| dacite |
Fine-grained igneous rock (volcanic)
consisting of feldspar (sodium and potassium
aluminium silicate), quartz and amphibole
(calcium, magnesium, iron, aluminium silicate) |
|
| danckwerts equation |
equation used to calculate grazing capacity based on veld condition and rainfall. |
|
| dassie/hyrax |
Small, stocky gregarious mammals of the Order Hyracoidea. They range in colour from light to dark brown. Please see Mod #7 Comp #2 of the Game Ranging Course for more information. |
|
| death rate |
the percentage of individuals in a population dying in a specified time interval |
|
| deciduous |
trees or shrubs that lose their leaves every year |
|
| decomposer |
an organism that obtains energy from the breakdown of dead organic matter to more simple substances; more precisely refers to bacteria and fungi |
|
| decreaser |
a grass species that is dominant in good veld, but is replaced by other species when the area is under- or over grazed. |
|
| defoliation |
plants loosing thier leaves |
|
| density dependent |
varying in relation to population density |
|
| density independent |
unaffected by population density |
|
| desiccation |
drying out, losing all moisture content |
|
| detrital |
From the word detritus, the term given to dead or decaying organic matter. |
|
| detrital food web |
The detrital food web involves consuming a dead animal for example, a vulture. The decomposing remains of the carcass become nutrients for the soil, thus returning the minerals back into the ground, possibly nitrates would be involved in the process. |
|
| detritivore |
an organism that feeds on dead organic matter; usually applies to detritus feeding organisms other than bacteria and fungi |
|
| dewclaw |
A vestigial digit that fails to contact the ground; the inside (first) digit in carnivores (cf false hooves of ungulates). |
|
| dextral |
right-handed or pertaining to the right |
|
| diamictite |
Sedimentary rock whose particles are
completely unsorted by size, consisting of both
very fine-grained and large particles; often
deposited under glacial conditions |
|
| diapause |
a period of arrested growth and activity in which metabolism is greatly decreased; usually seasonal in nature and common among insects |
|
| diapirism |
Slow, upward movement of a less-
dense mass of material through a denser
medium (e.g. a hot air balloon) |
|
| diapsid |
Member of the group of reptiles characterised by two accessory openings in the skull
behind each eye, to accommodate jaw muscles; includes all the Archosauria, as well as
the ancestors of all modern lizards and snakes |
|
| diapsids |
Diapsid skull - having two openings in the skull behind eyes. |
|
| diatom |
a microscopic unicellular marine or freshwater colonial alga having cell walls impregnated with silica. It is a type of plankton. |
|
| dicotyledon |
A plant with two seed leaves; the subclass of angiosperms containing most higher plants, Dicot. Short for dicotyledon. |
|
| dicroidium |
Generic name for the leaves of the
extinct seed fern that has bifurcating fronds
and was dominant during deposition of the
Molteno Formation (Upper Triassic Period) |
|
| dicynodont |
Large and diverse group of mammal-
like reptiles (therapsids) which lived from the
middle Permian to the Late Triassic; these animals were the dominant land-living herbivores
of the Permian Period and were characterised
by a horny beak rather than many teeth |
|
| differentiation |
Processes by which crystals are
separated from magma as it crystallises,
resulting in the formation of layers of rocks of
different mineral composition |
|
| digestibale energy |
energy made available to the animal through the digestion process |
|
| digestion |
process of fermentation and uptake of nutrients in the digestive system. |
|
| digit |
a finger or toe in mammals |
|
| digitigrade |
an animal that walks on its toes, characteristic of all dogs and cats |
|
| dikkop |
Southern African bird species,English name -Thickknee. |
|
| dimorphic |
A species that has two distinctly different body forms, most frequently due to different genders i.e sexual dimorphism. Eg. Humans are distinctly sexually dimorphic, zebra are not. |
|
| dimorphism |
The differences in appearance between males and females of the same species, such as in colour, shape, size, and structure, that are caused by the inheritance of one or the other sexual pattern in the genetic material |
|
| dinocephalian |
Diverse group of carnivorous and
herbivorous mammal-like reptiles (therapsids)
that lived during the Permian; they were the
first large vertebrates to live on land, and
formed an important component of the earliest
therapsid faunas of South Africa and Russia |
|
| dioecious |
a plant species that has separate flowers for each sex, i.e. it has male flowers and female flowers |
|
| diorite |
Coarse-grained igneous rock (plutonic)
consisting mainly of amphibole (calcium, aluminium, iron and magnesium silicate) and plagioclase (calcium, sodium, aluminium silicate) |
|
| diplopoda |
millipedes |
|
| diptera |
the order which includes flies |
|
| dispersal |
the spreading of seeds by wind, water, animals etc |
|
| dispersion |
distribution of organisms in a given area |
|
| displacement activity |
the performance of a behaviour pattern different from its normal functional context of behaviour |
|
| display |
a technique used by birds to send a signal to another bird by means of a pose, movement, sound, or combination of these, in order to get a particular response |
|
| distemper |
a viral disease causing flu-like synptoms in canids |
|
| distribution |
the area in which a given species is likely to be found |
|
| disturbed area |
an area that has been dug up, altered by man, or heavily overgrazed |
|
| diurnal |
active during the day |
|
| diversity |
difference, the range of species in a given area |
|
| dolerite |
Medium-grained igneous rock consisting
of plagioclase (calcium aluminium silicate) and
pyroxene (calcium, magnesium, iron silicate);
occurs as dykes or sills |
|
| dolomite |
Mineral, calcium magnesium carbonate,
or rock entirely comprising grains of this mineral |
|
| dome |
Uplift that is more or less circular in plan,
with rock layers dipping away from its centre |
|
| dominance hierarchy |
a social system whereby animals of the same species are ranked, and behave accordingly |
|
| dominant |
a population possessing ecological dominance in a given community and thereby governing the type and abundance of other species in their community |
|
| donga |
hole of various dimensions usually due to the act of erosion |
|
| dormant |
the state of cessation of growth and suspended biological activity during which life is maintained |
|
| dorsal |
on or referring to the back |
|
| drift |
the term given to soils which develop from previously weathered material |
|
| dronksiekte (drunk disease) |
plant poisoning disease with symptoms of severe shivering in animals |
|
| dung |
the faeces or droppings of herbivores |
|
| duplex |
type of soil where a sandy topsoil overlies a swelling clay |
|
| dwarf medlar |
A non-indigenous member of the rose family (Rosaceae) that can cause rapid death upon ingestion. In African mammals this is known as gousiekte (quick sickness). |
|
| dyke |
Tabular intrusive rock that cuts across
other rocks |
|
| dynamic |
constantly changing |
|
| dynamic equilibrium |
with reference to plants, a community where change is constant, but the effects are not cumulitive. |
|
| dystrophy |
pertains to a weakening, commonly associated with muscles. |
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