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178 Cards in this Set

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What are three ways that rocks are formed?
-Igneous rocks form when a hot mix of liquid rock called magma cools
-Sedimentary rocks: form from material deposited in lakes or oceans. Layers of sediments accumulate to form rocks and wear away over time
-Metamorphic Rocks: formed when igneous or sedimentary rocks are heated or put under pressure in the earth
What are four ways parent material may be broken down or added to soil?
-Mechanical weathering by water, wind and freezing
-chemical weathering: esp by rainwater with Co2 that dissolves rock
-may be aded by rivers or glaciers: till
-may be added by winds: loess
How does chemical weathering of parent material occur
can be by rainwater with disolved Co2 which becomes carbonic acid that dissolves the rock
What is the difference between till and loess
Till: parent material is added by rivers or glaciers
Loess: parent material is added by winds
What role do biological growth and decomposition play in soil formation
-contribute to breakdown of parent material
-accumulation of organic material in soil called humus
What role does climate play in soil formation?
Govern:
-the rate of weathering of parent material
-decomp of material and organic matter
-leaching and movement of minerals and organic matter
-accumulation of soil parent material
-dev of soil layer
-nature of biotic interactions w/in soil
What role do biotic factors play in soil formation?
-animals, bacteria, fungi contribute
-veg is responsible for organic material in the soil and the color of the surface layer and the nutrient content
How does topography affect soil ecology?
-amout of water in the soil (more water runs off and less enters soil at steep slopes)
-low or flat lan: extra water enters soil and subsoil is wet and gray
-influences rate of erosion and downhill transport of soil material
How do young and old soils compare in terms of their fertility and why??
Young: not so deeply weathered and are more fertile becaue they haven't been expoesd to the leaching process for a long time
-Old tend to be infertile cuz of long time leaching without replacement of fresh
What is the soil horizon O (Oi and Oa)
surface layer resting on a mineral layer
-composed of fresh or partially decomposed organic material that hasn't been mixed with mineral soil
-home to most soil organisms
-Oi: litter layers
-Oa: humus layer: has partially decomp organic material
What is the soil horizon A
Upper layer of mineral soil char by:
-accumulation of organic material: humus
-loss of some clay, inorganic, and soluble material by eluviation or leaching
-chem and structure are altered by downward mvment of mat thru weathering or leaching
-minerals are disolved by water (mobilized) so plant roots are concentrated here
What is the soil horizon B
zone of extensive illuviation
-deposit of material (silicates, clay, iron, Al, humus) that is leached out of A horizon
What is the soil horizon C
-primarily weakly weathered material that resembles parent rock
-some weathering still takes place
-very little effected by soil forming processes
What is the soil horizon R
unweathered parent material (bedrock)
What is the difference between eluviation and illuviation
-Eluviation: The sideways or downward movement of dissolved or suspended material within soil caused by rainfall
-Illuviation: accumulation of dissolved or suspended soil materials in one area or horizon as a result of eluviation from another
In what soil horizon does eluviation happen
A horizon
In what soil horizon does illuviation happen
B horizon from A horizon
What kind of info can be gained from soil color
-Dark brown colors: indicates organic matter
-red and yellow: presence of iron oxides and can conclude these are good for drainage and aeration
How is soil color normally determined
Munsell color charts
Characterize gravel in soil texture
Particles larger than 2mm
-not considered part of the fine fraction of soil
what is texture of sand
Ranges from 0.05-2.0mm and is seen and feels gritty to the touch
What is texture of silt
particles 0.002-0.05mm which can be scarcely seen by the human eye
What is texture of clay
so small they can't be seen by the naked eye
-feels and ooks like flour
-clay controls plasticity of soil and ability to change/retain shape when press applied
-can control exchange of ions b/w soil particles and soil solns
What are two important properties of the soil controlled by clays
-plasticity
-changing shape when pressure applied
-retaining shape when pressure gone
-exchange of ions b/w soil particles and soil solns
How does soil depth differ from one place to another
depends on the slope, weathering, parent material, and veg
-under grasslands: sev meters deep
-under forests: shallow
-deserts: very shallow
-bottom of slopes, ground level, and on alluvial (outwash): deep
-ridgetops, steep slopes: shallow w/ bedrock close to surface: poor for plant growth
What is field capacity and permanent wilting point and how do they relate to water capacity
Field cap: max amt of water the soil can hold against gravity
-doesn't rep water available to plants
Perm wilting pt: when soil dries out to a pt when plants are unable to absorb enough h2o to replace what was lost by transpir.
Available water cap: water retained b/w field cap and the permanent wilting pt
What are 3 factors that play a role in determining soil moisture regimes
-ability of soil to retain moisture against drainage
-texture: max soil moisture holding is in med. textured soils. Water percolates thru course and fine holds water so not avail to plants
-amt of organic matter
-topographic position: can range along slope
What type of soil marks the beg of wetlands in respect to soil drainage class??
somewhat poorly drained soils
What are micelles and what role do they play in soil chem
-particles and complexes of clay and humus which make ions limited in their mobility
What is the structure of a clay molecule
contail Al, silica, oxygen in a tetrahedral fashion
-can make isomorphous substitutions
What are isomorphous substitutions
They substitued one element in their arrangement w/o changing their structure
-ex: aluminum can be sub for silica
-changes the charge of the molecule: this makes it neg
What type of cmpds do clays attract and why?
Surfaces tend to have neg charges that must be balanced by pos
-attracts cations, water, and organic substances
what does the cation exchange cap of the soil represent and how does it prevent leaching of soil nut
total number of neg charged exchange sites on clay and humus particles that attract cations
-neg charges enable soil to prevent downward mvmt (leaching) of + charged nutrient cations
-some ions cling more than others
What does percent base sat represent?
percentage of sites ocupied by ions other than H
How are H ions added to the soil
-by rainwater (carbonic acid)
-by acids from organic matter, metabolic acids from microorg and plants: makes soil acidic
Why do acidic soils have a low percent base saturation
-acidic soils (with lots of H's) have low % base sat: high number of exchangeable H ions
-
What is the relationship b/w soil acidity and soil fertility and aluminum toxicity
soil acidity inc, fertility dec because fewer cation exchange sites left to hold on to nutrients
-high soil acidity can lead to AL tox which can kill plants
Assuming they are not saline or do not contain toxic heavy metals, what types of soils are most fertile with respect to their cation exchange cap and precent base sat
high cation exchange cap and high percent base sat
what are 4 char of soil that make it a good place to live
-stable struct and chem
-underground climate is less variable
-atmosphere stays pretty much sat w/ water
-don't have to deal w/ temp, wind, evap, light, and dryness
What are some prob of living w/in the soil
-movement
-must depend on size of pore spaces cuz these deter avail of living space, humid, and oxygen
-only a part of upper layer is suitable for living space
What is the imp of water to org w/in soil
-many org live w/in a thin film of water around the soil particles
-after heavy rains, may flood this pore space and org dies
-some org just require high humidities and may die if this isn't there
what are 4 char of soil that make it a good place to live
-stable struct and chem
-underground climate is less variable
-atmosphere stays pretty much sat w/ water
-don't have to deal w/ temp, wind, evap, light, and dryness
What types of microorg are found in the soil
bacteria, fungi, protozoans, and nematodes
What are some prob of living w/in the soil
-movement
-must depend on size of pore spaces cuz these deter avail of living space, humid, and oxygen
-only a part of upper layer is suitable for living space
What are the most abundant arthropods living w/in the soil pore spaces
-mites which are tiny arachnids
-and springtails (wingless hexapods)
What is the imp of water to org w/in soil
-many org live w/in a thin film of water around the soil particles
-after heavy rains, may flood this pore space and org dies
-some org just require high humidities and may die if this isn't there
What role to millipedes play in soil ecology?
consume partially decomposed leaves to obtain nourishment from fungi growing on the litter
-mechanical breakdown of the litter which makes it more vulnerable to attach by microbial decomp
What types of microorg are found in the soil
bacteria, fungi, protozoans, and nematodes
What role do snails and slugs play in soil ecology
-possesss enzymes to break down cellulose and other plant polysacc
What are the most abundant arthropods living w/in the soil pore spaces
-mites which are tiny arachnids
-and springtails (wingless hexapods)
What types of human activity disturb natural patterns of soil ecology?
soils get buried under fill, overturned, and moved by excavation, surface mining, and road construction
-upper horizones get mixed with other stuff and compacted: reduces sizes of pores
-trampling on lawns and stuff does compacting
What role to millipedes play in soil ecology?
consume partially decomposed leaves to obtain nourishment from fungi growing on the litter
-mechanical breakdown of the litter which makes it more vulnerable to attach by microbial decomp
What types of human activities result in soil compaction and what are the effects of such compaction on soil ecology?
heavy machinery, plowing, footpaths, riding trails, off-the-road vehicle use
-soil can't absorb water
-so water flows across the surface
-soil erosion occurs which carries away soil particles by running water
What role do snails and slugs play in soil ecology
-possesss enzymes to break down cellulose and other plant polysacc
How is topsoil removed and what are the consequences of this removal?
-gets exposed by agriculture, construction, and road building
-topsoil is easily removed by wind and water faster than its formed
-cause prob if topsoil ends up in rivers, lakes, ponds, or reservoirs when it fills them with sedmients
-exposes less stable less fertile layers to further erosion
What types of human activity disturb natural patterns of soil ecology?
soils get buried under fill, overturned, and moved by excavation, surface mining, and road construction
-upper horizones get mixed with other stuff and compacted: reduces sizes of pores
-trampling on lawns and stuff does compacting
What types of human activities result in soil compaction and what are the effects of such compaction on soil ecology?
heavy machinery, plowing, footpaths, riding trails, off-the-road vehicle use
-soil can't absorb water
-so water flows across the surface
-soil erosion occurs which carries away soil particles by running water
How is topsoil removed and what are the consequences of this removal?
-gets exposed by agriculture, construction, and road building
-topsoil is easily removed by wind and water faster than its formed
-cause prob if topsoil ends up in rivers, lakes, ponds, or reservoirs when it fills them with sedmients
-exposes less stable less fertile layers to further erosion
What soil problem char the "dust bowl" of the 1930s ini the midwest
top soil is picked up by wind and carried dust clouds that can travle for miles
What is the principle role of the soil conservation service
prevent soil mismanagement
What kinds of soil mismanagement problems continue to plague the us in spite of efforts by the soil conservation service
top soil are being lost be erosion or poisoned by pollutants
What is the climate in Arctic and alpine tundra?
cold, dry, short growing season
What is cryoplanation and how is it imp to the dev of tundra landforms?
frost action that molds the arctic tundra
-wears it down by alternate freezing and thawing of the surface layers of the soil
-makes frost hummocks: small earth mounds
-makes stone polygons
What is permafrost and how does it affect life in the arctic tundra?
beneeath surface layers of soil
-forms and impenetrable barrier to drainage and plant roots
-is impervious to water so forces all water to move above it
What are solufluction terraces and how do they form?
On hillsides, supersat soils may creep downward over underlying permafrost
-this morms solufluction (SOIL FLOWING) terraces
Why is the arctic tundra a fragile biome that is slow to heal from human-caused damage?
Slow rate of plant growth and slow rate of decomp
List some of the herbivores found in arctic tundra?
-muskox, caribou, arctic hares, lemmings
What are some carnivores found in the arctic tundra biome?
Snowy owls and ______
What are 3 ways the alpine tundra differs from the arctic tundra
-alpine doesn't have permafrost
-alpine plants req shorter periods of daylight
-propagate by seed rather than vegetavily
What are some mammals found in the alpine tundra in the western US
marmots, pikas, mountain goats
-big horn sheep and elk
What is Krummholz and where is it found??
transition zone b/w forest and tundra
-called (crooked wood) marks the edge of the tree line
-has shunted and gnarled trees and are hard to walk thru but can be walked upon
What is the muskeg and where is it found
grassy flooded bogs
-found in an extensive region of spruce, pine, fir, larch, and hemlock trees
What are the plants of the boreal forest?
spruce, pine, fir, larch, and hemlock trees
-have continuous stands of coniferous trees and moss with an understory of low shrubs
-on distubed sites: aspens, poplars and birches (successional trees)
What are some mammals found in the boreal forest?
elk, moose, wolverine, timber wolf, lynx
What kinds of trees dominate the higher and lower elevations of the montane coniferous forests of canada and the US?
higher: spruces and firs
Lower: ponderosa pines
What is the temperate rain forest and where is it found in N america
parallels the pacific coast from alaska to CA
-has some of worlds tallest trees: sitka spruce, western hemlock, redwoods
What is the Pinon-juniper woodlands of weatern N america
extensive stands of pinon pine and junifer
-where climate is too dry for montane coniferous forests
-open growth of small trees and well developed understory of grass and shrubs
what are the southern pine forests found in the US and what are they used for?
along coastal planes of south atlantic and gulf states
-used for lumber and production of paper products
What are the temperate deciduous forests of the US and describe the climate conditions under which they form?
-have been cleared by agriculture and settlement
-require high rainfall throughout year
-lose leaves in fall as protection against cold and extensive water loss
What are 3 reasons why tropical rainforests are being cleared?
-valuable hard wood trees for lumber
-land cleared for mining or to raise cattle
Why are tropical rainforests soils so poor?
-due to leaching of nutrients from high rainfall
-and decomposers break down organic material to return it to existing plants
Describe the environmental problems experienced by tropical dry forests and their consequences.
Experience a dry period during which the trees and shrubs drop their leaves.
Give 4 names used to describe grassland communities around the globe.
North America- "Prairie"
Asia- "Steppe"
South America- "Pampas"
Africa- "Veldt"
Characterize grassland biomes in terms of climate and where they are found.
interiors of the continents where moist air from sea is blocked by mountain ranges (High rates of evaporation and periodic severe droughts)
Distinguish between sod-formers and bunch grasses.
-sod-formers: develop a solid mat of grass over the ground
-bunch grasses: grow in bunches w/ the space b/w them occupied by other plants
Distinguish between tallgrass and shortgrass prairie and where each is found in the U.S.
-tallgrass: From the forest-grassland ecotone in Wisconsin, Indiana, & Illinois to Minnesota, Eastern South Dakota, Kansas and Nebraska= trees shrubs and rolling hills (now farm land)
-shortgrass: grassland ecotone= shallow-rooted grass that grade into desert or forest at higher elevations
What was the "Dust Bowl" of the 1930s and what caused it?
strong winds, drought, and poor farming practices caused the topsoil of the western prairie to be blown in massive clouds
Characterize tropical savannas and where they are found.
-grasslands with varying degrees of tree and shrub growing in soils low in nutrients and moisture
-cover the broad, semi-arid plains of Africa, South America and Australia
List some mammals found in the African savanna.
-grazing and browsing herbivores such as Zebras and Gazelles in Africa
What are shrubs and for what type of environment conditions are they adapted?
-tough, small broadleaf shrubs and trees
-heavily waxed leaves that grow together into a nearly impenetrable mass
Characterize a "Mediterranean climate" and the type of vegetation it supports.
mild, rainy winters and long, hot, dry summers
Characterize the chaparral biome and where it is found.
In North America dry shrublands are called "chaparral" and cover 5 million acres of southern California hillsides.
How is fire important to the chaparral biome?
-Fires clear away old growth, making way for new and recycling nutrients, all of which leads to vigorous growth.
-Some species require it to germinate.
Characterize the northern desert shrub community and where it is found.
-continental climate with hot summers and prolonged winters
-Found in the arid Great Basin of North America
-sagebrush and saltbush
Why are most deserts located under high-pressure areas?
-descending air masses are heated and dried.
-30 degree N-S
-deflect moisture-laden air coming from low pressure areas
Under what conditions do temperature inversions form?
warm air floats over cold
How do "rain shadow" deserts form?
-found on the leeward side side of mountain ranges b/c as air rises, it cools as follows according to adiabatic lapse rate
Characterize the climate and plants of deserts.
-low rainfall, high evaporation, daily fluctuations in temperature.
-Succulents (cacti) that have water storing tissues.
What are washes and arroyos and how do they form?
When rain falls it is often heavy and since the earth is unable to absorb it most of the rain rushes across the land carving...
-washes: Dry riverbeds
-arroyos: Deep canyons
What types of organisms form a living crust on the surface of desert soils and how are they important to the ecology of this biome?
-lichens, green algae and cyanobacteria
-have high rates of nitrogen fixation
What is desertification and what are its consequences?
Many grassland areas are being converted into dry wastelands due to human activities.
What is "slash-and-burn" agriculture and what are its consequences for tropical rainforests?
-Leaching of nutrients from the high rainfall, decomposers rapidly break down organic matter and return it quickly to existing plants.
-Inspite of impressive plant growth, the soil is very poor.
Give 3 important reasons for preserving tropical rainforests.
1.significant loss of the Earth's biodiversity
2.Increases global warming by releasing more CO2
3.Loss of medicinal plants
Why are tropical rainforest trees so often buttressed?
plant-like extensions of roots that help support trees in the shallow, poorly developed soil.
What are lianas and epihytes?
lianas: climbing plants (vines)
epiphytes: grow on the trunk and limbs (bromeliads)
Where are tropical rainforests found today?
-Amazon Basin in South America= largest
-Equatorial Africa, Indonesia, New Giunea, Central America and Austrailia
How do "rain shadow" deserts form?
-Moist air is forced to rise over a mountain range, as it descends on the leeward side the air will be heated and dried producing a rain shadow
Characterize the climate and plants of deserts.
-low rainfall, high evaporation and wide daily fluctuations in temperature.
-Succulents (Cacti) plants, woody shrubs
What are washes and arroyos and how do they form?
washes: when rain falls heavily the earth is unable to absorb it and rain rushes across the land carving otherwise dry riverbeds
Arroyos: Deep canyons
What types of organisms form a living crust on the surface of desert soils and how are they important to the ecology of this biome?
-lichens, green algae, cyanobacteria (blue-green) that have unusually high rates of nitrogen fixation
What is desertification and what are its consequences?
-grasslands areas are being converted into dry wastelands due to human activities.
Distinguish between the following lake zones; limnetic zone, profundal zone and benthic zone.
Limnetic zone: open sunlit waters down to the depth where photosynthesis is no longer significant
Profundal zone: deep open water below the depth of effective light penetration
Benthic zone: Bottoms of lakes and ponds which often contain sediments rich in organic matter
Define the following terms; limnology, lentic, lotic, plankton, nekton, neuston, phytoplankton, zooplankton, and benthos.
limnology: study of freshwater ecosystems
lentic: standing water habitats
lotic: running water habitats
plankton: suspended organisms
Nekton: free-swimming organisms
neuston: small organisms that live on top of or just below the surface film
phytoplankton: photosynthetic organism in limnetic zone
zooplankton: small animals that eat phytoplankton
benthos: decomposing anerobic bacteria and a variety of other organisms
Characterize each of the following layers of the stratified lake; the epilimnion, hypolimnion, and metalimnion. What is the thermocline?
Epilmnion: the upper, warmer portion
Hypolimnion: cold, dark region entirely cut off from surface air
Metalimnion: In between these two layers.
Thermocline: steep temperature gradient dropping about 1 degree C for each meter.
What is the relationship between BOD and the productivity of a lake? Why?
-If the lake is very productive, the amount of dead matter to be decomposed will be large, and the BOD can exceed the lake's oxygen reserve.
-If this happens the hypolimnion becomes entirely anoxic by late summer.
Distinguish between oligotrophic and eutrophic lakes and give examples of types of fish that might be found in each.
Oliographic: nutrient-poor, little productivity
Eutrophic: nutrient-rich, tolerate low dissolved oxygen conc.
Describe the relationship between redox-potential of lake sediments and nutrient availability.
what happens to the nutrients depends on whether the sediments in contact with the water are oxidized or reduced.
oxidized-unavailable
reduced-available
Describe the events occuring during the fall and spring turnover in temperate lakes.
nutrients are brought up from the bottom sediments, prompting blooms of phytoplankton growth.
Describe the process of stratification that occurs in temperate lakes during the winter.
lakes become stratified, the coldest water will be just beneath the ice, warmest near the bottom.
Characterize the following zones of a swiftly flowing stream: riffles, pools, runs.
riffles: shallow, turbulent stretches where water flow swiftly over a rough bottom of sand and rock
pools: deep water flowing slowly over a smooth, sand, gravel or mud bottom.
Runs: fast-flowing stretches of streams that flow over bedrock or rock and sand with smooth surface water.
What is meant by the aufwuchs, or periphyton?
These are the sites of most primary production in the stream, where an extensive mat of photosynthetic organisms develops.
Describe a type 1 survivorship curve and what is an animal population in it.
Low mortalitiy throughout most of the lifespan, followed by decline in later stages
Ex: invertebrates, humans
Describe a type 2 survivorship curve and what is an animal population in it.
Contant mortalitiy throughout lifespan (looks like neg constant slope)
-Ex: birds, Connell's barnacles, etc
Describe a type 3 survivorship curve and what is an animal population in it.
high initial mortality, followed by period of much lower constant losses
-ex: fishes, oysters, clams
Why do population data typically result in a J-shaped mortality cure?
Juvenile phase of high mortality and mortality decreases and then rises again with increased age (mortality=death)
Why may it be preferable to use a mortality curve instead of a survivorship curve to track the fate of a population over time??
independent of the younger age classes
-free from biases inherent in Ix column and survivorship curves that plot Ix against age
-if first values of qx are wrong, the error doesn't effect other values (page 127)
How is net reproductive rate (Ro) defined? What does it mean when Ro>1, Ro=1, Ro<1?
-the mean number of offspring produced by an individual during its life
-Ro=1 = population is replacing itself
-Ro>1 = the population is increasing
What 2 things does Ro represent in a population with descrete (no-overlapping) generations?
1. the average number of offspring produced by an individual during its lifetime
2. the overall extent by which the pop has increased or decreased over that time
-aka its multiplication factor
-if Ro=2, the pop doubles each generation
What does Ro represent in a population with overlapping generations?
ONLY to the number of offspring produced by an ind during its lifetme
Why might it be preferable to express population growth rate as an exponential constant (r) rather than a geometric constant (R)
to find out a more instantaneous rate of pop change. -how much a pop is changing at any particular moment in time
Give 5 factors that influence an organism's intrinsic rate of population growth?
1. death rate of org under ideal cond
2. # of offspring produced by an org over its lifetime (fecundity)
3. Length of organism's reproductive life span and ability to conceive
4. Freq with which the org reproduces
5. age of first reproduction
which of the 5 factors that influencd an organisms intrinsic rate of pop growth leads to the greatest increase in r
producing offspring as early as possible!! decreasing generation time
distinguish b/w semelparity and iteroparity and give examples of some plants and animals that are each
semelparity: reproduce once in their lifetime: ex: salmon, mayflies, bamboo, annuals
iteroparity: produce young throughout their lifecylce: perennials
in terms of pop, what is meant by stable age-structure
proportion of ind in each age-class will remain constant over time
why are survivorship normally plotted on a semi-logarithmic scale
cuz interested in per capita rate of change rather than absolute
-numbers lost are greatly different but the RATE is the same: good
-this wouldn't show up correctly on a arithmetic scale
-pg 125
what kinds of information might you use to construct a life-table for species such as annual plants and insects that do not have overlapping generations
use stages of dev.
-use stages (eggs, instars, adults) and then record the number of ind alive at start of each interval
give 4 assumptions that are required for static life-table to be valid
1. each age class is sampled in proportion to its number in the population
2. the birthrates and death rates are constant
3. the pop is neither inc nor dec, it is stable
4. the survivors of the one ear age class were teh survivors from the year before (just as if they all belonged to the same cohort
distinguish b/w unitary and modular organisms and give ex of each
Unitary: individuals form and dev are highly determinate (limited)
-most animals start out as zygote and end up in same form quickly
Modular: zygote dev into module that produces more modules like first
-branched and immobile (except for juv phase)
-have highly variable # of basic elements
-unpredictable dev and dep on environ.
how are animal pop sizes estimated?
-mark/recapture techniques for animals
How are plant pop sizes estimated?
-plants: sampling techniques involve sampling randomly selected plots (quadrats) of varying size and shape and generalizing from these samples
How are random, contagious (clumped) and regular (uniform) patterns of dispersion defined?
-random: distance b/w each ind is indep of the location of other ind in the pop
-clumped: some plots have a greater than expected # of ind.
-may arise in animals organized in social groups (prairie dogs)
-most common
Regular (uniform): ind are equally spaced
-biotic interactions: territoriality in animals
-allelopathy in desert plants that deposit chem barriers around selves to prevent growth of other plants nearby
What might a pop in nature show a contagious pattern of dispersion
organized in social groups or their resources are distrubuted in patches
What kinds of biotic interactions might a uniform pattern of dispersion suggest?
-territoriality in animals
-allelopathy in desert plants (creosote bushes) that deposit chemical barriers around selves to prevent growth of other plants nearby
What information is required to construct a a dynamic (cohort) life table?
1. survivorship observed directly: number of ind alive in successive intervals of time is recorded for a cohort born at same time
2. age observed at death
What info is req to construct a static-life table?
based on age-structure of a pop at a given time: constructed from a single sample
-ecological info on age structure easy to obtain
-ex: deer: examine tooth wear
-trees count rings
What assumptions must be met for a population to grow exponentially as described in the density independent model??
-Assumes r is constant (this parameter may differ from one year to next or one environ to next)
-model will only fit precisesly when the pop has reached stable age structure
What is meant by a "stable age distribution"
Ex: if the proportion of young people in the pop were increasing, r will also be increasing
-NEED MORE
According to the density-dep population growth model, what happens to the rate of pop increase as N approaches K?
the rate of population slows to zero
-(k=carrying capacity and N=population size)
What does the value (K-N)/K in logistic equation for population growth represent?
unitilized opportunity for population growth!
=the percentage of the available resources remaining in the environment
According to the logistic eq, what is the relationship b/w the intrinsic (per capita) growth rate (r) of a population and population size (N)?
r is decreased by a constand amount for each individual added to the population
-relationship b/w density and rate of increase is linear
Give 4 assumptions of the density-dep population growth model?---- logistic equation??
1. Pop has stable age distribution
2. relationship b/w density and rate of increase is linear
3. response to inc density is instantanous
4. environment remains constant
Does the growth of short-lived organisms such as insects fit the logistic growth model? if not, why not?
No because they never reach their carrying capacities
-they continue to grow exponentially until they suffer a dramatic crash
-do a j shaped curve
What is meant by a "stable limit cycle"?
oscillating above and below the carrying capacity
What is one of the main prob with the logistic eq describing population growth?
???
What are density-ind population control factors and what types of org are controlled by such factors?
-magnitiude of their effects is independent of pop density
Ex:natural disasters, winter storms
-short lived, fast growing species such as insects, annual plants may be limited by these control factors
what are density-dep control factors
-the mag of their effect is directly related to population density
-as pop density increases, teh effect such factors exert increases
Give six types of density dep population control factors and how each factor may act to limit a pop size
-Comp: intensity increases w/ number of ind competing
-Pred: increase as prey densities increase
-Disease: more dense the population, the easier for disease to spread
-parasitiism: same as disease
-self-poisoning: some org can make wastes if kept in closed environment
-emigration: if pop pressure too severe, individuals may leave to seek out new hab to find resources
How does the nature of a stream-bottom influence productivity in the stream?
-sandy bottoms are least productive b/c they offer little substrate for animals or periphyton
-Gravel and rubble bottoms allow greatest surface area for attachment and provide nooks and crannies for insect larvae
Describe the abiotic and biotic changes that occur as current decreases in slow water streams.
As current slows, slit and decaying organic matter accumulate at the bottom, and fine detritus from upstream provides the main source of energy
How do regulated rivers and streams differ from free-flowing ones?
water levels and water flows are controlled, channels have been straightened and their waters have been isolated from their flood plains by levees
-biodiversity drops and periphyton communities become dominated by a few species of algae
Contrast the effects of releasing water from the epilimnion and hypolimnion of a reservoir on the receiving stream.
-discharge from the hypolimnion, river receives cold oxygen-poor water carrying iron, other minerals and organic materials.
-epilmnion: warm, nutrient-rich well oxygenated water
List two ways in which the effects of hypolimnial release on a receiving stream can be reduced.
1. gated withdrawal structures
2. artificial circulation
Distinguish between basin wetlands, riverine wetlands, and fringe wetlands.
-basin wetlands: develop in shallow basins ranging from upland topographic depressions to filled-in lakes and ponds.
-riverine wetlands: found along shallow and periodically flooded banks of river and streams
-fringe wetlands: along the coastal areas of large lakes or at the edge of marine estuaries
Distinguish between swamps and marshes.
-swamps: dominated by woody vegetation
-marshes: wetlands dominated by emergent herbaceous vegetation
Describe the problem of wetland depletion in North America.
more than 11million acres of wetlands in the US were lost during the period of 1955-75
-conversions to farmland is responsible for 87% of the losses
-urban development is 8% responsible
In addition to being areas of high productivity, give 3 useful functions performed by wetlands.
1. providing overflow areas for flood control
2. serving as nurseries and prime habitat for fish, waterfowl, and other wildlife
3. cleaning and filtering water, removing sediments, nutrients, and even toxins
Distinguish between the pelagic and benthic regions of the marine ecosystems.
-pelagic region: the whole body of water
-benthic region: the bottom sediments
Where does most productivity occur in marine ecosystems?
in shallow sunlit waters where phytoplankton form the base of the food chain
Under what conditions are areas of open-ocean very productive?
regions where upswelling currents bring nutrients
Characterize each of the following areas of the rocky intertidial zone: the supralittoral fringe, littoral, and infralittoral fringe.
-supralittoral fringe: upper margins where salt water comes only every once in a while on the highest tifes or as wind-blown salt spray
-littoral: a region covered and uncovered daily by tides, here grow algae as well as barnacles and various gastropods
-infralittoral fringe: may uncover only the lowest tides or never if wave action is strong
Contrast life on sandy shores and mudflats with that on rocky shores.
-sandy shores: difficult b/c sand provides no surface area for attachment
-mudflats: without the protection of a rocky shore, most organisms must remain buried in the sand or mud where they live as deposit-feeders that ingest organic matter.
In what type of waters are coral reefs found?
in warm, nutrient-poor waters
Describe the relationship between the zooxanthellae and coral polyps.
zooxanthellae carry out photosynthesis and directly transfer organic material to the coral tissue as well as helping them to deposit the calcium carbonate necessary to form their exoskeletons.
Why are coral reefs restricted to well sun-lit waters?
for the photosynthetic zooxanthellae that the coral organisms require.
What are estuaries and how would you characterize their productivities?
-partly enclosed coastal ecosystems that occur where the oceans meet the land
-seawater mixed with freshwater from rivers or streams and runoff from the land, creating a nutrient-rich and very productive ecosystem
Where are salt marshes found?
form on alluvial plains around the margins of the estuaries or in the shelter of offshore islands and sand bars
Characterize a mangrove swamp.
dominated by salt-tolerant, woody plants characterized by shallow, widely spreading roots that come from the trunk and branches
What is the function of the pneumatophores possessed by many mangrove trees?
they take in oxygen for the roots.