Biological basis of life and Mendel
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Take home quizHow it works-Friday, June 30 at 5pm the quiz will be emailed and available on the course website
DUE DATE: Sunday, July 2 at midnight-students must email their answers (in the email body or as an attachment) before the date above
Format20 questions total - 15 multiple choice and 5 short answer (must answer all five)
ContentChapters 3 and 4
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Modern Evolutionary Theory5. Natural selection - acts on the variation produced and distributed by 1-4-Directs change in the allele frequencies of a population relative to environmental factors
Microevolution - small genetic changes that occur w/in a species
Macroevolution - large-scale changes that occur in populations over many generations-result in speciation
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Current theory of natural selectionNatural selection provides directional change in allele frequencies relative to specific environmental factors
If the environment changes, then selective pressures change too
If there's long-term directional change, then allele frequencies will shift gradually each generation
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Ch 5 Macroevolution
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Taxonomy and Species ConceptsBiological Species Concept (BSC) - isolated populations gradually change over time and become distinct taxonomic groups-Taxonomic grouping heavily influenced by genetic drift and natural selection
Kingdom: AnimaliaPhylum: Chordata
Class: Mammalia Order: Primates
Family: HominidaeGenus: Homo
Species: sapiens
We are Homo sapiens (also H. sapiens for short).6
Macroevolution - synonymous with speciation
Focus: large-scale evolutionary processes
Synthesize our understanding of modes of evolutionary change, geologic time, and taxonomic classification
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Macroevolution aka speciation
HomologiesHomologies - Structures shared by species due to common descent
E.g., Humans, birds, and bats: same basic bone structure but modified
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AnalogiesAnalogies - similar structures arise in other lineages in response to different functional demands
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Classification schemes: Systematics and Cladistics
Evolutionary Systematics: -use homologous traits to trace evolutionary relationships over time
-focus: identify common ancestry between groups
Cladistics:-uses homologous traits to separate organisms into taxonomic groups
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Similar: Both use homologies to trace evolutionary relationships
Differ: Systematics uses homologies to trace common ancestry over timevs.
Cladistics uses homologies to separate organisms into groups
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Classification schemes: Systematics and Cladistics
Overview Slide (will be on site)Mendelian = discrete categories of variationPolygenic = continuous
Both -determined by Mendelian principles at specific loci-Dominance and recessiveness still a factor
Evolution now defined in two stages
1. Variation - inherited differences among organisms is produced and redistributed through various processes2. Natural selection acts on variation resulting in differential reproductive success (85p).-Both mutations and natural selection contribute to evolution
Current definition of Evolution - Change in allele frequency from one generation to the next.
Allele frequencies = indicators of a group/population's genetic composition -Described as proportions or percentages of a total
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Cladistics more explicit and rigorous Ancestral traits - similarities shared by many distantly-related groups that are inherited from a remote ancestor
E.g., Grasping hand in humans-Mice, bears, and lizards all have lungs-Remember the similar bone structures between whales, bats, and humans?
Derived traits - reflect specific evolutionary lineages-modified traits from last common ancestor unique to a given group
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Adaptive radiation and ecological niche
Adaptive radiation - rapid expansion and diversification of new life forms into open ecological niches.
Speciation results in as many variations as allowed by
(1) its adaptive potential; and
(2) adaptive opportunities
E.g., reptilian egg evolution spawned an adaptive radiation event by opening new adaptive niches on land.
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Processes of MacroevolutionAdaptive Radiation - rapid expansion and diversification of organisms into other ecological niches-Individuals of a species become diverse due to the differing environmental factors associated with a given ecosystem
Generalized and Specialized Characteristics - adaptive radiation results in generalized characteristics *Generalized traits - adapted for multiple functions*Specialized species have more adaptive potential
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Identifying paleospecies-grouped by the clusters of derived traits-use living species as proxy
Concerns-variation spatially (over space) and temporally (through time) -fossils separated by millions of years.-expanded time frame = more dynamic image of species morphology-blurs taxonomic boundaries-Still a disputed process because of the concern with homoplasy
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Variation in the fossil recordCladistics and the fossil recordIndividual variation - the variation seen in an individual's phenotype due to recombination
Age change variation - some fossil forms have deciduous teeth (20) while others are matured to having permanent teeth (32)
Sexual dimorphism - physical characteristics differ between males and females
Remember these variables to avoid errors.
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Intraspecific - variation = individual, age, sex differences within species-If variation in fossils compares to related extant organisms, then disignate single species
Interspecific - such variation represents differences between species
Splitters - speciation occurred more often
Lumpers - more likely intraspecific variability
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Types of variation continued
Fossil Genera-a genus has at least 2 species that are distinct from each otherExtinct genera -share adaptative zone.
Adaptive zone = broader than ecological niche or econiche which are used to identify individual species.
Ecological niche = position of a species in a physical/environmental context-diet, terrain, vegetation, predation, interaction with other species, etc.
Anthro e.g., Fossilized primate teeth
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Fossils preservationMineralization - hard tissues are impregnated with other minerals and eventually solidify
Insects encased in tree sap - No oxygen = well preserved insects (we can extract DNA from them!).
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Fossils preservationImpressions of leafs/things - clay hardens into stoneAnthr e.g., 47 mya well preserved primate skeleton with soft-body imprint and fossilized remains associated with the digestive tract (Franzen et al 2009).
Footprints from dinosaurs and early Hominins
Teeth: hardest, most durable portion of vertebrate skeleton and so most likely to mineralize
Most available fossil data is inferred from teeth - including primates
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Fossils preservation-depends on how and where individual diedMarine fossils are more frequent than land fossil organisms
-circle of life leaves nothing left of the individual to fossilize-Need rapid sedimentation to cover up the individual or volcanic ash
Taphonomy: studies how fossils are preserved - look at bone preservation and sedimentary processes
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Vertebrate Evolutionary historyGeographical changes in Paleozoic and Mesozoic influenced vertebrate evolution
Continental drift - continents move like sliding plates on the Earth's surface (still happening today - slow process)-Large landmasses shifted dramatically throughout geologic time-Induces volcanic activity (Pacific Rim); mountain building (Himalayas); earthquakes
Pangea - singular land mass during the late Paleozoic -large chunks split to the north and south in the early Mesozoic ~65 mya
Isolation - isolated by oceans => distributed mammals and other land vertebrates
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Vertebrate evolution-spans Paleozoic, Mesozoic, and the Cenozoic eras
Fish ~500 mya in the Paleozoic (earliest out of reptiles, mammals, and birds)
Continental drift = continents move like sliding plates on the Earth's surface-Large land masses move in geologic time
Pangea - late Paleozoic singular land mass -Large chunks split to the north and south in the early Mesozoic ~65 my
Mammal-like reptiles ~250 mya - diversify in Late Paleozoic
Reptiles/dinosaurs ~252 mya = most dominant land vertebrates cf Mesozoic -expanded into a wide array of econiches
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Cretaceous-Tertiary Mass Extinction~66 mya = Cretaceous-Tertiary or K-T boundary
-Large asteroid impacted the Earth caused dramatic changes in the global environmentEx: Plants and plankton could not photosynthesis
75% of plants and animals went extinct
-Dinosaurs died off = empty ecological niches
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~75 mya diverged -became dominant land-living vertebrates-rapid growth starting the Cenozoic Era
Major Mammal Groups
*Monotremes - egg-laying = most ancestral
*Marsupials - pouched = immature young complete development in external pouch
*Placental - long development period in utero and placental tissue specialized to provide nourishment
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Mammalian Evolution
Distinctive mammalian featuresLarge brains - complex information processingE.g., cerebrum enlarged - trend continued to increase in primates
Placental - give live birth
Heterodont - ancestral mammalian teeth patterns -generalized
Endothermic - maintained constant internal temperature thru metabolic activities
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