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affinity index

affinity index   Quick reference

A Dictionary of Ecology (5 ed.)

Reference type:
Subject Reference
Current Version:
2015
Subject:
Science and technology, Life Sciences, Social sciences, Environment
Length:
74 words
Illustration(s):
2

A measure of the relative similarity in composition of two samples. For example, A= c a+b, where ...

age structure

age structure   Quick reference

A Dictionary of Ecology (5 ed.)

Reference type:
Subject Reference
Current Version:
2015
Subject:
Science and technology, Life Sciences, Social sciences, Environment
Length:
60 words
Illustration(s):
1
Within a *population, the number or proportion of individuals in each age group (e.g. in a human population, the number of individuals aged 0–4, 5–14, 15–29, 30–44, 45–59, 60–69, over 70). ... More
aklé

aklé   Quick reference

A Dictionary of Ecology (5 ed.)

Reference type:
Subject Reference
Current Version:
2015
Subject:
Science and technology, Life Sciences, Social sciences, Environment
Length:
66 words
Illustration(s):
1
A French name for a network of sand *dunes that is found especially in the western Sahara. The basic unit of the network is a sinuous ridge, at right angles to the wind, made up of ... More
alfisols

alfisols   Quick reference

A Dictionary of Ecology (5 ed.)

Reference type:
Subject Reference
Current Version:
2015
Subject:
Science and technology, Life Sciences, Social sciences, Environment
Length:
67 words
Illustration(s):
1

Mineral soils that are grouped as an order. These soils have *clay-enriched *argic horizons, are alkaline to intermediate in reaction, with the ...

aneroid barometer

aneroid barometer   Quick reference

A Dictionary of Ecology (5 ed.)

Reference type:
Subject Reference
Current Version:
2015
Subject:
Science and technology, Life Sciences, Social sciences, Environment
Length:
56 words
Illustration(s):
1
An instrument for measuring atmospheric pressure as represented by the height (or thickness) of a sealed, flexible, metal, concertina-shaped drum from which air has been partially ... More
aquifer

aquifer   Quick reference

A Dictionary of Ecology (5 ed.)

Reference type:
Subject Reference
Current Version:
2015
Subject:
Science and technology, Life Sciences, Social sciences, Environment
Length:
82 words
Illustration(s):
1
A body of permeable rock (e.g. unconsolidated gravel or a *sand stratum) that is capable of storing significant quantities of water, that is underlain by impermeable material, and through ... More
area cladistics

area cladistics   Quick reference

A Dictionary of Ecology (5 ed.)

Reference type:
Subject Reference
Current Version:
2015
Subject:
Science and technology, Life Sciences, Social sciences, Environment
Length:
84 words
Illustration(s):
1
A technique that employs relationships between organisms to reconstruct past distributions and the positions of continents, independently of geological data. Genetic and morphological ... More
areagram

areagram   Quick reference

A Dictionary of Ecology (5 ed.)

Reference type:
Subject Reference
Current Version:
2015
Subject:
Science and technology, Life Sciences, Social sciences, Environment
Length:
63 words
Illustration(s):
1
A diagram derived from a *cladogram but with the addition of data referring to the former geographic distribution of organisms. The areagram resembles a cladogram, but instead of showing ... More
aridisols

aridisols   Quick reference

A Dictionary of Ecology (5 ed.)

Reference type:
Subject Reference
Current Version:
2015
Subject:
Science and technology, Life Sciences, Social sciences, Environment
Length:
62 words
Illustration(s):
1

An order of *mineral soils found in arid environments. These soils have very little organic matter in their surface ...

artesian well

artesian well   Quick reference

A Dictionary of Ecology (5 ed.)

Reference type:
Subject Reference
Current Version:
2015
Subject:
Science and technology, Life Sciences, Social sciences, Environment
Length:
112 words
Illustration(s):
1
A well that flows at the surface without pumping, because it is sunk into a confined *aquifer with a hydraulic head (sometimes called the potentiometric or piezometric head) that lies ... More
auger

auger   Quick reference

A Dictionary of Ecology (5 ed.)

Reference type:
Subject Reference
Current Version:
2015
Subject:
Science and technology, Life Sciences, Social sciences, Environment
Length:
61 words
Illustration(s):
1
A tool used primarily for soil sampling, but also for sampling peats and other unconsolidated sediments. The simplest and most universal form has a screw head to bore the soil or sediment. ... More
Baermann funnel

Baermann funnel   Quick reference

A Dictionary of Ecology (5 ed.)

Reference type:
Subject Reference
Current Version:
2015
Subject:
Science and technology, Life Sciences, Social sciences, Environment
Length:
90 words
Illustration(s):
1
A device used to extract nematodes (*Nematoda) from a soil sample or plant material. A muslin bag containing the sample is submerged in water in a funnel sealed at the lower end by a ... More
Baltic Shield

Baltic Shield   Quick reference

A Dictionary of Ecology (5 ed.)

Reference type:
Subject Reference
Current Version:
2015
Subject:
Science and technology, Life Sciences, Social sciences, Environment
Length:
112 words
Illustration(s):
1
A region underlain by *Precambrian rocks that covers the Kola Peninsula in western Russia, Finland, Sweden, and Norway. The region extends from the Arctic Ocean to the island of Bornholm, ... More
barchan

barchan   Quick reference

A Dictionary of Ecology (5 ed.)

Reference type:
Subject Reference
Current Version:
2015
Subject:
Science and technology, Life Sciences, Social sciences, Environment
Length:
59 words
Illustration(s):
1
A crescent-shaped mobile *dune in a sand desert in which the wind blows predominantly from one direction. The dune moves by the erosion of sand from the windward slope and its accumulation ... More
Beringia

Beringia   Quick reference

A Dictionary of Ecology (5 ed.)

Reference type:
Subject Reference
Current Version:
2015
Subject:
Science and technology, Life Sciences, Social sciences, Environment
Length:
47 words
Illustration(s):
1

An area comprising the Bering Strait and adjacent Siberia and Alaska. At various times in the late *Mesozoic and ...

bevelled cliff

bevelled cliff   Quick reference

A Dictionary of Ecology (5 ed.)

Reference type:
Subject Reference
Current Version:
2015
Subject:
Science and technology, Life Sciences, Social sciences, Environment
Length:
45 words
Illustration(s):
1
A sea cliff whose upper slope has been trimmed to a relatively low angle by *Quaternary *periglacial processes, while the lower part is still steep as a result of recent marine activity. ... More
bilateral symmetry

bilateral symmetry   Quick reference

A Dictionary of Ecology (5 ed.)

Reference type:
Subject Reference
Current Version:
2015
Subject:
Science and technology, Life Sciences, Social sciences, Environment
Length:
99 words
Illustration(s):
1
The arrangement of the body components of an animal such that one plane divides the animal into two halves which are approximate mirror images of each other. Bilateral symmetry is ... More
Bray–Curtis similarity

Bray–Curtis similarity   Quick reference

A Dictionary of Ecology (5 ed.)

Reference type:
Subject Reference
Current Version:
2015
Subject:
Science and technology, Life Sciences, Social sciences, Environment
Length:
83 words
Illustration(s):
1

A statistic that is used to measure the similarity in species composition between two sites, yielding a value ranging from 0 (no species in common) to 1 (identical composition). ...

broken stick model

broken stick model   Quick reference

A Dictionary of Ecology (5 ed.)

Reference type:
Subject Reference
Current Version:
2015
Subject:
Science and technology, Life Sciences, Social sciences, Environment
Length:
125 words
Illustration(s):
1
A statistical method, devised in 1957 by Robert *MacArthur, for calculating the abundance of a particular species in an environment where several species occupy contiguous but ... More
buttress root

buttress root   Quick reference

A Dictionary of Ecology (5 ed.)

Reference type:
Subject Reference
Current Version:
2015
Subject:
Science and technology, Life Sciences, Social sciences, Environment
Length:
61 words
Illustration(s):
1
A root that is similar to a *stilt root, but has a solid connection to the stem throughout its length. It is a means of providing stability to tall tropical trees in high winds. If the ... More

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