Which statement best describes an immune response that occurs in invertebrates? a)cytotoxic t cells recognize infected cells and then bind to and destroy them. b)enzymes such as lysozyme break down the cell walls of harmful bacteria. c) t cells produce antibodies when a foreign antigen is recognized. d)natural killer cells engulf infected cells, destroying them via phagocytosis.

Ans.

Lysozymes are hydrolytic enzymes, synthesized and secreted by various organisms as a defense mechanism against bacterial infections. Invertebrates show type-i lysozymes (invertebrate lysozyme).

Lysozyme kills gram-positive bacteria by breaking bacterial cell walls as it prevents polymerization of components, required for cell wall synthesis. Invertebrates do not have immune cells, such as T cell, B cells, and natural killer cells.

Thus, the correct answer is 'option b). enzymes such as lysozyme break down the cell walls of harmful bacteria.'

his research revealed two genetically different groups of prokaryotes, which justified splitting kingdom monera into two kingdoms. the genetic and cellular differences were so great, that these two kingdoms were eventually placed into different domains in the current three-domain system.

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.