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Ecology Study Notes
Ecology
- Ecological Maxims
o 1. Organisms interact and are interconnected
o 2. Everything goes somewhere
o 3. No population can increase in size forever
o 4. Finite energy and resources result in tradeoffs
o 5. Organisms evolve
o 6. Communities and ecosystems change over time
o 7. Spatial scale matters
- Biosphere > ecosystem > community > population > organism
- Net Primary Productivity (NPP) – energy captured by produces, minus the amount lost as heat
in cellular respiration
- Some declines in amphibian populations may be due to:
o Pesticides causing less white blood cells to fight parasites
o Fertilizer runoff increase algal growth, more food for snails, more parasites
o Climate change favouring growth and transmission of disease organisms
i.e. chytrid fungus that causes a lethal skin disease
o pollution
o UV exposure
o habitat loss
The Physical Environment
- Climate is characterized by average conditions; but extreme conditions are also important
because they can contribute to mortality
- Without greenhouse gases (water vapour, carbon dioxide, methane, nitrous oxide) earth’s
climate would be about 33 degrees cooler
- Warm air rising because it is less dense than cool air is called uplift
- Air pressure decreases with altitude so the rising air expands and cools
- Three major climatic zones in each hemisphere
o Tropical
o Temperate
o Polar
- Areas of high and low pressure created by the circulation cells result in air movements called
prevailing winds
o Winds appear to be deflected due to the rotation of the Earth – the Coriolis effect
- Semipermanent high and low pressure cells:
o Summer – air over oceans is cooler, high pressure develops
o Winter – air over continents is cooler, high pressure develops
- Downwelling - warm surface currents reach polar area, water freezes, becomes more saline and
dense and sinks
- Upwelling – prevailing winds blow parallel to a coastline, surface water flows away and deeper,
colder ocean water rises to replace it (influence coastal climate)
- Most productive areas in the open ocean is the photic zone where upwellings bring nutrients
from the deep sediments to the area where light can penetrate and phytoplankton can grow
- Maritime climate (coastal areas): little daily and seasonal variation in temperatures, high
humidity
- Continental climates – much greater variation in daily and seasonal temperatures
- Albedo – capacity of a land surface to reflect solar radiation – influenced by vegetation type,
soils and topography (configuration of the earth’s surface)
- ITCZ – intertropical convergence zone: the northeast and southeast trade winds converge
around the equator and air rises forming a low pressure zone where there is lots of precipitation
- Temperate zone lakes
o Epilimnion – warm water
o Hypolimnion – colder water
o Thermocline – transition zone
- Milankovitch cycles – regular changes in the shape of the earth’s orbit and the tilt of its axis
The Biosphere
- Biomes are large scale biological communities shaped by the physical environment
- Sclerophyllous shrubs – seasonally dry/moist and warm/cool
- Deciduous trees – moist, seasonally warm/cool or cool/cold on fertile soils or warm, seasonally
wet/dry
- Cacti and shrubs; succulent stems or leaves – dry, seasonally hot/cool
- There are 9 major terrestrial biomes:
o Tropical rainforests
High annual temperature, high precipitation
High biomass, high diversity – about 50% of earth’s species
About half of biome has been altered
o Tropical seasonal forests and savannahs
High annual temp., high precipitation from October - May with period of water
stress (lower precip than temp on chart) from june to august
Savannahs are more grass dominated
Wet and dry seasons associated with movement of the ITCZ
Fire promotes establishment of savannahs
Less than half remain
Human pop growth has a major influence
o Hot Deserts
High temperatures, low precip
Sparse vegetation and animal population
Low water availability constrains plant abundance and influences form
Many plants have succulent stems that store water
Cacti and euphorbs show convergence
Agriculture depends on irrigation, and results in soil salinization because of high
amounts of evaporation
Long term drought can result in desertification, makes it harder for plants to be
re-established in the area
o Temperate Grasslands
Warm moist summers; cold, dry winters
Grasses dominate; maintained by frequent fires and large herbivores
About 1% of tall grasslands remain in Ontario
Grasses grow more roots than stems and leaves to cope with dryness
Results in accumulation of organic matter and high soil fertility
Most have been converted to agriculture
In arid grasslands, grazing can exceed capacity for regrowth, leading to
degradation and desertification
o Temperate Shrublands and Woodlands
Mediterranean like systems, opposite growing cycle to what we see in Ontario
Evergreen leaves allow plants to be active during cooler, wetter periods
Plants don’t have to develop new leaves every year
Sclerophyllous leaves – tough and leathery – deter herbivores and prevent
wilting
After fires, shrubs sprout from underground storage organs or produce seeds
that sprout and grow quickly
Without regular fires at 30-40 year intervals, shrublands may be replaced by
forest
o Temperate Deciduous Forests
i.e. Ontario
Fertile soil and climate make this biome good for agriculture
Shifts in species composition due to nutrient depletion by agriculture and
invasive species
o Temperate Evergreen Forests
Biome has been logged extensively
Very little old growth remains
In some areas, trees have been replaced with non-native species
Suppression of fires has increased the density of forest stands, which results in
more intense fires when they happen
Air pollution has damaged some temperate evergreen forests
o Boreal Forests
Long severe winters
Permafrost prevents drainage and results in saturated soils
Trees are conifers - pines, spruces, larches
Cold wet conditions limit decomposition, so soils have high organic matter
In summer droughts, fires can burn both trees and soil
In low lying areas, extensive peat-bogs form
Have not been as effected by human activity
Climate warming may increase soil decomp rates, releasing carbon and creating
a positive feedback to warming
o Tundra
Arctic has experienced significant climate change, with warming almost double
the global average
On mountains, temp and precip change with elevation
Smaller scale variations are associated with slope aspect, proximity to streams,
and prevailing winds
- Streams and rivers are lotic (flowing water) systems
o Benthic organisms are bottom dwellers, including many kinds of invertebrates
o Some feed on detritus (dead organic matter) others are predators
o Some live in the hyporheic zone – the substratum below and adjacent to the stream
- Lakes and stillwaters (lentic) occur where depressions in the landscape fill with water
o Littoral zone is near shore where the photic zone reaches the bottom
Macrophytes occur in this zone
o Pelagic zone: open water; dominated by plankton
o Phytoplankton are photosynthetic, restricted to the upper layers in the photic zone
(extends about 200m deep)
o Zooplankton are non-photosynthetic protists and tiny animals
- Estuaries occur where rivers flow into oceans
o Salinity varies as fresh water from the river mixes with salt water from the sea
o Are increasingly threatened by pollution carried in rivers
o Nutrients from agricultural runoff can create local dead zones and loss of biodiversity
- Salt marshes: shallow coastal wetlands dominated by grasses and rushes
o Terrestrial nutrients enhance productivity
o Tides produce salinity gradients
- Kelp beds support a diverse marine community
o Large brown algae with leaf like fronds, stems, and holdfasts which anchor to solid
substrates
- Pelagic zone: open ocean beyond continental shelves
- Below photic zone, energy is supplied by falling detritus, temp drops and pressure increases
Coping with Environmental Variation: Temperature and Water
- Energy supply can influence and organism’s ability to tolerate environmental extremes
- Actual distribution of a species also relates to factors such as disturbance and competition
- Plants are good indicators of physical environment
- Acclimation is short term, adaption is a long term change to environmental stress
o Over time genetic traits become more frequent in population
- Ecotypes – populations with adaptions to unique environments
o Can eventually become separate species due to divergence and become reproductively
isolated
o Speciation if isolated enough
- Survival and functioning of organisms is strongly tied to their internal temperature
- Some species produce isozymes that allow acclimatization
- At low temps, membranes can solidify not allowing proteins to function
- Some insects have high concentrations of glycerol, a chemical that lowers the freezing point of
body fluids
- Cost of being an endotherm is a high demand for energy
- Rate of heat loss is related to body size and surface area-to-volume ratio
- Insulation limits conductive and convective heat loss
- Some organisms enter state of dormancy in which little or no metabolic activity occurs
- Torpor: body temp and BMR are low which conserves energy
o Energy reserves needed to come out of torpor
- Long periods of torpor is called hibernation
- Desiccation-tolerant organisms can lose 80-90% of their water, going into suspended animation
- Sweat glands in mammals are a trade-off between water loss resistance and evaporative cooling
- Conduction: transfer of energy from warmer to cooler molecules
- Convection: heat energy is carried by moving water or air
- Pubescence: hairs on leaf surfaces that reflect solar energy and reduce conductive heat loss
o If air temp is lower than leaf temp, heat can be lost by convection
Related to speed of air moving across leaf
- Boundary layer: a zone of turbulent flow due to friction, next to leaf surface
o Lower convective heat loss
o In cold, windy environments, convection is the main heat loss mechanism
Coping with Environment Variation: Energy
- Holoparasites: plants that have no photosynthetic pigments and get energy from other plants
o Ex. Dodder – can significantly reduce biomass in the host plant
- Hemiparasite: photosynthetic, but obtain nutrients, water, and some of its energy from the host
plant
o Ex. Mistletoe
- Chemosynthesis: energy from inorganic compounds is used to produce carbohydrates
o Important in nutrient cycling bacteria, and in some ecosystems
- Light response curves show the influence of light levels on photosynthetic rate
- Light compensation point: where CO2 uptake is balanced by CO2 loss by respiration
- Saturation point: when photosynthesis no longer increases as light increases
- Plants can acclimatize to changing light intensities with shifts in light response curves
- Higher nitrogen levels in a leaf correlated with higher photosynthetic rates
- Increasing nitrogen increases risk of being eaten
- RuBisCo can catalyze two competing reactions
o Carboxylase reaction: photosynthesis
o Oxygenase reaction: O2 taken up, carbon compounds are broken down, CO2 is released
Photorespiration
- Arapidopsis thaliana plants have a mutation that knocks out photorespiration
o These plants die under normal light and CO2
- Photorespiration may protect plants from damage at high light levels
- C4 plants
o CO2 is taken up in the mesophyll by PEPcase
Has greater affinity for CO2, does not take up O2
o CO2 concentration is increased in bundle sheath cells where rubisco is operating in the
calvin cycle, which reduces O2 uptake by rubisco
o More ATP required for C4 pathway
- Creasulacean acid metabolism (CAM) plants minimizes water loss
o Open stomates at night when it is cooler and humidity is higher, close them during the
day
o Often succulent, with thick, fleshy leaves or stems
- Optimal foraging theory: animals will maximize the amount of energy gained per unit time,
energy and risk involved in finding food
o Assumes that evolution acts on the behaviour of animals to maximize their energy gain
o Profitability of a food item (P) depends on how much energy (E) the animal gets from
the food relative to the amount of time (t) it spends finding and obtaining the food
P=E/t
o Does not apply as well to animals that feed on mobile prey
- Marginal value theorem: an animal should stay in a patch until the rate of energy gain has
declined to match the average rate for the whole habitat (giving up time)
o Also influenced by distance between patches
Evolution and Ecology
- Directional selection: individuals at one phenotypic extreme are favoured
o Ex. Darwin finches during drought
- Stabilizing selection: individuals with an intermediate phenotype are favoured
o Ex. Parasitic wasps select small gall sized of eurosta flies while birds select large gall sizes
- Disruptive selection: Individuals at both phenotypic extremes are favoured
o i.e. fish that are bigger or smaller and faster
Life Histories
- the life history strategy of a species is the overall pattern in average timing and nature of life
history events
- phenotypic plasticity: one genotype may produce different phenotypes under different
environmental conditions
o growth and development may be faster in higher temps
- Allometry: different body parts grow at different rates, resulting in differences in shape or
proportion
- Isogamy: gametes are equal in size
o Green alga have two mating types that produce isogametes
- Anisogamy: gametes of different sizes; usually egg is much larger and contains nutritional
material
- Complex lifecycles have at least two stages with different body forms and that live in different
habitats
- Metamorphosis: abrupt transition in form between the larval and juvenile stage
- Plants and most algae have alternation of generations in which a multicellular diploid
sporophyte alternates with a multicellular haploid gametophyte
- Semelparous: species reproduce only once
o Annual plants
o Agave
o Giant pacific octopus
- Iteroparous: species can reproduce multiple times
o Trees such as pines and spruces
o Most large mammals
- R-selection
o R is the intrinsic rate of increase of a population
o For high population growth rates; an advantage in newly disturbed habitats and
uncrowded condition
o Live fast, die young
o Short lifespans, rapid development, early maturation, low parental investment, high
reproduction rate
Most insects, small vertebrates
- K-selection
o K is the carrying capacity for a population
o For slower growth rates in populations that are at or near K; this is an advantage in
crowded conditions; efficient reproduction is favoured
o Slow and steady
o Long lived, develop slow, late maturation, invest heavily in each offspring, low
reproduction rates
large mammals, reptiles, long lived plants
- most life histories are intermediates between these extremes
- Ruderal plants: short life span, rapid growth rates, heavy investment in seed production
- Lack clutch size: maximum number of offspring a parent can successfully raise to maturity
o Named after david lack who noticed a birds clutch size increased with latitude
More daylight, more foraging and feeding more offspring
Larger clutches, offspring have less chance for survival
- Senescence: decline in physiological function with age
o Semelparous species undergo very rapid senescence and death following reproduction
- Sessile organisms (can’t move freely) disperse as pollen, seeds, spores, gametes or larvae
o Small and easily carried on wind or water currents
- Dormancy: state of suspended growth and development in which an organism can survive
unfavourable conditions
- Niche shift: individuals may have different ecological roles depending on size and age
- Ecological niche: the physical and biological conditions that an organism needs to grow, survive,
and reproduce
- Paedomorphic: maturing sexually while retaining larval morphology and habitat
- Sequential hermaphroditism: change in sex during the course of the life cycle
o Common in fish and invertebrates
o Timing should take advantage of high reproductive potential of different sexes at
different sizes
Population Distribution and Abundance
- Distribution: geographic area where individuals of a species occur
- Abundance: number of individuals in a given area
o Population size (# of individuals)
o Population density (# of individuals per unit area)
o Can change over time and space
- Dynamic: change over time and space
- Genet: single genetic individuals – colony of clones
- Ramet: members of a genet are independent physiologically – individual in colony
- The distributions and abundance of organisms are limited by habitat suitability, historical
factors, and dispersal
- The dispersion of individuals within a population depends on the location of essential resources,
competition, dispersal, and behavioural interactions
- Dispersion: spatial arrangement of individuals within a population
- Relative population size: number of individuals in one time period or place relative to the
number in another
o Based on data presumed to be related to absolute population size
- Area-based counts used most often to estimate abundance of immobile organisms
- To estimate total population size (N) for marked recaptured:
o M/N = R/C or N=(MxC)/R
M = marked
C = captured
R = recaptured
- GARP compares grid cell data with habitat rules for species
o Correct 75-80% of the time
Population Growth and Regulation
- Ecological footprint: total area of productive ecosystems required to support a population
- A life table is a summary of how survival and reproductive rates vary with age
o Sx = survival rate: chance that an individual of age x will survive to age x + 1
o Ix = survivorship: proportion of individuals that survive from birth to age x
o Fx = fecundity: average number of offspring a female will have at age x
- In some species age is not important
- Survivorship curve: the number of individuals from a hypothetical cohort that will survive to
reach different ages
o Type I: most individuals survive to old age
Dall sheep, humans
o Type II: the chance of surviving remains constant throughout lifetime
Some birds
o Type III: high death rates for young, those that reach adulthood survive well
Species that produce a lot of offspring
- Growth rate (λ): ratio of population size in year t + 1 (Nt+1) to population size in year t (Nt)
o λ= Nt+1/Nt
o If survival rates or fecundity rates change, population growth rate will change
- Geometric growth: a population reproduces in synchrony at discrete time periods and growth
rate doesn’t change
o Nt+1 =λNt
- Exponential growth: when individuals reproduce continuously, and generations can overlap
o dN/dt = rN
dN/dt = rate of change in population size at each instant in time
r = exponential population growth rate
- Population regulation: denisity-dependent factors cause population to increase when density is
low and decrease when density is high
- Logistic growth: population increases rapidly, then stabilizes at the carrying capacity
o Growth rate decreases as population nears carrying capacity because resources begin to
run short
dN/dt = rN(1-N/K)
N= population density
r= per capita growth rate
K= carrying capacity
o At CC, growth rate is 0
o When densities are low, logistic growth is similar to exponential
o When N is small (1-N/K) is close to 1, and the pop increases at a rate close to r
Population Dynamics
- Population dynamics: the ways in which populations change in abundance over time
- Jump dispersal: species colonize new regions by long-distance
- Population outbreak: number of individuals increase rapidly
- Delayed density dependence: delays in the effect that density has on population size
- Logistic equation can be modified to include time lags (τ)
o dN/dt = rN[1-N(t-τ)/K]
N(t-τ) = population size at time t-τ in the past
- Stable limit cycle: fluctuating population
o When rτ is small (0< rτ<0.368), there is no fluctuation
o At intermediate levels, (0.368< rτ<1.57), damped oscillations result
Oscillations getting closer and closer to cc
o When rτ is large (rτ>1.57), the population fluctuates indefinitely about the cc
- Demographic stochasticity: chance events affect survival and reproduction of individuals
o Change in average birth or death rates from year to year
- Environmental stochasticity: unpredictable changes in the environment that can cause
extinction of small populations
o Birth and death rates are constant, but actual fates differ
- Metapopulations: suitable habitat existing as a series of spatially isolated patches, resulting in
isolated populations, linked by dispersal of individuals or gametes
o Characterized by repeated extinctions and colonizations of the small individual
populations, but the metapopulation persists
- Extinction and colonization of patches (Levins)
o dp/dt = cp(1-p)-ep
p= proportion of habitat patches occupied at time t
c= patch colonization rate
e= patch extinction rate
o Equation makes several assumptions
1. There is an infinite number of identical habitat patches
2. All patches have an equal chance of receiving colonists
3. All patches have an equal chance of extinction
4. Once a patch is colonized, its pop increases to cc faster than colonization and
extinction rates (allows pop dynamics within patches to be ignored)
o For a metapopulation to persist for a long time, the ration e/c must be <1
o Habitat fragmentation: large tracts of habitat are converted to isolated patches,
resulting in a metapopulation
As patches get smaller and more isolated, colonization decreases and extinction
rate increases
If e/c becomes >1, the metapopulation will go extinct
- Rescue effect: high rates of immigration protect a population from extinction
- Two types of causation in ecological communities
o Bottom up control
o Top down control
Competition
- G. Tansley did one of the first experiments on competition in 1917 using species of bedstraw
- Competition occurs between species that share the use of a resource that limits the growth,
survival, or reproduction of each species
- Interspecific competition: interaction between two species in which each is harmed when they
both use the same limiting resource
- Intraspecific competition: between individuals of a single species
- Exploitation competition: species compete indirectly – individuals reduce the availability of a
resource as they use it
- Interference competition: species compete directly for access to a resource
- Allelopathy: plants of one species release toxins that harm other species
- Competing species are more likely to coexist when they use resources in different ways
- Competitive exclusion principle: two species that use a limiting resource in the same way
cannot coexist
- Resource partitioning: species using a limited resource in different ways
- Lotka-Volterra competition model:
o dN1/dt = R1N1[1-(N1+αN2)/K1]
o dN2/dt = R2N2[1-(N2+βN1)/K2]
o alpha and beta are competition coefficients – constants that describe effect of one
species on the other
o coexistence occurs when α<K1/K2<1/β
if a and b are equal, and close to 1, the species are equally strong competitors
and have similar effects of each other
o if a = b = 0.95; 0.95<K1/K2<1.053
coexistence is predicted only within a narrow range of values for the carrying
capacities, K1 and K2
- The outcome of competition can be altered by environmental conditions, species interactions,
disturbance, and evolution
- Fugitive species: species that must disperse from one place to another as conditions change
- Natural selection can influence the morphology of competing species and result in character
displacement
o The phenotype of competing species become more different over time
Parasitism
- Symbionts: Organisms that live in or on other organisms
o More than half of earth species
- Pathogens: parasites that cause disease
- Parasitoids: insects whose larvae feed on a single host and almost always kill it
- Macroparasites: large species such as arthropods and worms
- Microparasites: Microscopic, such as bacteria
- Ectoparasites: live on the outer body of the host
- Endoparasites: live inside their hosts, within cells or tissues or in the alimentary canal
- Secondary Compounds: chemical weapons against parasites
Mutualism and Commensalism
- Positive Interactions or Facilitation: occur when neither species is harmed and the benefits of
the interactions are greater than the costs for at least one species
- Mutualism: Mutually beneficial interaction between individuals of two species (+/+)
- Commensalism: individuals of one species benefit, while individuals of the other species do not
benefit and are not harmed (+/0)
- Symbiosis: A relationship in which the two species live in close physiological contact with each
other, such as corals and algae
o Can include parasitism, commensalism, and mutualism
- Micorrhizae: symbiotic associations between the roots of plants and various fungi
o Fungi increase the surface area for the plant to take up water and nutrients
- Ectomycorrhizae: the fungus grows between root cells and forms a mantle around the root
- Arbuscular mycorrhizae: The fungus grows into the soil, extending away from the root; and also
penetrates into some of the plant root cells.
- Trophic Mutualisms: mutualist receives energy or nutrients from its partner
- Habitat Mutualisms: one partner provides the other with shelter, living space, or favourable
habitat
- Service Mutualisms: one partner performs an ecological service for the other
o Include pollination, dispersal, and defence
- Communities: groups of interacting species that occur in the same place at the same time
- Community Structure: set of characteristics that shape communities
- Species Richness: the number of species in a community
- Species Evenness: relative abundances compared with one another
- Species Diversity: combines species richness and evenness
- Shannon Index: species diversity index
o
s
i
ii ppH1
ln
o Pi = proportion of individuals in the ith species
o S = number of species in the community
- Rank abundance curves plot the proportion abundance of each species relative to the other in
rank order
- Species Accumulation Curves: species richness is plotted as a function of the total number of
individuals that have been counted
- Species Composition: identity of species in a community
- Trophic Cascade: a carnivore eats a herbivore which has an effect on primary producers
- Trophic Facilitation: a consumer is indirectly facilitated by a positive interaction between its
prey and another species
- Competitive Networks: competitive interactions among multiple species in which every species
negatively interacts among multiple species in which every species negative interacts with every
other species
- Ecosystem Engineers: species that create, modify, or maintain physical habitat for themselves
and other species
Change in Communities
- Succession: the directional change in species composition over time as a result of abiotic agents
of change
- Facilitation Model: early species modify the environment in ways that benefit later species. The
sequence of species facilitation leads to a climax in communities
o Inspired by Clements
- Tolerance Model: assumes the earliest species modify the environment, but in neutral ways
that neither benefit nor inhibit later species
- Inhibition Model: assumes early species modify conditions in negative ways that hider later
successional species
- Hysteresis: an inability to shift back to the original community type, even when original
conditions are restored
Biogeography
- Biogeography: the study of patterns of species composition and diversity across geographic
locations
- Alpha Diversity: species physiology and interactions with other species are important factors in
the resulting species diversity
- Beta Diversity: change in species number and composition, or turnover of species from one
community type to another
o Connects local and regional scales
- Earth’s landmass is divided into 6 biogeographic regions
o Nearctic, Neotropical, Ethiopian, Palearctic, Oriental, Australasian
- Vicariance: evolutionary separation of species by barriers
- Higher productivity leads to lower extinction rates, greater coexistence, higher species richness,
and promotes a large population because cc is higher
- Species-area curves
o S=zA+c
S= richness of a sample
A= area of a sample
Z = slope
C= y intercept
- Equilibrium theory of island biogeography: the number of species on an island depends on a
balance between immigration or dispersal rates and extinction rates
Species Diversity in Communities
- Distribution and abundance of species in communities depends on:
o Regional species pools and dispersal ability
Provides upper limit on the number and types of species that can be present
o Abiotic conditions
A species may be able to get to a community but be unable to tolerate the
conditions
o Species interactions
Coexistence with other species required for community membership
- Resource Partitioning: competing species coexist by using resources in different ways
- Dynamic Equilibrium Model: considers how disturbance frequency and rate of competitive
displacement combine to determine species diversity
- Diversity Stability Theory: species richness is positively related to community stability
Production
- The term ecosystem first used by Tansley in 1935
- Gross Primary Production (GPP): total amount of carbon fixed by autotrophs
- NPP is the ultimate source of energy for all organisms in an ecosystem
- Normalized Difference Vegetation Index (NDVI): = NIR – Red/NIR + Red
- Fertilizing oceans with iron could reduce global warming because CO2 uptake by phytoplankton
would increase
Energy Flow and Food Webs
- Allochthonous Inputs: external energy inputs
- Autochthonous Energy: energy produced by autotrophs
- Amount of energy transferred from one trophic level to the next depends on food quality and
consumer abundance and physiology
- Trophic Efficiency: amount of energy at one trophic level divided by the amount of energy at
the trophic level immediately below it
- Trophic Cascades: changes in the abundance of organisms at one trophic level can influence
energy flow at multiple trophic levels
- Bioaccumulation: chemicals become more concentrated in tissues over an organisms lifetime
- Biomagnification: concentration increases in animals at higher trophic levels
Nutrient Supply and Cycling
- Cation Exchange Capacity: the ability of soil to hold and exchange cations; related to the
amount and types of clay particles present
- Litter: fresh, undercomposed organic matter on the soil surface
- Mean Residence Time (Turnover Rate): amount of time on average that a molecule spends in
the pool
- Catchment: the land area that is drained by a single stream
- Phosphorus originates from weathering of the mineral apatite
Conservation Biology
- Extinction Vortex: a small population declines even further and becomes ever more vulnerable
to processes that lead to extinction
- Habitat Loss: conversion of an ecosystem to another use
- Habitat Fragmentation: breaking up continuous habitat into patches amid a human-dominated
landscape
- Habitat Degradation: changes that reduce quality of the habitat for many, but not all species
- Flagship Species: a charismatic organism that people will want to give protection to, such as a
giant panda
- Umbrella Species: protection of its habitat will serve as an umbrella to protect many other
species with similar habitat requirements
Landscape Ecology and Ecosystem Management
- Scale: the spatial or temporal dimensions of an object or process, characterized by grain and
extent
- Grain: size of the smallest homogeneous unit of study
- Extent: boundary of the area or time period encompassed by the study
- Primary objective of reserve configurations are:
o Maintenance of the largest possible populations
o Habitat for species throughout their area of distribution
o Enough area to maintain natural disturbance regimes