生态学复习题

Chapter 1

# Ecology

the science that treats the spectrum of interrelationships existing between organisms and their environments and among groups of organisms.

# species

a natural group of actually or potentially interbreeding individuals reproductively isolated from other such groups.

# Ecosystem Components

Nonliving parts:energy source, nutrient and water source

Living parts:Producer,Consumer,Decomposer

# food chain

Each pathway that transfers energy from a given source plant or plants through a given series of consumers

# standing crop

Within each trophic level or population, the amount of living material at any instant in time

# biogeochemical cycles

Among many of the chemical elements and compounds in ecosystems there is a cycling back and forth between organisms and the physical environment. Such repeated transfers are called biogeochemical cycles

The most significant cycles: carbon cycle, nitrogen cycle, phosphorus cycles.

# niche

niche in ecology is usually defined as the role of an organism in a community.

# dominants

The numerically abundant species in communities

# Species diversity

a measure that combines into a single figure both the number of species and the distribution of the total number of individuals among the species.

# Leibig’s law of the minimum.

Each species requires a certain minimum amount of various materials. If the concentrations of these necessities, such as nitrate, fall below the minimum, the species disappears.

# Shelford's Law of Tolerance

a species' distribution is controlled by the environmental factors for which it has the narrowest tolerance. This law explains why a species is present in some areas, but absent in others. Remember that tolerance has both a lower limit and an upper limit - not enough or too much of a resource will limit a species' ability to survive. When any one of these factors exceeds the tolerance, the species will die out.

# ecological succession

1.classical model by Clement(1936)Communities are not static units. They change in structure and composition with time. Some tend to change in an orderly fashion until they reach a persistent stage. This orderly process of community change controlled through modification of the physical environment is called

2.inhibition model by Egler(1954)In this model, succession is not an orderly predictable process and there is no climatic climax.

3.tolerance model by Connel and Slayter (1977), is intermediate between the other two. In this model early colonizing (定居) species are not necessary, and any species can start succession. Community change occurs as species are more tolerant or competitively superior.

# Competition

an ecological term referring to the interaction among organisms for a necessary resource that exists in short supply.

Competition may be intraspecific or interspecific.

Resouece that can be competed: light, food, nutrients, water and space.

The competition case:

The competitors share the limited sources. In this case both individuals are hampered.

One competitor excludes the other. In this case one individual is eliminated.

# Competition exclusion principle

no two species with the same requirements can coexist in the same place at the same time; that is, complete competitors cannot exist.

# Comparison of Terrestrial and Marine Ecosystems

Physical and Chemical Differences: Greater density; Water absorbs light stronger; Gravity difference; Oxygen differences

Structural and Functional Differences: The dominant autotrophs are microscopic plants and the dominant herbivores(copepods) of the sea are also small; The plant of the sea is short-lived; Most marine food chains have about 5 links, whereas terrestrial food chain tend to be shorter, averaging three links; The small herbivores of the seas