Geo 5

food chains
Energy, principally sunlight, is extracted from the physical environment and converted into organic matter by plants.
Each food chain has 3-4levels of energy transfer called trophic levels.
Producers (Trophic Level 1)
plants are producers of organic energy. Land: macrophytes (trees, ferns & grass)
Sea: main producers are phytoplanktons (foundation of oceanic ecosystems)
Primary, Secondary, Tertiary Consumers
Primary consumers (level 2): Herbivores like cattle, buffalo, squirrels, etc.
Secondary Consumers (level 3): Carnivores like wolves, lions, and weasels
Tertiary consumers (level 4): specialized carnivores like hawks, eagles, sharks who eat other carnivores.
organisms that live on refuse of ecosystems
include scavengers like vultures & crabs and decomposers like fungi & bacteria that break down plant debris, animal droppings, etc.
energy attenuation
massive loss or release of energy because of organism respiration
*the maintenance process of plants and animals
*accounts for 90% of energy @ each trophic level and virtually all is discharged as heat & remaining energy is passed on to next trophic level
energy pyramid
the pyramid that shows how much energy is lost in each trophic level as it is passed on. At each trophic level, organisms receive and give energy, but at each trophic level, less is received and even less is given.
All ecosystems have this component. It means living organisms. Made up of 3 groups of organisms: producers (plants), consumers, and detritivores.
nonliving component in an ecosystem. Includes sunlight, soil, heat, air, and water.
specific process by which plants take in solar radiation, combine it with carbon dioxide, water, and heat, and convert it into chemical energy. This chemical energy takes the form of organic compounds of sugars and carbohydrates that build and maintain the cells in leaves, flowers, wood, bark, seeds, etc.
net photosynthesis
This is what’s left over after photosynthesis because some of the energy is lost in the process because of respiration.
net primary production/plant productivity
Measure of net photosynthesis in grams of organic matter added to the landscape, a lake bed, or ocean floor per year
percentage of solar energy that plants are able to convert into organic energy through photosynthesis
Productivity; limitations, disturbances
important measure of ecosystem’s vitality. depends on 2 factors: 1. limitations on availability of basic resources for photosynthesis; 2. disturbances imposed by external envronment
5 basic ingredients to maximize photosynthesis
light, heat, water, carbon dioxide, nutrients
If any of 5 ingredients for photosynthesis is missing, plant gets stressed out
principle of limiting factors
rate of productivity is governed by the one ingredient required for photosynthesis that is in least supply.
optimum conditions
when the conditions are between the lower and upper limits lie for an organism. When it is most successful.
tolerance thresholds
Actual levels at which organism’s life processes are arrested. They can be acute, such as extreme low temperatures brought by sudden change in weather; or chronic such as gradual buildup of toxic substances in living cells of plants & animals
effect productivity. Not part of plant’s photosynthesis system but include fires, floods, diseases, droughts, pollution, land use. Disrupt the flow of basic resources to the plant.
climatic limitations
1. environments with no limitations; 2. environments with seasonal limitations; 3. environments with permanent (year round) limitations.
Stable environments with a dependable flow of resources are most favorable to high productivity rates (like rain-forest)
Types of ecosystems
1. terrestrial ecosystems (60% of earth’s photosynthesis)
2. saltwater (39%)
3. freshwater (1%)
large biogeographical unit characterized by a particular combination of vegetation and animals whose distribution is associated with a general climatic type. Also, a complex of ecosystems with broadly similar biogeographical characteristics over the region occupied.
Terrestrial class
forest, savanna, grassland, desert, and tundra
Biological organization
Order or arrangement of organisms in an ecosystem.
Species diversity
total number of species occupying a given area
total weight of living matter in an area
The population of every species occupies a particular geographic area. Ex. North American bison had a range originally extending over most of the grasslands of the praries, plains, and forest margins before it was hunted to near extinction in 1800s.
A number of different species with overlapping ranges that live together in an interdependent fashion.
an intimate association between dissimilar species. It may result in benefits for both species (mutualism)
one species benefits from symbiosis and the other is neither benefited nor harmed
One benefits from symbiosis and the other is harmed. Common trait of many tropical diseases in humans.
another form of species interaction that ties species such as lions and wildebeests together in communities.
The harsher the environment, the fewer the species and the larger the populations of individual species.
controls on the distribution of ecosystems
1. elevation: as land rises, climate grows colder and harsher; bioclimatic environment on mountain slopes characterized by altitudinal zonation (or belts with different ecosystems at successive levels)
2. drainage networks: all land areas are drained by streams. Each drains an area of land called a watershed. Within most watersheds, distribution of ecosystems is strongly influenced by availability of a dependable water supply.
exotic rivers
Include the colorado and Nile, run through a desert so it allows for wetland ecosystems and aquatic to thrive under a desert climate.
Ex. There is a retreating glacier, abandoned farmland, etc. (denuded surface) and little organisms come in (called pioneers) like algae, mosses, grasses, etc. They stabilize environment and make way for another community that is usually larger and more complex.
Successional stage
Each community changes the surface environment favorable to another community, until it is at a relatively stable condition called a climax community
Disturbance theory
external environment is forceful and variable and causes constant change in ecosystems. The Earth’s surface is constantly undergoing string of such harsh events and ecosystems are in a state of continuous adjustment to these forces
6 human impacts on ecosystems
1. Reduction
2. Fragmentation
3. Substitution
4. Simplification
5. Contamination
6. Overgrowth
loss in area or coverage of an ecosystem as a result of burning, agricultural development, urbanization, and lumbering.
Occurs when ecosystems are broken down from large, continuous areas into smaller parcels.Agricultural, cities, highways, dams, reservoirs are primary causes of stream valley fragmentation. 80% of major streams in North America & Eurasia are interrupted by dams and related facilities. Dams either destroy segments of the corridor environment or create constrictions in it that many of the ecosystem’s functions are hampered or eliminated.
replacing on set of organisms in an ecosystem with another. Ex. Agriculture will replace native grasses with corn, wheat, etc.
replacing on set of organisms in an ecosystem with another. Ex. Agriculture will replace native grasses with corn, wheat, etc.
Accompanies substitution. Replacement set of organisms is less diverse than original set of organisms.
Primary cause is habitat loss from expanding land use. Rate of extinction is 1000% higher than natural rate b/c of human activity.
Involves the incorporation of pollutants into the ecosystem. Once in the system, they pass through the food chains in the tissue of plants & animals.
Include peristent chemicals: they are not quickly broken down in the environment but linger for months or years.
Ex. Striped bass that migrate into SF Bay on annual spawning runs accumulate such heavy loads of toxic matter from urban & agricultural runoff that an annual die-off event has developed. When fish or their remains are eaten by other organisms, like gulls & eagles, the contaminants are passed up the food chains and the concentrations grow with each trophic level.
effects of two things such as two persistent chemicals acting together is greater than the sum of the two if they acted separately.
Contamination can lead to this. Contaminants are usually plant nutrients and accelerate plant growth, leading to high productivity.
Population density
-measure to analyze population and environmental issues by relating # of people in a country to its land area
-crude density: (# of people)/(total land area)
Physiologic density
A measure of population density based on the # of people in a country relative to the total are of cropland
Total fertility rate
The avg # of live children a woman will bear during her childbearing years (age 14-44)
Poverty cycle
A vicious cycle of human life characterized by the decline in available food, expansion of farming into marginal lands, degradation of the environment, abandonment of the land, and migration to cities
Renewed and updated Malthusian theory arguing that population in some parts of the world is currently outgrowing available food supply, leading to poverty, urban crowding, disease, and social unrest.
Agricultural, cultural, radiation diffusion
Agricultural: The spread of crop species and farming practices.
Cultural: The spread of ideas and technology to other peoples and lands
radiation: The scattering of incoming solar radiation by molecules and particles in the atmosphere.
simultaneous production of several crops on the same field; planting of secondary crops such as fruit trees w/in and on the margins of fields as a part of intensive subsistence agriculture.
Major elements utilized by living organisms such as nitrogen, phosphorus, and calcium
Trees planted with crops such as oats and potatoes in tree farms or plantations
Strip cropping
The practice of planting strips of erosion-prone crops such a s corn alternately with more soil, protective crops such as oats or alfalfa
Conservation tillage
Various techniques being adopted by farmers to reduce soil erosion and labor including reduced plowing and cultivation with heavier herbicide applications
Contour plowing
The practie of plowing fields and planting crops along slopes, parallel to the elevation contour, to retard runoff and soil erosion

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