Habitat = The type of environment in which an organism or group normally lives or occurs. It is the natural environment in which an organism lives, or the physical environment that surrounds, influences and is utilized by a species population. A microhabitat or microenvironment is the immediate surroundings and other physical factors of an individual plant or animal within its habitat. Habitat destruction is a major factor causing a species population to decrease, eventually leading to it?s being endangered, or even to its extinction. Large scale land clearing usually results in the removal of native vegetation and habitat destruction.
Global warming = Global warming is the increase, in recent decades, of the average temperature of the Earth's near-surface air and oceans. Causes can be natural, such as the natural greenhouse effect caused by the presence in the atmosphere of gases such as water vapour which prevent the sun?s energy from escaping into outer space, and changes in the Earth?s orbit around the sun and changes in the amount of heat energy released by the sun. Man?s activities can also lead to global warming, such as the release of large amounts of the gases carbon dioxide and methane through the burning of fossil fuels and from the rearing of livestock.
Species = A group of individuals which share some common characteristics and which generally can interbreed to produce a fertile offspring. No one actually knows how many species currently inhabit the Earth, with different scientists putting the number at between 5 and 20 million (hence, Noah?s Ark must have been pretty large!). Sometimes, it is difficult to distinguish between two different species since they are very similar, although each species plays a different role in the ecosystem. To date, about 2 million species have been described, but many others still await discovery!
Weathering = The destructive processes that change the physical and chemical characteristics of rocks at the earth's surface. This process results in the breakdown of rocks into loose sediments, such as soil, and, unlike erosion, it takes place in the absence of movement. This means that no currents are needed. There are 3 types of weathering: physical (as a result of physical forces, such as heat and water); chemical (as a result of the action of chemicals, such as the weak acids found in rain pouring through a rock); and biological (as a result of the action of living things, such as the roots of a tree).
Eroded = Worn away as by water or ice or wind. This is the breakdown of solids, such as soil, into smaller particles by water or wind currents, and the transport of these downhill by the action of gravity. There are natural and anthropogenic (through the actions of man) causes of erosion. Te latter include overgrazing, deforestation, off-roading, intense farming practices, over-irrigation, etc.
Surf = The breaking of waves once shallow water depths are reached. The surf zone is rich in nutrients and filled with the larvae (young) of many fish. After breaking in the surf zone, the waves (now reduced in height) continue to move in and run up onto the sloping front of the beach, forming an uprush of water called swash. The water then rsn backs down again as backwash.
Anoxic = Marked by a severe deficiency/shortage of oxygen. The term is often applied to sediments, such as sand and mud, which as a result turn black and are foul-smelling (due to the production of a gas ? hydrogen sulphide ? which stinks of rotten eggs). Such sediments usually arise from man?s activities, including the release of large amounts of nutrients in waters. These nutrients are broken down by bacteria and other micro-organisms which use large amounts of oxygen in the process, resulting in anoxic conditions.
Succulent Tissue = Fleshy water-containing tissue acting as a water reservoir, found in a group of plants known as succulents. Like cacti, these are xerophytic plants (i.e. they can resist long periods of drought in hot and arid environments, such as deserts) but rely on their water reservoir. Such plants possess other adaptations to prevent the loss of water, such as reduced leaves and a thick cuticle.
Buoyancy = The ability to float. The lifting force of an object placed in a fluid is equal to the weight of the fluid it displaced. The concept is also known as Archimedes's principle, after the Greek mathematician, physicist, and inventor Archimedes (c. 287-212 B.C.), who discovered it. Archimedes's principle is applied in many fields, including shipbuilding.
Spawn = To reproduce, usually by laying eggs. The timing of spawning depends on a range of environmental parameters, including temperature, concentration of nutrients in the water and light intensity. The term is often applied to fish, including salmon.