ecology: the study of the interactions of living things with each other and their physical environment
population: all the members of a species inhabiting a given location
community: all the interacting populations in a given area
ecosystem: the living community and the physical environment functioning together
biosphere: that portion of the earth where life exists
** The biosphere is composed of numerous complex ecosystems.
** An ecosystem involves interactions between abiotic (physical) and biotic (living) factors. The members of the community in the ecosystem and environment must interact to maintain a balance.
An ecosystem is self-sustaining if the following requirements are met:
1. A constant source of energy and a living system capable of incorporating
2. A cycling of materials between organisms and their environment.
In all environments, organisms with similar needs may compete with each other for resources, including food, space, water, air, and shelter.
Abiotic factors: those physical and chemical factors which affect the ability of
Some Abiotic Factors:
1. intensity of light
** Each of the prior listed abiotic factors varies in the environment and,
1. A low annual temperature common to the northern latitudes
2. The amount of oxygen dissolved in a body of water will help
3. The dry environment of desert regions limits the organisms that can live there.
carrying capacity -- the maximum number of organisms the resources of an area can support
The carrying capacity of the environment is limited by the available abiotic and biotic resources, as well as the ability of ecosystems to recycle the residue of dead organisms through the activities of bacteria and fungi.
Biotic factors: all the living things that directly or indirectly affect the environment
** Thus, the organisms, their presence, parts, interaction, and wastes are all biotic factors.
autotrophs: can synthesize their own food from inorganic compounds and a usable
heterotrophs: can NOT synthesize their own food and
[Types of Heterotrophs]
saprophytes: include those heterotrophic plants, fungi, and bacteria which live on dead matter AKA decomposers
herbivores: plant-eating animals
carnivores: meat-eating animals
omnivores: consume both plants and meat
(Types of Carnivores)
predators: animals which kill and consume their prey
scavengers: those animals that feed on other animals that they have not killed
symbiosis: living together with another organism in close association
Types of (symbiosis): mutualism, commensalism, parasitism
commensalism: one organism is benefited and the other is unharmed (+,0)
mutualism: both organisms benefit from the association
parasitism: the parasite benefits at the expense of the host
** Recent experimental research indicates that lichens may represent a controlled
** If an ecosystem is to be self-sustaining it must contain a flow of energy.
** Those life activities that are characteristic of living organisms require an expenditure of energy.
** The pathways of energy through the living components of an ecosystem are represented by food chains and food webs.
** Producers convert the radiant energy of the sun into the chemical energy of food.
Food chain: involves the transfer of energy from green plants through a series of organisms with repeated stages of eating and being eaten
Food web: In a natural community, the flow of energy and materials is much more complicated than illustrated by any one food chain.
Since practically all organisms may be consumed by more than one species, many interactions occur along the food chains of any community
Food Web interactions)
producers: (plants) -- the energy of the community is derived from the organic compounds in plants (grass in the web above)
primary consumer: (always a herbivore) -- feeds on plants (mice, grasshoppers, and rabbits in the web above)
secondary consumer: (always a carnivore) -- feeds upon other consumers (frogs, sparrows, snakes, and foxes above) (The hawk is a secondary or 3rd level consumer depending on the availability of food.)
** Omnivores may be primary or secondary consumers.
decomposers: break down organic wastes and dead organisms to simpler substances (ex. bacteria of decay)
** Through decomposition, chemical substances are returned to the environment where they can be used by other living organisms.
Energy flows through ecosystems in one direction, typically from the Sun, through photosynthetic organisms, including green plants and algae, through herbivores, to carnivores, and finally decomposers.
** There is a decrease in the overall energy in each level as you move up the food web. This means that there is much more energy in the producer level in a food web than at the consumer levels. Also, this means that there is more energy at the primary consumer level than at the secondary consumer level.
** Each consumer level of the food pyramid utilizes approximately 10% of its ingested nutrients to build new tissue. This new tissue represents food for the next feeding level.
** The remaining energy is lost in the form of heat and unavailable chemical energy. Eventually, the energy in an ecosystem is lost and is radiated from the earth.
** Thus, an ecosystem can not survive without the constant input of energy from the sun.
biomass: amount of organic matter
** The decrease of energy at each successive feeding level (trophic level) means that less biomass can be supported at each level.
*** Thus, the total mass of carnivores in a particular ecosystem is less than the total mass of the producers. (A pyramid of biomass illustrates this.)
level D = producers
level C = primary consumers
level B= secondary consumers
level A = tertiary consumers
Above is a typical representation of a NY State terrestrial energy pyramid.
succession: replacement of populations in habitat as it moves toward a stable state
The environment may be altered in substantial ways through the activities of organisms, including humans, or when the climate changes. Although these alterations are sometimes abrupt (ex. natural disasters), in most cases species replace others, resulting in long-term gradual changes in ecosystems.
** Ecosystems tend to change with time until a stable system is formed.
pioneer organisms: the first organisms to inhabit a given location
** Pioneer organisms modify their environment -- thus establishing conditions
(ex. seasonal dieback and erosion, for example, would create pockets of "soil" in the crevices and hollows of the bare rock inhabited by the lichen)
** Each community modifies its environment, often making it more difficult for itself and, apparently, more favorable for the following community which infiltrates the first
primary succession: the development of plant communities on newly formed habitats that previously lacked plants (ex. a lava flow)
secondary succession: return of an area to its natural vegetation following
(ex. An example of a PRIMARY SUCCESSION ex. (Adirondack Bog Succession)
1. water plants at pond edge
An example of a SECONDARY SUCCESSION
1. plowed field
climax community: a self-perpetuating community in which populations remain stable and exist in balance with each other and their environment
** The climax community of a region is always its dominant plant species.
** Altered ecosystems may reach a point of stability that can last for hundreds or thousands of years.
** A climax community persists until a catastrophic change of a major biotic or
(ex. forest fires, abandoned farmlands, floods, areas where the topsoil has been removed)
** After the original climax community has been destroyed, the damaged ecosystem is likely to recover in stages that eventually result in a stable system similar to the original one.
** Ponds and small lakes, for example, fill in due to seasonal dieback of aquatic vegetation and erosion of their banks, and eventually enter into a terrestrial succession terminating in a terrestrial climax communit
flora -- plant species -- dominate in the sense that they are the most abundant food sources
** Plant succession is a major limiting factor for animal succession.
** Climax communities are identified by the dominant plant species -- the one that exerts the most influence over the other species present.
Competition: occurs when two different species or organisms living in the same environment (habitat) utilize the same limited resources, such as food, water, space, light, oxygen, and minerals.
** The more similar the requirements of the organisms involved,
(Competitive Exclusion Principle)
If two different species compete for the same food source or reproductive sites,
niche: the organism's role in the community
[ MATERIAL CYCLES ]
** In a self-sustaining ecosystem, materials must be cycled among the organisms
1. Carbon-Oxygen Cycle -- involves the processes of respiration and photosynthesis
3. Water Cycle: involves the processes of photosynthesis, transpiration, evaporation
and condensation, respiration, and excretion
Evolutionary processes have resulted in a diversity of organisms and a diversity of roles in ecosystems.
biodiversity -- the differences in living things in an ecosystem
Increased biodiversity increases the stability of an ecosystem.
Increased biodiversity increases the chance that at least some living things will survive in the face of large changes in the environment.
monoculture -- planting one species over a huge area
Monoculture leaves an area more vulnerable to predation or disease.
What are some other reasons biodiversity is valuable?
1. Biodiversity ensures the availability of a rich variety of genetic material that may lead to future agricultural or medical discoveries with significant value to humans. (if this is lost we lose the sources of these materials for discovery)
2. Biodiversity adds aesthetic qualities to the environment.