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startle response

startle response   Quick reference

A Dictionary of Ecology (5 ed.)

Reference type:
Subject Reference
Current Version:
2015

...response The reaction of an animal to sudden danger, by a threat display (e.g. when certain butterflies and moths reveal eyespots on the wings) or flight (e.g. on average it takes 20 milliseconds for a puff of air from an approaching missile to set an American cockroach...

Svedberg unit

Svedberg unit   Quick reference

A Dictionary of Ecology (5 ed.)

Reference type:
Subject Reference
Current Version:
2015

...unit ( S ) The unit of measurement in which sedimentation coefficients are expressed. It is equal to 10 −13 seconds and is usually given for the solvent water at 20°C. It is named after the Swedish physical chemist Theodor Svedberg ( 1884–1971 ) and is written with no space between the number and the symbol (e.g....

quadrat

quadrat   Quick reference

A Dictionary of Ecology (5 ed.)

Reference type:
Subject Reference
Current Version:
2015

...surveys. Traditionally 1 m 2 quadrats were used to sample short, non-woody communities such as grasslands and heathlands . More recently circular and rectangular quadrats have been used, as well as squares of all sizes, depending on the purpose of the survey (e.g. 10 m 2 and 20 m 2 quadrats are commonly used in woodland...

breeze

breeze   Quick reference

A Dictionary of Ecology (5 ed.)

Reference type:
Subject Reference
Current Version:
2015

...A relatively light wind, often of convective origin, or a particular local air movement (e.g. mountain, land and sea breezes ). On the Beaufort scale breezes are classed as light (force 2, 6–11 km/h), gentle (force 3, 12–19 km/h), moderate (force 4, 20–28 km/h), fresh (force 5, 29–38 km/h), and strong (force 6, 39–49...

leaf physiognomy

leaf physiognomy   Quick reference

A Dictionary of Ecology (5 ed.)

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Subject Reference
Current Version:
2015

...studies the percentage of leaves with entire (i.e. not serrated) margins indicates temperature (e.g. if 68–70 per cent of leaf margins are entire the mean annual temperature ( MAT ) is 20°C, a deviation of 4 per cent in the proportion of entire leaf margins indicating a temperature deviation of 1°C), and the length of leaves is related to the availability of water. For more reliable interpretation, these measurements are used in conjunction with other factors (e.g. the percentage of leaves with apices that are attenuated (drip tips) rather than rounded; the...

albedo

albedo   Quick reference

A Dictionary of Ecology (5 ed.)

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Subject Reference
Current Version:
2015

...cloud 0.70–0.90 Stratiform cloud 0.59–0.84 Cirrostratus 0.44–0.50 Sea ice 0.30–0.40 Dry sand 0.35–0.45 Wet sand 0.20–0.30 Desert 0.25–0.30 Meadow 0.10–0.20 Field crops 0.15–0.25 Deciduous forest 0.10–0.20 Coniferous forest 0.05–0.15 Concrete 0.17–0.27 Black road 0.05–0.10 Radiation that is reflected cannot be absorbed and consequently light-coloured surfaces absorb less radiation than dark surfaces. Altering a surface often changes the albedo (e.g. by clearing coniferous forest, 0.05–0.15, to grow field crops,...

Hooker, Sir William Jackson

Hooker, Sir William Jackson (1785–1865)   Quick reference

A Dictionary of Ecology (5 ed.)

Reference type:
Subject Reference
Current Version:
2015

...and northern Italy ( 1814 ). He was appointed regius professor of botany at the University of Glasgow in 1820 . He wrote prolifically, his works including Tour of Iceland ( 1811 ), two volumes of Musci Exotica ( 1818–20 ), Flora Scotica ( 1821 ), Icones Filicum (with R. K. Greville , 1829–31 ), British Flora (with G. A. W. Arnott et al. , 1830 ), and British Ferns ( 1861–2...

statistical significance

statistical significance   Quick reference

A Dictionary of Ecology (5 ed.)

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Subject Reference
Current Version:
2015

...means is equal to or greater than 1.96 times the standard error of the mean . Since there is an approximately 20 : 1 likelihood that such a difference occurs by chance, 95 per cent of the means will be enclosed, assuming a normal distribution of the data. The result is thus significant at the 95 per cent level or, to express it more precisely, it is significant at level p = 0.05. Higher levels of significance are possible and yet more convincing, e.g. p = 0.01 is equivalent to 1 chance in 100 (99 per cent probability) that the original (null) hypothesis of...

chromosome

chromosome   Quick reference

A Dictionary of Ecology (5 ed.)

Reference type:
Subject Reference
Current Version:
2015

...structures that lack protein and contain only DNA or RNA: these are not chromosomes, though they serve a similar function. Chromosomes occur in pairs, which associate in a particular way during meiosis . Each species tends to have a characteristic number of chromosomes (e.g. 20 in maize, 23 in humans), found in most nucleated cells within most organisms. The presence of pairs of homologous chromosomes is referred to as the diploid state and is normal for the sexual phase of an organism. Gametes (reproductive cells), and cells of the gametophyte...

gene bank

gene bank   Quick reference

A Dictionary of Ecology (5 ed.)

Reference type:
Subject Reference
Current Version:
2015

...upon when required. For example, a crop may be needed that possesses a quality (e.g. tolerance to adverse climatic conditions) which cannot be found in currently exploited cultivars but was present in more antiquated varieties. The normal method of storage is to reduce the water content of seed material to around 4 per cent and keep it at 0°C (pollen material may also be used but its longevity is considerably less). Stored this way, the material often remains viable for 10–20 years. When the desiccating process proves fatal, as is the case with tropical...

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