dead zone

Examples of dead zone in the following topics:

• The Phosphorus Cycle

  • This process is responsible for dead zones in lakes and at the mouths of many major rivers .
  • A dead zone is an area within a freshwater or marine ecosystem where large areas are depleted of their normal flora and fauna.
  • The number of dead zones has been increasing for several years; more than 400 of these zones were present as of 2008.
  • One of the worst dead zones is off the coast of the United States in the Gulf of Mexico, where fertilizer runoff from the Mississippi River basin has created a dead zone of over 8,463 square miles.
  • Worldwide, large dead zones are found in coastal areas of high population density.

• Freshwater Biomes

  • Light can penetrate within the photic zone of the lake or pond.
  • At the bottom of lakes and ponds, bacteria in the aphotic zone break down dead organisms that sink to the bottom.
  • The resulting dead zones are found across the globe.

• Marine Biomes

  • Each zone has a distinct group of species adapted to the biotic and abiotic conditions particular to that zone.
  • Beyond the neritic zone is the open ocean area known as the oceanic zone.
  • The majority of organisms in the aphotic zone include sea cucumbers and other organisms that survive on the nutrients contained in the dead bodies of organisms in the photic zone.
  • The bottom of the benthic realm comprises sand, silt, and dead organisms.
  • Due to the dead organisms that fall from the upper layers of the ocean, this nutrient-rich portion of the ocean allows a diversity of life to exist, including fungi, sponges, sea anemones, marine worms, sea stars, fishes, and bacteria.

• Growth of Bone

  • The zone of maturation and hypertrophy contains chondrocytes that are older and larger than those in the proliferative zone .
  • The zone of calcified matrix, the zone closest to the diaphysis, contains chondrocytes that are dead because the matrix around them has calcified .
  • After the zone of calcified matrix, there is the zone of ossification, which is actually part of the metaphysis .
  • The topmost layer of the epiphysis is the reserve zone.
  • The second zone, the proliferative zone, is where chondrocytes are continually undergoing mitosis.

• Types of Root Systems and Zones of Growth

  • The root tip has three main zones: a zone of cell division, a zone of elongation, and a zone of maturation.
  • The root tip can be divided into three zones: a zone of cell division, a zone of elongation, and a zone of maturation .
  • All three zones are in approximately the first centimeter of the root tip.
  • A longitudinal view of the root reveals the zones of cell division, elongation, and maturation.
  • Describe the three zones of the root tip and summarize the role of each zone in root growth

• The Role of Prokaryotes in Ecosystems

  • Related to this, one very significant source of carbon compounds is humus, which is a mixture of organic materials from dead plants and prokaryotes that have resisted decomposition.
  • The most important contributor of carbon dioxide to the atmosphere is microbial decomposition of dead material (dead animals, plants, and humus).
  • This methane moves into the zone above the sediment, which is richer in oxygen and supports bacteria called methane oxidizers that oxidize methane to carbon dioxide, which then returns to the atmosphere.

• Meristems

  • Apical meristems are organized into four zones: (1) the central zone, (2) the peripheral zone, (3) the medullary meristem and (3) the medullary tissue .
  • Surrounding the central zone is the peripheral zone.
  • The rate of cell division in the peripheral zone is higher than that of the central zone.
  • Each zone of the apical meristem has a particular function.
  • Pictured here are the (1) central zone, (2) peripheral zone, (3) medullary meristem and (3) medullary tissue.

• Stem Anatomy

  • Sclerenchyma cells also provide support to the plant, but unlike collenchyma cells, many of them are dead at maturity.
  • The latter two types conduct water and are dead at maturity.
  • The central pith (greenish-blue, in the center) and peripheral cortex (narrow zone 3–5 cells thick, just inside the epidermis) are composed of parenchyma cells.

• Dead Space: V/Q Mismatch

  • There are two types of V/Q mismatch that produce dead space.
  • Dead space is characterized by regions of broken down or blocked lung tissue.
  • Dead space is created when no ventilation and/or perfusion takes place.
  • Anatomical dead space, or anatomical shunt, arises from an anatomical failure, while physiological dead space, or physiological shunt, arises from a functional impairment of the lung or arteries.
  • Compare and contrast anatomical and physiological dead space and their role in V/Q mismatch

• Energy Sources

  • Toward the bottom of a lake, pond, or ocean, there is a zone that light cannot reach.
  • As a result, the nutrients once contained in dead organisms become available for reuse by other living organisms .