Ch 5 Macroevolution

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Announcements and summary*April 19 = Midterm and Essay 1 due and MUST bring in hard copy of essay

Midterm - 3x5 flash card

Extra credit study-guide and outline on course website

Today: fossils, vertebrates and mammals

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Species ConceptsBiological Species Concept - BSC - Species boundaries form due to reproductive isolation-New species form due to some type of isolation-The accumulated effects of drift and natural selection are emphasized

Other concepts - Ecological, Morphological, Phylogenetic, etc.

Speciation - Most basic process of macroevolution - process through which new species emerge from earlier species

Various types of isolation - geographical, behavioral, reproductive

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Macroevolution - synonymous with speciation

Focuses on large-scale evolutionary processes

Synthesize our understanding of modes of evolutionary change, geologic time, and taxonomic classification

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Unit 3: Macroevolution and primates

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).5

Similar: use homologies to trace evolutionary relationships

Differ: Systematics - uses homologies to trace common ancestry over timevs.

Cladistics - uses homologies identify different evolutionary lineages

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Classification schemes: Systematics and Cladistics

Cladistics more explicit and rigorous Ancestral traits - similarities shared by many distantly-related groups that are inherited from a remote ancestorE.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

CLADISTICS uses DERIVED TRAITS7

Cladistics more explicit and rigorous Shared Derived traits - shared traits between two life-forms that are the most useful in constructing cladogramsE.g., feathers in the proposed relationship between some (theropod) dinosaurs and birds is an example.

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Adaptive radiation and ecological niche

Adaptive radiation - rapid expansion and diversification of new life forms into open ecological niches.

Ecological niche - Micro-habitat in a shared environment to which populations adapt.-diet, terrain, vegetation, predation, interaction with other species, etc.

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Generalized and Specialized TraitsGeneralized - adapted for many functions-retaining ancestral traits-give flexible evolutionary springboard for rapid diversification which leads to:

Specialized - modification to narrow ecological niche-derivedE.g., Hominin feet evolution

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Fossils and fossilization processesFossils - traces of ancient organisms manifested through various physical processes

-Most fossil evidence = pieces of shells, bone, teeth - basically the hard parts of an organism

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Fossils preservationTaphonomy - studies the processes preserving fossils are preserved

Teeth - hardest, most durable portion of vertebrate skeleton and so they're most likely to mineralize

Preservation depends on how and where the individual died

-Need rapid sedimentation to cover up the individual or volcanic ash

Land - the circle of life makes fossilization rare

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Fossils and fossilization processesMineralization - After an organism dies the hard tissues slowly replaced by other minerals, then solidify

Insects are trapped in tree sap - hardens over time. The lack of oxygen results in very well preserved insects (we can extract DNA from them!).

Impressions of leafs/things left in clay which 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, too, are preserved

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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.-blurs taxonomic boundaries

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Different types of variation in morphology

Individual 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

Macroevolution - the long conGeographical changes in Paleozoic and Mesozoic influenced vertebrate evolution

Continental drift = continents move like sliding plates on the Earth's surface-Large landmasses shifted dramatically throughout geologic time-Induces volcanic activity (Pacific Rim); mountain building (Himalayas); earthquakes

Pangea - late Paleozoic singular land mass but large chunks split to the north and south in the early Mesozoic ~65 mya-isolated by oceans => distributed mammals and other land vertebrates

-Continental drift is still happening today - slow process (uniformitarianism)

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Geological Time Scale

Vertebrate evolution-spans Paleozoic, Mesozoic, and the Cenozoic eras

Fish ~500 mya in the Paleozoic (earliest out of reptiles, mammals, and birds)

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 SO 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