Populations, Their changes and Their measurement
IB syllabus: 2.1.6, 2.3.1, 2.3.2, 2.6.1-2.6.4, 2.7.2
AP syllabus
Ch 9
Syllabus Statements
2.1.6: Define the terms species, population, habitat, niche, community and ecosystem with reference
to local examples
2.3.1: Construct simple keys and use published keys for the identification of organisms
2.3.2: Describe and evaluate methods for estimating abundance of organisms
2.6.1: Explain the concepts of limiting factors and carrying capacity in the context of population
growth
2.6.2: Describe and explain s and J population curves
2.6.3: Describe the role of density-dependent and density-independent factors and internal and
external factors, in the regulation of population
2.6.4: Describe the principles associated with survivorship curves including K and r-strategists
2.7.2: Describe and evaluate methods for measuring change in abiotic and biotic components of an
ecosystem due to a specific human activity
Population
A group of individuals of the same species found in the same area at the same time
like
The gopher tortoises in scrub habitats in Volusia county
The bottlenose dolphins of the Indian River Lagoon
Sea Otters: A case study
Sea otters keystone species in Pacific kelp forests
Daily consume 25% body weight in urchins & molluscs
Population > 1 million before settlers arrived
1700’s hunted to near extinction – 1000 in the Aleutians, AK only 20 off California
In 1971 A1973 Endangered Species Act passes, 1976 Marine Mammal Conservation Act
1989 1000’s died in Exxon Valdez Oil spill
Otters recovering in most places after 1970’s
The spring 2008 survey found 2760 sea otters, down 8.8-percent from the record 2007 spring survey.
Why are they declining now?
Population characteristics
Populations are dynamic – change in response to environment
Size (# of individuals)
Density (# of individuals in a certain space)
Dispersion (spatial pattern of individuals)
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Age distribution (proportion of each age)
Changes called Population dynamics
Respond to environmental stress & change
Limiting Factors & Population Growth
4 variables govern changes in population size
Birth, Death, Immigration, emigration
Variables are dependent on resource availability & environmental conditions
Population change = (Birth + Immigration)– (Death + Emigration)
Capacity for Growth
Capacity for growth = Biotic potential
Rate at which a population grows with unlimited resources is intrinsic rate of increase (r)
offspring each time
BUT – no population can grow indefinitely
Always limits on population growth in nature
Carrying Capacity
Environmental resistance = all factors which limit the growth of populations
Population size depends on interaction between biotic potential and environmental resistance
Carrying capacity (K) = # of individuals of a given population which can be sustained infinitely in a given
area
Limiting Factors
Carrying capacity established by limited resources in the environment
Only one resource needs to be limiting even if there is an over abundance of everything else
Ex. Space, food, water, soil nutrients, sunlight, predators, competition, disease
A desert plant is limited by…
Birds nesting on an island are limited by…
Minimum Values
(r) depends on having a certain minimum population size MVP – minimum viable pop.
Below MVP
1 – some individuals may not find mates
2 – genetically related individuals reproduce producing weak or deformed offspring
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3 – genetic diversity may drop too low to enable adaptation to environmental changes –bottleneck
effect
Forms of Growth
J curve results
Occurs with few or no resource limitations
S curve results
Population will fluctuate around carrying capacity
Population Growth Curves Ideal
Sketch the two curves and label the parts of the S curve
Carrying capacity alterations
In rapid growth population may overshoot carrying capacity
Consumes resource base
Reproduction must slow, Death must increase
Leads to crash or dieback
Carrying capacity is not fixed, affected by:
Seasonal changes, natural & human catastrophes, immigration & emigration
Density Effects
Density Independent Factors: effects regardless of population density
Mostly regulates r-strategists
Floods, fires, weather, habitat destruction, pollution
Weather is most important factor
Density dependent Factors: effects based on amount of individuals in an area
Operate as negative feedback mechanisms leading to stability or regulation of population
External Factors
Competition, predation, parasitism
Disease – most epidemics spread in cramped conditions
Internal Factors
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Natural Cycles: Predation
Over longer time spans populations cycle
Canadian lynx & Snowshoe hare - 10 year cycles
rol
Reproduction Strategies effect Survival
Asexual reproduction
Produce clones of parents
Common in constant environments
Sexual reproduction
Mating has costs – time, injury, parental investment, genetic errors
Different male & female roles in parental care
MacArthur – Wilson Models
Two idealized categories for reproductive patterns but really it’s a continuum
r-selected & K-selected species depending on position on sigmoid population curve
r-selected species: (opportunists) reproduce early, many young few survive
Common after disturbance, but poor competitors
K-selected species: (competitors) reproduce late, few young most survive
Common in stable areas, strong competitors
r versus K
Most organisms somewhere in the middle
-selected, livestock = K-selected
Reproductive patterns give temporary advantage
Resource availability determines ultimate population size
Survivorship curves
Different life expectancies for different species
Survivorship curve: shows age structure of population
Late loss curve: K-selected species with few young cared for until reproductive age
Early loss curve: r-selected species many die early but high survivorship after certain age
Constant loss curve: intermediate steady mortality
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Sketch them
Humans Impact Natural Populations
Fragmenting & degrading habitats
Simplifying natural ecosystems
Using or destroying world primary productivity which supports all consumers
Strengthening pest and disease populations
Eliminating predators
Introducing exotic species
Overharvesting renewable resources
Interfering with natural chemical cycling and energy flow
Sampling populations
Step 1: Identify the organism
Use dichotomous keys, field guides, observe a museum collection, or consult an expert
http://www.earthlife.net/insects/orders-key.html#key
Sample key for insect ID
http://people.virginia.edu/~sos-iwla/Stream-Study/Key/Key1.HTML
Macroinvertebrate key
Construct you Own Dichotomous Key
Mark & Recapture Method
Used for fish & wildlife populations
Traps placed within boundaries of study area
Captured animals are marked with tags, collars, bands or spots of dye & then immediately released
After a few days or weeks, enough time for the marked animals to mix randomly with the others in the
population, traps are set again
The proportion of marked (recaptured) animals in the second trapping is assumed equal to the
proportion of marked animals in the whole population
Repeat the recapture as many times as possible to ensure accuracy of results
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Marking method should not affect the survival or fitness of the organism
Mark & Recapture Calculation
# of recaptures in second catch = # marked in the first catch
Total # in second catch
Total population (N)
Assuming no births, deaths, immigration, or emigrat
Index)
N =
MEMORIZE THIS EQUATION
Example
50 snowshoe hares are captured in box traps, marked with ear tags and released. Two weeks later, 100
hares are captured and checked for ear tags. If 10 hares in the second catch are already marked (10%),
provide an estimate of N
**Realize for accuracy that you would recapture multiple times and take an average**
Quadrat Method
Used for plants or sessile organisms
Mark out a gridline along two edges of an area
Use a calculator or tables to generate two random numbers to use as coordinates and place a quadrat
on the ground with its corner at these coordinates
Count how many individuals of your study population are inside the quadrat
Repeat steps 2 & 3 as many times as possible
Measure the total size of the area occupied by the population in square meters
Calculate the mean number of plants per quadrat. Then calculate the population size with the following
equation
Quadrat Method
N=
This estimates the population size in an area
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Ex. If you count an average of 10 live oak trees per square hectare in a given area, and there are 100
square hectares in your area, then
In addition to population size we can measure…
Density = # of individuals per unit area
Good measure of overall numbers
Frequency = the proportion of quadrats sampled that contain your species
Assessment of patchiness of distribution
% Cover = space within the quadrat occupied by each species
Distinguishes the larger and smaller species
How can changes in these populations be measured?
Necessary because populations may change over time through processes like succession
But also because human activities may impact a population and we want to know how
Can still use CMR or quadrat method
Just do it repeatedly over time
Also could use satellite images taken over time
1. Do pre and post impact assessments in one area
2. Measure comparable areas – one impacted, one not at a given time
Capture – Mark - Recapture
Practice Problems
Question 1
In a mark – recapture study of lake trout populations, 40 fish were captured, marked and released. In a
second capture 45 fish were caught; 9 of these were marked. What is the estimated number of
individuals in the lake trout population
Question 2
Woodlice are terrestrial crustaceans that live under logs and stones in damp soils. To assess the
population of woodlice in an area, students collected as many of the animals as they could find, and
marked each with a drop of fluorescent paint. A total of 303 were marked. 24 hours later, woodlice
were collected again in the same place. This time 297 were found, of which 99 were seen to be already
marked from the first time. What approximately, is the estimated population of woodlice in this area?
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Review points
Dispersion patterns
Carrying capacity and limiting factors
r and K selection
Natural population cycles
Human effects
http://www.otterproject.org
Succession
IB Syllabus: 2.3.5 – 2.3.7
Ch. 8
Syllabus Statements
2.1.6: Define the terms species, population, habitat, niche, community, ecosystem with reference to a
named example
2.6.5 – Describe the concept and process of succession in a named habitat
2.6.6 – Explain the changes in energy flow, gross and net productivity, diversity and mineral cycling in
different stages of succession
2.6.7 – Describe the factors affecting the nature of climax communities
Community
A group of populations interacting in a particular area
The fish community of Ponce Inlet
The plant community of the scrub habitat
Communities Change
Ecological Succession: the gradual change in species composition of a given area over time
Species do change spatially within an area at a certain point in time, this is zonation not succession
2 Types depending on start point
Primary succession: gradual establishment of biological communities on lifeless ground
Secondary succession: reestablishment of biotic communities in an area where they already existed
Zonation II
Horizontal bands or zones of animals and organisms
Vertical layers in a rainforest
Differing plant communities as you go up a mountain
Created by physical and biological factors
Change in these factors is called an environmental gradient
In a rocky intertidal zone these would be
Drying (tides), salinity, competition, grazing
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So how could you measure changes in biota along an environmental gradient?
Biota = living organisms
Change in benthic (bottom) community of rocky intertidal with increased depth
Gradient in moisture or drying
Use modified quadrat method
run transect into deeper water
At set depths place quadrat and sample organisms
Do repeated transects along your sample area
Calculate differences in communities with depth
Primary Succession
Begins in area with no soil on land, no sediment in water
Cooled lava, bare rock from erosion, new ponds, roads
Must be soil present before producers consumers and decomposers can exist
Pioneer Communities
Lichens and Mosses
Survive on nutrients in dust and rock
Start soil formation
Trap small particles
Produce organic material - photosynthesis
Chemically weather the rock
Patches of soil form
Seral Stages: Early Successional Plant Species
Small perennial grasses and herbs colonize, wind blown seeds
Grow close to the ground
Est. large pop. quickly in harsh conditions
Short lived
Break down rock
Seral Stages: Mid to Late Successional Species
After 100’s of years soil deep enough
Moisture & nutrients
Also called Seral Community
Shrubs then trees colonize
Trees create shade
Shade tolerant species establish
Seral stages
A seral community (or sere) is an intermediate stage found in ecological succession in an ecosystem
advancing towards its climax community.
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An example of seral communities in secondary succession is a recently logged coniferous forest;
during the first two years, grasses, heaths and herbaceous plants such as fireweed will be abundant,
after a few more years shrubs will start to appear
about six to eight years after clearing, the area is likely to be crowded with young birches.
Each of these stages can be referred to as a seral community.
Climax community
Characterized by K-selected species
Determined by
climate in the area – temperature, weather patterns
Edaphic factors – saturated wet, mesic, arid
Climax community structure is in stable equilibrium for each area
Humans & other factors may maintain an equilibrium below climax
E.g. current warming trends make climax rainforest communities w/ softer wood, faster growing species
End Result = Complex Community
Complex community mix of well established trees shrubs and a few grasses
Disturbance may change the structure
Fire, Flood, Severe erosion, Tree cutting, Climate change, Grazing, habitat destruction
Natural or Human processes
Specific successional stage is dependent on the frequency of disturbance
Disturbance and Diversity
Disturbance = any change in conditions which disrupts ecosystem or community structure
Catastrophic or Gradual
Disturbance eliminates strong competitors allowing others a chance
Promotes diversity
The intermediate disturbance hypothesis (graph it)
Secondary Succession
Begins when natural community is disturbed BUT soil & sediment remains
Abandoned farms, burned forests, polluted streams
New vegetation can germinate from the seed bank
In both cases succession focuses on vegetation changes
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What changes occur through Succession?
1. Diversity
Starts very low in harsh conditions few species tolerate – r selected species types
Middle succession mix of various species types – most diverse (role of disturbance)
Climax – k selected species strong competitors dominate
2. Mineral Cycling
Pioneer, physical breakdown & make organic, Later processing increase – cycles expand
3. Gross productivity changes (total photosynthesis)
Pioneer = Low density of producers at first
4. Net Productivity (G – R = N)
Pioneer = little
5. Energy flow
# of trophic levels increases over time
Energy lost as heat increases with more transfers
Graph these changes in successional time
Factors in Succession
Facilitation
One species makes an area suitable for another in a different niche
Legumes add nitrogen so other plants thrive
Inhibition
Early species hinder establishment and growth of later specie
Allelopathy by plants is an example
Tolerance
Late successors not affected by earlier ones
Explains mixture of species in Climax Communities
Predictability of Succession
Generally predictable end of succession is a Climax community
Only real rules are Continuous change, Instability, and unpredictability
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Ever changing mosaic of patches in different successional stages
No real progression to an end, rather we see a reflection of an ongoing battle for resources and
reproductive advantage
Ecological Stability & Sustainability
Maintained by constant dynamic change
Positive and Negative feedback systems
Community may change but you will still recognize it as a particular type of community
Inertia = The ability of a living system to resist disturbance
Constancy = the ability of a system or population to keep its numbers within limits imposed by resources
Resilience = the ability of a system to bounce back after a disturbance
Diversity vs. Stability
Once thought that higher diversity = more stability for a community or ecosystem
Recent studies by D. Tilman on grasslands suggest
Population #’s for individual species in diverse ecosystems fluctuate more widely
Some level of diversity does provide insurance against disasters
Nature is in a continual state of change
The Precautionary Principle
Human disturbances are disrupting ecosystem processes
Our ignorance of long term effects means we should be cautious
Thus, “When there is considerable evidence that and activity threatens human and ecosystem health,
we should take precautions to minimize harm, even if the effects are not fully known.”
Better safe than sorry…
The following succession info is bonus material – if it helps use it if not then don’t
Hydrosere
A hydrosere is simply a succession which starts in water. A wetland, which is a transitional area between
open freshwater and dry land, provides a good example of this and is an excellent place to see several
stages of a hydrosere at the same time.
In time, an area of open freshwater such as a lake, will naturally dry out, ultimately becoming woodland.
During this process, a range of different habitats such as swamp and marsh will succeed each other.
This succession from open water to climax woodland is likely to take at least two hundred years
(probably much longer). Some intermediate stages will last a shorter time than others. For instance,
swamp may change to marsh within a decade or less. How long it takes will depend largely on the
amount of siltation occurring.
http://www.countrysideinfo.co.uk/successn/hydro.htm
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Hydrosere
Halosere
The term Halosere is an ecological term which describes succession in a saline environment. An example
of a halosere would be a salt marsh.
In river estuaries, large amounts of silt are deposited by the ebbing tides and inflowing rivers.
The earliest plant colonizers are algae and eel grass which can tolerate submergence by the tide for
most of the 12-hour cycle and which trap mud, causing it to accumulate. Two other colonisers are
salicornia and spartina which are halophytes -i.e. plants that can tolerate saline conditions. They grow
on the inter-tidal mudflats with a maximum of 4 hours' and exposure to air every 12 hours.
Spartina has long roots enabling it to trap more mud than the initial conlonizing plants and salicornia,
and so on. In most places this becomes dominant vegetation. The initial tidal flats receive new
sediments daily, are waterlogged to the exclusion of oxygen, and have a high pH value.
The sward zone, in contrast, is inhabited by plants that can only tolerate a maximum of 4 hours
submergence everyday (24 hours). The dominant species here are sea lavender and other numerous
types of grasses.
Halosere
Xerosere
Xerosere is a plant succession which occurs in conditions limited by water availability or the different
stages in a xerarch succession.
Xerarch succession of ecological communities originated in extremely dry situation such as sand deserts,
sand dunes, salt deserts, rock deserts etc.
A xerosere may include lithoseres and psammoseres.
Psammoseres
In geography, a psammosere is a sand sere - an environment of sand substratum on which ecological
succession occurs.
In a typical succession on a sea-coast psammosere, the organisms closest to the sea will be salt tolerant
species such as littoral algae and glasswort. Progressing inland the succession is likely to include
meadow grass, sea purslane, and sea lavender eventually grading into a typical non-maritime terrestrial
eco-system.
www.sanddunes.20m.com/Evolution%20.htm
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Community Ecology
IB: 2.1.6, 2.1.7
Ch. 8
Videos – extinction clip on exotics, clip on coral reefs
Syllabus Statements
2.1.6: Define the terms species, population, community, niche and habitat with reference to local
examples
2.1.7: Describe and explain population interactions using examples of named species
Definitions
Halifax river
s who can interbreed to produce fertile, viable offspring: FL panthers
mammals in the forest
Community Structure
Consider the spatial distribution of organisms
Physical appearance: Size, stratification, distribution of populations and species
Species diversity and richness: number of different species
Species abundance: number of individuals of each species
Niche structure: number, uniqueness and interaction of niches available
Community Differences
Physical structure varies
Most habitats are mosaics, vegetation patches
Sharp edges or broad ecotones (transition zones)
Physical properties differ at edges = edge effect
Forest edge may be sunnier, drier, warmer
different species at the edge
Many wild game species found here
What is a niche
The organisms role in its environment
How it responds to the distribution of resources
Many dimensions to it – therefore an n-dimensional hypervolume
No two species can occupy the same niche for any period of time
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If a niche is vacant organisms will quickly adapt to fill it
environment
Biodiverse Communities
Top species rich environments are tropical rainforests, coral reefs, deep sea, large tropical lakes
Usually high diversity but low abundance
Factors for increased diversity
Latitude: most diverse near equator
Depth: marine communities peak about 2000m
On land increases in solar radiation, precipitation, seasonal variation, decreased elevation
The Island Effect
Isolated ecosystems studied by MacArthur and Wilson in 1960’s
Diversity effected by island size & degree of isolation
Island Biogeography theory: diversity effected by
Rate of species immigration to island
Rate of extinction on island
Equilibrium point = species diversity
Island Biogeography
Immigration and Extinction Effected by
Size:
small island has less immigration (small target),
Small island has fewer resources, more extinction
Distance from mainland:
Applied in conservation for “habitat islands” like national parks surrounded by development
Island Biogeography Data
South Pacific Islands study looked at bird diversity as distance from New Guinea increased
Caribbean Island study found bigger islands had more species diversity than smaller islands which were
otherwise similar
Communities have different “Types” of Species
Native species = species that normally live and thrive in a particular community
Nonnative species = species that are accidentally introduced into an area
Keystone species = species that are more important than their abundance or biomass suggest
Indicator species = species that serve as early warnings of damage in a community
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Nonnative Species
Also called exotics, aliens, or introduced sp.
FL examples include fire ants, hydrilla, potato vine, peacock bass, …
Occupy niches excluding native organisms
Reproduce rapidly in absence of natural predators
Usually are very adaptable to human disturbed environments
Common Florida Exotics
Indicator Species
Mostly species that respond quickly to changes in the environment
Birds indicate tropical forest destruction
Trout indicate pollutant presence in water
Amphibians are a classic indicator
Frogs case study p 170
Frog decline and deformities
Keystone Species
Strong interactions with other species affect the health and survival of those species
They process material out of proportion to their numbers
Roles include: pollination, seed dispersion, habitat modification, predation by top carnivores, efficient
recycling of animal waste
Sea Otters
Habitat modification
Elephants – knock over trees in savannah to promote grass growth & recycle nutrients
Bats & birds – regenerate deforested areas by depositing plant seeds in their droppings
Beavers – create ponds forming habitats for many pond dwelling species like fish, ducks, & muskrats
tain species
Wolves, leopards, lions, gators, sharks, otters
Over 300+ species are found on the wolf kills made in Yellowstone
http://www.wolfquest.org/index.php
Waste removal
Species Interactions
Interactions may be harmful, beneficial, or have no effect at all
Competition: Intraspecific or Interspecific
Predation, Mutualism (Symbiosis), Commensalism, Parasitism
Intraspecific Competition
Competition between members of the same species for a common resource
Resource: food, space, mates, etc.
Territoriality
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Organisms patrol or mark an area
Defend it against others
Good territories have
Abundant food, good nesting sites, low predator pop.
Disadvantage = Energy, Reduce gene pool
Territoriality Examples
Interspecific Competition
2 or more different species involved
Competing for food, space, sunlight, water, space, nesting sites or other limited resource
If resources abundant, they can be shared but in nature they are always limited
One of the species must…
Migrate if possible
Shift feeding habits or behavior = Evolve
Suffer a sharp population decline
Become extinct
Connell’s Barnacles
Methods of competition
Interference
One species limits access of others to a resource, regardless of its abundance
Hummingbird territoriality, Desert plant allelopathy
Exploitation
Species have equal resource access, differ in speed of use
Quicker species = more of it & hampers growth, reproduction and survival of other species
Allelopathy
Competitive Exclusion Principle
One species eliminates another in an area through competition for limited resources
Two Paramecium species
Identical conditions grown apart both do well
Grown together one eliminates the other
The niches of two species cannot overlap significantly for a long period of time
Avoiding Competition
Resource partitioning = dividing of scarce resources to species at different
Times
Methods of use
Different locations
Species occupy realized niche, a small fraction of their fundamental niches
Lions vs leopards, hawks vs. owls
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Predation
Members of one species feed directly on all or part of a living organism of a different species
Predator plays important ecological role
Predation
Predation strategies
Herbivores – sessile prey, no need to hurry
Pursuit – speed (cheetah), eyesight (eagles), cooperation (wolves)
Ambush – camouflage for hiding (praying mantis), lures (anglerfish)
Ambush Predators
Prey defenses
Camouflage – change color, blend with environment,
Chemical warfare – produce chemicals which are poisonous, irritating, bad smelling or tasting
Warning coloration – bright colors advertise inedibility (mimics take advantage of this)
Behavioral strategies – Puffing up, mimicking predators, playing dead, schooling
Warning coloration
Batesian mimicry
Mullerian mimicry
Parasitism
One species feeds on part of another organism (the host) without killing it
Specialized form of predation
Parasite Characteristics
Usually smaller than the host
Closely associated with host
Draws nourishment from 7 slowly weakens host
Rarely kills the host
Examples = Tapeworms, ticks, fleas, fungi
Parasites
Mutualism
Symbiotic relationship where both species benefit
Pollination, Nutrition, Protection are main benefits
Not really cooperation, both benefit by exploiting the other
Mutualism II
Examples
Lichens –
ets sugars the other gets nitrogen
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Human Intestinal Symbionts
Commensalism
One species benefits the other is neither harmed nor helped
Examples
Herbs growing in the shade of trees
Birds building nests in trees
Epiphytes = “Air plants” which attach themselves to the trunk or branches of trees
-they have a solid base to grow on and better access to sunlight & rain
Energy in Ecosystems II
IB syllabus: 2.1.1-2.1.5, 2.2.1, 2.2.3
A.1.1, A.1.2
AP syllabus
Ch. 4
Syllabus Statements
2.1.1: Distinguish between biotic and abiotic (physical) components of an ecosystem
2.1.2: Define trophic level
2.1.3: Identify and explain trophic levels in food chains and food webs selected from a local
environment
2.1.4: Explain the principles of pyramids of numbers, pyramids of biomass and pyramids of
productivity, and construct pyramids from given data
2.1.5: Discuss how the pyramid structure effects the functioning of an ecosystem
Syllabus Statements
2.2.1: List the significant abiotic (physical) factors of an ecosystem
2.2.3: Describe and evaluate methods for measuring at least three abiotic factors in an ecosystem
2.3.3: Describe and evaluate methods for estimating the biomass of trophic levels in an ecosystem
Syllabus Statements
2.5.1: Explain the role of producers consumers and decomposers in an ecosystem
2.2.3: Describe and explain the transfer and transformation of energy as it flows through an
ecosystem
Ecosystems
Are communities and their interactions with the abiotic environment
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Ecosystem Components
2 parts
Abiotic – nonliving components
(water, air, nutrients, solar energy)
Biotic – living components
(plants, animals, microorganisms)
Biota
Significant abiotic factors
What abiotic factors effect this Aquatic food chain?
The abiotic influence
Species thrive in different physical conditions
Population has a range of tolerance for each factor
Optimum level
Highly tolerant species live in a variety of habitats with widely different conditions
The Law of Tolerance: The existence, abundance and distribution of a species in an ecosystem are
determined by whether the levels of one or more physical or chemical factors fall within the range
tolerated by
that species
Abiotic factors may be Limiting Factors (2.6.1)
Limiting factor – one factor that regulates population growth more than other factors
Too much or too little of an abiotic factor may limit growth of a population
Determines K, carrying capacity of an area
Examples
Temperature, sunlight, dissolved oxygen (DO), nutrient availability
Techniques to measure abiotic factors
Terrestrial
Light intensity or insolation ( lux) – light meter; consider effect of vegetation, time of day…
Temperature (°C) – themometer; take at different heights, points, times of day, seasons…
Soil moisture (centibars) – tensiometer of wet mass dry mass of soil; consider depth of soil sample,
surrounding vegetation, slope…
Aquatic (specify marine or fresh)
Salinity (ppt) – hydrometer; consider role of evaporation
Dissolved Oxygen (mg/L) – DO meter, Winkler titration; consider living organisms, water circulation,
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pH – pH probe or litmus paper; consider rainfall input, soil and water buffering capacity
Turbidity (FTU) – Secchi disk or turbidity meter; consider water movement,
Techniques (2.2.2)
For any of them you should know the following
What apparatus is used for measurement and its units
How it would vary or be used to measure variation along an environmental gradient
Scientific concerns about its implementation
Evaluation of its effectiveness or limitations
Terminology and Roles of Biota
Producers (Autotrophs) – Through photosynthesis convert radiant to chemical energy (energy
transformation)
Consumers (Heterotrophs) – Must consume other organisms to meet their energy needs
Herbivores, Carnivores, Omnivores, Scavengers, Detritivores
Decomposers – Break down organisms into simple organic molecules (recycling materials)
Food chains and Food webs
First trophic level = producer
Second trophic level = consumer, herbivore
Third trophic level = consumer, carnivore
Highest trophic level = top carnivore
Arrows indicate direction of energy flow!!!
Decomposers are not included in food chains and webs
For complexity of real ecosystem need food web which shows that individuals may exist at multiple
trophic levels in a system (omnivores)
Figure 53.10 Examples of terrestrial and marine food chains
Local examples write them in
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Food Web
Summarizes the trophic relationships of a community through a diagram
Most consumers are not exclusive to one level (ex. we are omnivores)
Figure 53.11 An antarctic marine food web: Identify the trophic levels
Antarctic pelagic (open ocean) community found in seasonally productive Southern Ocean
Zooplankton: dominant herbivores in Antarctic are euphausids (krill) and herbivorous plankton called
copepods
The zooplankton are eaten by carnivores including penguins, seals, fish, baleen whales
Carnivorous squid feeding on fish and zooplankton are important link in food web
Seals and toothed whales eat squid
During whaling years humans became top predators in the system
the sun
Food Webs
Food webs are limited by the energy flowing through them and the matter recycling within them
Ecosystem is an energy machine and a matter processor
Autotrophs: make their own food (plants algae & photosynthetic prokaryotes)
Heterotrophs: directly or indirectly depend on photosynthetic output of primary producers
Producers
Transform energy into a usable form
Starting form may be light energy or inorganic chemicals
Turned into organic chemical energy
This is the form that is used at other trophic levels
Photoautotrophs
Consumers
Heterotrophs: get energy from organic matter consumed
Primary, Secondary & Tertiary consumers
– termites, deer
Figure 53.0 Lion with kill in a grassland community
Decomposition
Decomposers obtain energy by breaking down glucose in the absence of oxygen
Anaerobic respiration or fermentation
End products = methane, ethyl alcohol, acetic acid, hydrogen sulfide
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Decomposition Process
Consumers or Decomposers
feces, fallen leaves, wood
May link producers to consumers
Dung beetles, earth worms
Saprophytes = feed on dead organic material by secreting digestive enzymes into it and absorbing the
digested products
Producers can reassimilate these raw materials
Fungi (mold, mushrooms), bacteria
Energy in living systems
Food chains, webs and pyramids, ultimately show energy flow
Obey the laws of thermodynamics
Obey systems laws – input, transfer, transformation, output
Thermodynamics Review
Universal laws that govern all energy changes in the universe, from nuclear reactions to the
buzzing of a bee.
The 1st law: Energy can be transferred and transformed but not created or destroyed
Energy flow in the biological world is unidirectional:
Sun
energy enters system and replaces energy lost from heat
Energy at one trophic level is always less than the previous level
The 2nd law: Energy transformations proceed spontaneously to convert matter from a more ordered,
less stable form, to a less ordered, more stable form
Energy lost as heat from each level
Energy at one level less than previous because of these lossed
Energy Flow in Communities
Energy comes from the sun
Converted by autotrophs into sugars
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Primary Production GPP
NPP = GPP - R
The Source of All energy on Earth is the …
Figure 3-10
Page 52
What is the sun?
72% hydrogen, 28% helium
Temp and pressure high so H nuclei fuse to form He releasing energy
Fusion energy radiated as electromagnetic energy
Earth receives 1 billionth of the suns Energy
Most reflected away or absorbed by atmospheric chemicals
Energy to Earth
30% solar energy reflected back into space by atmosphere, clouds, ice
20% absorbed by clouds & atmosphere
50% remaining
Warms troposphere and land
Evaporates and cycles water
Generates wind
< 0.1% captured by producers for photosynthesis
Energy eventually transformed to heat and trapped by atmosphere “Natural Greenhouse Effect”
Eventually reradiated into space
So if sunlight in = sunlight + heat out
What state is the system in?
Stable Equilibrium
Summary of solar radiation pathways – sketch it
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Incident radiation comes in, it is then…
Lost by reflection (ice caps) and absorption (soil, water bodies)
Converted from light to chemical energy (photosynthesis in producers)
Lost as chemical energy decreases through trophic levels
Through an ecosystem completely converted from light energy into heat
Reradiated as heat back to the atmosphere
Energy Flow II
Energy measured in joules or kilojoules per unit area per unit time
Energy conversion never 100% efficient
Some energy lost as heat
Of visible light reaching producers, only 1% is converted to chemical energy
Other levels are 10% efficient – only assimilate %10 of energy from previous level
Figure 54.1 An overview of ecosystem dynamics
Energy Flow and Food webs
Biomass = the total dry weight of all organisms in one trophic level
Usable energy degraded with each transfer
Loss as heat, waste, metabolism
-20%
More trophic levels = less energy available at high levels
Energy Flow through Producers
Producers convert light energy into chemical energy of organic molecules
Energy lost as cell respiration in producers then as heat elsewhere
When consumers eat producers energy passes on to them
In death organic matter passes to saprophytes & detritivores
Energy Flow through Consumers
Obtain energy by eating producers or other consumers
Energy transfer never above 20% efficient, usually between 10 – 20%
Food ingested has multiple fates
Large portion used in cell respiration for meeting energy requirements (LOSS)
Smaller portion is assimilated used for growth, repair, reproduction
Smallest portion, undigested material excreted as waste (LOSS)
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Figure 54.10 Energy partitioning within a link of the food chain
Energy flow through Decomposers
Some food is not digested by consumers so lost as feces to detritivores & saprophytes
Energy eventually released by process of cell respiration or lost as heat
Construct and analyze energy flow diagrams for energy movement through ecosystems
Trophic level boxes are storages – biomass per area (g m-2)
Energy Flow in arrows – rate of energy transfer
(g m-2 day-1)
Using Pyramids to express ecosystem dynamics
Pyramids
Graphic models of quantitative differences between trophic levels
By second law of thermodynamics energy decreases along food webs
Pyramids are thus narrower as one ascends
Pyrami
– large forests
in time – open ocean
Losses in the pyramid
Energy is lost between each trophic level, so less remains for the next level
Respiration, Homeostasis, Movement, Heat
Mass is also lost at each level
Waste, shedding, …
Pyramids of Biomass
Represents the standing stock of each trophic level (in grams of biomass per unit area g / m2)
Represent storages along with pyramids of numbers
How do we get the biomass of a trophic level to make these pyramids?
Why can’t we measure the biomass of an entire trophic level?
Take quantitative samples – known area or volume
Measure the whole habitat size
Dry samples to remove water weight
Take Dry mass for sample then extrapolate to entire trophic level
all individuals at that trophic level are the same
The sample accurately represents the whole habitat
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Pyramids of Numbers
Needs sampling similar to Biomass and therefore has the same limitations
Also measures the storages
Pyramids of productivity
Flow of energy through trophic levels
Energy decreases along the food chain
Lost as heat
Productivity pyramids ALWAYS decrease as they go higher – 1st and 2nd laws of thermodynamics
Shows rate at which stock is generated at each level
Productivity measured in units of flow (J / m2 yr or g / m2 yr )
Figure 54.11 An idealized pyramid of net production
Figure 54.14 Food energy available to the human population at different trophic levels
Take an Economic Analogy
1. If you look at the turnover of two retail outlets you can’t just look at the goods on the shelves
Rates of stocking shelves and selling goods must be known as well
A business may have substantial assets but cash flow may be limited
So our pyramids of Biomass and numbers are like the stock or the assets and our pyramids of
Productivity are like our rate of generation or use of the stock
How does pyramid structure effect ecosystem function?
Limited length of food chains
Rarely more than 4 or 5 trophic levels
Not enough energy left after 4-5 transfers to support organisms feeding high up
Possible exception marine/aquatic systems b/c first few levels small and little structure
Vulnerability of top carnivores
Effected by changes at all lower levels
Small numbers to begin with
Effected by pollutants & toxins passed through system
Effects II: Biomagnification
Mostly Heavy metals & Pesticides
Insoluble in water, soluble in fats,
Resistant to biological and chemical degradation, not biodegradable
Accumulate in tissues of organisms
Amplify in food chains and webs
Sublethal effects in reproductive & immune systems
Long term health effects in humans include tumors, organ damage, …
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Practice Problems
The insolation energy in an area of rainforest is 15,000,000 cal/ m2/day. This is the total amount of sun
energy reaching the ground. The GPP of the producers in the area, large rainforest trees, is 0.0050
g/cm2/day and 25% of this productivity is consumed in respiration. By laboratory tests we found that 1
gram of rainforest tree contains 1,675 calories of energy.
A. What trophic level are the trees considered? (2 point)
B. Calculate the NPP of the system. (5 point)
C. Find the efficiency of photosynthesis. (5 point)
D. If a monkey population eats the fruit from the trees how many square meters of forest will
each individual need to feed in if they require 400 calories each day?
Practice
Create a food web for the following FL organisms
largemouth bass, panther, racoon, white tailed deer, bullfrog, shiner (small fish), water beetles,
zooplankton, phytoplankton, marsh grass, rabbit, water moccasin, dragonfly, duckweed, egret, wood
duck,
http://www.indianriverlagoon.org/stats.html
Cycling of matter
IB Syllabus: 2.2.3, 2.2.6
Ch. 4
Syllabus Statements
2.5.4: Describe and explain the transfer and transformation of materials as they cycle within an
ecosystem
Biogeochemical cycles
Nutrients needed for life are continuously cycled between living and nonliving things
Driven by incoming solar energy
Connect past – present – future by recycling chemical compounds
Oxygen, Carbon, Nitrogen, Phosphorous, and water
Water Cycle
Collects, purifies and distributes earth’s constant water supply
Evaporation – converts water into vapor
Transpiration – evaporation from plant leaves
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Condensation – vapor to liquid
Precipitation – rain, sleet, snow, hail
Infiltration – movement of water into soil
Percolation – flow of water to aquifers
Runoff – movement of water over land surface
Sun powers the cycle – 84% vapor from ocean
Warmer air holds more water
Relative humidity = amount of water vapor in a mass of air expressed as a % of the maximum the air
could support at that temp
Wind and air masses transport water around the earth
Precipitation – needs condensation nuclei to occur
Soil dust, volcanic ash, smoke, sea salt, particulates
Some locked in glaciers, most into oceans as surface runoff
Runoff sculpts earth’s surface & transports nutrients
Water purification happens at many steps
Human Influences
Withdrawing large quantities of fresh water from surface and ground water
Aquifer depletion and saltwater intrusion
Clearing vegetation for agriculture, mining, construction
Increase runoff, flooding, erosion, Decrease infiltration
Modifying water quality
Adding nutrients, changing natural processes
Systems model: Water Cycle
Carbon cycle
“C” is the basic building block of life
Global gaseous cycle based on CO2
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Producers remove CO2 from the atmosphere in photosynthesis
Respiration of organisms puts CO2 back into atmosphere
Organic carbon stored in living tissues and fossil fuel deposits
Terrestrial Carbon cycle
Carbon storages
Organisms store most of the carbon
organic compounds
Sedimentary rocks such as limestone
Carbon reenters cycle when sediments dissolve naturally or by acid rain
Oceans
Gas dissolves into ocean at surface
Removed by marine algae in photosynthesis
Marine organisms
Reaction of CO2 with Ca in organisms to produce CaCO3 for shells and
Human effects
Adding Carbon to the Atmosphere
Clearing trees and plants that absorb CO2 through photosynthesis
Burning fossil fuels and wood increasing CO2
Enhance the greenhouse effect
Raise sea level
Disrupt food production
Destroy habitats
Systems model: Carbon Cycle
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Nitrogen cycle
1. Nitrogen Fixation
Specialized bacteria convert atmospheric N2 into NH3
Done by
Cyanobacteria – in soil and water
Rhizobium – bacteria living in root nodules of a variety of legume plants
2. Nitrification
A two step process
Ammonia in soil converted to nitrite and nitrate
Aerobic bacteria complete this process
- (toxic to plants)
NH3
- (easily taken up by plants as nutrient
3. Assimilation
Plant roots absorb inorganic nitrogen ions
nitrates, ammonium
Ions used to make nitrogen containing organic molecules
DNA, amino acids, proteins
Animals get nitrogen by eating plants or other plant-eating animals
4. Ammonification
After N has been used in living things and it leaves as waste or death…
Bacterial decay results
Producing
Simpler inorganic compounds like NH3
Water soluble salts containing NH4+
5. Denitrification
Anaerobic bacteria in waterlogged soils and bottom sediments
Convert nitrogen compounds back into gas forms and release into the atmosphere
NH3
NH4+
NO2-
N2
NO3-
N2O
Human effects on the N-cycle
Inputs of commercial inorganic fertilizer
Adding NO to the air through combustion of fuels
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Removing “N” from the crust by mining
Removing “N” from soil
Harvest crops, irrigation, deforestation
Adding “N” to aquatic systems from runoff
Systems model: Nitrogen Cycle
The Phosphorous cycle
Very little in the atmosphere
Found as phosphate salts in terrestrial rocks and ocean sediments
Into organisms by uptake & assimilation by plants, consumption & assimilation by animals, then animal
waste returns it to water or to the land (guano)
Often a limiting factor in plant growth both terrestrial and aquatic
Human effects
Mining large amounts of phosphate rock
Inorganic fertilizers, Detergents
Reducing available phosphate in tropical forests by removing trees
Soil nutrients washed away w/out trees
Adding excess phosphate to aquatic systems
Runoff of animal waste, commercial fertilizer from farmland, municipal sewage discharge
Florida Phosphate mining
Systems model: Phosphorous Cycle
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The sulfur cycle
Most “S” stored underground in rocks and minerals including salts in ocean sediment
Enters the atmosphere from volcanoes, sea spray, decomposition in aquatic habitats
Marine algae may produce DMS sulfur compounds in large quantities
In atmosphere it may mix into hydrologic cycle to form sulfuric acid – acid rain
Human effects
Burning “S” containing coal and oil for electricity production
2/3 of human SO2 inputs
Refining “S” containing petroleum into gasoline, heating oil, etc.
Smelting of “S” compounds of metallic minerals producing pure metals
Copper, Lead, Zinc
Cycle types
With all cycles common features allow grouping
Groups based on storages
Sedimentary cycle – major storage in the ground
E.x. phosphorous cycle
Atmospheric cycle – major storage in the atmosphere
E.x. nitrogen cycle
You should be able to create a flow diagram of Carbon, Water and Nitrogen cycles
http://www.colorado.edu/GeolSci/courses/GEOL1070/chap04/chapter4.html
Ecosystem Productivity
IB Syllabus: 2.2.1-2.2.6, A.3.1, A.3.2, A.2.3
AP
Chapter 4
Syllabus Statements
2.5.2: Describe photosynthesis and respiration in terms of inputs, outputs and energy
transformations.
2.5.5: Define the terms gross productivity, net productivity, primary productivity, and secondary
productivity
2.5.6: Define the terms and calculate the values of gross primary productivity (GPP) and net primary
productivity (NPP) from given data.
2.5.7: Define the terms and calculate the values of gross secondary productivity (GSP) and net
secondary productivity (NSP) from given data.
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Figure 10.1 Photoautotrophs
Photosynthesis in Plants
Chloroplasts are the location of photosynthesis in plants
In all green parts of plants – leaves, stems,…
Green color from chlorophyll (photosynthetic pigment)
Found in cells of mesophyll – interior tissue of leaves
Gases exchanges through the stomata
Water enters through xylem of roots
Figure 10.2 Focusing in on the location of photosynthesis in a plant
Energy Processes
Photosynthesis (Green Plants)
Respiration (All living things)
ATP is molecular energy storage
Producers
Make their own food - photoautotrophs, chemoautotrophs
Convert inorganic materials into organic compounds
Transform energy into a form usable by living organisms
Photosynthesis
Inputs – sunlight, carbon dioxide, water
Outputs – sugars, oxygen
Transformations – radiant energy into chemical energy, inorganic carbon into organic carbon
Respiration
Inputs - sugars, oxygen
Outputs - ATP, carbon dioxide, water
Transformations – chemical energy in carbon compounds into chemical energy as ATP, organic carbon
compounds into inorganic carbon compounds
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Definitions
gross productivity – total biomass produced
net productivity – total biomass produced minus amount used by organism
primary productivity – productivity at 1st trophic level
secondary productivity – productivity at higher trophic level
gross primary productivity – rate at which producers use photosynthesis to make more biomass
net primary productivity – rate at which energy for use by consumers is stored in new biomass
Distribution of World Productivity
Gross Productivity
Varies across the surface of the earth
Generally greatest productivity
In shallow waters near continents
Along coral reefs – abundant light, heat,
nutrients
Where upwelling currents bring nitrogen & phosphorous to the surface
Generally lowest
In deserts & arid regions with lack of water but high temperatures
Open ocean lacking nutrients and sun only near the surface
Ocean Area vs Productivity
Effects of Depth
Net Productivity
Some of GPP used to stay alive, grow and reproduce
NPP is what’s left
Most NPP
Estuaries, swamps, tropical rainforests
Least NPP
Open ocean, tundra, desert
Open ocean has low NPP but its large area gives it more NPP total than anywhere else
Agricultural Land
Highly modified, maintained ecosystems
Goal is increasing NPP and biomass of crop plants
Add in water (irrigation), nutrients (fertilizer)
Nitrogen and phosphorous are most often limiting to crop growth
Despite modification NPP in agricultural land is less than many other ecosystems
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Productivity Calculations
chemical energy by photosynthesis per unit time
Joules / Meter2 / year
– R, or GPP – some energy used for cell respiration in the primary
producers
Represents the energy storage available for the whole community of consumers
Standing crop = Total living material at a trophic level
Producers
NPP = GPP – R
Consumers
GSP = Food eaten – fecal losses
NSP = change in mass over time
NSP = GSP – R
Measuring Primary Production
Measure aspects of photosynthesis
In closed container measure O2 production, CO2 uptake over time
Must measure starting amount in environment then amount added by producers
Use dissolved oxygen probe or carbon dioxide sensor
Measure indirectly as biomass of plant material produced over time (only accurate over long timer
Light and Dark Bottle Method – for Aquatic Primary Production
Changes in dissolved oxygen used to measure GPP and NPP
Measures respiration and photosynthesis
Measure oxygen change in light and opaque bottles
Incubation period should range from 30 minutes to 24 hours
Use B.O.D. bottles
Take two sets of samples measure the initial oxygen content in each (I)
Light (L) and Dark (D) bottles are incubated in sunlight for desired time period
NPP = L – I
GPP = L – D
R=I-D
Sample Data
Method evaluation
Tough in unproductive waters or for short incubation times
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Accuracy in these cases can be increased by using radioactive isotopes C14 of carbon
Radioactivity measured with scintillation counter
Can use satellite imaging: Nutrient rich waters of the north Atlantic
Measuring Secondary Productivity
Gross Secondary Production
Measure the mass of food intake (I) by an organism (best if controlled diet in lab)
Measure mass of waste (W) (excrement, shedding, etc.) produced
GSP = I – W
Net Secondary Production
Measure organism’s starting mass (S) and ending mass (E) for experiment duration
NSP = E-S
Method evaluation
GSP method difficult in natural conditions
Even in lab hard to get exact masses for waste
NSP method hard to document mass change in organism unless it is over a long time period
What types of things effect productivity?
What can we measure for an experiment?
Effects of light exposure – strength, time, color, …
Effects of temperature
Differences between types of plants
Differences between types of producers
Effects of nutrient additions
Effects of salinity
Other parameters to change
Terrestrial vs. aquatic
Oxygen, carbon dioxide
Biomass
B.O.D. bottles
GPP estimates
Problems
Problems
The GPP of the producers in the area, large rainforest trees, is 0.0050 g/cm2/day and 25% of this
productivity is consumed in respiration. Calculate the NPP.
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Terrestrial Biomes
IB Syllabus: 2.1.7-2.1.9
AP Syllabus
Ch 6
Video – planet Earth – pole to pole
Syllabus Statements
2.1.7: Define the term Biome
2.1.8: Explain the distribution, structure and relative productivity of tropical rainforests, deserts,
tundra and any other biome
What is a biome?
World climate is variable
Differences in temperature and precipitation
Biomes = Regions of the earth characterized by specific climates and community types
Remember they cross national boundaries
Real biomes do not have sharply defined boundaries. Ecotones = Transitional zones
Biomes not uniform, mosiac of patches
Vary in microclimate, soil types, disturbances
Major Terrestrial Biomes
Desert
Tundra
Forests
Tropical Rainforest, Tropical deciduous forest
Temperate Rainforest, Temperate deciduous
Tiaga (Boreal)
Grasslands
Scrublands
Mountains
For each Biome you should comment in the distribution, climate (read climatograms), structure, relative
productivity and limiting factors
Main Biome Effects
Vegetation changes
Plants in cold regions have traits to limit heat & water loss
Winter dormancy (drop leaves), smaller size, evergreens have needles
Plants in dry areas must lose heat and conserve water
No leaves, water storage, nocturnal activity
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Plants in rainforests must get light and remove water
Broad leaves, drip tips, radiate heat
Deserts
Climate
Precipitation < 25 cm / yr – scattered unevenly through year Arid
May be Tropical, Temperate and Cold types – always extremes
High to moderate insolation
Distribution
30%
Gobi (Asia), Mojave (N. america)
Structure
Simple – very little vegetation
Most complex is temperate desert which has largest cacti
Relative Productivity
Low – limited by water availability
World Distribution of Deserts
– Major ones Saraha (Africa),
Desert Types
Tropical Deserts
High temp. year round
Little rain, only 1-2 months
Driest places on earth
Few plants
Hard windblown surface: sand & rock
Middle East areas
Desert Types
Temperate Deserts
Day temp. high in summer, low in winter
More precipitation
Sparse vegetation – suculents, cacti, animals
Southern CA (Mojave)
Desert Types
Cold deserts
Winters cold
Summers warm to hot
Precipitation low
Gobi desert, China
Plant Adaptations
Every drop of water counts
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Wax coated leaves limit transpiration
Deep roots tap underground water
Wide spread shallow roots gather falling water
Drop leaves & dormancy in heat & dry periods
Store biomass in seeds
Animal Adaptations
Hiding in cool areas during day
Thick skin
Dry feces, concentrated urine
Water from dew & food
Dormancy in heat & drought
Human Impacts on Deserts
Temperate Grasslands
Climate
Precipitation 25-45 cm / yr – enough to grow grass, erratic Semiarid
fire, drought, animals prevent tree growth
May be Tropical, Temperate
Moderate insolation
Distribution
– Major onesNA tall grass prairie, steppes, pampas, veldt
Grasslands overall up to 40% of earth’s surface
Structure
Simple – grasses and herbaceous plants
Relative Productivity
Medium to high – high turnover of grasses, rich soils
World Distribution of Grasslands
Grassland Types
Temperate grasslands
Vast plains and rolling hills
Summer hot & dry
Winter cold
Sparse, uneven precipitation
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Thick fertile soils
Grassland Types
Tropical Grasslands
Savannas
High average temp
Moderate rainfall
Prolonged drought
Herds of herbivores
Grazing & Browsing
Africa, SA, Australia
Migrations in dry season
Herbivore coexistence
Minimize competition by resource partitioning
African animals differ by region & niche
1. Giraffes eat leaves from tree tops
Elephants eat leaves and branches further down
Gazelles & Wildebeasts eat short grasses
Zebras eat longer grass & stems
Human effects on Grasslands
Tundra
Climate
Precipitation < 15 cm / yr – mostly snow & summer rain Arid
-57 – 50 °C - permafrost
low insolation gives short growing season
Distribution
60 –
– northern North America, Asia, Greenland
About 20% of the earth’s surface
Structure
Simple – low spongy mat of vegetation, lichens, mosses
Even trees are less than knee high
Relative Productivity
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Low – limited by temperature and insolation
Tundra Distribution
Tundra
Treeless spongy mat of low growing plants
Common breeding area b/c predators visible
Organisms migratory
Cold & Windy & Dark
Ice & snow cover
Low precipitation but poor drainage b/c Permafrost
Forest Types
Undisturbed areas with moderate to high rainfall
Dominated by various species of trees and other vegetation
3 main types of forest – Tropical, Temperate, Boreal
World Distribution of Forests
Tropical Rainforest
Climate
Precipitation over 150 cm / yr – Wet – still rainy and dry seasons
high insolation gives short growing season
Distribution
– Tropic of Capricorn to Cancer
About 2% of the earth’s surface
Three chunks – S. & C. America, C. Africa, SE Asia
Structure
Complex – stratified layers
High diversity - 50-80% of terrestrial species
Relative Productivity
Highest in terrestrial system – unlimited by temperature and insolation
Tropical Rainforest
Broadleaved evergreen trees
High biological diversity, Specialized niches,
Much of animal life found in canopy layer
Stratification of life in different tree layers increases niche partitioning
ersity but very poor soils
Rapid recycling of nutrients
Little nutrients stay in soil most taken back into plants
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Temperate Forests
Significant seasonal changes
Abundant precipitation throughout year
Dominated by a few broadleaved deciduous trees
Simple structure
Thick layer of leaf litter
Once diverse, now predators gone
Boreal Forests (Tiaga)
Just below tundra
Dominated by coniferous tree species
Withstand cold, rapid growth in summer
Low temperature
Low decomposition, high soil acidity
In summer soil is waterlogged = muskegs
Human Effects on Forests
Climatograms Review
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