Coordination & Homeostasis

Today we are going to study about Coordination & Homeostasis. First, We will give our attention to Coordination. Coordination is a very important thing to living beings to continue their lives. Animals unlike plants, have two different but related systems for coordination.

1. 1      Nervous system
2. 2      Endocrine system

Types of nervous organization of animals

               •    All multicellular animals except sponges use a network of nerve cells to gather

                   information about the  external environment, process and integrate that information, and

                   to issue signals to the  muscles and glands.

               •    Unicellular

                     No nervous organization ,ability to respond to stimuli. Cell functions as the receptor and

                   effecter.

               •    Multicellular

               •      Cnidaria – Development of nerve cells. Presence of a nerve net composed of multipolar

                   neurons, synapses. Conduction tracts in sea anemones. Development of receptors.

               •    Platyhelminthes – longitudinal solid nerve cords, organized  from a nerve ring or pair of

                   cerebral ganglion in the anterior region of the body - cephalization. Development of

                   receptors. E.g., eyespots, sensory cells.

               •    Annelids  Cerebral ganglia, double ventral nerve cord, ventral ganglia, giant nerve fibers

                     in some. Receptors E.g.,  eyes and sensory cells.

               •    Athropoda – More developed nervous system than that of Annelids. Cerebral ganglion

                   present. Well developed receptor organs of various type. E.g.,  eyes, antenna, palps

               •    Mollusca – Well developed nervous system .Consists of ganglia and nerve fibers

                     Presence of Receptor organs. E.g., well developed eyes

               •    Echinodermata – Radial nerve cord & nerve net

               •    Chordates – Single, dorsal, hollow nerve cord. Anterior region enlarged to form the brain.

                   Complexity increased gradually. Highest complexity is in mammals.

               

Transportation

       Transport is a very important action for living beings. So today we’ll study about Transportation..

          •   Water and minerals move upward through the xylem

          •   Dissolved sugars and hormones are transported in the phloem

          •    Methods of water and solute movement

          •    Basic principles underlying movement of water across membranes, phenomena of diffusion,

               imbibition, osmosis, mass flow and concept of water potential.

          •    Diffusion ; evaporation as an example

           •    Osmosis as a special kind of diffusion taking place when two solution of different concentrations       are  separated by a selectively permeable membrane which allows passage of water molecules but not of solute molecules.

               

           

                  

                   

               •    Imbibition as adsorption of water molecules to hydrophilic substances such as proteins, agar             etc,

               •    Mass flow as a method of movement of water and dissolved solutes in bulk (not in the form of

                   molecules) due to pressure gradient or gravity .

 Concept of water potential:

                   •    Any system containing water has a water potential. Water potential is related to kinetic energy of

                      water molecules, affected by factors like pressure, dissolved substances, hydrophilic substances,

                      etc.

                   •    Water potential is denoted by  Ψ  and is measured by the units of pressure (atm, Pa, M Pa).

                                               

                   •    Pure water at atmospheric pressure has the highest water potential.

                   •    Arbitrarily, the water potential of pure water at atmospheric pressure is considered as zero.

                   •    When solutes dissolve in water, the water potential is decreased and it becomes negative.

                   •    Therefore, the water potential of most naturally occurring aqueous systems is negative.

                   •    As the solute concentration increases, the water potential decreases.

                   •    Therefore, the water potential is inversely proportional to solute concentration of the system.

                   •    The component of water potential decreased due to the solute concentration is called solute

                      potential and is denoted by  Ψ s.

                                          

Diversity of respiratory structures

Animals have different respiratory structures depending mainly on the environment they live. So , we can study various type of respiratory structures  in animals. the area where gaseous exchange takes place with the environment is called the respiratory surface. An effective respiratory surface must have the following properties.

•   It must be permeable, and wet so that gases can pass through

•   It must be thin because diffusion is only efficient over the thin surfaces.

•   It should possess a large surface area to allow  sufficient volumes of gases  to be

      exchanged according to the organism’s need.

 •   It should possess a good blood supply.

Diffusion and surface to volume ratio

                      Respiratory gas exchange occurs due to diffusion. In small animals diffusion through

                      body surface is adequate as they are simple and the energy requirement is very low.

                      However, when surface volume ratio decreases, sufficient area is needed for gas

                      exchange and thus respiratory structures with large surface area were developed.

 Respiratory structures in animals

                      •   Body surface   e.g.,   Earthworm, flat worm

                      •   External gills   e.g.,   Polycheate worms, Arenicola tadpole of frog, salamander

                      •   Internal gills    e.g.,   Bony fish, lobster

                      •   Trachea       eg:    Insects, Millipedes, Centipedes

                      •   Book lungs    e.g.,   Spider, scorpion

                      •   Lungs         e.g.,   Human, Reptiles, Birds