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Leaf lamina (blade) petiole: simple vs. compound
- simple: one leaf coming off of petiole
- compound: multuple leaflets coming off of one petiole
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Leaf lamina (blade) petiole: palmate vs. pinnately compound
- simple: one leaf from one petiole
- palmate: 5 leaflets from one petiole, usually radial
- trifolate: 3 leaves from one petiole
- once pinnately compound: petiole-->rachi
- bipinnately compound: petiole-->petiole-->rachi
- tripinnately compound: petiole-->petiole-->petiole-->rachi
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Leaf attachment
- Alternate
- Opposite (distichous)-- all in the same plane
- Opposite (decussate)-- rotate each pair 90 degrees from the one before
- Whorled
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Leaf shape
- Elliptic- widest part in middle of leaf
- Ovate- widest part near bottom of leaf
- Obovate- widest part near top of leaf
- Oblong- two equal planes near top and bottom of leaf
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Leaf bases
- cuneate- pointy
- convex- pointy and rounded
- rounded- half circle
- decurrent- swoops in at very bottom of base (similar to cuneate)
- cordate- looks like the top of a heart
- truncate- looks like it was cut off abruptly
- concave- similar to decurrent but wider
- sagittate- looks like the tails of an arrowhead
- lobate- similar to cordate but much globbier
- hastate- looks like a sombrero
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Types of leaf apices
- straight- narrow like a knife
- convex- large and convex with a slightly pointed tip
- rounded- half circle
- truncate- similar to convex, but more of a point
- acuminate- drip tip
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Lobing
- unlobed- no lobes
- palmately lobed- lobing from one central point
- pinnately lobed- lobing from midrib all down the leaf
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Leaf venation, primary
- pinnate- straight down the middle
- basal- all primary veins connect at very base
- suprabasal- all primary veins connect just above the base, and one big vein connects to the base
- acrodromous- primary veins go from base to tip and only connect at base and tip (follow shape of leaf)
- paralleldromous- veins are parallel to one another and all start and end at same place (grass)
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Leaf venation, secondary
- craspedodromous- straight secondary veins
- brochidodromous- curved secondary veins
- festooned brochidodromous- secondary veins loop back on themselves
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Relationship between leaf size, leaf margin, and climate
large, entire margin leaves decrease with decreasing lattitude
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Physiologically dry environments
dominated by entire-margined leaves
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Climate deterioration through the Tertiary
stepwise decline of temperatures
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Nearest Living Relative Method (NLR)
- - assumes fossils are closely related to modern forms and that recent taxa have the same climate requirements
- - strengths: relatively easy; good for recent floras where taxonomy is known; rapid results; can use fruits, seeds, and floras
- - weaknesses: easy to misidentify specimens; method incorporated many assumptions; cant use on earlier flora
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Leaf Margin Analysis (LMA)
- - uses only leaf margin to infer Mean Annual Temperature
- - strengths: taxon-free; don't need to ID leaves; single measurement is easy to score; agrees with estimates from other sources
- - weaknesses: measures fewer aspects of paleoclimate
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CLAMP
- - a method of obtaining ancient climate information from the architecture of fossil leaves of woody dicot flowering plants
- -strengths: don't need to identify fossils; infers many paleoclimate paameters
- - weaknesses: time consuming; lower mean than with LMA; need a minimum of 20 to 30 leaves to work properly
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Empirical studies and paleostudies
selective transport, preservation of leaves show forest canopy, the leaf litter, then transported leaves even less
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What are the 7 major biomes in North America?
- Tundra
- Coniferous Forest
- Deciduous Forest
- Grassland
- Desert
- Shrubland, woodland, savanna
- Tropical
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Tundra
- - treeless; mostly shrubs and herbs
- - polar (tundra) and high altitude (alpine)
- - short growing season, cold and windy
- - permafrost
- - mostly perennials
- - tiny leaves
- - vegetative reproduction and selfing
- - low biodiversity
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Coniferous forest
- - physiological aridity
- - needle leaves, thick cuticle, sunken stomata
- - tannins, reduce water loss
- - Boreal is frozen, Gulf Coast is sandy
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Deciduous forest
- - 11% of continent
- - enough rain for hardwoods
- - most diverse and species rich in the US
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Grasslands
- - 22% of land mass
- - seasonal rainfall and extreme temperatures
- - too dry for deciduous
- - fire ecology is important
- - legumes, composites, grasses
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Shrubland, woodland, savanna, chapparal
- - 1% of north america
- - dry lowland areas resulting from uplift of western mountains
- - shrubland/chapparal has thickets of small trees and shrubs
- - woodland is open, tree canopies dont touch
- - savannas have less than 30% trees, grass is dense
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Deserts
- - Chihuahuan desert in Mexico; high plateau covered by stony areas and sandy soil; many mountains and mesas
- - Great Basin desert in ID NE OR and UT; covered by sand, gravel, and clay; many mountain ranges, basins, and salt flats
- - Sonoran desert in AZ, CA and mexico; covered by sand, soil, and gravely pavement; gets more rain than any other N. american desert
- - Mohave desert in AZ, CA, NE; covered by sandy soil, gravely pavement, and salt flats;
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Tropical
found in southern FL, swamplands
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What are some of the major land forms in eastern and western north america that resulted from the Pleistocene glaciations?
- 1. Great lakes
- 2. Diverted Rivers
- 3. Great Salt Lake and Death Valley
- 4. Scablands
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How did the Teays River contribute to the formation of the Ohio River?
Teays was originally NW flowing, glaciers forced the new direction W creating the Ohio River.
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In the West, what current day lake resulted from Lake Bonneville?
The Great Salt Lake
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Where and how did Lake Missoula create the Channeled Scablands? Why did people not believe Bretz’s hypothesis about this geologic event?
This glacial lake was released and flooded the areas of the basalt plateaus and scoured them into long parallel hills and valleys that became the Channeled Scablands
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Generally how did the distribution of biome types in the Pleistocene differ from today?
The Pleistocene had boreal and deciduous biomes. They covered much more of the US than they do now.
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What is a multiproxy study and what are its advantages?
A multiproxy study looks at several sets of factors that serve as stand-ins or “proxies” in order to understand a large scale question.
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What has been the conventional wisdom about the relationship between Pleistocene deglaciation, climate and vegetation change, human migration and the loss of the giant megafauna in North America? What do
Gill et al. say?
There is a complex interaction, not just a single cause and effect.
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