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BIO 150 Lecture 8
Distribution and Abundance
Terms in this set (41)
group of interacting (or potentially interacting) individuals of the same species living in the same geographic area (or space) at the same time
the pattern of where organisms live
the way in which individuals of a population are physically dispersed over an area;
includes the size, shape, and location of the area that a population occupies
related to density; but may also be differentiated as follows:
is the actual number of individuals in a population.
measurement of population size per unit area, i.e., population size divided by total land area.
refers to the relative representation of a species in a particular ecosystem.
1. environment limits the geographic distribution of species,2. on small scales distribution is random, regular or clumped, 3. On large scales,there is significant environmental variation 4. Population declines with increasing organism size 5. Rare species are often vulnerable to extinction while abundant are seldom so
Key Concepts: 5
1. The _________ limits the geographic distribution of species.
Law of Tolerance
this explains the distribution limits of populations
no single species
While there are few environments on Earth without life, ____________can tolerate the full range of Earth's environments.
Because of _______ (remember the concept of trade-offs; losses and gains need to be balanced), the physical environment places limits on the distributions of populations.
Climatic factors, Biotic factors, other abiotic factors
Environmental factors known to limit species distributions are as follows:
temperature, precipitation, humidity/moisture, light intensity; the effect of climate is sometimes indirect, affecting other factors such as food availability, water supply, habitat, incidence of other biotic factors
parasites, pathogens, competitors, etc.
Other abiotic factors
salinity, pH, intertidal exposure, nutrients, soil/substrate conditions, etc.
2. On _______, individuals within populations are distributed in patterns that may be random, regular, or clumped.
intensity of interactions
Distribution patterns may also change as individuals of the population grow/mature, or depending on _______ (e.g. level of aggression)
individuals are aggregated in patches
Environmental heterogeneity, social behavior, nature of propagation
factors of clumped dispersion (3)
pattern of dispersion where there are even spacing
Antagonisitic interactions of individuals in the population, intraspecific competition, territoriality
factors of regular dispersion (3)
spacing varies in an unpredictable way
Absence of strong interactions or repulsions among individuals of a population, uniform environment, resources equally available (rare)
factors of random dispersion (3)
3. On large scales, individuals within a population are __________.
On a large scale, there is significant _________.
4. Population density declines with increasing
the size of a population in relation to a definite unit of space
measure of the number of individuals per unit area
all the space
But populations don't occupy _____within a unit
measured in terms of the amount of area available as living space/habitat space (e.g. number of birds per km of hedgerow rather than per hectare)
actual population size
It is generally & usually very difficult, if not outright impossible, to know the _______, especially of small, minute &/or mobile organisms at any given time... so, estimate from a sample (e.g. Capture-Mark-Recapture)
_____ relationship between density and size; size-density relationship changes with maturity (e.g. self-thinning in plants)
5. Rare species are often vulnerable to _______, while abundant species are seldom so.
D. Rabinowitz (1981)
devised a classification of commonness and rarity based on combinations of 3 factors:
(1) the geographic range of species (extensive vs. restricted), (2) habitat tolerance / range of conditions tolerated (broad vs. narrow), (3) local population size (large vs. small)
factors of classification of commonness and rarity
There are __possible combinations of these factors (see figure in next page), 7 of which include at least 1 attribute of rarity.
Most species are _______; 7 combinations of range, tolerance, and population size each create a kind of rarity.
increased distribution and abundance
In nearly all cases, the key to a species' survival is ____________. This is often the key goal of programs aimed at preserving endangered species.
THIS SET IS OFTEN IN FOLDERS WITH...
BIO 150 lecture 2
BIO 150 lecture 3
BIO 150 lecture 9
BIO 150 lecture 10
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