Zoology

Zoology is the branch of biology in which we study animals

NUCLEUS

Nucleus contains most of the genes that control the cell. It is the most conspicuous organelle in the eukaryotic cell. Its average diameter is about 5. It performs two major functions: The information of DNA of nucleus is transcribed into RNA. This RNA is

ANIMAL SYSTEMATICS (CLASSIFICATION)

ANIMAL SYSTEMATICS (CLASSIFICATION) Following  groups used in animal classification: 1. Monophyletic Groups: The groups showing similarities due to single ancestors are called monophyletic groups. The classification based on monophyletic groups is called monophyletic classification. This classification show evolutionary relationship.  The species should have single

VACOULES AND VESICLES

Vacuoles and vesicles are membrane-enclosed sacs within the cell. But vacuoles are larger than vesicles. Vacuoles have various functions. They form food by phagocytosis. Many freshwater protists have contractile vacuoles These vacuoles pump excess water out of cell. Certain vacuoles are filled with pigments.

CENTRIOLES AND MICROTUBULE ORGANIZING CENTERS

Microtubule-organizing centers The specialized non membranous regions of cytoplasm near the nucleus are the microtubule-organizing centers. These centers contain dense material. This material gives rise to a large number of microtubules. These micotubules have different functions in the cytoskeleton. Centrioles One type of center

THE CYTOSKELETON

The cytoskeleton is a network of fibers suspended through the cytoplasm. There are three fibers in the cytoskeleton. These are microtubuies, microfilaments and intermediate filaments. Functions of Cytoskeleton – The cytoskeleton performs following functions in the organisms: They give mechanical support to the cell

MITOCHONDRIA

Mitochondria are commonly called as power house of the cell. They provide energy transuding system. This system is used to change the food into chemical energy by oxidative phosphorylation ATP is synthesized during oxidative phosphorylation. Structure of Mitochondria Mitochondria are rod shaped. Their diameter

LYSOMES

Lyso ome is a membrane-enclosed bag of hydrolytic enzymes that the cell uses to digest macromolecules. The lysosomal enzymes can hydrolyze prote ns. polysaccharides, fats, and nucleic acid. These enzymes work best in acidi environment at about pH 5. The lysosomal membrane maintains this

THE GOLGI APPARATUS

The Golgi apparatus consists of flattened membranous sacs. They look like a stack of pita bread. A cell may have several interconnected stacks. Each cisterns in a stack consists of a membrane. This membrane separates its internal space from the cytosol. Vesicles concentrated near

THE ENDOPLASMIC RETICULUM (ER)

The word endoplasmic means “within” the cytoplasm. The word reticulum means “network.” The ER consists of a network of membranous tubules and sacs called cisternae. The ER are extensive in the cell. They are composed of more than half of the total membrane in

RIBOSOMES

Ribosomes are non-membranous bounded strOctures. Ribosomes are the sites where the cell synthesizes proteins according to genetic instructions. A bacterial cell may have a few thousand ribosomes.But a human liver cell has a few million ribosomes. Cells hat have high protein synthesis have a