Which of the following does not lose their nucleus at maturity?

Bone matrix is rich in

Identify the simple permanent plant tissue with the following descriptions and also mention their location in the plant body:
$(a)$ Cells have irregular wall thickenings.
$(b)$ Tissues with large intercellular spaces and cells having large air cavity.
$(c)$ Cells are long,narrow,and dead in nature.

$(a)$ Give reasons for the following:
$(i)$ Multicellular organisms are considered more efficient.
$(ii)$ Sclerenchyma cells have a narrow lumen.
$(iii)$ Epidermis is thicker in desert plants though it is usually single layered.
$(b)$ Name the following:
$(i)$ Tissue that occurs in specific regions of growth.
$(ii)$ Tissue present at the growing tips of stems and roots.
$(iii)$ Tissue at the base of the leaves or internodes on twigs.
$(iv)$ Basic packing tissue in the form of a few layers of cells.

Nervous tissue is not found in

Describe the structure and function of different types of epithelial tissues. Draw a diagram of each type of epithelial tissue.