Cyanobacteria have been engineered to produce isobutanol directly what advantages does this have over other alternative biofuels

The advantage that engineered cyanobacteria have over other alternative bio fuels is that IT AVOID MULTIPLE PROCESSING STEPS.
Bio fuels are liquid fuels that are derived from waste plants and animal matters. Production of bio fuels involves many steps. Withe the advance of engineered cyanobacterial, multiple production steps can be avoided during the manufacturing of bio fuels. 

Fossil found in strata reveal that unused body part decrease in size

answer: - b cells

explanation: -

there are many types of white blood cells present in our body. one such class of white blood cells are the lymphocytes. the b cells belong to the lymphocyte class of wbcs. the b cells perform their action against the pathogen by producing specialised proteins called as antibodies. these antibodies are produced as and when the b cells encounter pathogens in response to the antigens present on the surface of the pathogen. these antibodies bind to the antigens present on the pathogen and then, target them for destruction by other cells of the immune system.

so, the b cells mediate their action by identifying the antigens present on the surface of the pathogens and then producing antibodies in return to mediate its effect.