ENV 220 final study Flashcards
1
Q
What is a food web?
A
Summary of the feeding interactions within a communityCommunity portrait based on feeding relationshipsDepicted with arrows that point in the direction of energy flow
2
Q
What is ecology?
A
The scientific study of interactions between organisms and their environment.
3
Q
Scientific method
A
The basis for scientific inquiry. 1. Ask a question2. Do research3. Form a hypothesis4. Perform experiments5. Analyze data and form a conclusion6. Record results
4
Q
Scale and manipulation
A
The changes to environments that occur over large spatial of temporal scales.
5
Q
Levels of ecological organization
A
- Biosphere - This is where all living things on Earth live.2. Biomes - A large naturally occurring community of flora and fauna occupying a major habitat.3. Ecosystem - A biological community of interacting organisms and their physical environment.4. Community - All the people living in a particular area or place: “local communities”.5. Populations - A particular section, group, or type of people or animals living in an area or country.6. Species - This is the most basic unit of biological organization.
6
Q
The 9 biomes
A
- Tropical Rainforests2. Tropical Dryforests3. Tropical Savannas4. Deserts5. Mediterranean Woodlands and Shrublands6. Temperate Grasslands7. Temperate Forests (Old Growth)8. Boreal Forests (Taiga)9. Tundras
7
Q
Tropical Rainforests
A
-Most occur within 10o latitude of the equator.-Little temperature variation.-Annual rainfall between 80 and 160 inches and occurs evenly throughout the year.-Quickly leaches soil nutrients.-Well developed, tall (up to 260 ft) canopy.-increasingly exploited for foods and medicines.
8
Q
Tropical Dryforests
A
-Most occur between 10o and 25o latitude of the equator.-Climate is more seasonal than tropical rainforests.-Alternates between very dry (winter) season and wet season.-Soils are richer in nutrients, but rain pulses make it vulnerable to erosion.-shares many animal and plant species with tropical rainforests.-Heavily settled by humans for dry season.
9
Q
Tropical Savannas
A
-Tropical grasslands at ground level.-Most occur north and south of tropical dryforests within 10o and 20o of the equator.-Climate alternates between wet and dry seasons.-Wet season is shorter and dryer than tropical dry forests.-Droughts in dry season lead to lightning-caused fires; maintains grasslands with scattered mature trees.-Soils have low water permeability with impermeable subsoils; helps persist as grassland.
10
Q
Deserts
A
-Occur in major bands at 30o N and S latitude of the equator.-Occupy about 20% of Earth’s land.-Water loss usually exceeds precipitation.-Soil is extremely low in organic matter.-influenced by plant/animal activity.
11
Q
Mediterranean Woodlands and Shrublands
A
-Also called chaparral.-Occur in all continents expect Antarctica.-Climate is cool/moist in fall, winter, and spring; and hot and dry in summer.-Fragile soils with moderate fertility.-Plants/animals adapted to drought/low nutrients.-Fire-resistant plants.-long history of human intrusion and clearing for agriculture.
12
Q
Temperate Grasslands
A
-Midwest prairies - “sea of grass.”-Largest biome in North America.-Annual rainfall between 15 - 40 in. with periodic droughts.-Winters are cold and dry with most rainfall in summer.-Soils are extremely nutrient rich and deep.-Dominated by herbaceous vegetation.-Fertile farmlands due to fertilizer addition.
13
Q
Temperate Forests (Old Growth)
A
-Occur between 40o and 50o latitude of the equator.-Annual rainfall up to 120 in.-Moderate variations in temperature.-Fertile soils.-Dominated by deciduous plants (longer growing seasons), conifers (redwoods).-High biomass production; high wood accumulation.-Many major human pops center on once old growth forests; Tokyo, Berlin, London, New York, Chicago.
14
Q
Boreal Forests (Taiga)
A
-Occur only in northern hemisphere.-Covers 11% of Land area.-Thin acidic soils, low in fertility.-Extreme climates have permafrost subsoils.-Large temperature variation with cold, dry climate.-Dominated by evergreen conifers.-High animal density.-Low levels of human intrusion.
15
Q
Tundras
A
-Covers most lands north of Arctic Circle-Cool dry climate with short summers.-7 to 23 inches of rain.-Low decomposition rate, resulting in peat.-Netlike soil surface.-Mostly mosses and dwarf trees.-Low human intrusion but for oil as of recent.
16
Q
The Hydrologic Cycle
A
-71% of Earth’s surface covered in water.-Oceans contain 97%.-Polar icecaps and glaciers contain 2%-Freshwater lakes, streams, and groundwater contain <1%.-Non-static distribution of water.-Solar energy drives cycle.1. Evaporation: water turns to gas and rises into the atmosphere.2. Condensation: clouds form.3. Precipitation: water rains down to Earth. Then evaporates again, is consumed by organisms, joins ground water, or joins surface water.
17
Q
Turnover time
A
Amount of time it takes for entire volume of water of a reservoir to be renewed.
18
Q
Evolution
A
Variation in phenotype of individuals in a population results from both genes and environment. Random processes (genetic drift), differences in survival and reproduction can effect it.
19
Q
Natural selection
A
The result of differences in survival and reproduction among phenotypes.
20
Q
What is the broadest (most inclusive) of the levels of ecological organization?
A
Biosphere
21
Q
Keystone Species
A
Keystone species exert strong effects on their community structure, despite low biomass
22
Q
What two examples did she use for keystone species (chap 17)
A
Fish (power California Roach and Steelhead Trout experiment)Power’s Experiment:- Set up enclosures/exclosures- Predatory fish enclosed in one treatment- Predatory fish excluded in another treatmentSnail:Lubchenko Lubchenko observed in tide pools:◦Tide pools with green alga densities had snail densities◦Pools w/ snail densities were dominated by red alga◦In absence of snails, green alga competitively displaces red alga
23
Q
What is a introduced species?
A
Introduced species:those that humans intentionally or accidentally move from the species’ native locations to new geographic regionsSometimes called non-native, exotic, alienExample:Exotic species have dramatic impacts on communities because they were outside the evolutionary experience of local prey populations◦Lake Victoria (E. Africa) harbored one of the greatest conc. of fish species in the world◦Nile Perch (Lates nilotica) exotic fish predatorSince introduced decline in species diversity.
24
Q
Why is a keystone species important?
A
A keystone species is important because it has great significance in promoting species diversity.
25
What are strong interactions?
Paine (1980):◦Suggested feeding activities of a few species may have a dominant influence on community structure – called these influential trophic relations strong interactions◦Suggested criterion for strong interaction is degree of influence on community structure and not quantity of energy flow
26
What is a ecosystem?
all of the organisms living in and area and the physical environment with which those species interact
27
What is primary production?
Production of biomass (organic matter) via fixation of energy by autotrophs in an ecosystem.Rate of primary production: Amount of energy fixed over a given period of timeGross primary production (GPP): Total amount of energy fixed by autotrophs◦Net primary production (NPP): Amount of energy leftover after autotrophs have met their metabolic needs; what you see as plant biomass
28
Types of Trophic Levels
Primary Producers (Plants)Primary Consumers (Herbivores and detritivores)Secondary consumers(Carnivores that comsume herbivores and detritivores)Tertiary, Quaternary (harder carnivores)Top Predators (Apex Predators)
29
Evapotranporation
Rosenzweig :◦moisture and temperature influence rates of primary production◦relationship between annual net primary production and annual actual evapotranspiration (AET)◦AET: Amount of water that evaporates (from surfaces) and transpires (from plants) off a landscapeAET is affected by both temperature and precipitationCold ecosystems (e.g. tundra) and dry ecosystems (e.g. deserts) tend to have low AET
30
What is soil fertility?
Variation in soil fertility can explain differences in terrestrial primary production◦Shaver and Chapin found arctic (tundra) net primary production was twice as high on fertilized plots as unfertilized plots
31
Limits on nutrient availability in freshwater?
Freshwater primary productivity is usually limited by nutrient availability◦Several studies have found quantitative relationship between phosphorus and phytoplankton biomass◦Several studies support generalization that nutrient availability (esp. phosphorus) controls rate of 1° prod. in freshwater ecosystemsThiik adding fertilizer will increases biomass taking away fertilizer decreases. Graneli Baltic sea.
32
How Do Consumers Influence Production?
Bottom-Up Controls◦Influences of physical/chemical factors of an ecosystem ◦e.g. temperature, nutrients, lightTop-Down Controls◦Influences of consumers◦HSS (1960): the earth is green◦Carpenter et al.: influence of predators on lake primary production propagate through the food webEx: apex predator down
33
Lake Production and Trophic Cascades
Carpenter et al. (1985) : Trophic Cascade Hypothesis◦Effects of predators on prey that alter abundance, biomass or productivity across more than one link in the food web◦Predators can influence ecosystem properties (1° prod) through effects on intermediary trophic levels◦Piscivores (fish that eat fish) and planktivorous (eat phytoplankton) most important◦Can cause significant deviations in primary productivity in lake ecosystems
34
Trophic Cascade Hypothesis:
- Piscivores reduce planktivorous fish directly by eating them- Piscivores then indirectly increase populations of large zooplankton and indirectly reduce phytoplankton biomass
35
Lake Trophic Cascade experiment
Carpenter and Kitchell◦Reduction in planktivorous fish populations led to reduced rates of primary production, via:In absence of planktivorous minnows, predaceous invertebrates became more numerous and ate smaller herbivorous zooplankton….…resulted in abundant, large herbivorous zooplankton that ate phytoplankton, biomass and rate of primary production declined…..
36
Trophic Dynamic View of Ecosystems defention
Lindeman (1942):◦ Ecosystem concept is fundamental to the study ofenergy transfer within an ecosystem◦ Suggested grouping organisms within an ecosysteminto trophic levels Each feeds on level immediately below As energy is transferred from one trophic level toanother, energy is degraded◦ Among the first ecologists toquantify the flux of energythrough an (lake) ecosystem
37
Trophic Dynamic View of Ecosystems defention 2nd law of thermodynamics
2nd Law of Thermodynamics:◦ As energy is transferred from one trophic level toanother, energy is degraded◦ Results in/from: Limited ability to consume and assimilate food source Consumer respiration Waste production Heat production Low ecological efficiency –percentage of energy inbiomass that is transferred tobiomass in next highertrophic level; varies from5-20%, usually ~10%
38
Ecological Pyrimad
Ecological Pyramids:◦ Seen in numbers, biomass, production◦ Results from energy losses at each successive energy transfer◦ Also called an “Eltonian pyramid”◦ The amount of energy available to top consumers is smallcompared to that of lower level consumers (=herbivores)
39
Reasons for decline in energy flow
This decline in the amount of available energyexplains why:◦ Top level consumers (whales, hawks) require so muchgeographic territory to get enough food◦ Most food chains are limited to 4-5 levels – not enoughenergy to support more◦ Are no non-human predators of large predators (lions,eagles) biomass of these predators is not sufficient to supportanother trophic level
40
Ecosystem Energetics and Human Nutrition
How do lessons about energy flow apply to human nutrition?Eating producers instead of consumers requires less photosynthetic productivity and reduces the impact on the environmentIt takes at least 10 lbs. of corn 1 lb. beef
41
Energy Flow in A Temperate Deciduous Forest: An Energy Budget
Most energy flowing through ecosystem is lost to heat, respiration, evapotranspirationNPP was <1% of the input of solar energy◦99% of solar energy unavailable for use by a second trophic levelAs energy losses between trophic levels accumulate, eventually there is insufficient energy left to support a higher trophic level◦Consumers lose significant energy to respiration◦Only ~10% of energy transferred to next successive levelEnergy flows, nutrients cycle
42
Nutrient Cycles (3 types)
Nitrogen Cycle, Phosphorous cycle, and Carbon cycle
43
Define Nutrients and Nutrients cycle
elements required for the development, maintenance and reproduction of organisms Ex: C, P, N, K, FeNutrient cycle – use, transformation movement and reuse of nutrients
44
Phosphorous significance
Biological/Ecological Significance:◦forms phospholipids, nucleic acids, ATP
45
Phosphorus forms
Forms:◦Not very abundant in the biosphere◦Primarily found as phosphate (PO4)◦Available to living things after decomposition of phosphate-containing organic matterReservoirs:◦Global phosphorus cycle does not include substantial atmospheric component (unlike C, N) – no gas
46
Phosphorous Resivors
◦Largest quantities found in mineral deposits and marine sediments – also mined for fertilizer◦Much phosphorus to rivers, ocean sediments◦Slowly released in terrestrial and aquatic ecosystems via weathering of rocks◦Human activity has moved cycle:land freshwater ecosystems
47
Nitrogen cycle signifigance
Biological/Ecological Significance◦amino acids (proteins), nucleic acids, chlorophyll, hemoglobin◦of high ecological importance, scarce
48
Nitrogen resivors
Largest pool is in the oceans◦Includes major atmospheric pool, but only one way to bioavailability - N2◦Human activity has moved cycle: land atmosphere
49
Nitrogen forms and fluxes
Forms and Fluxes:◦Only nitrogen fixers can use atmospheric supply directly - N2 reduced to ammonia (NH3) in an energy-demanding processOnce N is fixed it is available to organisms◦Ammonification: upon death & decomposition, N can be released by fungi and bacteria as NH4 (ammonium)◦Nitrification: Ammonium (NH4) nitrate (NO3) by bacteriaNH4, NO3 are used directly by bacteria, fungi, plants◦Denitrification: NO3N2 (via anaerobic respiration by specific bacteria)
50
Carbon cycle signifigance
Biological/Ecological Significance◦Component of all organic molecules, also CO2◦Important biologically as well as atmospheric forms to climate◦Moves between organisms and atmosphere through the reciprocal processes of photosynthesis and respiration
51
Carbon Resivors
Carbonate rocks and oceans are two largest pools◦Human activity has moved cycle: land atmosphere
52
Carbon forms and fluxes
Forms and Fluxes:◦Organic molecules - associated with living things – plants, animals, etc.; simplest is CH4◦Inorganic molecules – primarily CO2In aquatic ecosystems, CO2 must dissolve in water to be available for PS – HCO3 and CO3 inorganic formsRespiration (makes CO2) and photosynthesis (uses CO2 to make organic C) are reciprocal processes◦Although some C cycles rapidly, some remains sequestered in unavailable forms for long periods of time – fossil fuels, soils/rock◦Combustion (of fossil fuels, vegetation) adds CO2
53
Organic Carbon --> Inorganic Carbon: Rates of Decomposition
Mineralization –◦Process of conversion of organic inorganic◦Determines the rate at which nutrients (as inorganic molecules) are made available to primary producers◦This process occurs primarily during decompositionbreakdown of organic matter, CO2 and nutrients releasedNutrient exchange is therefore affected by decomposition
54
Decomposition in Terrestrial Ecosystems
Decomposition rates in terrestrial systems influenced by:◦chemical compositions of leaf tissue (N, P, lignin)◦moisture◦TemperatureDecomposition rates often expressed as % mass loss over time◦Leaf litter disappears over time◦Can also be expressed as decay rate (k) – mass lost per day
55
Decomposition in Temperate Forest Ecosystems
Melillo et.al.◦decomposition in temperate forests (NC, NH)◦leaves with higher lignin:nitrogen ratios lost less masslignin - complex chemical associated with woody speciesAlso differences between locations:◦higher soil N availability contributed to higher decomposition rates◦higher environmental temperatures may have also played a role
56
Decomposition in Temperate Forest Ecosystems
Both temperature and moisture influence decomposition rates – both combined into one factor as actual evaporation rate (AET)How would you expect rates to compare between tropical and temperate ecosystems?
57
Decomposition Rates in Aquatic Ecosystems
Most important controlling variables:◦chemical composition of litter◦nutrient concentrations in system◦leaf species◦temperature
58
Decomposition Rates in Aquatic Ecosystems
Gessner and Chauvet:◦Leaves with a higher lignin content decomposed at a slower rate◦Higher lignin inhibits colonization by fungi
59
Decomposition Rates in Aquatic Ecosystems
Suberkropp and Chauvet:◦leaves degraded faster in streams with higher nitrate concentrationsRosamond:◦Ficus decomposition in relation to tropical stream phosphorus◦Rates increased at low P levels, then leveled off at high P levels
60
How do aquatic organisms modify the distribution and cycling of nutrients?
Grimm:◦Aquatic inverts significantly increase rate of N cycling◦Inverts can ingest, egest, excrete, accumulate N◦80% were collector-gatherersIngested 131% of daily N (re-ingest fecal N)Excreted and recycled 15-70% of nitrogen pool as ammonia◦Suggested rapid recycling of N by macroinvertebrates may increase primary production when limited by N
61
How do terrestrial organisms modify the distribution and cycling of nutrients?
Huntley and Inouye:◦pocket gophers altered N cycle by bringing N-poor subsoil to the surface◦responsible for massive soil reorganization◦positive influence on plant diversity
62
Effects of Disturbance on Nutrient Cycling: An Introduced Tree in Hawaii
Vitousek and Walker:◦Invading N-fixing tree Myrica faya is altering N dynamics of Hawaiian ecosystems (4,600 exotic sp. in HI)◦Grows on lava flows in N. Atlantic (native)◦Introduced in late 1800’s as ornamental or medicinal plant, and later used for watershed reclamation
63
Disturbance & Nutrient Loss From Hubbard Brook Forest
Likens and Bormann◦Clear-cutting an entire watershed resulted in increased rates of nutrient (nitrate) loss◦Demonstrated the biological influences on nutrient loss from forest ecosystems
64
What is succession?
observed process of change in community structure over timegradual change in plant and animal communities in an area following disturbance
65
What is a pioneer community?
Pioneer community – first plants in a successional sequence of communities◦Primary succession on newly exposed geological substrates◦Secondary succession following disturbance that does not destroy soilAbandonment of agricultural lands, fire
66
What is a Climax community?
Late successional community that remains stable until disrupted by disturbance◦Nature of this community depends on environmental circumstances (grassland, forest)
67
Primary succession example "Glacier Bay"
Reiners et.al. studied changes in plant diversity during 1° succession, recent glacial retreat (10 yrs.) – 1,500 yrs◦Total number of plant species increased with plot age◦Species richness increased rapidly in early years of succession and more slowly during later stagesNot all groups increased in density throughout successionTiming of increasing species richness differed among plant forms
68
Secondary succession example "Temperate Forest"
Oosting found number of woody plant species increased during secondary succession at Piedmont Plateau, NCBegan with single woody plant invaderSpecies richness reaches plateau over time
69
Ecosystem Changes During Succession
Ecosystem changes during succession include increases in:◦Biomass◦Primary production◦Respiration◦Nutrient retention◦Ecosystem propertiesSoil nutrients/OM
70
Chronosequnces
◦Series of communities or ecosystems representing a range of ages or times since disturbance◦Share similar attributes but are of different ages◦Are limited (such as that at Glacier Bay)◦Hawaiian Islands have formed over hot spots on the Pacific tectonic plate, forming an island chain varying greatly in ageHedin et.al. found differing patterns of nutrient distribution across the chronosequence – high N, lower P loss rates
71
Recovery of Nutrient Retention Following Disturbance
Bormann and Likens found felling trees in Hubbard Brook substantially increased nutrient lossesHerbicide used to suppress regrowthWhen application stopped:◦succession proceeded◦nutrient losses decreased◦primary production increased
72
Drivers/Mechanisms of Succession?
Mechanisms that drive succession include:◦Facilitation – Clements (1917)◦Tolerance◦InhibitionConnell and Slayter (1977) – alternative successional mechanisms, included the three above
73
What is the Facilitation Model?
Proposes many species may attempt to colonize newly available spaceOnly certain species with certain characteristics will establishThese pioneer species modify environment◦environment becomes less suitable for themselves and more suitable for species of later successional stages◦“facilitate” colonization by other species, then are replaced
74
What is the Inhibition Model?
Assumes any climax adult will be able to colonize earlyEarly occupants of an area modify the environment in a way that makes it less suitable for both early and late successional species◦Early arrivals “inhibit” colonization by later arrivals◦Community culminates in long-lived, resistant speciesLate successional species wind up dominating an area because they live a long time and resist damage by physical and biological factors
75
Sousa Example Rocky Intertidal
Sousa investigated mechanisms behind succession of algae and barnacles in intertidal boulder fields◦If the inhibition model is in effect, early successional species should be more vulnerable to mortalityResults showed early successional species had lowest survivorship and were more vulnerable to herbivoresUlva prevented establishment of late-successional species
76
Causes of Community & Ecosystem Stability
Community stability may be due to:◦lack of disturbance◦resistance - ability to maintain structure and function in face of potential disturbance◦resilience - ability to recover from disturbanceStability◦absence of change◦persistence in the face of disturbance
77
What is Park Grass Experiment regards to Ecosystem Stability?
Hertfordshire, England - Rothamsted Experimental Station◦Studied effects of fertilizer treatmentsContinued for 150 years (1856 - )Silverton investigated ecosystem stability◦Used community composition variability as measure of stability – grasses, legumes, other plants, as proportion in community
78
Principle of Allocation
If organisms use energy for one function such as growth, the amount of energy available for other functions is reduced ◦Leads to trade-offs between functions such as size and number of offspring ◦Fish (darters) show tradeoff in egg size and number: fewer, larger eggs larvae that do not disperse as far greater isolation reduced gene flow more, smaller eggs (larger clutch size) higher rates of gene flow
79
R. vs K Selection
MacArthur and Wilson:◦r selection (per capita rate of increase)Characteristic high population growth rateStrongest in species colonizing new habitats◦K selection (carrying capacity)Characteristic efficient resource useMore prominent where pops. are near carrying capacity most of the timePianka : r and K are ends of a continuum, while most organisms are in-between (Table 12-1)◦r selection: Unpredictable environments◦K selection: Predictable environmentsRemember R per capita rate of increase and K carrying capacity
80
what is self thinning?
◦predicts that plant population density decreases as total pop. biomass increases ◦when total plant biomass is plotted against density, slope is -3/2, but not for all plant populations
81
Mycorrhizal symbiosis – who is involved? who gets what?
Think plants roots and fungimutualistic fungi that provide root absorptive area to host plant in exchange for photosynthetic product (i.e. sugar) Two most common types of mycorrhizae: ◦Arbuscular mycorrhizal fungi (AMF) Produces arbuscules (site of exchange between plants and fungi) and vesicles (energy storage organs) ◦Ectomycorrhizae (ECM) Forms mantle around roots Important in increasing plant access to phosphorus, other immobile nutrients
82
Difference between fundamental niche vs realized niche
Fundamental niche - The whole species niche and conditions which a species might live.Realized Niche - The real niche of a species.Hutchinsonian Niche: ◦Fundamental niche the hypervolume (total ecological niche of a species) physical conditions under which a species might live in absence of interactions with other species ◦Realized niche the actual niche includes interactions such as competition that may restrict environments where a species may live
83
What is Species diversity?
Diversity: evaluated at the community levelTwo factors define species diversity:◦Species RichnessNumber of species in the communityWho is present◦Species EvennessDistribution of who is presentRelative abundance of speciesContrasts with dominance – one species found in higher proportion than all other species
84
Why care about species diversity?
Provision of biological resourcesMedicine-penicillin, aspirin, natural medicinesRaw materials – e.g. woodDiversity of food crops (i.e. fruit, corn, grains…)Pollination (>90% of all plants require birds, bats, bugs)Economic benefits and income generationEcosystem productivity and stabilityEthicscultural, spiritual and individual aesthetic value
85
What is intermediate disturbance?
Connell proposed that disturbance is a prevalent feature that significantly influences community diversity◦Proposed both high and low levels of disturbance would reduce diversity◦Intermediate levels promote higher diversitySufficient time between disturbances allows wide variety of species to colonize, but not long enough to allow competitive exclusion
86
Age structure Population Growth
Expanding◦Children exceed number of adults◦Population is exceeding replacement level fertility (RLF)◦Pyramid-shaped distribution◦Seen in developing countries◦Stable◦Reproductive-age adults have only enough children to replace themselves◦Population has RLF◦Developed countries◦Shrinking◦Are fewer children than reproducing adults◦Population is below RLF◦Eastern Europe, Japan, Italy
87
Where do the majority of population growth occur?
The majority of future population growth will occur in developing countries:LDC (developing) countries (2003):◦average annual natural increase (births only) was 1.6%◦population doubling time of 42 yearsHDC (developed) countries:◦annual natural increase of 0.1%◦doubling time of 809 years
88
The Changing Human Population
Humans have encountered environmental resistance, but have devised ways to overcome it:◦Prehistoric (~12,000 B.C) development/use of fire, tools, shelters, clothing produced a cultural revolution◦Cultivation of crops and animals (~8000 B.C) led to agricultural revolution, dependable food supply◦Human growth rate exploded with the industrial-medical revolution of the mid-1700s to present – disease control and prevention, lifespan lengthening medicine
89
what are Density-independent factors
Abiotic factors that exert influences independent of population density such as:Natural disastersHuman activities (DDT in birds, habitat destruction)Abiotic factors can influence populations in density-dependent waysExample: cold strikes high density population that has fewer sheltered sites
90
What are density dependent factors
Two types of factors that maintain populations at/below carrying capacity:◦Density-dependent factors – effectiveness depends on population sizepredation – predator feeds on prey, often killing prey but not always; higher predator encounters w/ ↑ prey densityparasitism – a case of predation, in which parasite lives on/inside host without host death; spread rapidly w/high prey densitycompetition – for limited resources; may be indirect (plants block sunlight from others) or direct (territorial defense for food inhibits others)
91
Ecologists study what?
Rates of reproduction, rates of decomposition, and soil chemistry.
92
An association of interacting species is an
Ecosystem
93
MacArthur found that the five species of warblers that live together in the spruce forests of northeastern North America:a) feed on vastly different food sources. b) feed at different times of the day.c) feed in different species of trees.d) feed in different zones in spruce trees.
d) feed in different zones in spruce trees.
94
Research by Likens and Bormann showed that deforestation of small stream basins in the Hubbard Brook Experimental Forest __________ nutrient output from the ecosystem.a) slight decreasedb) slightly increasedc) substantially decreased d) substantially increased
d) substantially increased
95
A hypothesis is best described as a
Proposed explanation for an observed naturalphenomenon.
96
During the northern winter, the Northern Hemisphere:a) is tilted away from the sun.b) is tilted toward the sun.c) receives the same amount of solar energy asthe Southern Hemisphere.d) receives more solar energy than the SouthernHemisphere.
a) is tilted away from the sun.
97
Which of the following is the correct order from the longest to the shortest growing season?a) tropical rain forest, boreal forest, tropical dry forest, tundrab) tundra, tropical dry forest, boreal forest, tropical rain forestc) tundra, boreal forest, tropical dry forest, tropical rain forestd) tropical rain forest, tropical dry forest, boreal forest, tundra
d) tropical rain forest, tropical dry forest, boreal forest, tundra
98
Which of the following is not a characteristic of the tropical rain forest?a) deep, nutrient rich-soilsb) tall trees with well-developed canopy c) abundant epiphytesd) abundant climbing vines
a) deep, nutrient rich-soils
99
Recently human intrusion has increased on the tundra. How is the tundra being impacted by humans?a) conversion to agricultureb) replacement of native habitat with cattleranchesc) extensive loggingd) intense oil exploration and extraction
d) intense oil exploration and extraction
100
How much of Earth’s land surface is covered by desert?
20%
101
Which of the following is true of fire in the tropical savannas?a) kills grasses which resprout each year from an abundant seed bankb) kills young treesc) kills large, mature treesd) promotes trees by releasing an abundantsupply of nutrients into the infertile soil
b) kills young trees
102
Freezing and thawing brings stones to the surface, forming a netlike, or polygon pattern on the surface of the _________ soils.a) boreal forestb) temperate forestc) tundrad) mountain
c) tundra
103
What percentage of the earth’s water supply is seawater?
97%
104
Which of the following represents the largest reservoir in the global hydrologic cycle?a) ice caps and glaciers b) groundwaterc) riversd) atmosphere
a) ice caps and glaciers
105
Darwin believed the driving force behind evolution was selection by the environment.a) True b) False
a) True
106
Analysis of the Hardy-Weinberg principle leads us to conclude that the potential for evolutionary change in natural populations is minimal.a) Trueb) False
b) False
107
Types of Natural Selection
1. Stabilizing selection2. Directional selection3. Disruptive selection
108
Stabilizing selection
Acts to impede changes in a population by acting against extreme phenotypes and favoring average phenotypes.-Occurs where average individuals are best adapted to given set of environmental conditions.
109
Directional selection
Leads to changes in phenotypes by favoring an extreme phenotype over other phenotypes in the population.-Large body size is advantageous under current conditions.
110
Disruptive selection
Creates bimodal distributions by favoring two or more extreme phenotypes over the average phenotype in a population.-Average body size is less advantageous than either small or large.
111
In directional selection:a) the phenotype at one extreme is selected against.b) the phenotypes at both extremes are selected against.c) the average phenotype is selected against.d) the population becomes phenotypically more diverse.
a) the phenotype at one extreme is selected against.
112
Genetic drift:a) is most likely to occur in small populationsb) occurs in populations due to random chancec) reduces genetic diversity in a population d) all of the above are correct regardinggenetic drift
d) all of the above are correct regardinggenetic drift.
113
Aquatic environments generally show less temperature variation compared to terrestrial environments.a) True b) False
a) True
114
Aquatic organisms live in one of three conditions, what are they?
1. Isosmotic2. Hyperosmotic3. Hypoosmotic
115
Isosmotic
Body fluids and external fluid are at the same concentration.
116
Hyperosmotic
Body fluids have higher solute concentration (=lower water concentration) than the external environment.
117
Hypoosmotic
Body fluids have lower solute concentration (=higher water concentration) than the external environment.
118
Freshwater fish
Hyperosmotic-Water comes from food source.-Organism tends to gain water from the environment, lose salts.-Excrete excess water through large volumes of dilute urine.
119
Saltwater bony fish
Hypoosmotic -Organism tends to lose water to the environment, gain salts.-Drink saltwater to compensate for H2O loss via osmosis (gills).-Excrete excess salts through gills and urine, conserve water.
120
Thermal stability
The stability of a molecule at high temperatures; i.e. a molecule with more stability has more resistance to decomposition at high temperatures.Also described as the stability of a water body and its resistance to mixing. This is the amount of work needed to transform the water body (e.g. a lake) to a uniform water density.
121
Marine organisms with body fluid _________ to the surrounding seawater expend the least amount of energy for osmoregulation.a) isosmoticb) hyperosmotic c) hypoosmotic d) osmotic
a) isosmotic
122
Water vapor density (WV)
Measured as the water vapor per unit volume of air.
123
Saturation water vapor density (SWV)
Quantity of water vapor that air can potentially hold. Changes with temperature.
124
Vapor pressure deficit
Difference between water vapor pressure (WVP) and saturation water vapor pressure (SWVP) at a particular temperature; the concentration gradient.
125
Rates of evaporation
Higher the vapor pressure deficit (VPD) indicates that the vapor content in the air is well below saturation (dry), this results in a higher rate of evaporative losses by organisms.
126
Desert plants vs. Arctic plants
Desert plants are often swollen, spiny, and have tiny leaves. They often store water in fleshy leaves, stems or roots. The roots are deep and dense. They consist primarily of cacti and flowers and are fairly evenly distributed.Arctic plants have very shallow roots because they can't penetrate the permafrost. They consist of mosses, lichens, low-growing shrubs, and grasses, but no trees. They grow close together. They also have small leaves.
