Ch 5 Macroevolution 1 Announcements and summary * April 19 = - - PowerPoint PPT Presentation

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 Concepts

Biological 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 Concepts

Biological 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: Animalia Phylum: Chordata Class: Mammalia Order: Primates Family: Hominidae Genus: Homo Species: sapiens We are Homo sapiens (also H. sapiens for short).

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Similar: use homologies to trace evolutionary relationships Differ: Systematics - uses homologies to trace common ancestry over time vs. 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 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 CLADISTICS uses DERIVED TRAITS

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Cladistics more explicit and rigorous

Shared Derived traits - shared traits between two life-forms that are the most useful in constructing cladograms E.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 Traits

Generalized - adapted for many functions

• retaining ancestral traits
• give flexible evolutionary springboard for rapid

diversification which leads to: Specialized - modification to narrow ecological niche

• derived

E.g., Hominin feet evolution

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Fossils and fossilization processes

Fossils - 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 preservation

Taphonomy - 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 processes

Mineralization - 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 stone

Anthr 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 con

Geographical 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 environment Ex: 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