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171 Cards in this Set
- Front
- Back
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Ecological community
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is an assemblage of plant and animal populations that live in the same location
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Individualistic concept
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idealistic -- whole is greater than the sum of its parts
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Communities are structure in four ways
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Physio-gnomic, species compositions, trophic, temporal
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Physio-gnomic
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physical structure (ex: plant/community)
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Species composition
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diversity
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Trophic
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how is energy transferred from one part of community to other/ from one feeding group to another feeding group
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Temporal
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seasonal or diurnal activity (what type of patterns are occuring)
Ex of plant physical structure A. Location of Overwintering parts such as buds, bulbs or seeds B. Life fore, leaf form characteristics |
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Plant communities reflect
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many different growth forms with different characteristics
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Raunkiaer (Life forms)
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developed classification for plant based on ___ their over wintering structure and leaf characteristics structure (of buds, bulbs, seeds)
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Phancrophytes
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phyte-means plant
phanecro- means visible They carry buds at the tips/ends of their branches They are exposed to extremes of climate Most trees and large shrubs are phanerophytes Dominate in moist environments |
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Chammaephytes
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Chammae - on the ground
small shurbs and herbry close to the ground that have a prostrate life forme proximity of soil protects the bud (grows close to the ground) Buds low and close to ground Small shrubs and herbs that grown close to ground Prostrate life form - where they are lying down on ground Proximity to the soil protects the bud In winter, snow can provide additional protection Plants frequently occur in cool dry climates |
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Hemicryptophytes
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partially buried
Surviving buds are situated in soils surface Buds are protected by soil or leaf litter (partially hidden) Occur in cool moist climates |
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Cryptophytes or geophytes
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buds are completely hidden beneath the soil
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Therophytes
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thero means summer
they are plants that complete their life cycle from seed to seed and die within a season Die off during unfavorable season Do not have persistent buds (annuals) Occur in deserts and grasslands |
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Annual Herb
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seeds to seed in a span of a year, some do this in deserts in grasslands
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broad leaf evergreen
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liana growing on it AKA vine uses it as a trazan
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Drought Deciduous shrub
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drops leaves during dry season to cut transpiration
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Winter deciduous shrub
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drop leaves during winter (because decreased sunlight and if you decrease surface area for snow to build up less likely to drop branches)
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Stem succulent
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store water in the stem (leaves are modified spines)
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Bulbus hebaceous perennial
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comes back year after from the underground bulb
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Needle leaf evergreen
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pines, spruce, why be evergreen? See in places where nutrients are low
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Community physiognomy is either
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over wintering bud or growth form/leaf characteristics
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Animal communities are categorized based on feeding strategy (guilds)
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group of organisms that eat in the same way
Ex: Seeding eating guild, grainivore guild |
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guild is based on....
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When they are feeding?
Where they are feeding? What are they feeding on? How are they feeding? |
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All the growth forms combine to form
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a community of varying physical and/or biotic structure
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Species composition or species diversity
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The number of species in a community and their relative abundances in that community
Species richness number of species |
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Shannon Index
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What does Shannon Index do?
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Take number of species from A and B that's richness
Number of individuals for each species is equitably (evenness) Then you take proportion of those individual of species one out of total And that number is multiplied by natural log Takes into account richness and evennes Range of 0 - 4 *** A way to measure the amount of species diversity *** |
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Equitability/eveness
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relative abundance of species in that community (lots of rare species or lots of species but not rare) (higher species diversity)
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FIG 16.5
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Forest A = 5 species (84% come from one species)
Forest B = 5 species (each species represents 20% of total) Same species richness Different eveness. B has higher species evenness (have higher diversity) Higher species diversity tends to indicate more complex community With greater variety of species, allowing for a greater array of species interactions Numerous species indices over years |
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Factors affecting diversity within communities
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Climatic stability -- more stable more diversity (ex. Africa)
Resource division Predation Disturbance -- perturbations Productivity -- how productive is that ecosystem |
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NA and A graph
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Africa has more diversity because it has been around longer and therefore has had more time to evolve more species
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What effect does predation have on species diversity?
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Pinsaster seastar
With this predator -- 15 species of shellfish Without this predator -- 8 species of shellfish |
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Robert Paine
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rocky temperature intertidal coastline in Washington macroinvertebrates, chitons and snales
After 5 years only 2 species remained -- 1 gooseneck Barnacles, mussels Predators increase diversity of species in an area |
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Disturbance (perturbation)
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A relatively discrete event in time coming from the outside that disrupts ecosystems, communities or populations, changes substrates and resource availability, and creates opportunities for new individuals to become established
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Examples of disturbance
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Wind, flood, fire, drought, animal overuse and human activities (geese, deforestation by humans) ---> farming, mining, timbering, stream control, pollution, war...
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Disturbance Characteristics
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Size
Frequency - number event per unit time Turnover - time between disturbance (once every 5 years ) Intensity - physical force of the even (saffer-simpson hurricane scale) Severity - impact on the biota |
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J.H. Connells Intermediate Disturbance Hypothesis
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Moderate levels of disturbance increase species diversity
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High level of disturbance
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biodiversity is low (knocks populations back)
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Low levels of disturbance
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create competitive exclusion
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Medium levels of disturbances
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have the highest levels of species diversity
* when a tree falls in the forest the resulting gap created increases diversity* |
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Intermediate levels of disturbance
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there are is a sufficient time to allow a wide variety of species to colonize but not enough time to allow competitive exclusion
happens in both terrestrial and aquatic environments |
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Colonizing happens at high frequent levels of disturbances
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open up areas for new species to colonize
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Mixed medium diversity
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balanced, not as many disturbances so many thrive
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Climax in low levels of diversity
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in a climax community where you have very little disaster you'll end up with only the best predators
eventually in VA everything will be an Oak Forest |
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FIG 16.19
Disturbance and Diversity - Wayne Sosa |
Studied Algae in intertidal zone on boulders
Looked at levels of disturbance and looked at the affect on the algae Looked at large rocks that less distrubuted, small rocks easily moved found that they were only dominated by one colonizing species The largest rocks that moved the least with the least disturbances had a decreased number of species because of competition The intermediate levels of disturbance had highest levels of diversity (4-7 species) |
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FIG 16.21
Support for Connell's hypothesis in Terrestrial communities with prairie dogs |
Ex: Prairie dogs maintain a high level of disturbances by burrowing anc creating dirt mounds. Continues the high diversity of grasses in the plains
Burrowing and grazing by prairie dogs increases the number of kinds of grass species within their prairie |
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Disturbance Generalizations
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Disturbance affects community equilibrium and therefore species diversity
Disturbances is harmful to the individual and may be detrimental to the population or species, but often it is beneficial from the stand point of maintaining or enhancing species diversity |
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Two quick points
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Trophic dynamics
--> Webs --> Energy Flow Production --> Primary ---> Secondary |
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Facilitation
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enhanced growth, fitness, survivor-ship, etc. due to environmental modification by other species
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First thing to colonize after storm
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is grass
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Myrica cerifera
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facilitated by grass growth (with produced an environment preventing other species growth in the beginning, then as it ages and dies out makes good environment) the seeding will grow in a ticket
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Examples
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Red Cedar and cacti also do it
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Joshua Tree is desert
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modified environment around it, temperatures under it decrease causing growth of organic matter and it creates micro climatic conductive
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Nurse Plant syndrome (Joshua Tree)
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nucleation (the main center plant in the main part and plants will come around the original plant - a plant survives due to the microclimate created by the tree (the preexisting individual)
Plant facilitates advancement of other organisms |
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Crabtree vs Contrary creeks
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surface mining shaft mining and strip mining lead to the decrease in pH water which eliminates diversity in streams
Contrary creek acid mine drainage, yellow boy, low acidity and low pH water eats gills of fish and kills them Waste seeds form feces in DC spread to Contrary Riparian zone to promote growth In order to compare them you need index of biotic integrity (good = high) |
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FIG 3.42 Index of biological integrity (diversity) Gives IBI score from 12-60, 60 is good
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IBI to assess body of water
If you want to look at a community of stream and want to evaluate it you need a reference to compare it to ( to indicate diversity and water quality) Healthy aquatic community - is similar to an undisturbed habitat in same region Look at number of native kind of species, look at number of fish, number of macro invertebrates, the higher the different kind indicates the healthier |
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If you have more insectivores
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you have increased stream health
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More omnivores
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indicates decreased stream health
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MAIN POINT ABOUT IBI
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Quantitatively sampling the fish community of a stream or lake and developing a "score" for environmental quality is known as index of biological integrity
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Robert Pain
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looks at predators
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FIG 17.16
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LOOK AT BOOK
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Keytone species are
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those who influence on the the community is disproportionate to their biomass (abundance)
Despite low biomass (sometimes Apex Predators) All keytone species are those that despite low biomass exert strong affects on the stricture that they inhabit Sea otters, snails, Pisaster, fish, beaver, jaguar, elephant |
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Keytone species are unlike
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dominant species are one that have significant influence on community by virtue of high biomass
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Dominant species
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have an influence on the community because HIGH BIOMASS
Also by abundance affect on energy flow and environmental modification |
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Apex predators
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have a strong influence on the environment they live in
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Consumers can exert control
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on community or food web structure over the environment in which they live (FIG 17.6)
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Compare to the arctic food web in 17.3
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LOOK AT BOOK
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Introduced apex predator in the James River
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American shad - not so many anymore because new species
Blue catfish (ictalurus furcatus) - eat american shad (introduced by Department of Game and Fisheries_) |
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Blue catfish
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ictalurus furcatus
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Relate to Lake Victoria problem 17.17
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Over 400 species of fish evolved in that lake (prior to uninvasive species)
Nile perch (lates nilocticus) and Nile talapia introduced in 50's now only 3 dominant groups of fish in the lake Omena only native still existing Apex predators (top of food chain) in Lake Victoria largest catrastrophic ting now, hugely simplified food web |
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Introduced apex predator sin the Chesapeake Bay 17.17
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Snakehead fish eats everything and has no know predators
Can grow 1.5 meters long Introduced in MD and working its way down Introduced by foreigners, released open |
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Food Webs
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movement of energy from one area of community to another are of community FIG 17.4
Summarize feeding relationships in ecosystem or community Naturally occurring food webs are highly complex |
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Trophic dynamics
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transfer of energy from one part of the ecosystem to another
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Top trophic level
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apex predator (ex. owl - eastern screech owl - small but on top of trophic level)
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Eastern Deciduous Forest (where we are now) -- community portrait
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MANY COMPLEX AND INTERACTING FACTORS withing food webs
Energy made available by plants/producers Bottom is what makes everything possible! (plant!) Plants, trees, organic matter acorns, fruits Bees, mosquitos, flies, squirrels, beetles, butterflies Spiders, salamander, mouse Apex predator = owl (carnivore) When all these die, they become organic matter which is food for microbes |
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Food Chain
Trophic levels |
position in food web determined by the number of transfers of energy in that level
Produces (trees, herbs, etc) -- Autotrophs Primary Consumers (mice, moths, etc.) -- Herbivores, Heterotrophs Seconday Consumers (birds, spiders, etc.) -- Carnivores, Heterotrophs Tertiary Consumers (owl) -- Carnivores, Heterotrophs Decomposers -- Heterotrophs |
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18.17 Forest Energy Budget
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Energy enter into ecosystem bia
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primary producers and make it available to everything else
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Water shed #6
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measured photosynthestic photon flux density beaming down on forest and converted sunlight to calories was 480,000 kcal/m2 (100% solar radiation)
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1st law of thermodynamics
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energy cannot be created or destroyed
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2nd law of thermodynamics
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No transformation of energy is 100% efficient and the amount of usable energy decreases ***** Some is always lost to the surrounding as heat*****
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How much is reflected?
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15%
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How much is lost as heat?
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41%
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How much is used as evapotranspiration
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42%
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How much is used as plant production (fixed)?
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Only 2.2%
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Primary producers take in inefficient energy from photosynthetic photon flux active radiation
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only 1% at net primary production available to heterotrophs
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Most energy stored as
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DEAD organic matter (upper portion of soil surface and where you have leaf litter) largest single pool of energy --- 36 cm
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kilocalorie = meter square
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1 kilocalorie per meter square
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The majority of organic matter is found
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in the top 36 cm of soil
2nd major in the biomass |
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Energy losses
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limit number of trophic levels in ecosystem (rarely more than 3 levels above autotrophs)
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Assumptions
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50% of energy used for heat tax for respiration
10% of energy passed on to next trophic level --THE TEN PERCENT RULE 40% incorporated as biomass which eventually goes to decomposes |
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An ecosystem will always
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try to maximize its energy storage
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Assimilation Efficiency =
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Energy assimilated/Energy ingested X 100%
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Assimilation
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incorporated of any materials into tissues, cells, and fluids of an organism
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Why is it advantageous to exploit herbivory?
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Energy flow to humans -->
Lot of energy to support herbivores takes energy to support herbivores which are then eaten More energy available for transfer 88% of world food supply is plant Most common plant is rice -- comes from wetlands |
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There are only 4 countries that use more animal than plant
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US, Canada, Australia, New Zealand
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Biomass
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organic matter found in a defined area, usually living
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Necromass
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dead organic matter
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Production
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the amount of energy stored by an individual, population, community or ecosystem per unit time
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Primary production
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autotrophs
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Secondary production
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heterotrops
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gross production
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all energy initially assimilated
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Net production
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(gross respiration) energy remaining after repiration (it is the net primary production that is the energy available to consumers in an ecosystem)
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****NPP=
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GPP -R******
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****Net primary production
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amount of energy available to consumers in an ecosystem****
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Ecosystem productivity
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uses net productivity across ecosystems
R.J. Whitaker |
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NPP is measured
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as the energy stored or biomass (dry weight) added by producers per unit area over a given time span (g/m2y-1) grams per meter square per year
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NPP most productive
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tropical rainforest
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NPP least productive
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desert (lack of water) and open ocean (lack of nutrients)
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Estuaries
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lots of water, more nutrients (sesspools, too full of nutrients)
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What limit primary productivity
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Temperature, water, nutrients, pH
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Abiotic factors affecting primary production
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temperature, rainfall, photoperiod (how much sunlight an ecosystem is receiving), nutrients, disturbance, etc
Occur over the growth season (rainfall, outside growing season is not beneficial) |
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Biotic factors affecting primary production
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Plant (C3,C4, CAM) and animal biodiversity, community structure (is it grassland, shrub land is it forested?) Animal utilization (grazing no grazing? )
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18.2
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temperature and percipitation are extremely important in regulation of primary productivity
As actual evapotranspiration (amount of moisture evaporated off land surface over year) increase the net primary productivity increases -- warm moist is more productive increase in AET increase net primary production |
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18.3
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Increased precipitation alone will increase net primary production increases (controls variation of primary production in ecosystem type)
Total amount of water that evaporates or transpires off a landscape in a year |
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18.10
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If you increase nutrients, productivity increases
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Consumer can control
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rates of primary production of ecosystems
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18.15 Wildebeests - intermediate levels of disturbance can increase primary productivity
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Grazing increases growth rates of many grass species due to compensatory growth
lower rates of respiration in the grass because lower biomass Lower biomass also leads to improved water balance due to reduced leaf arcs Medium intensity have the highest primary production High intensity grazing is also associated with low production Wounded response -- |
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Bottom up control
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refer to influence of temperature and nutrients on productivity of ecosystems
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Top down control
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look at influence of consumers on ecosystem
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18.11 trophic cascade hypothesis
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when something happens to one level another level is affected
if you consumers the planktivorous fish will increase and zoo and phytoplankton go up |
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18.12
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Tropic cascade model predicts that manipulating piscivore biomass will lead and prodction of planktivores, herbivores and phytoplankton
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why do ecosystems rely on continuous energy input from the sun?
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energy flows without continuous input life cant survive
sun fuels primary production which provides energy to all other life but eventually this energy is released (nutrients remain) |
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Detritus
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energy and nutrients are locked in this organic matter and decompose organisms break it down
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Rule #6
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Energy must flow but nutrients cycle
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Importance of Decomposition
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The final release of energy
Nutrient mobilization c-compounds + O2 --> CO2 +H2O 2 forms: Biological and Fire |
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Controlling factors of decomp
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moisture, temp, pH, O2, substrate characteristics and nutrient content
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Decomp of organic matter is a
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universal process in ALL ecosystems
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Rates of decomp influence
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soil fertility, nutrient cycling, organic matter accumulation and are a forcing facor controlling ecosystem structures and function
General trend in litter as it starts to decompose |
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This is for leaf litter
Phase 1 |
regulated by nutrient level and readily available carbon (the labile fraction on the litter is lost completely)
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This is for leaf litter
Phase 2 |
reulated by lignin decomp rate the more lignin the slower it decomps
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This is for leaf litter
Phase 3 |
final stages
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Labile
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leeched fast
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Refractory compounds
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tough compounds -- slower
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factors that control the rate of decomp
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decomposing organisms, chemical composition of the litter and physical rates of determinance (macro and micro climates)
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Sugar
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labile
Fungi and bacteria |
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Cellulose
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refractory
Decomposers |
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Lignin
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refractory
decomposers |
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basidiomycetes
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(white rot fungus) ---lignin decomposers
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Importance of moisture
19.5 |
tropicals have the highest decomp rate because they are wet
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Importance of moisture
19.8 |
decomp rate is high in places that have a high AET
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Fig 19.9
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Importance of substrate characteristics
19.7 |
higher levels of lignin = decomp more = slower
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19.12
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19.13
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--------
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Nutrient
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any substance necessary for life
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Nutrient pool
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portion of components in a ecosystem that are located in a place
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Nutrient flux
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movement of nutrients
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Nutrient cycles
Gaseous |
Relatively fast
Ex: C, N, H20 Hybrid : S |
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Nutrient cycles
Sedimentary |
Relatively slow
Ex: P, Na, Ca Hybrid: S |
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Nitrogen is the most
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limiting nutrient in terrestrial ecosystems
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19.3
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The N cycle is a
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microbially mediated cycle
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Denitrofication
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is anaerobic process
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Nitrosomonass
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turns Ammonium (NH4+) into nitrate (NO2-)
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Nitrobacter
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nitrite (NO2-) into nitrate (NO3+)
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Example of a sedimentary cycle
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phosphorus cycle
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19.2
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Phosphorus is as limiting in aquatic ecosystems as nitrogen is in terrestrial
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What organisms can alter nutrient cycles?
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- nitrogen fixers
- "musseling" phosphorus - nurtient spiraling - man's effects |
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Only source of phosphorus
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The weathering of rock
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What is a climax community
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Final stable community some ecosystems never reach this stage
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What is a sere
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A series of ecological communities From lichens to grass to shrubs to woodland would be considered one sere
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What is a Seral stage
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On stage within a sere: from previous example shrubs would be one seral stage
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In VA what is an example of a sere
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From a field to grasses and weeds to a pine forest to in some cases an oak forest
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What is a pioneer species
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A pioneer species is one of the first species into an area after a disaster which begins regrowth
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What is the difference between primary and secondary succession
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In primary succession organisms are coming into an area which has not yet been colonized such as areas where glaciers are receding secondary is when organisms are rebuilding a community that has been wiped out by a disturbance such as an area burned clean by a fire
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more densely populate communities inhibit new growth/ ecological succession (just a note not a question)
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more densely populate communities inhibit new growth/ ecological succession (just a note not a question)
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Why is Geukenzia demissa important
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Ribbed mussel is important because it helps to recycle P
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Explain importance of Myrica
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Important because it has high nitrogen content leading to an increase in nitrogen within the community this changes community dynamic overtime
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Rhibozial Bacteria
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legumes
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