Write the differences between:  (a) Blood and Lymph(b) Open and Closed system of circulation(c) Systole and Diastole(d) P-wave and T-wave 
Blood Lymph
1. Blood is red in colour due to presence of haemoglobin Lymph is colourless due to absence of haemoglobin.
2. Blood consist of fluid matrix, plasma, and formed elements. Lymph consists of specialised lymphocytes.
Open System of CirculationClosed System of Circulation
1. The blood pumped by the heart passes through the large vessels into the open spaces of the body cavity. The blood pumped by the heart passes through a closed network of blood vessels called arteries veins and capillaries.
2. Open system of circulation is seen in arthropods and molluscus. Closed system of circulation is seen in Annelids and Chordates.
The contraction of ventricles is called systoleThe relaxation of the atria is called diastole.
P- waveT- Wave
This represents the electrical excitation of the atria leading to the contraction of both the atria.This wave represents the return of the ventricles from excited state to normal state.