyletic Group:

group that consists of a single ancestral species and all its descendants; includes individual clades

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Paraphyletic

Not all descendants are included in the grouping

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Polyphyletic

Specific traits evolve separately in different species (homoplasies /convergent evolution)

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Synapomorphy

Trait found in 2+ taxa that are present in recent common ancestors but missing in more distant ones

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Shared Primitive Character

Shared by 2+ taxa and is inherited from an ancestor older than the last known common ancestor

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Shared Derived Character

Shared by 2+ taxa, originated from the most common ancestor

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Outgroup

The most primitive ancestor, diverged before the rest of the species

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Parsimony

Simplest way to organize characters and states

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Neutral Theory of Evolution

Favorable mutations are rare, detrimental mutations are quickly eliminated, neutral mutations occur at a constant rate

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Horizontal Gene Transfer

Any process in which an organism incorporates genetic material from another organism without producing offspring

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Vertical Gene Transfer

Sexual reproduction, changes in groups due to descent from common ancestor

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Habitat Bias

Fossils are only found in areas where sediment is distributed

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Tissue Bias

Hard-bodied organisms are more likely to be preserved

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Temporal Bias

Recent organisms are more common than ancient fossils

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Abundance Bias

Common, widespread, long lasting species are more likely to be fossilized

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Life's Timeline

  1. Precambrian - unicellular organisms, no oxygen

  2. Panerozoic Era - Paleozoic: most lineages Mesozoic: Dinosaurs, gymnosperms Cenozoic: mammals, angiosperms

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Gymnosperm

Cone bearing plant

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Angiosperm

Flowering plant

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Adaptive Radiation

A single lineage produces many descendants with a wide range of adaptive forms

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HOX Genes

series of genes that controls the differentiation of cells and tissues in an embryo

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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

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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

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Impact Hypothesis

Extinction event caused by an asteroid - left high levels of iridium, shocked quartz, and leaolinite

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Evolution

The change of alleles in a population over time

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Aristotle

Life is perfect, there are no changes or variations - Scala naturae

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George Buffon

Proposed that living things change through time

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Catastrophism

Each boundary between strata correspond to a catastrophe

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Hutton/Levy

Geologists, studied the rocks in the grand canyon, proposed that Earth's forces pushed the rock layers upward

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Uniformitarianism

Processes stay the same over the course of Earth's history

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John Baptiste Lamarck

Theory of acquired traits, heritable experience

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Thomas Malthus

Economist, humans are born faster than they are dying, leading to overpopulation

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Alfred Wallace

Darwin's mentor, came up with the theory of evolution by natural selection using biogeography

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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

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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

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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)

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Transitional Forms

Intermediate states between ancestral and current forms Ex: Fishapods, or Tiktaalik, explains land vertebrate, missing link between aquatic and land organisms

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Evidence of Evolution: Biogeography

Species with a common ancestor are found in different geographic locations

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Convergent Evolution

2 species with different lineages develop similar characteristics

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Analogous Structures

Similar adaptive characteristics - species from different linages develop similar traits due to a shared environment Ex: birds and bats

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Artificial Selection

Reduces genetic variation, can be harmful to species Ex: bulldogs

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Homologous Structures

Similar structures with different functions Ex: a human hand v the flippers of marine mammals

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Vestigial Structures

Have no apparent function in one species, is homologous in another Ex: hip bone in whales

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Embryonic Development

More closely related species have similar embryonic development

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Genetic Homology

Similarities in DNA sequences or amino acid sequences that are due to inheritance from a common ancestor.

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Developmental Homology

seen in embryos of different species

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Divergent Evolution:

Traits held by common ancestor evolves into different variations over time

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Coevolution

Close interacting species exert selective pressures on one another, and they evolve together Ex: flowers and bees

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Gene Pool

All of the alleles for every gene in a given population

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Polymorphism

Presence of 2+ variants or traits for a given character

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Hardy Weinberg Equation

p2 + 2pq + q2 = 1 p + q = 1

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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

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Hardy-Weinberg equilibrium

-No mutation -No gene flow -Random mating -Large populations -No natural/sexual selection

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Genetic Variation

Relative frequency of alleles present in a particular population

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Adaptations

Changes in population of living organisms that increase the ability to reproduce

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Two categories of reproductive success

Adaptation - survive to reproductive age Reproductive traits - Traits that help organisms find mates

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Fitness

The measure of reproductive success

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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

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Stabilizing Selection

Average value of a trait doesn't change, reduces extremes, frequencies approach 0.5 Ex: average birth weight of human babies

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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

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Speciation

Product of disruptive selection, formation of new species

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