Life on an Ocean Planet

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• Choose to view chapter section with a click on
  the section heading.
• The Nature of Life
• How Energy Enters Living Systems
• The Oceans Primary Productivity
• Energy Flow Through the Biosphere

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The Nature of Life

• Theoretical physicist Stephen Hawking
• The laws of science do not distinguish between
  the past and the future.In order to survive,
  human beings have to consume food which is
  anordered form of energy, and convert it into
  heat, which is a disorderedform of energy The
  progress of the human race in understanding
  theuniverse has established a small corner of
  order in an increasinglydisordered universe.
• This principle of physics called entropy, or
  randomness, appears to be the driving force of
  all life in our universe.
• Defining life appears simple if you compare a
  fish and a rock. From a scientific point of view,
  its not quite so cut-and-dried. Often life and
  nonlife share the same elements matter, carbon
  atoms and energy reactions.
• Energy reactions found in living systems also
  exist outside of life.For example fire results
  when a reaction releases chemicalenergy within
  substances. Living systems use energy similarly
  by releasing chemical energy for life processes.
• All life uses energy. Therefore it is possible to
  define life basedon the characteristics living
  systems have apart from nonlivingsystems with
  respect to energy use.

The Nature of Life
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Elements Essential for Life
The Nature of Life
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Matter and Energy

• Life requires matter and energy to exist. All
  living organisms are composed of about 13 of 118
  known elements from the periodic table.
• Carbon, hydrogen, oxygen, and nitrogen account
  for 99 of the mass. Nine other elements account
  for the remaining 1. These elements, in
  combinations, account for all biological
  chemicals.
• Scientists recognize more than 1.6 million
  different species, as many as 30 million may
  exist.
• Despite this huge number, all organisms organize
  matter into biological chemicals and into cells.
• A cell is the smallest whole structure that can
  be defined as a living system.
• Organisms can consist of a single cell or
  billions of codependent cells.
• All life organizes matter into cells.

The Nature of Life
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Matter and Energy (continued)

• The first law of thermodynamics states that
  energy can be transferred from one system to
  another in many forms. However, it cannot be
  created nor destroyed.
• Energy is defined as the capacity to do work.
• Energy is necessary for life because living
  systems use it to accomplish the processes of
  life reproduction, growth, movement, eating,
  etc.
• Organisms need energy to help break down complex
  molecules into simple molecules. They need more
  energy to build distinct complex molecules from
  simple molecules.
• Organisms cannot create energy but can use it
  to perform useful work. Living systems must
  acquire energy from outside sources.

The Nature of Life
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Entropy

• The second law of thermodynamics states that
  disorder increases with time and eventually all
  energy and matter will be distributed evenly.
• Entropy is the measure of how much unavailable
  energy exists in a system due to even
  distribution. High entropy low organization and
  low energy potential.
• Living systems use energy to create order and to
  gather and store potential energy. The increased
  order is local and temporary, and requires more
  energy to create than it retains. Here, matter
  exists in a low-entropy (organized) state.
• Example About 85 of the energy required to
  organizeprotein into complex muscletissue is
  ultimately lost as heat in creating the tissue.

The Nature of Life
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Autotrophy and Heterotrophy

• Terrestrial and most marine organisms get their
  energy directly or indirectlyfrom the sun.
• Autotrophy is the process of self-feeding by
  creating energy-rich compounds called
  carbohydrates.
• Autotrophs obtain energy from the sun or chemical
  processes.
• They do this by converting the energy from
  sunlight and inorganic compounds into
  carbohydrates. Plants are autotrophs.
• Many organisms, including virtually all animals,
  cannot produce their own carbohydrates. These
  organisms get their energy and matter by
  consuming other organisms. This is called
  heterotrophy.
• Heterotrophs are organisms that rely on other
  organisms for sources of energy.
• We are heterotrophs. Humans rely on
  photosynthesizing plants, bacteria, and other
  micro-organisms for life.
• This is one reason why the health of the natural
  environment is a crucial issue.

How Matter and Energy Enter Living Systems
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Respiration

• Whether an organism is an autotroph or a
  heterotroph, it must convert carbohydrates
  intousable energy.
• Organisms use oxygen to engage in cellular
  respiration.
• Respiration is the process of releasing energy
  from carbohydrates to perform the functions of
  life. (This is not the same as breathing.)
• The chemical processfor respiration is

How Matter and Energy Enter Living Systems
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Photosynthesis

• Because they create energy-rich compounds,
  autotrophs are also known as primary producers.
• Primary producers combine energy from sunlight
  with inorganic materials to form energy-right
  organic compounds.
• Conduit through which the biosphere gets almost
  all its energy.
• Organisms with chlorophyll are the majority of
  primary producers.
• Chlorophyll allows for the collection of
  sunlight.
• The process of using light energy to create
  carbohydrates from inorganic compounds is called
  photosynthesis.
• Because carbon dioxide and water have more oxygen
  than is needed, the process also releases oxygen.
• Without photosynthesis we would not have the
  oxygen we need to breathe.

How Matter and Energy Enter Living Systems
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Photosynthesis (continued)

• Note that even organisms with chlorophyll
  respire. If youlook at photosynthesis you can
  see it is a complementaryprocess to respiration.
• The chemical process for photosynthesis is
• Aerobic respiration meaning respiration that uses
  oxygen.
• Anaerobic respiration releases energy through
  chemicalreactions that do not require oxygen.
• Anaerobic respiration is not as efficient as
  aerobic respiration.

How Matter and Energy Enter Living Systems
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Chemosynthesis

• Chemosynthesis is the process of using chemicals
  to create energy-rich organic compounds.
• It is similar to photosynthesis because
  itproduces carbohydrates.
• Chemosynthesis differs from photosynthesis it
  does not use sunlight as an energy source, it
  uses chemical energy within inorganic compounds.
• Chemosynthetic organisms are primary producers.
• Fixation is the process of converting, or fixing,
  an inorganic compound into an organic compound.
• In 1977, there was an important discovery of a
  major biological community in the deep ocean
  relying on chemosynthesis.
• These communities use chemical energy from
  minerals in the hot spring water coming from the
  hydrothermal vents.

How Matter and Energy Enter Living Systems
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Marine Biomass

• The main products of primary production are
  carbohydrates.
• Scientists measure primary productivity in terms
  of the carbon fixed (bound) into organic
  materials.
• Biomass is the mass of living tissue. The biomass
  at a given time is called the standing crop.
• Example The average standing crop in the oceans
  is 1-2 billion metric tons. On land, the average
  standing crop is 600 to 1,000 billion metric
  tons.
• Comparing primary productivity of the seas to
  that of the land, the lands primary production
  is slightly higher.
• How is it possible that the total primary
  production from marine ecosystems is only a bit
  less than that of terrestrial ecosystems?
  marine ecosystems cycle their energy and
  nutrients much more rapidly.

The Oceans Primary Productivity
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Plankton

• The term plankton does not describe a kind of
  organism, but a group of organisms with a common
  lifestyle and habitat. Plankton include
  autotrophs, heterotrophs, predators and grazers.
• Plankton drift/swim weakly at the mercy of water
  motion.
• Plankton are not a species, but include many
  species.
• Most are very small, some, like the jellyfish,
  grow severalmeters long.
• Some start life as planktonic larvae and then
  becomenektonic organisms that swim or attach
  themselvesto the bottom as benthic organisms.
• Meroplankton live part of their lives as
  plankton.
• Holoplankton remain plankton all their life.
• Phytoplankton are primary producers
  responsiblefor more than 92 of marine
  production.
• Zooplankton are primary and secondary
  consumersof other plankton.

The Oceans Primary Productivity
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Plankton (continued)

• Four most important kinds of phytoplankton
• 1. Diatoms are the most dominant and
  efficientphotosynthesizers known.
• They convert more than 50 of the light energy
  theyabsorb into carbohydrate chemical energy.
  They have a rigid cellwall made of silica called
  a frustule which admits light. This is anideal
  cell material for a photosynthesizer.
• 2. Dinoflagellates are characterized by one or
  two whip-likeflagella which they use to move in
  water.
• Most are autotrophs. They are the most
  significant primary producersin coral reefs.
  They are also the principal organismsresponsible
  for plankton blooms.
• 3. Coccolithophores are single-cell autotrophs
  characterizedby shells of calcium carbonate.
• They live in bright shallow water.
• 4. Silicoflagellates are micro-organisms with
  internal supportstructures made of silica and
  have one or more flagella.
• They are structurally and chemically more
  primitive than diatoms.

The Oceans Primary Productivity
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Plankton (continued)

• Understanding the role of picoplankton
  haschanged the way marine biologists thinkabout
  tropical region productivity.
• Picoplankton are extremely tiny plankton.
• May account for up to 79 of the
  photosynthesisin tropical waters.
• Many are cyanophytes, which are bacteriawith
  chlorophyll.
• Can also be called cyanobacteria orblue-green
  algae.
• Their role in primary productivity is to be
  foodfor heterotrophic bacteria.
• They may also play a significant role in
  producingoxygen and taking up carbon dioxide.

The Oceans Primary Productivity
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Limits on Marine Primary Productivity

• Limiting factors are physiological or biological
  necessities that restrict survival. Too much or
  too little of a limiting factor will reduce
  population.
• Limiting factors in the ocean include
• Inorganic nutrients such as nitrogenand
  phosphorus compounds.
• Sunlight due to season, depth, or water clarity.
• Tropical waters have low productivity.
• Warm upper water act to trap nutrients in the
  cold layers that are too deep forphotosynthesizin
  g autotrophs.
• The Arctic and Antarctic have little temperature
  difference allowing nutrients to cycle to
  shallower water.
• Temperate regions, coastal areas, have more
  primary productivity due to more nutrients from
  rain runoff.
• Shallow water keeps them from sinking too deep.
• Areas of highest productivity are in the
  Antarctic Convergence Zone and near shore
  temperate regions due to nutrient availability.

The Oceans Primary Productivity
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Limits on Marine Primary Productivity (continued)

• Light is an important limiting factor.
• The amount of daylight affects photo-synthesis
  and primary productivity. For example, the
  Antarctic Convergence Zone has optimum nutrients
  available, seasonal sunlight limits its
  productivity.
• Depth is a limiting factor too.
• Depth affects photosynthesis and primary
  productivity. Suspended particles and the lights
  angle limit how much light penetrates water. Even
  in very clear water, very little photosynthesis
  takes place below 100 meters (328 feet).
• Too much light can be bad too. Photo-inhibition
  takes place when too much light overwhelms an
  autotroph. It cannot photo-synthesize when water
  is too shallow.

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Limits on Marine Primary Productivity (continued)

• Different phytoplankton species have
  differentoptimal depths.
• As light conditions change, the advantage
  shiftsfrom species to species.
• Autotrophs produce carbohydrates and oxygen,but
  they also respire.
• They use carbohydrates and some oxygen
  forrespiration. The less light, the less
  photosynthesisand the less carbohydrates are
  produced.
• At some point, the amount of carbohydratesproduce
  d exactly equals the amount requiredby the
  autotrophs for respiration.
• The point of zero net primary production is
  calledthe compensation depth.
• This is the depth at which about 1 of the
  surfacelight penetrates.
• If phytoplankton remain below compensationdepth,
  they will die within a few days.

The Oceans Primary Productivity
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Trophic Relationships

• The hierarchy of what-eats-what can be
  illustrated with a trophic pyramid.
• It is a representation of how energy transfers as
  they consume each other.
• Primary producers, mainly photosynthesizers,
  makeup the base. Most of these are plants. In
  the ocean,phytoplankton are primary producers.
• Primary consumers, the first level of
  heterotrophs, eat the primaryproducers. Most of
  these are herbivores (animals that eat plants).
  In the ocean, zooplankton are primary consumers.
• Secondary consumers, eat primary consumers.
• Each level eats the level below and has
  significantlyless biomass (living matter) than
  the level it eats.
• Energy Loss Through Trophic Levels
• Only about 10 of the energy transfers from one
  level to the next, so each level is about a tenth
  of the size of the level underneath. 90 of the
  energy is lost to entropy.

Energy Flow Through the Biosphere
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Food Webs and Decomposition

• A food web is a way to illustrate different
  levels of consumers and energy flow. In real
  life, organisms consume across levels, not just
  below. The food web better represents the flow of
  energy through consumption in nature.
• Decomposers break down organic material
  intoinorganic form. They take out the very last
  usableenergy from organic matter to sustain
  themselves.
• Decomposers are primarily bacteria and fungi,
  their job is to convert dead organisms into the
  compounds primary producers use.
• Bacteria are the most important decomposers.
• Decomposition is important because it completes
  the materials cycle.
• Within systems, energy flows andmatter cycles.

Energy Flow Through the Biosphere
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