DEFINE LEUKAEMIA AND ITS CAUSES AND DESTRUCTION?

LEUKAEMIA:
Leukaemia is a malagnant disorder of haemophoietic tissues,associated with increase number of tissues in the blood.
OBSTRUCTION :
They obstruct normal blood cells formation in the bone marrow .theses are progressive and fatal conditions resulting in death.
CAUSES:
The cause of leukaemia is unknown several factors however are associated with the development of leukaemia like ionising  radiation,cytotoxic drugs,retroviruses ,genetic etc.    

HEART BEATS

HEART STARTS BEATING BEFORE THE BIRTH AND NEVER STOPS TILL DEATH

EXPLAIN REPRODUCTION IN NOSTOC?

REPRODUCTION OF NOSTOC:-
There is no report of sexual reproduction in nostoc.but sexual reproduction take place by following methods....
1:HORMOGONIA
2:AKINETES

            HORMOGONIA
Hormogonium is a portion of filament between two heterocyst.during favourable condition, filaments breakup at the junction of each heterocyst.this results in the formation of a number of pieces called hormogonia.the end cells of each hormogoniumdivide to form long filament of nostoc.
          AKINETES 
Akinetes are non-motile spores formed from certain vegetative cells during unfavourable condition.When conditions are not favourable .certain vegetative cells become enlarge and thick walled containing reserve food called AKINETES .these are somewhat oval  with outer layer EXOSPORIUM and inner ENDOSPPORIUM .At the approach of favourable conditions they germinate by rupturing by exospore and form independant filaments by simple cel division   

DEFINE IMPORTANCE OF CYANOBACTERIA?

IMPORTANCE OF CYANOBACTERIA(BLUE GREEN ALGAE) 
                      They are capab;e of making organic compound from water and carbon dioxide.
                      They flourished and change the world by releasing O2 as by-product of their                
                      photosynthesis.
                      Many are capable to fix atmospheric nitrogen,and this together with their ability
                     to photosynthesis means that their natural requirements are simple(mainly co2 and 
                    nitrogen from the air plus some material) for this reason they are often first colonisers 
                    of moist soil