Ecology after midterm Flashcards
What is exploitation?
- an individual increasing their fitness while decreasing fitness of others
- eg; herbivory, predation, manipulation, parasitism, competition
What is the general relationship between plant herbivory and productivity?
- mostly decreases plants growth and reproduction but in grasses increases productivity (overcompensation)
- eg; snow goose grazing, feces grazing and time of year graphs ; as biomass decreases, productivity increases
What are the forms of plant defence?
- under strong NS pressures due to intense herbivory - develop chemical and physical defences - herbivores must evolve to overcome those defences
Describe the physical plant defense?
- thorns and spikes; effective against large,not small
tough tissue deters eating
sticky hairs/trichomes
Describe the chemical defences?
- plants have many metabolites, often shared
- most smell bad, taste bitter, toxic
- toxins: chemicals that kill, repel, or impair herbivores (alkaloids: bitter and smelly)
- digestive enxymes (tannin eg;) make itahrd to digest
What are the 3 forms of chemicals?
- alkaloids: if eaten followed by atropin can be lethal to animals
- phenolics: eg; tannin - bitter and toxic - causes rivers to turn brown, found in grape skin (wine flavour)
- terpenoids: in over 25000 plant species - many functions, also for odor - repel herbivores and attract polinators - used inertial medicine
What are the two forms of plant defense states?
Constitutive (constantly produced regardless of environment) and induced (comes from shift in environment)
Do introduced herbivores always negatively impact plants?
no!
What is one of the best studied relationships for understanding impacts of predation?
lynx and hares
- graph represents very obvious relationship in cycles between populations, as one increases the other decreases
Name and describe the 2 hypotheses that were proposed to describe the clear relationship between hares and lynx?
- the sunspot hypothesis: sunspot cycles increase and decrease light availability and alters plant growth causing variation in hare population size - lynx main predator responds - BUT patterns don’t align - rejected
- Lloyd Kieth: overpopulation theories
- period of high growth followed by
- decimation by predators and disease
- physiological stress at high desnity
- starvation due to reduced food at high density
- alternative hypothesis: predators increase in response to high prey density and eventually reduce prey
What are the drivers of population cycles between prey and predators?
- cycles through a number of co-occuring mechanisms : food availability, high density impacts, predator regulation eg
What is the role of food supply in hares and lynx?
- hares live in boreal forests with dense growth of understory shrubs
- have high rates of increase can double each generation during growth phases
- extensively browse buds of shrubs and trees- during winter food shortages during peak densities and chemical defense : plants unusable or reduced quality
what are the roles of predators in hare populations?
- 50-90% of mortality can be due to predation during high densities
- functional response of lynx capped at half density, but coyotes functional response increases beyond maxed hare values
-lynx and coyotes show large numerical response to highharedensity
What is functional response?
- increased predator numbers in relation to prey numbers
a function of immigration as more move in and incrasedreproduction as resources are abundant
what were the results of the ‘rabbit chow’ experiment?
- no predation impacts the least, food some, and both increases abundance greatly
What are consumptive and non-consumptive effects?
consumptive: predators impact the population directly through capture/consumption
non-consumptive: only fraction of prey is consumed - non consumptive are impacts of predators on prey even when not consuming
ie: morphological response, stress physiology, altered behaviour eg; rabbit stress increases (cortisol) when predators present, also decreased reproduction.
What is the major conclusion on the impacts on prey?
- prey population are influenced by food availability, consumptive and non-consumptive impacts of predators
What is the lot volterra conclusion?
- predator impacts prey in a cyclic cycle - predator delayed response to prey which is the driving factor
How do prey avoid predators ?
- animal display and use of refuges
- display: mimicry, batsman mimicry, mullein mimicry, cryptic coloration, physical defences, predation satiation
What is predator satiation? Provide an example
- predation satiation seeks to protect individuals simply by sheer numbers available
- example: cicada which arise very 13-17 years and overwhelm the ecosystem; animals gorge, trees get nutrients and growth spurt, no defense mechanism just numbers - can’t eat them all
Why is size a refuge?
- if large individuals are ignored by predators than large size may offer a form of refuge
- elephants can kill lions, starfish removed and mussels grow big enough to avoid predation when star fish reintroduced
Can limiting resources change over time?
Yep!
What are some of the ecosystem changes associated with succession?
-increased biomass, respiration, nutrient retention, primary production
- time may also influence ecosystem through weathering
How does succession impact soil depth and layering? Define the horizon layers as well.
- soil depth and layering both increase
- A is the top soil: get the nutrients which leach into layer B
B: different colour buildups (dense, high nutrient content, less fertile than A) - As succession continues, A and B increase and organic matter and litter also increase
What were some observed changes at glacier bay regarding phosphorus, moisture, bulk density, and organic matter?
- moisture and organic matter increased while bulk density and phosphorus decrease as plants take up more space and resources
Why do the Hawaiian islands make an ideal chronosequence? What were the observed relationships? (think C, N, and P)
-islands vary in age across million of years, formed above hot spot over tectonic plate in pacific
- different patterns of nutrient distribution
- Carbon and N peaked after 150,,000 years of soil development, while total phosphorus remained the same but refractory increased and weatheable decreased
- N and P had opposite patterns of change
Is vegetation responsible for all nutrient loss?
- accounts for some, but not all: but consider other sources (erosion, runoff, microbial processes)
What process can reduce the loss of nutrients caused by disturbance?
- succession
Define the model of ecosystem recovery?
- disturbance always induces recovery phases
- disturbance followed by 1) aggradation 2) transition phase 3) steady state phase
What are the two mechanisms of succession?
Two historical viewpoints:
1) clements: serial replacement sof speies during succession, each wave facilitates establishment of the next
- climax could maintain itself indefinitely
2) Gleason: Speies distributed independently of each other, individualists approach succession with specific conditions and random events altering outcome
What did egler do? what were his conclusions?
- clarified distinctions between Clements and Gleason: proposed alternate ways succession might work
relay floristics: one wave of species replaced by next, very little overlap
initial floristics: different species dominate at different times following disturbance, but great deal of overlap: most always present but change in abundance over time
What are the 3 models for mechanisms of succession?
- facilitation:
only species with specific characterics can establish, pioneers may modify environment so it becomes less suitable for them but more suitable for later successional species - environment less suitable for early species, more suitable for later ones
- tolerance: species unaffected by other colonists, initial stages not limited to a few species- juveniles dominant at climax can establish very early on
- environment less suitable for early species, later successional species are ones able to tolerate, no other can tolerate (climax community)
-inhibition
- environment not suitable for all species, resident species inhabit establishment of any others
- early occupants modify environment to make it less suitable for any other species,
- climax: long living species resent to damage by physical or biological factors
What are the mechanisms of primary succession following deglaciation?
- multiple methods of succession may operate during succession in the same system
- horse weed inhibits growth of aster (shading, competition, root chemicals)
- aster facilities growth of the broomsedge
- later on broad leaf trees that are resistant to shade
- climax community shade tolerant trees
What is stability? How might it arise?
Stability: biologically uninteresting, lack of disturbance , absence of change
- may also arise from:
- resistance: ability to maintain structure/function in face of disturbance
- resilience: ability to recover from disturbances
Does primary succession occur on substrate or soil?
Substrate!
What is a guild?
- group of organisms that make their living in similar ways (eg; seed eaters in the desert)
What are the ecologist terms ?
- life forms, growth form and functional group (reproduction / consumption)
What is relative abundance?
The percentage each species contributes to overall species present
What two factors make up diversity?
- species richness and species evenness
What is the difference between species abundance and relative abundance?
- species abundance : total number of individuals
- relative abundance: percentage each species contributes to the total number
What makes species ruchness susceptible to sample size?
- higher sample size = higher species richness
What does dominant mean?
- one or few species substantially more abundant than other species in a community
What level of abundance are most species in a community?
Most species are relatively abundant (few dominant few rare)
What is the lognormal distribution of species abundance?
- curves typically bell shaped: typically only part of the bell curve visible: more samples = lognormal curve!
What is required for ecologists in order to have accurate estimates of abundance?
- must conduct substantial sampling
What is a widely used measurement of species diversity? Can it be sued to calculate evenness?
- species richness uses Shannon wiener index
(-) sum of proportion x log e x proportion. (proportion is the number of individuals out of the total number) - Pileou’s evenness : (0-1) J used to calculate evenness, H can not
- J = H’ / H max (the highest possible proportion used to find H max)
What is the relationship between H value and diversity?
- measured 0.5 - 3.5, higher the number the greater the diversity
Why is the Shannon diversity index useful to ecologists?
Useful for ecologists studying rare species and their impact on the environment
What is a common method used for comparing patterns of abundance and richness?
- plot relative abundance of each species against rank
- longer = more species
- gradual descent = more evenness
generally more diverse population will have gradual slope
What is the relationship between environmental heterogeneity and diversity?
Generally diversity increases with environmental complexity or heterogeneity
- eg; warbler species increase when vegetation increases
Describe the relationship between niches of algae and plants ?
- Tilman found:
coexistence depends on the nutrient availability - different species dominate different parts of the lake depending on nutrient availability
- asterionella takes up phosphate at a faster rate than cyclotella
- in phosphorus limiting areas: asterionella dominates
- in silicate limited areas”cyclotella dominates
coexistence when both nutrients are limiting!
What do mathematical models predict about populations densities?
Once they reach equilibrium they will not change
- stability maintained by opposing forces, if disturbance occurs population will get back to equilibrium
- forces equal at every point (reproduction and respiration)
Why is disturbance difficult to define?
- it is classified as a departure from average conditions (but environmental variability may be an average condition)
- so we say anything that alters environment, ecosystem functioning and processes, dynamics, etc
What are the two main factors of disturbance?
Frequency and disturbance
What are the two forms of disturbance factor?
Biotic and abiotic
What is the intermediate disturbance hypothesis ?
- species richness is highest in areas of intermediate levels of disturbance
- promotes higer diversity
(disturbance is a prevalent feature that significantly influences community diversity)
- too much wipes out species, not enough allows for dominant competitors to take over
Define the impacts of different levels of disturbance
low: competitively dominant species would outcompete all other, predominantly K selected species
high: species continuously driven to extinction, colonsiers return (mainly r selected)
medium: yay!
example: pine savannahs on coastal plains of the us have frequent fires- shade making shrubs removed and can’t dominate
how does Sousas boulder experiment support the intermediate hypothesis theory?
- large boulders have 1% turnover per month, 1 species modal
- small boulders: have 42% turnover, 2 species
- medium: 9%, 4 species (highest diversity! )
What are some other examples of ecosystems that do well under mid disturbance ?
- coral reefs: hurricanes , diverse
- boreal forests with a lot of forests :
- bomb army sites have get diversity
How do prairie dogs encourage diversity?
- by burrowing they leave dirt in piles, in grasslands : a very common source of disturbance is burrowers
- dogs burrow and remove and eat vegetation : open for plant colonization
- intermediate allows persistence of species that are good colonizers and species that are good competitors
–> grass diversity increases, shrubs diversity invariant
Why might different groups of species respond differently to different levels of disturbance?
- different life history and niches
is the intermediate disturbance hypothesis true?
- less than 20% of studies expressed relationship
- most systems showed no relationship between diversity and disturbance
what was the overall outcome of the park grass fertilizer experiment?
- individual species changed a lot but group proportions remained relatively consistent
- individual plant species have shown. wide variety of abundance changes during the course of the experiment
Why does diversity increase stability?
- diversity increase stability because it increases the probability of there being some species able to cope with any particular disturbance
- diversity “buffers” a community from the potential consequences of a disturbance or any environmental change
What are biomes?
large scale classifications of terrestrial habitats classified by predominant plant types and mean climates (temperature and precipitation)
What are two fundamental components of biomes apart from climate and plants?
- geographic and seasonal variation in temperature and precipitation
Why are there global seasons? what is the equinox?
Spherical shape and is tilted at a 23.5 degree angle : earth has different mean surface temperatures:
- produces predictable latitudinal variation in climate
equinox: when the earth crosses the celestial equator and day and night is the same length (2 times per year)
What are the tropics?
23.5 degrees north of the equator is the Tropic of Cancer, 23.5 degrees south of the equator is the Tropic of Capricorn: space in between is called the tropics, anywhere above and below those lines experience intense seasonal changes
What is solar driven air circulation?
- heating of the earth’s surface and atmosphere drives circulation of the atmosphere and influences patterns of precipitation
- warm air rises, cools and absorbs moisture from the land
What are the 3 cells on the earth?
polar cell - subtropical and polar air masses meet creating temperate moist climate
ferrel cell - has the temperature forest
- at the line, dry descending air absorbs moisture forming deserts
also tropical rainforests
Hadley cell : warm air rising at the equator associated with moist tropical climate
What is the coriolois effect?
Wind deflected in patterns based on earth’s rotation
- northern hemisphere wind goes clockwise
- southern hemisphere: wind goes counter clockwise
What are climate diagrams? Describe the axis
- climate diagrams are a tool to summarize the climate of a region
- horizontal: months (shaded = above freezing mean low temp)
- left vertical : temperature
- right vertical : precipitation
yellow if dry, blue if wet
What is soil in terrestrial biomes? what is it made up of?
- soil is the foundation of terrestrial biomes
- made up of living organisms, organic material, gas, water, minerals
What is the soil profile?
- vertical sections of the soil from the ground surface downwards to underlying rock
- so cool wow it provides a snapshot of soil in a constant state of flux! It’s ever-changing! Wowee!
Define the soil horizons
- separation of soil into their respective layers
- O (surface litter and organic matter)
A: topsoil: mix of minerals, clay, silt, sand
B: gets nutrients leached from A, humus, often plant roots
C: weather parent material
R: bedrock
how do we classify soil?
horizons!
What is illuviation?
this is the accumulation of dissolved or suspended materials
What is eluvation?
This is the movement of soil materials downwards into the lower layers through precipitation
Describe the geographic distribution of the tundra (biology, climate, soil, human influences)
- climate: dry and cold, short summer/growing seasons, 200-600 mm of precipitation
- soil: frozen; permafrost, low rates of decomposition
- biology: habitat for many large predators; wolves, bears, caribou
- dominated by grasses, sedges, lichen, mosses
Human influences: historically undisturbed but recently increased disturbance due to human activity for mining oil, gas, and minerals ( diamond) - unique opportunity for concern over melting permafrost and consequences (carbon released)
Describe the important information regarding tundras in us, Norway, and Russia
- Norway and Russia have higher mean precipitation
- norway warm for 2 months
- russia and US above zero for 4 months
- Norway has higher average temperature
- note that proximity to ocean regulates temperatures
What is the hydrological cycle? What is a reservoir?
- exchanges of water between reservoirs
- reservoirs are areas where water is stored, natural or manmade eg; ice, animals, atmosphere, lakes, rivers, oceans
How much of earth’s surface is covered in water? how much of this is usable? How much freshwater is in Canada?
91.5% of earth is covered in water, 97.5 is salt, only 2.5% is freshwater and only 1.2% of that is accessible (groundwater and surface water)
- 20% of the world’s freshwater is in Canada
Describe the steps of the hydrological cycle
- water enters reservoir as precipitation/surface or subsurface flow
- exits as evaporation / flow
- sun drives wind and evaporates water using solar energy, mostly from the ocean
- water vapour cools as it condense forming clouds which are blown to different areas to yield snow and rain
- majority falls into ocean, some on land
What occurs when water falls on land?
- either:
- immediately evaporated back into atmosphere
- consumed by terrestrial organisms
- percolates into soil to ground water
- enters lakes/ponds, rivers and streams to go back to sea
- contributes to ice fields/glaciers
What is turnover time?
how long it takes for volume of water to be renewed in a body of water
- atmosphere: 9 days
- river : 10-12 days
- oceans: 3100 years
Describe the ocean
Single largest biome on earth, composed of 5 major oceans (pacific, Atlantic, Indian, southern, arctic); a continuous connected mass of water
Describe oceanic circulation
- driven by the prevailing winds, moderates earth’s climates
- oceans are never still - wind driven surface currents across ocean creates gyres that move it right in the N hemisphere and left in the S hemisphere
gyres: whirling fluid that transports warm equatorial waters towards poles
- deeper water moves by oceanic currents on the sea floor
How is water moved on the bottom of the sea floor?
- water moved by underwater currents
Describe the geography of oceans?
- average depth:
pacific 4000m
atlantic/india: 3900m
trenches eg; Marian 10000+ m
Describe oceanic structure
- vertical structuring of oceans associated with amount of light and temperature -
littoral zone (intertidal) - shallow, disturbed by waves
- neritic: area between shore and continental shelf
- oceanic zone: beyond the shelf
- epipelagic: 0-200m
- mesopelagic : 200 - 1000m
- bathypelagic : 1000 - 4000m
- abyssal: 4000-6000
- hadal: 6000+
benthic: floor
pelagic: habitat not on seafloor
Describe the light conditions of the ocean
- 8% of light is absorbed within the first 10 m
- very little if any goes beyond 600m
- the rest is dark black water
Describe the temperatures of the ocean?
- sunlight stimulates kinetic energy in water molecules, makes them less dense so they float on top
What is a thermocline?
- separate warm and cold layers of water
- layer of water through which temperatures change rapidly with depth
What is thermal stratifa=icatoin?
- layering of water column by temperature
What is a gyre?
- whirling mass of water driven by wind currents - moves water from equator to the poles (on ocean floor driven by underwater currents)
What is the salinity of the ocean ?
- varies from 34-36.5 ppt
- less salinity near equator and beyond 40 degrees latitude because precipitation exceeds transpiration
- tropical zones saltier because evaporation exceeds transpiration
Describe the oxygen levels in the ocean. what is the exception?
- in one L of sea water, 9mL dissolved at most
- oxygen high near surface of ocean and drops off, then at 1000m deep increases again because cold water holds a lot of oxygen
- Oxygen consumption low compared with he supply of cold oxygen rich deep waters from polar regions
- exception: Black Sea
Describe the oxygen levels of the Black Sea
– devoid of oxygen
- isolated prevents vital circulation, layers do not mix so deeper waters low on oxygen
- organic material decomposes in anaerobic conditions, releases H2S
Describe the biology of oceans?
- photosynthetic organisms limited to upper epilagic zone - zooplankton and phytoplankton
- ocean contribues to 1/4 of photosynthesis in bipshee
- chemosynthesis occurs
- 11 phyla, 28 phyla in sea
What is chemosynthesis? Where is it found?
- found near vents in deep sea, organisms use Ep and H2S to form sugar
Describe the number of phyla on land and in the water?
- on land: 11 phyla, 1 is endemic
- in water; 28 phyla, 15 are endemic (echinoderms ; starfish and ctenophores)
What are the human influences on the ocean?
- vastness historically acted as buffer to intervention
- now human threats becoming apparent: pollution, over harvesting, deep sea mining
Describe the geography of shallow marine waters
- kelp forests occur in temperate to sub polar regions, wherever there is a solid bottom and no grazing
- replace kelp forests near equator, confined to latitudes <30 degrees of equator - Deep sea reefs exist worldwide
Describe some key components of shallow marine waters
- reefs and kelp grow in shallow enough water for photosynthesis - both limited by temperature
- current deliver oxygen and nutrients, move waste away (may depend on waste removal for porducitiy)
- among most productive and diverse ecosystems
How do reefs and help get food?
Currents bring in nutrients and oxygen, flush away waste
Describe the reef categories (3)
- fringing reefs: close to shore
- barrier reefs: between open sea )shelf) and lagoon, parallel to shore
- coral atolls - inlets built from sunken islands,- range shaped reef, island, or chain of islands formed of coral
How do kelp beds resemble terrestrial ecosystems?
- similar to terrestrial forests, canopy at the surface of water
That are the light conditions for the shallow marine water?
- need sufficient light for photosynthesis, form 10-1000m
Describe the temperature requirements for shallow ocean water?
- kelps less than 10-20
- coral: no more than 29m, never below 19/20 - ideal 23-25
Describe the salinity of shallow ocean water?
- coral may die with less than 27% salinity, kelp better adapted due to freshwater runoff
Descibe oxygen levels of. shallow marine environments
- kelp and coral require well oxygenated waters, in shallow areas oxygen rich
Describe the biology of shallow marine waters?
- coral reefs subject ti most complex biological dsitrbacne.: urchins and starfish
- grazing good, opens up space
- bad when reduces zooplankton on coral,
What is the recovery of coral and kelp like?
- help regenerates quickly, coral does not
Describe the human influences on shallow marine waters
- kelp extensively harvested for additives and fertilizers, corals harvested for decor
- fish dn shellfish over harvested for food and aquariums, desutrcve fishing includes dynamite and poisons
- 60% of area covered by coral has been destroyed mostly by climate change
What is the biggest threat to coral reefs?
human impact
- 60% of area has been lost, mostly due to climate change (coral bleaching)
Describe the boreal forest?
- AKA the taiga
- Geography: forms nearly circumpolar band for 50-65 degrees N latitude, covers 11% land area
Climate: - winter > 6 months, 200-600 mm
Soils: thin, acidic, low fertility
Biology: dominated by evergreen conifers - bogs scattered throughout, home to many year round and migratory animals : wolves, bears, moose, caribou, mouse, beavers, squirrels
human influences: boreal forest animals consumed by humans for tens of thousands of years
- human development historically light, but recent increase in logging, oil extraction, and animal trapping
Describe old growth temperate forest
Geography: mostly within 40-50 degrees latitude
Climate: moderate temperatures, 650-3000+ mm precipitation
Biology: Low diversity, large biomass, vertically stratified
Soils: very fertile
Human influences: heavily developed, logged and used for agriculture for many centuries, limited amounts of virgin old growth forests, encouraging ability of forest recovery when farming and logging stopped
Describe the temperate grasslands
- Geography: globally widespread
- Climate: moderate temperatures, 300-1000m precipitate annually, can experience drought
- soils: rich in organic matter
- Biology: dominated by herbaceous vegetation, mostly grasses but also wildflowers, support large herds of herbivores as well as mammalian and insect herbivores
- human influences: most critically endangered biome due to agriculture use
Describe mediterranean woodlands and scrublands
geography: occur between 30 and 40 degree latitude
climate: cool, except summer typically hot and dry
soils: low to moderate fertility
Biology: low diversity, lard biomass, plants and animals resistant to drought frequent fire , diverse inhabitants, most animals are small and nocturnal
Human influences: landscape structure strongly influenced by humans, typically sustainable agriculture practices, high population densities in some areas
Describe the desert
Geography: ~20% of earth’s land surface, ring glove at 30 degrees north and 30 degrees S latitude some deep in continents interior or in ran shadow of mountains
Climate: characterized by a lack of available water, temperature varies by desert
Soils: mostly sand and rock
biology: vegetation very sparse, plants adapted to reduce evaporation loss , animal abundance low but diversity can be high
human influences: increasing plowing, overgrazing, and deforestation lead to soil erosion and desertification
Describe the tropical savanna
Geography: Most occur north and south of tropical dry forests within 10 - 20° of equator
Climate: Alternating dry and wet seasons
- Lightening fires common
- Mean annual rainfall of 300 500 mm
Soils: Dense and impermeable
Biology
Populated by wandering animals and fire-resistant plants
Human Influences
Tropical savanna is birthplace of humankind
High density of humans and domestic livestock are devastating some regions
Describe the tropical dry forest
- geography: occupy large part of land between 10 and 25 degree latitude
- climate: seasonal - dry season of 6-7 months followed by heavy rainfall for 5-6 months
- rainfall occurs during warmer months
Soils - rich in minerals, highly susceptible to erosion - Biology : vegetation structure influenced by abiotic facts, many migratory animals that also sue savannah and tropical rain forest
- human influences: devastated by human dense settlements and agricultural practices - in Mexico and Central America <2% of tropical dry forest remains
Where is the vast majority of human settlement in forests?
- large focus on preserving tropical rain forests, but vast majority of human settlement in dry or moist tropical forests
Describe the tropical Rain Forest
Biology: trees dominate, very high diversity esp. of trees and insects, complex and specific relationships among species,
Human Influences: many staple foods and drugs derived from tropical plants, palm oil plantation are significantly harmful oil
geography: most occur within 10 degrees of the equator
climate : warm and wet year round, 2000-4000 mm of annual rainfall
soils: Nutrient-poor, acidic, low in organic matter (nutrient poor because in warm areas decomposers highly active, plans take up all nutrients, nothing remaining in soil - acidic because H+ takes place of the nutrient cations -
Describe mountains
Geography: built by geological processes such as volcanism and movement in earth’s crust
Climate: changes with elevation, patterns change depends on latitude
Soils: change with elevation, generally well drained, vulnerable to erosion, persistent winds bring soil particles and organic material
Biology: vegetation changes with elevation, isolation on mountains leads to populations and species with unique gene pools
human influence: historically used for raw materials, effects of human exploitation mixed
Which biome is MOST impacted by human settlement? How has it impacted soil?
- human settlement most impacts grasslands/woodlands
- agricultural development has left grasslands among the most critically endangered biomes
- 35 to 40 years continuous agriculture has caused the loss of 35 to 40% of soil organic material
What is the intertidal zone?
- an area partially covered by water and partially exposed to air
- one of the most dynamic environments in the biosphere (subject to so much change)