Ecosystem Structure and Dynamics

37.14-37.16

37.1-37.7

37.8-37.9

37.18-37.21

37.10-37.11

37.19

37.8-37.9

37.17

Concept = An organism's ecological niche describes its functional position in the ecosystem, including its habitat and its relationships with other species

Concept = Organisms can be classified by how they obtain their energy (food) Producers make their own food, consumers obtain their food from eating other organisms

Chemical energy in carbon compounds flows through food chains by means of feeding
A food chain provides a model of energy, in the form of food, passes from one organism to another. Food chains can be connected to form food webs.

Concept = Biodiversity contributes to ecosystem stability.

Concept = Energy and matter are transferred through trophic levels. At each level, energy is lost as heat, so ecosystems require a continuous input of light energy to sustain them.
Living organisms cannot convert heat to other forms of energy

Concept = Ecological pyramids provide a model of the number of organisms or the amount of energy or biomass.

Concept = Chemical elements cycle through the ecosystem, important nutrient cycles include the water, carbon, oxygen, phosphorus and nitrogen cycles

Concept = Most ecosystems rely on a supply of energy from sunlight. Light energy is converted to chemical energy in carbon compounds by photosynthesis.

37.1

Biological community = an assemblage of all the populations of organisms living close enough together for potential interaction.
Community dynamics = the variability or stability in the species composition of a community caused by biotic and abiotic factors.
Community ecology helps in the conservation of endangered species, management of wildlife, controlling disease, and can also be applied to agriculture.

37.2

Interspecific interactions are relationships with individuals of other species in the community.
Interspecific competition occurs when populations of two different species compete for the same limited resource.
Predation = one species kills and eats another (+/-)
Herbivory = consumption of plant parts or algae by an animal (+/-).

37.3

Ecological niche - sum of a species' use of biotic and abiotic resources in its environment.
Interspecific competition lowers the carrying capacity.
If two species have the same requirements it could be challenging for them to co-exist.

37.4

Mutualism - both populations benefit (+/+)

37.5

Predation leads to diverse adaptions in prey species.
Predator + / Prey -
Prey populations use camouflage, mechanical defenses (ex. sharp quills), chemical defenses (ex. vivid color patterns), etc.

37.6

Herbivory is not too destructive, but after a plant has its parts eaten, it must use energy to make up/ replace the loss.
Plants have evolved to protect themselves from herbivores (ex. thorns, spines, chemical toxins).
Co-evolution = a series of reciprocal evolutionary adaptations in two species
Coevolution occurs when a change in one species acts as a new selective force on another species, and the resulting adaptations of the second species in turn affect the selection of individuals in the first species.

37.7

A parasite lives on or in a host from which it obtains nourishment
Pathogens are disease causing bacteria, viruses, fungi, or protists that can be thought of as microscopic parasites.
Parasites and pathogens can impact species composition and community structure.

37.14

Energy flow = the passage of energy through the components of the ecosystem.
Chemical cycling = the transfer of matter within the ecosystem
Every use of chemical energy by organisms involves a loss of some energy to the surroundings in the form of energy.

37.15

Primary production is the conversion of solar energy to chemical energy - as organic compounds - by photosynthesis
Gross primary production = total amount of primary production during a given time period
Net primary production = amount of new organic material added to an ecosystem in a given period.

37.16

An energy pyramid illustrates the cumulative loss of energy with each transfer in a food chain.
10% of the energy available at each trophic level becomes incorporated into the next higher level.
The amount of energy available to top-lvel consumers is small compared with that available to lower-level consumers.

37.17

The dynamics of energy flow apply to the human population. (Humans can be primary, secondary, and tertiary, or quaternary consumers).

37.8

Trophic structure = a pattern of feeding relationships consisting of several different levels.
A food chain is a sequence of food transfer up the trophic levels, this transfer moves chemical nutrients and energy from organism to organism up through the trophic levels in a community.
Producers/Autotrophs = support all other trophic levels; photosynthetic producers use light energy to power the synthesis of organic compounds.
Heterotrophs = consumers; all consumers other than herbivores are mostly carnivores
Primary Consumers/Herbivores = eat plants, algae, or phyto-plankton.
Secondary Consumers to Tertiary Consumers to Quaternary Consumers
Scavengers/Detrivores = feast primarily on decaying ogranic material.
Decomposers = secrete enzymes that digest molecules in organic material and convert them to inorganic forms.

37.9

A food web is a network of interconnecting food chains.
Producers to Primary Consumers to Secondary Consumers to Tertiary Consumers to Quaternary Consumers

37.8-37.9

Biomass = the total quantity or weight of organisms in a given area or volume

37.10

Species diversity is based on two factors - species richness and relative abundance.
Species richness = the number of different species in a community
Relative Abundance = the proportionate representation of each species in a community
A diverse tree community promotes animal diversity (due to a broader range of habitats and food sources).
The issue with species diversity is that when so many potential hosts live together, it is easy for a pathogen to spread from one to another.
Polyculture (diverse agricultural ecosystems) vs. Monoculture --polyculture is better

37.11

Ecologist Robert Paine' hypothesis: the species diversity of a community is directly related to the ability of predators to prevent any one species from monopolizing local resources.
Interspecific interactions are crucial to create specific diversity in a community
A keystone species is a species whose impact on its community is much larger than its abundance or total biological mass would indicate.
If a keystone is removed, the arch collapses. A keystone species occupies a niche that holds the rest of its community in place.

The carbon cycle depends on photosynthesis and respiration.

Photosynthesis removes carbon dioxide from the atmosphere and incorporates it into organic molecules, which are
passed along the food chain by consumers.
Cellular respiration by producers and consumers returns carbon dioxide to the atmosphere
Decomposers break down the carbon compounds in detritus; that carbon too is eventually released as carbon dioxide.
The increased burning of wood and fossil fuels is raising the level of carbon diovide in the atmosphere.

37.18

Life depends on the recycling of chemicals
Chemical cycles in an ecosystem include both biotic and abiotic components, they are known as biogeochemical cycles.
Abiotic reservoirs = where chemicals accumulate or are stockpiled outside of living organisms
Biogeochemical cycles can be local or global.

37.21

1) Some bacteria live symbiotically in the roots of certain species of plants, supplying their hosts with a direct source of unstable nitrogen.
2) Free-living nitrogen-fixing bacteria in soil or water convert N2 to ammonia NH3, which then picks up another H+ to become ammonium NH4+.
3) After nitrogen is "fixed", some of the NH4+ is taken up and used by plants
4) Nitrifying bacteria in soil also convert some of the NH4+ to nitrate NO3- which is more readily...
5) assimilated by plants. Plants use the nitrogen they assimilate to synthesize molecules such as amino acids, which are then incorporated into proteins.
6) When a herbivore eats a plant, it digests the proteins into amino acids and then uses the amino acids to build the proteins it needs. Nitrogen-containing waste products are formed during protein metabolism; consumers excrete some nitrogen as well as incorporate some into their body tissues.
7) Decomposition releases NH4+ from organic compounds back into the soil, replenishing the soil reservoir of NH4+ and, with the help of nitrifying bacteria NO3-.
8) Under low oxygen conditions, soil bacteria known as dentrifiers strip the oxygen atoms from NO3-, releasing N2 back into the atmosphere and depleting the soil reservoir of ustable nitrogen.

37.20

1) Producers incorporate chemicals from abiotic reservoirs into organic compounds
2) Consumers feed on the producers, incorporating some of the chemicals into their own bodies.
3) Both producers and consumers release some chemicals back to the environment in waste products.
4) Decomposers play a central role by breaking down the complex organic molecules in detritus.

37.20

Organisms use phosphorus as an ingredient of nucleic acids, phospholipids, and ATP, and as a mineral component of bones and teeth for some animals.
In the Model
1) the weathering of rock gradually adds inorganic phosphate to the soil.
2) Plants assimilate the dissolved phospate ions in the soil and build them into organic compounds.
3) Consumers obtain phosphorus in organic form by eating plants.
4) Phosphates are returned to the soil by the action of decomposers on animal waste and the remains of dead plants and animals.
5) Some phosphate drains from terrestrial ecosystems into the sea, where it may settle and eventually become part of new rocks.
6) The phosphorus will not cycle back into living organisms until geologic processes uplift the rocks and expose them to weathering, a process that takes millions of years.

37.19

The carbon cycle depends on photosynthesis and respiration
Carbon, the major ingredient of all organic molecules, has an atmospheric reservoir and cycles globally.