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Summary chapter 3
Summary study book Ecology of Robert E. Ricklefs, Rick Relyea (chapter 3 ) - ISBN: 9781319187729, Edition: 8th ed. 2018, Year of publication: - (chapter 3)
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Adaptations to aquatic environmentsThe evolution of whales
Highly streamlined body
Regulating body temperatures – a thick layer of fat used for insulation, a higher
metabolic rate and whale’s vascular structure help maintain heat
Two evolutions for finding food in water: baleen whales have long plates in their
mouths to filter tiny prey out of the water, whereas toothed whales have teeth in
their mouth to grab prey
Modern toothed whales used echolocation
Water has many properties favourable to life
Because it can dissolve inorganic compounds, it is an excellent medium for the
chemical processes of living systems
Thermal properties of water: ice at 0 degrees, gas over 100 degrees, high specific
heat, transfers heat rapidly, resistance from changing from one state to another,
changing density with change of temperature
Density and viscosity of water: because air is less dense than water, have air sacs or
lungs filled with air allow organisms in the water to slow down the rate of sinking or
float and the highly streamlined bodies of water inhabiting organisms allow them to
swim fast through the high viscosity of water and long filamentous appendages
cause greater drag allowing them to slow down sinking
Water is a powerful solvent with an impressive capacity to dissolve substances,
which makes them accessible to living systems. Because of this property, water also
provides a medium in which substance can react chemically to form new compounds
The polar nature of water molecules also allows them to be attracted to other polar
compounds – water is not a good solvent for oils and fats because they are nonpolar
compounds
Hydrogen ions, because of their high reactivity, dissolve minerals from rocks and
soils, enhancing the natural solvent properties of water
Effects of acid rain
In forests, acid deposition has several affects. First, it leaches the calcium out of the needles
of conifer trees. It also caused increased leaching of soil nutrients that trees require. Finally,
acid deposition causes aluminium to dissolve in water. Dissolved aluminium can negatively
affect a plant’s ability to take up nutrients. Collectively, these effects make trees more
susceptible to drought, diseases and extreme temperature.
The challenge of salt and water balance
The movement of water occurs at the cellular level, at the same time solutes attempt to
move across the semipermeable membrane to equalise the concentration of solutes. The
challenge for most aquatic organisms is that they live in water with a solute concentration
that differs from the solute concentration of their bodies. This difference causes water and
solutes to attempt to move in or out of the organism’s body, which makes it difficult for
organisms to maintain the proper amount of water and solutes in their bodies. Maintaining
a particular solute concentration, in the body is important because solute concentrations
affect the wat proteins interact with other molecules so can disrupt cell functions.
Adaptations for osmoregulation in freshwater animals
Freshwater animals are hyperosmotic so face a constant challenge as water attempts to
enter its body while solutes attempt to leave. Fish respond to this influx of water by
eliminating the excess water through their urine. They add solutes to their bloodstream by
, using their gill cells to actively transport solutes into the body from the water. In addition,
their kidneys remove ions from their urine.
Adaptations for osmoregulation in saltwater animals
Saltwater animals are hypoosmotic so face a constant challenge to maintain the balance of
water and solutes in their tissues. Water tries to leave their bodies and solutes try to enter.
To replace the loss of water, saltwater animals drink large amounts of saltwater and release
only small amounts of urine. To counteract, the influx of solutes the excess solutes are
actively excreted out of the body using the kidneys and gills. Sharks and rays have evolved
to retain ammonia as urea so that the movement of water across the animal’s body surface
becomes balanced in relation to the surrounding saltwater, meaning they don’t need to
drink lots of saltwater. They accumulate high concentrations of trimethylamine oxide to
protect proteins from the harmful effects of urea.
Adaptations for osmoregulation in aquatic plants
Some aquatic plants face major challenges of salt balance. Mangrove trees maintain high
concentrations of organic solutes and possess salt glands to counter the high concentration
of salt in salt-water.
The uptake of gases from water is limited by diffusion
Carbon dioxide
Getting enough CO2 for photosynthesis is a challenge for aquatic plants and algae because
CO2 diffuses very slowly through water. CO2 is converted to bicarbonate ion in water so
plants can either directly uptake the bicarbonate ion or they can use adaptations to convert
the bicarbonate ion to CO2. One way to do this is by secreting an enzyme into the water
that is highly effective at converting bicarbonate ions into CO2, which can then be taken up
by the organism. Plants and algae can also obtain CO2 by secreting hydrogen ions into the
surrounding water. This helps drive the chemical equilibrium in a direction that converts
more of the bicarbonate ions into CO2.
Oxygen
For marine mammals they obtain oxygen from the air and store copious amounts in the
haemoglobin and myoglobin. Other aquatic animals have gills to extract oxygen from the
water. When water passed over the gills, oxygen diffuses across the membranes of the gill
cells and enters the capillaries. Species that live in habitats with low amounts of oxygen
have evolved many adaptations; increasing the amount of haemoglobin in their bodies,
swimming to the surface to take gulps of air and store this air in a swim bladder.
Heat and biological molecules
temperature influences physiological processes because of the way in which heat affects
organic molecules. Heat impacts kinetic energy to living systems, causing biological
molecules to change shape. Heat also accelerates chemical reactions by increasing the rate
of molecule movement. Higher temperatures allow organisms to do many things more
rapidly, however at a certain point high temperature can depress life processes. The
molecular motion caused by heat tends to denature the structure of molecules.
Temperature also affects other biological compounds. For instance, the physicals properties
of fats and oils, which are major components of cell membranes and constitute the energy
reserved of animals, depend on temperature. When fats are cold, they become stiff; when
they are warm, they become fluid.
Cold temperatures and freezing
When living cells freeze, the crystal structure of ice disrupts most life processes and may
damage delicate cell structures, eventually causing death. Many organisms successfully cope
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