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.

• Functional Anatomy of the Respiratory System

  • Dead Space Ventilation (VD): The amount of air per unit of time that doesn't reach the alveoli.
  • It is defined as volume of dead space times the respiratory rate.
  • Dead space is any space that isn't involved in alveolar gas exchange itself, and it typically refers to parts of the lungs that are conducting zones for air, such as the trachea and bronchioles.
  • If someone breathes through a snorkeling mask, the length of their conducting zones increases, which increases dead space and reduces on alveolar ventilation.
  • As air moves from zones of high pressure to zones of low pressure, the contraction of the diaphragm allows the air to enter the conducting zone (such as the trachea, bronchioles, etc.), where it is filtered, warmed, and humidified as it flows to the lungs.

• Pressure Changes During Pulmonary Ventilation

  • It is defined as $VA=(Tidal Volume-Dead Space Volume)* Respiratory Rate$
  • Dead space ventilation (VD): The amount of air per unit of time that is not involved in gas exchange, such as the air that remains in the conducting zones.
  • It is defined as $VD=DeadSpaceVolume*Respiratory Rate$.
  • This is most apparent in changes of the dead space volume.
  • Differentiate among the types of pulmonary ventilation: minute, alveolar, dead space

• Trachea

  • The trachea is part of the conducting zone for air into and out of the lungs.
  • As a part of the conducting zone of the lungs, the trachea is important in warming and moistening air before it reaches the lungs.
  • The trachea is also considered a part of normal anatomical dead space (space in the airway that isn't involved in alveolar gas exchange) and its volume contributes to calculations of ventilation and physiological (total) dead space.
  • It is not considered alveolar dead space, a term that refers to alveoli that don't partake in gas exchange due to damage or lack of blood supply.

• The Structure of Cities

  • In the 1960s, urban planners moved away from grids and began planning suburban developments with dead ends and cul-de-sacs.
  • The innermost ring represents the central business district (CBD), called Zone A. .
  • It is surrounded by a zone of transition (B), which contains industry and poorer-quality housing.
  • The outermost ring (E), or commuter's zone, is residential suburbs.
  • An industrial park is an area zoned and planned for the purpose of industrial development.

• Alveoli

  • The alveoli are located in the respiratory zone of the lungs, at the distal termination of the alveolar ducts.
  • The alveoli are the site of alveolar ventilation, and are not normally considered dead space.
  • However, alveoli that are injured and can no longer contribute to gas exchange become alveolar dead space.
  • Physiological dead space is the sum of normal anatomical dead space and alveolar dead space, and can be used to determine the rate of ventilation (gas exchange) in the lungs.
  • When any type of dead space increases, the rate of ventilation in the lungs will decrease.

• 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