How have useful traits been accumulated in plants and animals over the centuries

Useful traits have been accumulated in plants and animals over the centuries by how plants have undergone through certain phases, specifically called selection. Most of these traits are accumulated naturally but others may be acquired in the opposite way through man-made cultivation. Hope this answers your question.

white blood cells or wbc s are mainly 2 types-

1.agranulocytes

2.granulocytes

the monocytes or macrophages of agranulocytes , dendritic cells which are accessory leucocytes, and b cells which is one type of lymphocytes   identify the antigens present on the pathogen's surface. these three cells are called antigen presenting cells(apc) which are phagocytes and destroy the antigens by secreting antitoxins. besides this leukocyte is always plays vital role in the immunity of the body.

this transfer is call conjunction