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lamina -- Any broad and flattened region of a plant or alga, which allows for increased photosynthetic surface area.
laminarin -- a beta-glucan polysaccharide produced by many chromists through photosynthesis.
larva -- Among invertebrates, an immature stage in the life cycle which usually is much smaller than, and morphologically different from, the adult. In insects with metamorphosis, the larva must become a pupa before reaching adulthood.
Laurasia -- n. A supercontinent that existed from the Jurassic to Early Tertiary after splitting from Pangea; composed of Laurentia, Baltica, Avalonia, (modern North America, Scandinavia, Greenland, Western and Central Europe); eventually fragmented into Eurasia and North America in the Tertiary with the opening of the North Atlantic Ocean.
Laurentia -- n. A separate continental plate that existed from the Late Precambrian to Silurian, consisting of the major part of North America, northwest Ireland, Scotland, Greenland, and pieces of Norway and Russia.
lava -- Any molten material that is extrusive or volcanic, or the rock that forms from a molten extrusive.
leaf -- An organ found in most vascular plants; it consists of a flat lamina (blade) and a petiole (stalk). Many flowering plants have additionally a pair of small stipules near the base of the petiole.
leaf trace -- The strand of vascular tissue which connects the leaf veins to the central vascular system of the stem.
leaflet -- In a compound leaf, the individual blades are called leaflets.
librigenae -- The "free cheeks"; separate, detachable portions of the trilobite cephalon. More info?
limestone -- A carbonate sedimentary rock composed of more than 50 percent of the mineral calcium carbonate (CaCO3).
limnology -- The study of river system ecology and life.
limy -- adj. Describes sediments, soils, or rocks that contain a significant amount of lime (calcium oxide, CaO).
lineage -- Any continuous line of descent; any series of organisms connected by reproduction by parent of offspring.
lipids -- a class of biochemical compounds which includes fats, oils, and waxes.
litter -- Leaf litter, or forest litter, is the detritus of fallen leaves and bark which accumulate in forests.
loess -- n. A widespread, loose deposit consisting mainly of silt; most loess deposits formed during the Pleistocene as an accumulation of wind-blown dust carried from deserts, alluvial plains, or glacial deposits.
lophophore -- Complex ring of hollow tentacles used as a feeding organ. The tentacles are covered by cilia, which generate a current to bring food particles into the mouth. The structure is only found in the brachiopods, phoronids, and bryozoans. More info?
lorica -- A vase-shaped or cup-shaped outer covering. Found in many protists, including some flagellates, ciliates, chrysophytes, and choanoflagellates, as well as in some animal cells.
lowland -- n. (adj.) Large area of relatively low relief, usually applied to coastal regions that do not rise high above sea level. upland, highland – ant.
luciferase -- enzyme which activates luciferin to produce bioluminescence.
luciferin -- compound whose activated form emits light.
lysosome -- Eukaryotic organelle which carries digestive enzymes. The lyzosome fuses with a vacuolar membrane containing ingested particles, which are then acted upon by the enzymes.