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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