Final Chapters 17,18,19,20

Question 1

What is a food web?

Answer 1

Summary of the feeding interactions within a community
Community portrait based on feeding relationships
Depicted with arrows that point in the direction of energy flow

Question 2

What is ecology?

Answer 2

The scientific study of interactions between organisms and their environment.

Question 3

Scientific method

Answer 3

The basis for scientific inquiry.

1. Ask a question
2. Do research
3. Form a hypothesis
4. Perform experiments
5. Analyze data and form a conclusion
6. Record results

Question 4

Scale and manipulation

Answer 4

The changes to environments that occur over large spatial of temporal scales.

Question 5

Levels of ecological organization

Answer 5

1. 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.

Question 6

The 9 biomes

Answer 6

1. Tropical Rainforests
2. Tropical Dryforests
3. Tropical Savannas
4. Deserts
5. Mediterranean Woodlands and Shrublands
6. Temperate Grasslands
7. Temperate Forests (Old Growth)
8. Boreal Forests (Taiga)
9. Tundras

Question 7

Tropical Rainforests

Answer 7

• 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.

Question 8

Tropical Dryforests

Answer 8

• 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.

Question 9

Tropical Savannas

Answer 9

• 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.

Question 10

Deserts

Answer 10

• 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.

Question 11

Mediterranean Woodlands and Shrublands

Answer 11

• 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.

Question 12

Temperate Grasslands

Answer 12

• 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.

Question 13

Temperate Forests (Old Growth)

Answer 13

• 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.

Question 14

Boreal Forests (Taiga)

Answer 14

• 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.

Question 15

Tundras

Answer 15

• 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.

Question 16

The Hydrologic Cycle

Answer 16

• 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.

Question 17

Turnover time

Answer 17

Amount of time it takes for entire volume of water of a reservoir to be renewed.

Question 18

Evolution

Answer 18

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.

Question 19

Natural selection

Answer 19

The result of differences in survival and reproduction among phenotypes.

Question 20

What is the broadest (most inclusive) of the levels of ecological organization?

Answer 20

Biosphere

Question 21

Keystone Species

Answer 21

Keystone species exert strong effects on their community structure, despite low biomass

Question 22

What two examples did she use for keystone species (chap 17)

Answer 22

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 treatment

Snail: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

Question 23

What is a introduced species?

Answer 23

Introduced species:
those that humans intentionally or accidentally move from the species’ native locations to new geographic regions
Sometimes called non-native, exotic, alien

Example:
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 predator

Since introduced decline in species diversity.

Question 24

Why is a keystone species important?

Answer 24

A keystone species is important because it has great significance in promoting species diversity.

Question 25

What are strong interactions?

Answer 25

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

Question 26

What is a ecosystem?

Answer 26

all of the organisms living in and area and the physical environment with which those species interact

Question 27

What is primary production?

Answer 27

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 time

Gross 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

Question 28

Types of Trophic Levels

Answer 28

Primary Producers (Plants)
Primary Consumers (Herbivores and detritivores)
Secondary consumers(Carnivores that comsume herbivores and detritivores)
Tertiary, Quaternary (harder carnivores)
Top Predators (Apex Predators)

Question 29

Evapotranporation

Answer 29

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 landscape
AET is affected by both temperature and precipitation
Cold ecosystems (e.g. tundra) and dry ecosystems (e.g. deserts) tend to have low AET

Question 30

What is soil fertility?

Answer 30

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

Question 31

Limits on nutrient availability in freshwater?

Answer 31

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 ecosystems

Thiik adding fertilizer will increases biomass taking away fertilizer decreases. Graneli Baltic sea.

Question 32

How Do Consumers Influence Production?

Answer 32

Bottom-Up Controls
◦Influences of physical/chemical factors of an ecosystem 
◦e.g. temperature, nutrients, light
Top-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 web
Ex: apex predator down

Question 33

Lake Production and Trophic Cascades

Answer 33

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

Question 34

Trophic Cascade Hypothesis:

Answer 34

• Piscivores reduce planktivorous fish directly by eating them
• Piscivores then indirectly increase populations of large zooplankton and indirectly reduce phytoplankton biomass

Question 35

Lake Trophic Cascade experiment

Answer 35

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
…..

Question 36

Trophic Dynamic View of Ecosystems defention

Answer 36

Lindeman (1942):
◦ Ecosystem concept is fundamental to the study of
energy transfer within an ecosystem
◦ Suggested grouping organisms within an ecosystem
into trophic levels
 Each feeds on level immediately below
 As energy is transferred from one trophic level to
another, energy is degraded
◦ Among the first ecologists to
quantify the flux of energy
through an (lake) ecosystem

Question 37

Trophic Dynamic View of Ecosystems defention 2nd law of thermodynamics

Answer 37

2nd Law of Thermodynamics:
◦ As energy is transferred from one trophic level to
another, 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 in
biomass that is transferred to
biomass in next higher
trophic level; varies from
5-20%, usually ~10%

Question 38

Ecological Pyrimad

Answer 38

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 small
compared to that of lower level consumers (=herbivores)

Question 39

Reasons for decline in energy flow

Answer 39

This decline in the amount of available energy
explains why:
◦ Top level consumers (whales, hawks) require so much
geographic territory to get enough food
◦ Most food chains are limited to 4-5 levels – not enough
energy to support more
◦ Are no non-human predators of large predators (lions,
eagles)
 biomass of these predators is not sufficient to support
another trophic level

Question 40

Ecosystem Energetics and Human Nutrition

Answer 40

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 environment
It takes at least 10 lbs. of corn  1 lb. beef

Question 41

Energy Flow in A Temperate Deciduous Forest: An Energy Budget

Answer 41

Most energy flowing through ecosystem is lost to heat, respiration, evapotranspiration
NPP was <1% of the input of solar energy
◦99% of solar energy unavailable for use by a second trophic level
As 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 level
Energy flows, nutrients cycle

Question 42

Nutrient Cycles (3 types)

Answer 42

Nitrogen Cycle, Phosphorous cycle, and Carbon cycle

Question 43

Define Nutrients and Nutrients cycle

Answer 43

elements required for the development, maintenance and reproduction of organisms Ex: C, P, N, K, Fe
Nutrient cycle – use, transformation movement and reuse of nutrients

Question 44

Phosphorous significance

Answer 44

Biological/Ecological Significance:

◦forms phospholipids, nucleic acids, ATP

Question 45

Phosphorus forms

Answer 45

Forms:
◦Not very abundant in the biosphere
◦Primarily found as phosphate (PO4)
◦Available to living things after decomposition of phosphate-containing organic matter
Reservoirs:
◦Global phosphorus cycle does not include substantial atmospheric component (unlike C, N) – no gaso

Question 46

Phosphorous Resivors

Answer 46

◦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

Question 47

Nitrogen cycle signifigance

Answer 47

Biological/Ecological Significance
◦amino acids (proteins), nucleic acids, chlorophyll, hemoglobin
◦of high ecological importance, scarce

Question 48

Nitrogen resivors

Answer 48

Largest pool is in the oceans
◦Includes major atmospheric pool, but only one way to bioavailability - N2
◦Human activity has moved cycle: land  atmosphere

Question 49

Nitrogen forms and fluxes

Answer 49

Forms and Fluxes:
◦Only nitrogen fixers can use atmospheric supply directly - N2 reduced to ammonia (NH3) in an energy-demanding process
Once 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 bacteria
NH4, NO3 are used directly by bacteria, fungi, plants
◦Denitrification: NO3N2 (via anaerobic respiration by specific bacteria)

Question 50

Carbon cycle signifigance

Answer 50

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

Question 51

Carbon Resivors

Answer 51

Carbonate rocks and oceans are two largest pools

◦Human activity has moved cycle: land  atmosphere

Question 52

Carbon forms and fluxes

Answer 52

Forms and Fluxes:
◦Organic molecules - associated with living things – plants, animals, etc.; simplest is CH4
◦Inorganic molecules – primarily CO2
In aquatic ecosystems, CO2 must dissolve in water to be available for PS – HCO3 and CO3 inorganic forms
Respiration (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

Question 53

Organic Carbon –> Inorganic Carbon: Rates of Decomposition

Answer 53

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 decomposition
breakdown of organic matter, CO2 and nutrients released
Nutrient exchange is therefore affected by decomposition

Question 54

Decomposition in Terrestrial Ecosystems

Answer 54

Decomposition rates in terrestrial systems influenced by:
◦chemical compositions of leaf tissue (N, P, lignin)
◦moisture
◦Temperature
Decomposition 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

Question 55

Decomposition in Temperate Forest Ecosystems

Answer 55

Melillo et.al.
◦decomposition in temperate forests (NC, NH)
◦leaves with higher lignin:nitrogen ratios lost less mass
lignin - complex chemical associated with woody species
Also differences between locations:
◦higher soil N availability contributed to higher decomposition rates
◦higher environmental temperatures may have also played a role

Question 56

Decomposition in Temperate Forest Ecosystems

Answer 56

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?

Question 57

Decomposition Rates in Aquatic Ecosystems

Answer 57

Most important controlling variables:
◦chemical composition of litter
◦nutrient concentrations in system
◦leaf species
◦temperature

Question 58

Decomposition Rates in Aquatic Ecosystems

Answer 58

Gessner and Chauvet:
◦Leaves with a higher lignin content decomposed at a slower rate
◦Higher lignin inhibits colonization by fungi

Question 59

Decomposition Rates in Aquatic Ecosystems

Answer 59

Suberkropp and Chauvet:
◦leaves degraded faster in streams with higher nitrate concentrations
Rosamond:
◦Ficus decomposition in relation to tropical stream phosphorus
◦Rates increased at low P levels, then leveled off at high P levels

Question 60

How do aquatic organisms modify the distribution and cycling of nutrients?

Answer 60

Grimm:
◦Aquatic inverts significantly increase rate of N cycling
◦Inverts can ingest, egest, excrete, accumulate N
◦80% were collector-gatherers
Ingested 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

Question 61

How do terrestrial organisms modify the distribution and cycling of nutrients?

Answer 61

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

Question 62

Effects of Disturbance on Nutrient Cycling: An Introduced Tree in Hawaii

Answer 62

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

Question 63

Disturbance & Nutrient Loss From Hubbard Brook Forest

Answer 63

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

Question 64

What is succession?

Answer 64

observed process of change in community structure over time

gradual change in plant and animal communities in an area following disturbance

Question 65

What is a pioneer community?

Answer 65

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 soil
Abandonment of agricultural lands, fire

Question 66

What is a Climax community?

Answer 66

Late successional community that remains stable until disrupted by disturbance
◦Nature of this community depends on environmental circumstances (grassland, forest)

Question 67

Primary succession example “Glacier Bay”

Answer 67

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 stages
Not all groups increased in density throughout succession
Timing of increasing species richness differed among plant forms

Question 68

Secondary succession example “Temperate Forest”

Answer 68

Oosting found number of woody plant species increased during secondary succession at Piedmont Plateau, NC
Began with single woody plant invader
Species richness reaches plateau over time

Question 69

Ecosystem Changes During Succession

Answer 69

Ecosystem changes during succession include increases in:
◦Biomass
◦Primary production
◦Respiration
◦Nutrient retention
◦Ecosystem properties
Soil nutrients/OM

Question 70

Chronosequnces

Answer 70

◦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 age
Hedin et.al. found differing patterns of nutrient distribution across the chronosequence – high N, lower P loss rates

Question 71

Recovery of Nutrient Retention Following Disturbance

Answer 71

Bormann and Likens found felling trees in Hubbard Brook substantially increased nutrient losses
Herbicide used to suppress regrowth
When application stopped:
◦succession proceeded
◦nutrient losses decreased
◦primary production increased

Question 72

Drivers/Mechanisms of Succession?

Answer 72

Mechanisms that drive succession include:
◦Facilitation – Clements (1917)
◦Tolerance
◦Inhibition
Connell and Slayter (1977) – alternative successional mechanisms, included the three above

Question 73

What is the Facilitation Model?

Answer 73

Proposes many species may attempt to colonize newly available space
Only certain species with certain characteristics will establish
These 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

Question 74

What is the Inhibition Model?

Answer 74

Assumes any climax adult will be able to colonize early
Early 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 species
Late successional species wind up dominating an area because they live a long time and resist damage by physical and biological factors

Question 75

Sousa Example Rocky Intertidal

Answer 75

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 mortality
Results showed early successional species had lowest survivorship and were more vulnerable to herbivores
Ulva prevented establishment of late-successional species

Question 76

Causes of Community & Ecosystem Stability

Answer 76

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 disturbance
Stability
◦absence of change
◦persistence in the face of disturbance

Question 77

What is Park Grass Experiment regards to Ecosystem Stability?

Answer 77

Hertfordshire, England - Rothamsted Experimental Station
◦Studied effects of fertilizer treatments
Continued for 150 years (1856 - )
Silverton investigated ecosystem stability
◦Used community composition variability as measure of stability – grasses, legumes, other plants, as proportion in community

Question 78

Principle of Allocation

Answer 78

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

Question 79

R. vs K Selection

Answer 79

MacArthur and Wilson:
◦r selection (per capita rate of increase)
Characteristic high population growth rate
Strongest in species colonizing new habitats
◦K selection (carrying capacity)
Characteristic efficient resource use
More prominent where pops. are near carrying capacity most of the time
Pianka : r and K are ends of a continuum, while most organisms are in-between (Table 12-1)
◦r selection: Unpredictable environments
◦K selection: Predictable environments

Remember R per capita rate of increase and K carrying capacity

Question 80

what is self thinning?

Answer 80

◦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

Question 81

Mycorrhizal symbiosis – who is involved? who gets what?

Answer 81

Think plants roots and fungi

mutualistic 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

Question 82

Difference between fundamental niche vs realized niche

Answer 82

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

Question 83

What is Species diversity?

Answer 83

Diversity: evaluated at the community level
Two factors define species diversity:
◦Species Richness
Number of species in the community
Who is present
◦Species Evenness
Distribution of who is present
Relative abundance of species
Contrasts with dominance – one species found in higher proportion than all other species

Question 84

Why care about species diversity?

Answer 84

Provision of biological resources
Medicine-penicillin, aspirin, natural medicines
Raw materials – e.g. wood
Diversity of food crops (i.e. fruit, corn, grains…)
Pollination (>90% of all plants require birds, bats, bugs)
Economic benefits and income generation
Ecosystem productivity and stability
Ethics
cultural, spiritual and individual aesthetic value

Question 85

What is intermediate disturbance?

Answer 85

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 diversity
Sufficient time between disturbances allows wide variety of species to colonize, but not long enough to allow competitive exclusion

Question 86

Age structure Population Growth

Answer 86

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

Question 87

Where do the majority of population growth occur?

Answer 87

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 years
HDC (developed) countries:
◦annual natural increase of 0.1%
◦doubling time of 809 years

Question 88

The Changing Human Population

Answer 88

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

Question 89

what are Density-independent factors

Answer 89

Abiotic factors that exert influences independent of population density such as:
Natural disasters
Human activities (DDT in birds, habitat destruction)
Abiotic factors can influence populations in density-dependent ways
Example: cold strikes high density population that has fewer sheltered sites

Question 90

What are density dependent factors

Answer 90

Two types of factors that maintain populations at/below carrying capacity:
◦Density-dependent factors – effectiveness depends on population size
predation – predator feeds on prey, often killing prey but not always; higher predator encounters w/ ↑ prey density
parasitism – a case of predation, in which parasite lives on/inside host without host death; spread rapidly w/high prey density
competition – for limited resources; may be indirect (plants block sunlight from others) or direct (territorial defense for food inhibits others)

Question 91

Ecologists study what?

Answer 91

Rates of reproduction, rates of decomposition, and soil chemistry.

Question 92

An association of interacting species is an

Answer 92

Ecosystem

Question 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.

Answer 93

d) feed in different zones in spruce trees.

Question 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 decreased
b) slightly increased
c) substantially decreased
d) substantially increased

Answer 94

d) substantially increased

Question 95

A hypothesis is best described as a

Answer 95

Proposed explanation for an observed natural

phenomenon.

Question 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 as
the Southern Hemisphere.
d) receives more solar energy than the Southern
Hemisphere.

Answer 96

a) is tilted away from the sun.

Question 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, tundra
b) tundra, tropical dry forest, boreal forest, tropical rain forest
c) tundra, boreal forest, tropical dry forest, tropical rain forest
d) tropical rain forest, tropical dry forest, boreal forest, tundra

Answer 97

d) tropical rain forest, tropical dry forest, boreal forest, tundra

Question 98

Which of the following is not a characteristic of the tropical rain forest?

a) deep, nutrient rich-soils
b) tall trees with well-developed canopy
c) abundant epiphytes
d) abundant climbing vines

Answer 98

a) deep, nutrient rich-soils

Question 99

Recently human intrusion has increased on the tundra. How is the tundra being impacted by humans?

a) conversion to agriculture
b) replacement of native habitat with cattle
ranches
c) extensive logging
d) intense oil exploration and extraction

Answer 99

d) intense oil exploration and extraction

Question 100

How much of Earth’s land surface is covered by desert?

Answer 100

20%

Question 101

Which of the following is true of fire in the tropical savannas?

a) kills grasses which resprout each year from an abundant seed bank
b) kills young trees
c) kills large, mature trees
d) promotes trees by releasing an abundant
supply of nutrients into the infertile soil

Answer 101

b) kills young trees

Question 102

Freezing and thawing brings stones to the surface, forming a netlike, or polygon pattern on the surface of the _________ soils.

a) boreal forest
b) temperate forest
c) tundra
d) mountain

Answer 102

c) tundra

Question 103

What percentage of the earth’s water supply is seawater?

Answer 103

97%

Question 104

Which of the following represents the largest reservoir in the global hydrologic cycle?

a) ice caps and glaciers
b) groundwater
c) rivers
d) atmosphere

Answer 104

a) ice caps and glaciers

Question 105

Darwin believed the driving force behind evolution was selection by the environment.

a) True
b) False

Answer 105

a) True

Question 106

Analysis of the Hardy-Weinberg principle leads us to conclude that the potential for evolutionary change in natural populations is minimal.

a) True
b) False

Answer 106

b) False

Question 107

Types of Natural Selection

Answer 107

1. Stabilizing selection
2. Directional selection
3. Disruptive selection

Question 108

Stabilizing selection

Answer 108

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.

Question 109

Directional selection

Answer 109

Leads to changes in phenotypes by favoring an extreme phenotype over other phenotypes in the population.
-Large body size is advantageous under current conditions.

Question 110

Disruptive selection

Answer 110

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.

Question 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.

Answer 111

a) the phenotype at one extreme is selected against.

Question 112

Genetic drift:

a) is most likely to occur in small populations
b) occurs in populations due to random chance
c) reduces genetic diversity in a population
d) all of the above are correct regarding
genetic drift

Answer 112

d) all of the above are correct regarding

genetic drift.

Question 113

Aquatic environments generally show less temperature variation compared to terrestrial environments.

a) True
b) False

Answer 113

a) True

Question 114

Aquatic organisms live in one of three conditions, what are they?

Answer 114

1. Isosmotic
2. Hyperosmotic
3. Hypoosmotic

Question 115

Isosmotic

Answer 115

Body fluids and external fluid are at the same concentration.

Question 116

Hyperosmotic

Answer 116

Body fluids have higher solute concentration (=lower water concentration) than the external environment.

Question 117

Hypoosmotic

Answer 117

Body fluids have lower solute concentration (=higher water concentration) than the external environment.

Question 118

Freshwater fish

Answer 118

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.

Question 119

Saltwater bony fish

Answer 119

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.

Question 120

Thermal stability

Answer 120

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.

Question 121

Marine organisms with body fluid _________ to the surrounding seawater expend the least amount of energy for osmoregulation.

a) isosmotic
b) hyperosmotic
c) hypoosmotic
d) osmotic

Answer 121

a) isosmotic

Question 122

Water vapor density (WV)

Answer 122

Measured as the water vapor per unit volume of air.

Question 123

Saturation water vapor density (SWV)

Answer 123

Quantity of water vapor that air can potentially hold. Changes with temperature.

Question 124

Vapor pressure deficit

Answer 124

Difference between water vapor pressure (WVP) and saturation water vapor pressure (SWVP) at a particular temperature; the concentration gradient.

Question 125

Rates of evaporation

Answer 125

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.

Question 126

Desert plants vs. Arctic plants

Answer 126

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.