124 terms

Ecology

Ch. 1-4, 6 & 7, 24-26, 18, 21
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Ecology
is the scientific study of the relationships between organisms and their environment
Organisms
living things
Environment
physical & chemical conditions as well as biological (living) components
Relationships include interactions with the physical world as well as with members of the same and other species
"Tree of Life"
3 Domains:
Bacteria
Archaea
Eukaryota
Ecosystem
the biotic community and its abiotic environment, functioning as a system
Biotic
living components- plants, animals, fungi, and microbes that inhabit the forest
Abiotic
nonliving (physical & chemical) components-atmosphere, climate, soil, water
individual
organism forms the basic unit in ecology
The individual senses and responds to the prevailing physical environment
Individuals drive the collective properties of populations and communities
It is through the individual that genetic information is passed along
population
s a group of individuals of the same species that occupy a given area
community
includes all populations of different species interacting within an ecosystem
landscape
is the area of land (or water) that is composed of a patchwork of different communities and ecosystems
Biomes
are geographic regions with similar geological and climatic conditions, i.e.:
Tropical rain forest
Desert
Grassland
biotic units and are classified by predominant plant types (grasses, shrubs, trees, etc.)
Developed by E.E. Clements and V.E. Shelford
8 major terrestrial biomes:
Tropical forest
Temperate forest
Conifer forest (taiga or boreal forest)
Temperate grasslands
Tropical savanna
Chaparral (shrublands)
Tundra
Desert
biosphere
is the thin layer surrounding the Earth that supports all life
Spatial scales
relate to measurements of space (i.e. distance, size, area)
Temporal scales
relate to measurements of time (i.e. photosynthetic rate, generation time)
field study
an ecologist examines natural patterns across the landscape
The relationship between two or more variables is studied
The results suggest a relationship but do not prove cause and effect
independent variable
in a predetermined way and monitors the response of the dependent variable
field experiment
the test is applied in a natural setting
In this type of experiment, it is difficult to control other influencing factors (CON)
Results are more realistic because they are collected from a natural setting (PRO)
laboratory experiment
the ecologist has much more control over environmental conditions
Results are not directly applicable in the field
Responses may not be the same in the lab as they would be under natural conditions
Categorical (qualitative)
observations that fall into separate and distinct categories
Numerical (quantitative)
data that are a set of numbers
Weather
the combination of temperature, humidity, precipitation, wind, cloudiness, and other atmospheric conditions occurring at a specific place and time
Climate
is the long-term average pattern of weather
Solar radiation
is the electromagnetic energy or stream of photons produced by the sun
ntercepted at any point on Earth's surface varies by latitude with a gradient of decreasing temperature from the equator to the poles
At higher latitudes, solar radiation hits Earth's surface at a steeper angle
Sunlight is spread over a larger area
Radiation must pass through a deeper layer of air and so it encounters more particles in the atmosphere and is reflected back into space
The seasonality increases with latitude
provides the energy required to convert CO2 into simple sugars
The availability of light - photosynthetically active radiation (PAR) - to the leaf directly influences the rate of photosynthesis
The light compensation point (LCP) is the point at which the rate of net photosynthesis is zero
The light saturation point is the point above which no further increase in photosynthesis occurs
Photoinhibition is the negative effect of high light levels
Shortwave radiation:
emitted by a very hot surface (e.g., Sun = 5800°C)
Longwave radiation
emitted by a cooler object (e.g., average Earth = 15°C)
PAR
photosynthetically active radiation
rain shadow
forms on the leeward side of a mountain (or mountain range) due to the loss of moisture from air as it travels up and over the mountains from the windward side
microclimates
Most organisms live in local conditions that do not match the general climate profile of the larger region surrounding them
affected by:
aspect (direction that a slope faces)
local vegetation (i.e. under a tree)
local topography
structures (i.e. boulders, caves)
color of the ground
etc.
urban heat islands
areas create their own microclimates
are significantly different than those in rural areas
are generally several degrees hotter than the surrounding countryside
There is less vegetation
There are more buildings, streets, and sidewalks that absorb solar radiation and reradiate this energy
The urban landscape is nonporous and most rainfall is lost as runoff before evaporation can cool the air
Construction materials are great conductors of heat
thermocline
is the region of the vertical depth profile where water temperature declines most rapidly
The thermocline depth depends on solar radiation input and level of mixing
is located between the epilimnion (warm, lighter water above) and the hypolimnion (cold, denser water below)
Diffusion
is the general tendency of molecules to move from a region of high concentration to one of lower concentration
Oxygen (and carbon dioxide) gas diffuses from the atmosphere into the surface waters of aquatic environments
The rate of diffusion is dependent on the solubility of oxygen (greater in cold water) and the diffusion gradient
water (or hydrologic) cycle
is the process by which water travels in a sequence from the air to Earth and returns to the atmosphere
Solar radiation is the driving force behind the water cycle because it provides energy for the evaporation of water
Interception
occurs when precipitation falls onto vegetation, dead organic matter, and urban structures or streets. This water evaporates directly back to the atmosphere
infiltration
Precipitation that reaches the soil moves into the ground
Surface runoff
occurs when the soil is saturated
Evapotranspiration
the total amount of evaporating water
Surficial water in terrestrial and aquatic environments returns to the atmosphere by evaporation
Transpiration
the evaporation of water from the internal surfaces of plants
is the water loss through the stomata
The movement of H2O is based on a diffusion gradient
*Side note: in aquatic plants, there is direct diffusion of CO2 from the water to the leaf across the cell membrane (no stomata)
Dessication
the loss of water, is probably the greatest constraint imposed by terrestrial environments
Deciduous plants
shed their leaves during the winter months
In regions with distinct wet and dry seasons, plants may be drought-deciduous. There is increased light availability for the other plants that do not drop their leaves during dry conditions
macronutrients
nitrogen (N), phosphorus (P), potassium (K)
micronutrients/trace minerals
boron (B), chlorine (Cl), manganese (Mn), iron (Fe), zinc (Zn), copper (Cu), molybdenum (Mo), nickel (Ni), selenium (Se), and sodium (Na)
Soil
the medium for plant growth and habitat to a diversity of animal life
Soil is difficult to define
Soil is teeming with life and includes interactions between biotic and abiotic processes
Soil is a three-dimensional unit
Considerable time is required for soil to form
Well-developed soil may require 2,000 to 20,000 years to form!
Weathering
is the destruction of rock materials into smaller particles
Mechanical: results from the action of water, wind, temperature, and organisms (especially plant roots)
Chemical: occurs when particles are chemically altered (water, oxygen, acids) and are further broken down
Soil texture
the proportion of different-sized soil particles
Gravel > 2.0 mm
Sand = 0.05 to 2.0 mm
Clay < 0.002 mm
affects pore space and the movement of air and water into and through the soil
soil profile
is a sequence of horizontal layering
Soil horizons
are horizontal layers of soil material
Each horizon has distinct texture, mineral makeup, and water/nutrient content
O horizon
is dominated by organic material (dead leaves, twigs, dead animal parts, waste, etc.)
A horizon
is composed of mineral soil and organic material leached from above
Leaching = movement of solutes through the soil
B horizon
(subsoil) accumulates mineral particles and contains less organic matter than layers above
C horizon
is the unconsolidated material that lies under the subsoil The bedrock lies below the C horizon
ion exchange capacity
The ability of ions to bind to soil particles depends on the total number of positively or negatively charged sites Cation exchange is more prevalent in temperate soils because of negatively charged soil particles
This is important because the nutrients that plants need for growth often exist in ionic form
CO2
All life is built on a framework of carbon atoms
The ultimate source of carbon for organic molecules
transformed into organic molecules by autotrophs
Chemoautotrophs: energy supplied by the oxidation of inorganic molecules
Photoautotrophs: energy supplied by the Sun
Plants are photoautotrophs and carry out photosynthesis
Other photoautotrophs include algae and phytoplankton (Kingdom Protista, Domain Eukaryota) and cyanobacteria (Domain Bacteria)
Photosynthesis
the Conversion of Carbon Dioxide into Simple Sugars the process by which the Sun's energy (shortwave radiation) is used to fix CO2 into carbohydrates (simple sugars) and release O2 (as a by-product) 6 CO2 + 12 H2O (+ Sun's energy) → C6H12O6 + 6 O2 + 6 H2O
C3 Photosynthesis
Used by most plants and algae (~90%)
Ex: trees, wildflowers
Enzyme = RuBisCO
To "fix" carbon, plants must open stomata to let CO2 enter the leaf where it can be incorporated into carbohydrates via photosynthesis
Water gradient may allow water to escape out of the open stomata
RuBisCO (ribulose-1,5-bisphosphate carboxylase/oxygenase, the enzyme involved in the reaction) is inefficient - photorespiration
These plants are "CO2-limited"
C4 Photosynthesis
Often found in hot, bright environments
Ex: tropical grasses (corn, sugar cane, millet)
is only used by about 3% of all plants on Earth
has evolved in over 60 plant lineages, making it a striking example of convergent evolution
2-part process
2 specialized cell types: mesophyll & bundle sheath
Enzyme = PEP carboxylase in mesophyll and RuBisCO in bundle sheath cells
Increases rate of CO2 diffusion inward
Need fewer stomata open to let CO2 into leaf
Fewer stomata open = less water lost from leaf (conserves water in these hot, dry environments)
CAM Photosynthesis
(Crassulacean Acid Metabolism)
Found in hot, dry environments
16,000 plant species use this method
Ex: bromeliads, orchids, cacti, jade plants, spanish moss
Enzyme = PEP carboxylase
Carbon fixation (stomata open to let in CO2) takes place at night
Reduced water loss due to stomata being closed during the day when it is hot and bright
Low rates of photosynthesis
Extremely high water use efficiency
cellular respiration (aerobic respiration)
C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + ATP

Net photosynthesis =
Photosynthesis - Respiration
Autotrophs must use some of the energy they harness from sunlight to support their own growth and maintenance
Leaf
photosynthesis
Root
uptake of water and nutrients, storage
Stem
support and encounter of sunlight
Flowers/cones/fruit/seeds
reproduction
Under ideal conditions, carbon allocated to leaf tissue promotes the fastest growth
Increase of the photosynthetic surface
stomata
CO2 enters the leaf through openings on the surface O2 and H2O exit
heterotrophs
derive their energy and most nutrients from consuming organic compounds contained in other plants and animals
Key processes common to all animals
Acquire and digest food
Absorb oxygen
Maintain body temperature a
Maintain water balance
Adapt to light and temperature variations
Animals encounter different constraints in aquatic vs. terrestrial environments
Oxygen
required to carry out aerobic cellular respiration, which breaks down organic compounds to release energy
Terrestrial acquisition of oxygen - oxygen readily available in the air
Tracheal system in insects
Lungs in mammals, birds, and reptiles
Lungs and vascularized skin in amphibians
Air sacs in birds
Aquatic acquisition of oxygen - oxygen concentrations in water may be limiting
Lungs in marine mammals
Tracheal system in some aquatic insects
Diffusion by very small animals
Gills found in fish and other marine invertebrates (mollusks, echinoderms)
Homeostasis
the maintenance of a relatively constant internal environment in a varying external environment
Body temperature
Water balance
pH
Salt concentration in body fluids and tissues
Terrestrial animals face more extreme (and dangerous) changes in thermal environment than aquatic animals
Aquatic animals live in a more stable energy environment
Endotherms
animals that generate heat metabolically (internal heat production = endothermy)
This results in the maintenance of a fairly constant internal temperature independent of external temperatures (= homeothermy)
Ex: birds and mammals
Often called "warm blooded
Ectotherms
animals that acquire heat primarily from the external environment
Variable body temperature, as a result of ectothermy = poikilothermy
Ex: fish, amphibians, reptiles, insects, and other invertebrates
Often called "cold blooded" because they can be cool to the touch
Heterotherms
animals that regulate body temperature by both endothermy and ectothermy
Ex: bats, bees, and hummingbirds
Fluctuating metabolic rates - when at rest, these animals reduce their metabolisms drastically, which results in their body temperature dropping to that of the surrounding environment. This makes them homeothermic when active, and poikilothermic when at rest
torpor
the dropping of body temperature to approximately ambient temperature for a part of each day, regardless of the season
This helps reduce metabolic costs during periods of inactivity
Found in hummingbirds, bats, pocket mice, etc.
Nocturnal mammals (active at night, i.e. bats) go into torpor by day; diurnal mammals (active by day, i.e. hummingbirds) go into torpor at night
Hibernation
is a long, seasonal torpor characterized by cessation of activity
"True" hibernation - animals can't be roused from sleep-like state - bears & bats do not fall into this category since they can be awakened!
Some species of mammals hibernate while gestating young, which are either born while the mother hibernates or shortly afterwards
Homeothermic mammals - ground squirrels, European hedgehogs, etc.
Heart rate, respiration, and total metabolism fall, body temperature sinks below 10°C (close to ambient temp.) = hypothermia
Supercooling
body fluids takes place when the body temperature falls below the freezing point without actually freezing
The presence of solutes (e.g., glycerol) in body fluids functions to lower the freezing point of water
Characteristic of Arctic marine fish, some insects, reptiles, and amphibians
Some invertebrates survive the cold by freezing and then thawing out when the temperature moderates
In some species, > 90% of the body fluids may freeze
Countercurrent heat exchange
can conserve heat in a cold environment OR can cool vital parts of the body under heat stress
The mechanism involves transferring heat between cool venous blood (returning TO heart) and warm arterial blood (coming FROM heart)
Found in the flippers & flukes of porpoises & their relatives; legs of mammals & birds; tails of rodents (i.e. beavers)
Keeping heat IN
The porpoise & some marine turtles maintain body core temperature by exchanging heat between arterial (warm) and venous (cool) blood
Keeping heat OUT
The oryx (African desert antelope) cools the brain by cooling venous blood via evaporation in the sinus cavity
The rete of sharks and tunas allow them to maintain fairly constant body temperatures regardless of water temperature
water balance
offset water losses by the uptake of water from the external environment
Several ways that terrestrial animals gain water and solutes
Drinking
Eating
Metabolic production of water in cellular respiration
Desert camels store fat in their "hump" which can be metabolized to release water during drought
Kangaroo rats may never drink water - obtain water from eating / urine is concentrated crystalline waste (rather than liquid)
Estivation
a state of animal dormancy (similar to hibernation) characterized by inactivity and a lowered metabolic rate that is entered in response to high temperatures and arid conditions. It takes place during times of heat and dryness which are often the summer months
Ex: some species of land snails, land crabs, desert tortoises, crocodiles, frogs, and salamanders
Develop a hardened (watertight) casing
Evade the effects of drought
Reduce respiratory water loss
Nocturnal (nighttime) activity - cooler / less evaporation
Utilize metabolic water
hyperosmotic
and gain water spontaneously from the surrounding water (which, by comparison, is hypoosmotic) water moves into the body
They must prevent uptake, rid themselves of excess water, or replace salts lost to the environment
Strategies: absorb and retain salt, produce copious amounts of dilute urine
hypoosmotic
lose water spontaneously to the surrounding water (which, by comparison, is hyperosmotic) they are prone to dehydration
They must prevent accumulation of salts in the body by actively pumping salts across gill surfaces
Inhibit water loss through the body wall and produce highly concentrated urine; excrete salt through specialized glands
Sea birds (and some desert birds such as ostriches) have salt glands near the nostrils where they can "sneeze" out excess salts
Biological clocks
the internal mechanisms in organisms that control the periodicity of functions and activities
These "clocks" influence hormones that play a role in sleep cycles, metabolic rate, body temperature, etc.
The hormone melatonin more is produced in the dark - provides a way for animals to sense/measure day length
Biological processes fluctuate in cycles
A circadian rhythm is a cycle (daily rhythm) that results from a physiological response to the diurnal (day/night) environment
Photoperiod
(the hours of light and dark during a 24-hour period) plays a major role in the biological rhythms of animals
In the middle and upper latitudes of the Northern and Southern Hemispheres, daily periods of light and dark lengthen and shorten with the seasons
Increasing day length induces spring migratory behavior, stimulates gonadal development, and brings on the reproductive cycle in birds
Mammalian food storage and reproduction
Store food for times of shortage (winter months)
Reproduce in spring when food is plentiful and weather is less harsh
Reproductive periods "track" seasonal food availability (for the young especially)
Biogeography
the study of the spatial or geographical distribution of organisms, both past and present
Early plant geographers correlated the distribution of vegetation to climate
The world could be divided into zones representing broad categories of vegetation based on physical appearance
Regions of the globe with a given type of vegetation were characterized by similar climates
Forest
ecosystems are characterized by a closed canopy of trees
Woodland and savanna
ecosystems are characterized by the co-dominance of grasses and trees (or shrubs)
Desert
a general category used to describe a scarcity of plant cover
Deciduous
leaves live for only a single year or growing season
Winter-deciduous leaves are lost in response to low temperatures
Drought-deciduous leaves are lost in response to dry conditions
Evergreen
leaves live beyond a year
The broadleaf evergreen leaf is characteristic of environments with no distinct growing season, where growth continues year-round (i.e. tropical forests)
The needle-leaf evergreen leaf is characteristic of environments with a very short growing season or nutrient limitation (i.e. boreal forests)
tropical rain forest
dominated by broadleaf evergreen plants/trees
Rain forests are restricted to the equatorial zone between 10° N and 10° S
Temperatures are warm throughout the year and rainfall occurs almost daily
Mean temperature >18°C
Minimum monthly precipitation >60 mm
savanna
a range of vegetation types in the drier tropics and subtropics characterized by a ground cover of grasses with scattered trees or shrubs
Warm continental climate with mean temperature usually >18°C
Distinct seasonality in precipitation and large interannual variation in total precipitation
Natural grasslands
occupy regions where rainfall is between 25 and 80 cm/year
Many grasslands exist through the intervention of fire and human activity
Natural grasslands have shrunk to less than 12 percent of their original size
Grasslands occur in the midlatitudes in midcontinental regions where annual precipitation is reduced
shrubland
a plant community in which the shrub growth is dominant or codominant
A shrub is a plant with multiple woody, persistent stems and a height from 4.5 to 8 m
Mediterranean ecosystems are found along the western margins of the continents between 30° and 40° latitude
Dominated by evergreen shrubs and sclerophyllous trees
taiga, or boreal forest
it is the largest expanse of conifer forest
This is the largest biome on Earth
The taiga encompasses the high latitudes of the Northern Hemisphere and covers 11% of the Earth's terrestrial surface
The taiga primarily occupies formerly glaciated land and is a region of cold lakes, bogs, rivers, and alder thickets
Littoral zone
shallow-water zone in which light reaches the bottom
Habitat of rooted plants along lake edge
Limnetic zone
open water that extends to the depth of light penetration
Habitat of phytoplankton, zooplankton, and nekton (free-swimming organisms)
Profundal zone
open water beyond the depth of effective light penetration
Benthic zone
bottom region that is the primary place of decomposition
Periphyton / aufwuchs = organisms living on submerged substrate but that do not penetrate the substrate (mostly algae, diatoms, sponges, etc.)
Watershed
(or drainage basin) = an area of land where surface water from rain and melting snow or ice converges to a single point
Estuaries
semi-enclosed parts of the coastal ocean where freshwater joins saltwater
Estuarine organisms must maintain their position and adjust to changing salinity
Those that are mobile can swim against the tide or move with the tides
Sessile (attached to the substrate) and slightly motile organisms have an optimum salinity range
Anadromous
fish live most of their lives in saltwater and return to freshwater to spawn and are specially adapted to endure changes in salinity
Striped bass
Shad
Croaker
Oyster bed and oyster reef
Sea grasses — widgeon grass and eel-grass
Pelagic
whole body of water
Epipelagic / photic zone = vertical layer from the surface down to 200 m - where photosynthesis occurs
Neritic = water that overlies the continental shelf
Oceanic = "deeper" zones away from continental shelf
Phytoplankton
absorb nutrients directly from water and their greater surface-to-volume ratio makes a small body size an advantage
Dinoflagellates
concentrate near the surface in areas of low turbulence
Diatoms
dominate regions of upwelling
Upwelling = involves wind-driven motion of dense, cooler, and usually nutrient-rich water towards the ocean surface, replacing the warmer, usually nutrient-depleted surface water
Nanoplankton
(e.g. cyanobacteria) make up the largest biomass in temperate and tropical waters
vertical migration
a pattern of movement used by some organisms living in the ocean and in lakes
Occurs when organisms move up to the epipelagic zone at night and return to the mesopelagic zone of the oceans or to the hypolimnion zone of lakes during the day
15-50% of zooplankton biomass is estimated to migrate
Reasons may include predator avoidance, escaping UV damage
Nekton
swimming organisms, feed on zooplankton and pass energy to higher trophic levels
Sizes range from small fish to large whales
Some are restricted to a particular zone (e.g., predatory fish) while others move between pelagic zones (e.g., sperm whale)
Benthic
refers to the floor of the sea (or any other body of water) and benthos refers to plants and animals that live there
The bottom community is strictly heterotrophic (except in vent areas) and depends on the organic matter drifting to the bottom
Patches of dead phytoplankton as well as the bodies of dead whales, seals, birds, fish, etc. provide food for different bottom-dwelling species
food chain
is a descriptive diagram that represents the flow of energy from prey (the consumed) to predator (the consumer)
Grass → grasshopper → sparrow → hawk
Feeding relationships in nature are more complex (than food chains) and include an array of linkages among primary producers and consumers
Food webs
highly interwoven, with linkages representing a wide variety of species interactions
Links are the arrows from one species to another and indicate the consumed and the consumer
Basal species feed on no other species but are fed upon by others
Intermediate species feed on other species, and they themselves are prey of other species
Top (apex) predators prey on intermediate and basal species
Trophic Level
position in a food web
determined by number of energy transfers from primary producers to current level:
1st level = primary producers (autotrophs)
2nd level = primary consumers (herbivores and detritivores)
3rd level = secondary consumers (carnivores on primary consumers)
4th level = tertiary consumers (predators of carnivores)
Indirect effects
occur when one species does not interact with a second species directly, but instead influences a third species that does directly interact with the second
Indirect interactions can potentially arise throughout the entire community because of a single direct interaction between only two component species
Lynx predation on the snowshoe hare (that feed on white spruce) can positively affect the white spruce population
Keystone predation
is the indirect interaction where the predator enhances one or more inferior competitors by reducing the abundance of the superior competitors
Bottom-up controls
Influence of physical & chemical factors on ecosystems
the structure of food chains and food webs is controlled (limited) by the productivity and abundance of populations in the trophic level below
Top-down controls
Influence of consumers on ecosystems
the predator populations control the abundance of prey species, and the prey of the prey, and so on
Trophic cascades
May involve indirect interactions linked through intermediary species
Effects of predators on prey - alterations in abundance, biomass, or productivity
Can be top-down or bottom-up
Primary production
the production of organic compounds from atmospheric or aquatic CO2
mainly through photosynthesis
The driving force of the ecosystem is the Sun's energy The flow of energy through ecosystems begins with the harnessing of sunlight by autotrophs
chemosynthesis much less important
Gross primary productivity (GPP)
total rate at which organic matter is created by photosynthesis, or the energy assimilated by autotrophs
Autotrophs must expend energy in the process of respiration (R)
Net primary productivity (NPP)
the rate of energy storage as organic matter after respiration
NPP = GPP - Ra
Often measure change in standing biomass over time
Measure the biomass at one point in time, then return to the site and measure it again to find the amount of change during the interval
Other factors must be considered: below-ground productivity, herbivory, decomposition, turnover, litterfall, volatile organic compounds, root exudates, allocation to symbiotic microorganisms
energy available to heterotrophs to feed on or utilize
The fate of energy (in the form of plant material) varies once consumed by a heterotroph
Passes from the body as waste products
Maintenance
Heat loss
Secondary production (growth and reproduction)
Biomass
the amount of organic matter present at any given time
Standing crop biomass = mass of organic matter/area = g/m2
Productivity
the rate at which organic matter is created by photosynthesis
Units of productivity
Energy/area/time = kcal/m2/yr
Mass of organic matter/area/time = g/m2/yr
first law of thermodynamics
states that energy is neither created nor destroyed, it is merely transferred or transformed
second law of thermodynamics
states that when energy is transferred or transformed, part of the energy assumes a form that cannot pass on any further
Ecological rule of thumb
only 10% of the biomass in a given trophic level is converted to biomass at the next-higher trophic level
Ex: Herbivores eat 1000 kcal of plant matter → 100 kcal is converted to herbivore tissue → 10 kcal is converted into first-level carnivore production → 1 kcal is converted into second-level carnivo
Trophic dynamics
transfer of energy from one part of an ecosystem to another
Trophic pyramid
diagram depicting loss of energy in each successive trophic level due to respiration and heat loss
Trophic efficiency
the ratio of productivity in a given trophic level (Pn) to the trophic level it feeds on (Pn-1)