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Leaves of most plants include a flat structure called the blade or lamina supported by a network of veins, a petiole and a leaf base; [1] but not all leaves are flat, some are cylindrical. [citation needed] Leaves may be simple, with a single leaf blade, or compound, with several leaflets.
A leaf (pl.: leaves) is a principal appendage of the stem of a vascular plant, [1] usually borne laterally above ground and specialized for photosynthesis.Leaves are collectively called foliage, as in "autumn foliage", [2] [3] while the leaves, stem, flower, and fruit collectively form the shoot system. [4]
GCSE Bitesize was launched in January 1998, covering seven subjects. For each subject, a one- or two-hour long TV programme would be broadcast overnight in the BBC Learning Zone block, and supporting material was available in books and on the BBC website. At the time, only around 9% of UK households had access to the internet at home.
1. A space between the threads of a net, e.g. that part of a leaf surface defined by each of the elements of a vein network; as with cacti, the area between the veinlets of a leaf. 2. A structure on the stem node of a cactus, morphologically a specialised branch; the region of a cactus upon which spine s, glochid s, and flowers are borne. aril
Succession is the relatively gradual structure and taxonomic composition change that arises as the vegetation modifies various environmental variables over time, including light, water, and nutrient levels. These modifications change the suite of species most adapted to grow, survive, and reproduce in an area, causing floristic changes.
Dendritic drainage: the Yarlung Tsangpo River, Tibet, seen from space: snow cover has melted in the valley system. In geomorphology, drainage systems, also known as river systems, are the patterns formed by the streams, rivers, and lakes in a particular drainage basin. They are governed by the topography of land, whether a particular region is ...
The BBC Learning Zone (previously The Learning Zone) was an educational strand run by the BBC as an overnight service on BBC Two. It broadcast programming aimed at students in Primary, Secondary and Higher Education as well as to adult learners.
Original mapping by John Snow showing the clusters of cholera cases in the London epidemic of 1854, which is a classical case of using human geography. Human geography or anthropogeography is the branch of geography which studies spatial relationships between human communities, cultures, economies, and their interactions with the environment, examples of which include urban sprawl and urban ...