Tag: unicellular and multicellular organisms

The cell is the structural unit of life with various shapes and size. The size of the cell ranges from 0.5 micrometers to 100 micrometers. Mycoplasma gallicepticum, a parasitic bacterium is thought to be the smallest known organisms with the size from 0.2 to 0.3 micrometer, capable of independent growth and reproduction. Later, the name for mycoplasma was pleuropneumonia-like organisms or PPLO.

The tissues which cover or protect the body are called epithelial tissues. Cells of the epithelial tissues are tightly packed and have a small amount of cementing material in between them. These are small cells covering the organs and cavities of the body.  
Mast cells are a type of cells belonging to areolar connective tissues. It fills the space around the organs. 
Kupffer cells are star-shaped macrophages present in the liver lining. 
Nerve cells possess a cell body and one or many thin fiber-like axons. Some nerve cells possess axons as long as 1 meter and thus, are the largest cell in the human body. It is also known as the longest cell in the human body. Thus, the correct answer is option A.

The ostrich egg is the largest cell known. These eggs are 15 cm long and 13 cm wide. 

• The cell is the structural unit of life. Unicellular organisms are made up of one cell that performs all the functions. Its size is 0.5-10 micrometers, whereas, in multicellular organisms, cell size is 10-100 micrometers.

Sclerenchyma, in plants, support tissue composed of any of various kinds of hard woody cells. Mature sclerenchyma cells are usually dead cells that have heavily thickened secondary walls containing lignin. The cells are rigid and nonstretchable and are usually found in nongrowing regions of plant bodies, such as the bark or mature stems. Sclerenchyma is one of the three types of ground, or fundamental, tissue in plants.Sclerenchyma fibers can be found below the epidermis of monocotyledons, organized in two or three layers of cells. They are known as cortical fibers. Thus correct option is D.

Human sperm consists of a head and tail, the head carrying the genetic material and tail has mitochondria which derives the movement of sperm. It is very small in size (0.05mm) and a drop of serum contains millions of sperms. The human egg consists of genetic material along with core cytoplasm surrounding nucleus that has all the cellular components such as ribosomes, RNAs which are essential for protein synthesis and which ultimately gives rise to the whole body of an organism. Human egg measures 2cm against human sperm 0.05mm.

The egg size of Ostrich egg is 15cm, duck egg is typically larger than hen eggboth of which are roughly between 3-10cm. Human female egg is very small about 1-2cm and hence the smallest egg among all other options.