what is ecosystem (part – 2)


The amount of biomass or organic matter produced per unit area over a time period by plants during photosynthesis.

  • It is expressed in terms of weight (g-2)  or energy (kcal m-2)
  • The rate of biomass production is called productivity.

Gross primary productivity: (GPP) is the rate of production of organic matter during photosynthesis.

Net primary productivity: A considerable amount of energy is utilized by plants in respiration.

Gross primary productivity minus respiration losses (R) is the net primary productivity.

GPP – R = NPP.

Net primary productivity is the available biomass for the consumption to heterotrophs (herbivore and decomposers.

Secondary productivity: is defined as the rate of formation of new organic matter by the consumer.

DECOMPOSITION: Earthworm is said to be ‘friends’ of farmer:

  • Breakdown the complex organic matter.
  • Loosening of the soil helps in aeration and entry of root.

The decomposers break down complex organic matter into inorganic substances like carbon dioxide, water and nutrients, called decomposition.

Dead plant remains such as leaves, bark, flowers and dead remains of animals, including fecal matter, constitute the detritus.

The process of decomposition completed in following steps:

Fragmentation:  Break down of detritus into smaller   particles by detritivore   (earthworm).

Leaching: Water soluble inorganic nutrients go down into the soil horizon and get precipitated as unavailable salts.

Catabolism:  Bacterial and fungal   enzymes degrade detritus into simple inorganic   substances.

Humification: Accumulation of dark coloured amorphous substances called humus.

most important question

  1. With the help of neat labelled diagrams describe the various kinds of connective tissues.
  2. Describe various kinds of protective tissues in plants.
  3. List the different type of complex permanent tissues in plant. Give function of each also.
  4. What is cartilage? How is it different from bone?
  5. Draw a diagram of neuron and labelled it.
  6. Which one of the following is the correct definition of the tissues?  (a) Group of dissimilar cells which perform similar function  (b) Group of similar cells which perform similar functions. (c) group of similar cells which perform specific functions  (d) Group of dissimilar cells which perform different functions. 
  7. A long tree has several branches. The tissue that helps in the side ways conduction of water in the branches is: (a) collenchyma  (b) xylem parenchyma  (c) parenchyma  (d) xylem vessels 
  8. White blood corpuscles: (a) help in blood clotting  (b) help in transport of oxygen (c) are enucleated  (d) protect the body from diseases
  9. A person met with an accident in which two long bones of hand were dislocated.
  10. Name the two main types of plant tissues.  
  11. Water hyacinth floats on water surface. Explain. 
  12. Name the two types of vascular tissues. 
  13. How many types of element are present in the phloem? 
  14. Which among the following may be possible reason? (a) tendon break  (b) break of skeletal muscles  (b) ligament break   (d) Areolar tissue break 
  15. If you are provided with three slides, each containing one types muscles fibres, how will you identify them.

what is neuron


Nerve cell is the unit of nervous system. A neuron is a microscopic structure composed of three major parts, namely, cell body, dendrites and axon. The cell body contains cytoplasm with typical cell organelles and certain granular bodies called Nissl’s granules. Short fibers which branch repeatedly and project out of the cell body also contain Nissl’s granules and are called dendrites. These fibers transmit impulses towards the cell body. The axon is a long fibre, the distal end of which is branched. Each branch terminates as a bulb-like structure called synaptic knob which possess synaptic vesicles containing chemicals called neurotransmitters. The axons transmit nerve impulses away from the cell body to a synapse or to a neuro-muscular junction.

  • Based on the number of axon and dendrites, the neurons are divided into three types, i.e., multipolar (with one axon and two or more dendrites; found in the cerebral cortex), bipolar (with one axon and one dendrite, found in the retina of eye) and unipolar (cell body with one axon only;found usually in the embryonic stage). There aretwo types of axons, namely, myelinated and non myelinated.

are you know about blood platelets

  1. Blood platelets: Also called thrombocytes, blood platelets are non-nucleated, round or oval, biconvex disc-like bodies. They are 2-3 micrometers in diameter and their number normally varies from 0.15 to 0.45 million per microlitre of blood. They bud off from the cytoplasm of very large Mega-karyocyte cells of bone marrow. Their normal life-span is about a week. When a blood vessel is injured, platelets get clumped at the injured spot and release certain chemicals called Platelet Factors. These promote blood coagulation. Thrombocytopenia, decrease in platelet count. Purpura, is a group of bleeding disease due to thrombocytopenia Blood coagulation: When blood oozes out of a cut, it sets into gel within a few minutes. This is called coagulation. Coagulation is brought about by hydrolysis of soluble fibrinogen of plasma to insoluble fibrin. This is catalysed by an enzyme called thrombin. Fibrin precipitates as a network of fibers. This network traps many blood cells, particularly RBCs, to form a red solid mass called the Blood Clot. The clot seals the wound in the vessel to stop the bleeding. The straw coloured fluid left after clotting of blood is called Serum. The serum cannot be coagulated as it lacks fibrinogen.

Thrombin occurs in normal blood as an inactive globulin called Prothrombin. It must be activated to thrombin before blood coagulation can occur. In case of injury to a blood vessel, coagulation promoting substances called Thromboplastins are released into the blood from clumped platelets and damaged tissues. Thromboplastins help in the formation of the enzyme Prothrombinase. This enzyme hydrolyses prothrombin to thrombin to initiate coagulation. Ca2+ ions are essential for both the activation and action of thrombin.

Blood normally contains an anticoagulant; Heparin which prevents activation of prothrombin, Heparin is released from mast-cell granules. Blood also contains Antithrombin which inhibits any thrombin formed accidentally.

Blood drawn from a blood vessel can be kept un-coagulated by adding a pinch of oxalate (sodium or potassium oxalate) to it. Oxalate precipitates Ca2+ and consequently prevents coagulation. Chilling of blood also delays coagulation because cold depresses the action of coagulation promoting enzymes.

most important Tissues

Bone – it is hardest connective tissues its matrix is so much hard due to presence of salts, such as calcium phosphate, etc. it help in locomotion. It protect internal delicate organ.

Vascular tissues: it is the fluid tissues that form supportive frame work of body. It is of two types:

  1. Blood — Blood is a special connective tissue consisting of a fluid matrix, plasma, and formed elements.

Blood is a fluid connective tissue. Its cells are quite distinct from other connective tissue cells, both in structure and functions. The extracellular material in blood is a fluid devoid of fibers. Fluids outside the cells are generally called Extracellular Fluids (ECF).

The extracellular material in blood is a straw-coloured, slightly alkaline aqueous fluid called Plasma.


Constituents, having characteristic forms, float in the plasma. They are collectively called the Formed Elements of blood. They include the blood cells and blood platelets. Blood cells are of three types-Erythrocytes, Leukocytes & platelets. Blood circulates within blood vessels in higher

Animals. But other extracellular fluids such as cerebrospinal fluid, interstitial fluid, lymph and aqueous humour occur outside blood vessels.

Plasma contains three major classes of plasma proteins viz, serum albumin, serum globulins and fibrinogen. Plasma proteins serve as a source of proteins for tissue cells. Tissue cells may utilize plasma proteins or forming their cellular proteins. Additionally, albumin and globulins retain water in blood plasma by their osmotic effects. A fall in plasma proteins leads to filtering out of excessive volumes of water from blood to tissues. This is why hands and feet get swollen with accumulated fluid (oedema) in persons suffering from dietary deficiency of proteins. Albumins and globulins also transport many substances such as thyroxin and Fe3+ in combination with them One class of globulins, called-immunoglobulins act as Antibodies. Plasma proteins also maintain the blood pH by neutralizing strong acids and bases. Thus they act as Acid-Base-Buffers.