The Knowledge

Movements across plasma membrane/How molecules move through plasma membrane? Membrane allows specific substances to cross through it (selective permeability).This feature prevent harmful substances to enter inside. There are different types of movements by which molecules enter or exit the cell. We will discuss on each type one by one. 1.Simple diffusion Spontaneous molecular motion triggers the molecules to move randomly from an area of higher concentration to an area of lower concentration. The molecules continue to move until they are equally distributed on both sides and they reach dynamic equilibrium. This type of movement of molecules is called simple diffusion. (L. diffundere , to spread).This type of movement occurs mostly for short-distance transport of substances moving in or out of the cell.  Related topics: Facilitated Diffusion

Cell membrane/Plasma membrane Difference between cell membrane and plasma membrane: Plasma membrane and cell membrane are quite different terms used in biology. These are the differences between plasma membrane and cell membrane. Cell membrane Plasma membrane It sorrounds the cell. It sorrounds the cell organelles. Cell membrane has initial receptors for signalling and is the first step in signalling. Plasma membrane is not first step but is involved in signalling. It can be transformed and is involved in movement in organisms such as amoeba. It cannot be transformed.. During the cell division, It plays an important role in cytoktnesis (division of cytoplasm). Plasma membrane does not play an important role in cytokinesis. It contains cilia for feeding and locomotion. It does not contain cilia.   Cell membrane Cell membrane sor

  Why are most cells small? Most cells(See  cells ) are small and can be seen only with the aid of a microscope. (Exceptions include egg of most vertebrate [fishes, amphibians, reptiles, and birds] and long some nerve cells.) One reason for the smallness of cells is that the ratio of the volume of the cell’s nucleus to the volume of its cytoplasm must not be so small that the nucleus, the cell’s major control center, can not control the cytoplasm. Another aspect of cell volume works to limit cell size, as the radius of a cell lengthens, cell volume increases more rapidly than cell surface area.The need   for nutrients and the rate of waste production are proportional to cell volume.The cell takes up nutrients and eliminates wastes through its surface plasma membrane.If cell volume becomes to large, the surface area to-volume ratio is too small for an adequate exchange of nutrients and wastes.

What are cells? Cells   Cells are the organizational units of life.In other words we can say that cells are fundamental units of life,in which all of the chemical reactions necessary for the maintenance and reproduction   of life takes place.Because all animals are made of cells,the cell is as fundamental to an understanding of zoology as atom is to an understanding of chemistry.Cells are smallest independent units of life.Structurally speaking,cells are either prokaryotic are eukaryotic. Types of cells on the basis of structure  There are two types of cells on the basis if structure. Prokaryotic cell Eukaryotic cell    Difference between prokaryotes and eukaryotes      All prokaryotes (“before nucleus”) are independent,single-celled organisms(e.g.,bacteria)The word “prokaryote” describe cells in which DNA is localized in a region but is not bound by a membrane.                                                                                                                          

Cichlids Cichlid is a large group of fish that is found in Africa with 1000 species, Central and South America with 300 species, India   with 3 species and North America with 1 species. The member of this group have enormous variety of color patterns, habitats and body forms. Ichthyologists have described a wide variety of feeding habits in cichlids. These fish include algae scrapers, like Eretmodus, that nip food with chisel-like teeth; insect pickers, like Tanganicodus; and snail eaters All cichlids have two pairs of jaws. The mouth jaws are used for scraping or nipping food and throat jaws are used for crushing or macerating food before it is swallowed. Many cichlid mouth brood their young. A female takes egg into her mouth after the eggs are spawned. She then inhales sperms released by male, and fertilization and development takes place within the female’s mouth! Even after the eggs hatch, younger are taken into the mouth of female if danger threatens. Hundreds of variations i

Define Zoology Zoology (From Greek,zoon,+logous,to study) is the study of animals.It is a broad field of science because there is immense variety of animals and complexity occuring within them.Zoologists are specialized in specific subdisciplines.Ichthyology,for example ,is th e study of fishes,and ichthyologists study deeply the function,ecology,structure and evolution of fishes.These studies have uncovered   an amazing diversity of fishes.One large group of fishes known as cichlids is found in africa(1000 species),Central South America (300 species),India (3 species) and North America (1 species).Different color patterns,habitats and body forms are   found among species of this group of fishes. Subdisciplines/fields/branches that are studied in zoology are as under: Anatomy: It is the study of internal structure of entire organisms and their body parts. Cytology: It is the study of structure and function of cells. Ecology: It is the study of interaction between orgsnisms