Page 493 - (DK) Ocean - The Definitive Visual Guide

GLOSSARY 491

group is mainly marine but also equator, while high latitudes are nearer some subgroups have lost the shell is broken up by storms or waves.
includes the land-living woodlice. the poles. during their evolution. See also fast ice, sea ice.
isostasy A state of equilibrium; levee A natural raised bank around mucus A sticky or slimy substance pancake ice Stage of formation of
applied especially to the relatively some rivers, or an artificial bank secreted by animals for protection, sea ice consisting of small flat areas
light rocks of the continental crust, built around a river or estuary. trapping prey, helping with of ice, curled at the edges where
which can be thought of as floating littoral Relating to the area of shore movement, or other purposes. they bump into each other.
like icebergs among the heavier rocks between high- and low-water marks. mutualism A close relationship pectoral fin Either of the front pair of
of the ocean floor and mantle. longitude A position on Earth between two different species in fins in most fish and marine mammals,
Isostatic rebound is the tendency of expressed in terms of its angle east which both benefit. mainly used for steering but sometimes
land that was formerly ice-covered to for propulsion. See also pelvic fin.
or west of an agreed line called the
rise slowly to its equilibrium level,
prime meridian circling Earth from pelagic Relating to or living in the
often creating emergent coasts. See N
pole to pole and passing through waters of the open ocean, without
also continental crust, emergent coast.
Greenwich, London, UK. immediate contact with the shore or
IUCN The initials still used to designate longshore drift Process by which nanoplankton Planktonic organisms the sea bottom. See also demersal.
the World Conservation Union sediment is transported along a coast of 0.002–0.2 mm in diameter. Not pelvic fin Either of the pair of fins
(formerly the International Union as a result of waves breaking at an as small as picoplankton. See also located further back than the pectoral
for the Conservation of Nature). This oblique angle to the shoreline. picoplankton, plankton. fins in most fish. See also pectoral fin.
organization carries out conservation- neap tide The tide with the smallest perennial Of plants: living for three
related activities, including gathering range within an approximately two- or more years.
current status of endangered species. M week cycle, caused by the gravity pheromone An odor produced by an
and publishing information on the
of the Sun partly canceling out the
magma Molten rock rising from deep effect of the Moon. See also spring animal to communicate with others
of the same species, to attract the
tide, tides.
J inside Earth. nearshore The part of the shore opposite sex, for example.
mangrove Any of various trees growing
affected by waves and tides under photic zone see sunlit zone.
jawless fishes Two groups of primitive on muddy shores in the tropics and normal conditions. It includes the photophore A light-producing organ.
fish called lampreys and hagfish, adapted to live with their roots and foreshore plus an area beyond whose photosynthesis Process in green
which branched off the line of fish lower trunks immersed in salt water. bed is shallow enough to be stirred plants, algae, and cyanobacteria
evolution before jaws had evolved. mangrove swamp Forestlike up by wave action. See also foreshore. whereby the Sun’s energy is used
jellyfish Cnidarians that typically drift ecosystem formed by mangroves nekton Animals of the open ocean that to build energy-containing food
among the plankton and catch prey growing in muddy tidal areas and can swim strongly enough not to be molecules from carbon dioxide and
using stinging tentacles. The body river mouths. Mangrove swamps only at the mercy of ocean currents. water. See also chemosynthesis,
form of true jellyfish is a medusa. occur in the tropics and subtropics.
Nekton include squid, adult fish, and chlorophyll.
Some apparently similar forms such mantle All the rock lying between
marine mammals. See also plankton. phylum The highest-level grouping
as the Portuguese man-of-war are Earth’s crust and its core. The mantle in the classification of the animal
not true jellyfish, but siphonophores. extends to a depth of about 1,800 nematocyst The coiled structure kingdom. Each phylum has a unique
See also cnidarians, medusa, miles (2,900 km). within the stinging cell of a jellyfish basic body plan. Mollusks, arthropods,
siphonophores. medusa One of the two main body or other cnidarian that shoots out
and injects toxin via a dartlike tip. and echinoderms are examples.
forms of cnidarians. Medusae are See also cnidarians. phytoplankton Planktonic organisms,
K wide and saucer-shaped, as well as nudibranchs see sea slugs. such as microscopic algae and
usually free-floating and able to swim.
A jellyfish is an example of a medusa. cyanobacteria, which produce their
katabatic wind A wind that blows See also cnidarians, polyp. own food by photosynthesis.
downward from an ice sheet, glacier, O picoplankton The smallest planktonic
meroplankton Planktonic animals that
or cold valley, usually at night. organisms, typically bacteria, of
are the larvae of animals that are not ocean basin A region of low-lying
krill Swimming, shrimplike crustaceans planktonic as adults, such as crabs. 0.0002–0.002 mm in diameter. See
typically growing to ¾–2/3 in (2–6 cm) oceanic crust within which a deep also nanoplankton.
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long, which form a large part of the metamorphosis The process of ocean (or part of one) is contained, plankton Marine or freshwater
zooplankton and an important link transforming body form from that of and usually surrounded by land or organisms, living in open water, that
the young (larval) form to a radically shallower seas.
in the Southern Ocean’s food chain. cannot swim strongly and so drift
different adult form. It is common in oceanic crust The type of Earth’s crust with the currents. Although small
marine invertebrates such as starfish, that forms the deep ocean bed. Made life forms dominate, larger creatures,
L whose larvae live in the plankton mainly of basalt, it is thinner, denser, such as jellyfish, are also planktonic.
but whose adults live on the sea floor. and heavier than continental crust. See also nanoplankton, nekton,
La Niña see El Niño. mid-ocean ridge A submerged range ocean trench Elongated low-lying phytoplankton, zooplankton.
lagoon A stretch of coastal water of mountains running along any part region of the ocean floor. Trenches plate boundary A border between two
almost cut off from the sea by a spit of the deep-ocean floor, marking the are the deepest parts of the ocean. tectonic plates. The plates may be
or other barrier; also, the shallow place where seafloor spreading is See also subduction. converging (destructive boundary),
water within the ring of an atoll. taking place. Also called a spreading ooze Sediment on the deep ocean diverging (constructive boundary), or
larva A young stage of an animal, ridge. See also seafloor spreading. floor containing a large proportion sliding past (conservative or strike-slip
especially when completely different mimicry Phenomenon in which one of the remains of the skeletons of boundary). See also transform fault.
in structure from the adult. The species of animal has evolved to look planktonic organisms, such as plate, tectonic see tectonic plate.
larvae of many marine animals, such similar to another, unrelated animal. foraminiferans or radiolarians. plate tectonics Phenomena linked to
as starfish, live as part of the plankton. mixed layer The upper layer of the overfall A stretch of rough water the relative movement of Earth’s
See also metamorphosis. ocean that is kept mixed by winds produced when a tidal current flows tectonic plates, including continental
latent heat The heat absorbed or and currents, so that its temperature in the opposite direction to the wind. drift, seafloor spreading, earthquakes,
released when a substance changes and chemical characteristics are ovoviviparous Producing live young and mountain-building; also, the
its state—from gas to liquid, for roughly uniform throughout. theory explaining these occurrences.
by retaining eggs so that they hatch
example. The heat released when mollusks A major group (phylum) of while still in the female’s body. polychaetes A large subgroup of
water vapor condenses is the main invertebrate animals that includes the segmented worms common in the
source of energy for hurricanes. gastropods (snails and slugs), bivalves oceans, often with bristles down the
latitude A position on Earth expressed (clams and relatives), and cephalopods P sides of the body. (Polychaete means
in terms of its angle north or south (octopuses, squid, cuttlefish, and “many bristles”). Some species can
of the plane of the equator. Low nautiluses). Mollusks are soft-bodied pack ice A mosaic of floating ice move around, while others anchor
latitudes are those close to the and typically have hard shells, though formed when continuous sea ice themselves within tubes or burrows