All the organisms of this kingdom are prokaryotes. Monera are considered as the most primitive group of organisms. They include various types of bacteria and blue-green algae. Bacteria were the first organisms to evolve on planet earth after life originated around 3.5 billion years ago and were the only organisms on earth for almost the next two billion years. They have circular chromosome.
Structure of a Bacterial Cell
The single celled bacterium has a cell wall made of compound peptido-glycan covering the cell membrane. It consists following parts;
Cell wall: All prokaryotes have a rigid cell wall, which protects cell from bursting in a hypotonic medium and gives shape to the cell. The cell wall is made up of a chemical, glycoprotein murein.
Pill: Pili are short and smaller than flagella like structures projecting out from the cell wall and help in reproduction during conjugation.
Flagella: Some bacteria move with the help of one or two flagella and are a rigid rotating tail. It helps the cell to move in clockwise and anticlockwise, forward and also helps the cell to spin.
Plasma Membrane: Plasma membrane, present below the cell wall and made up of lipids and protein. The main function of cell wall is it helps in providing support, mechanical strength and rigidity to cell.
Genetic Material: Single, double stranded, circular DNA is located in a region of the cytoplasm called nucleoid. Bacteria do not have true nucleus (prokaryotes), many bacteria have rings of DNA called plasmids which replicate and form antibiotic resistance for genes.
Cell Organelles: Endoplasmic reticulum, mitochondria, chloroplast, Golgi complex is absent. Only ribosomes are present.
Monera - General Body Functions
Asexual Reproduction: Binary fission; occurs during favourable conditions, DNA of the nucleoid replicates while still attached to the mesosome and mesosome develops and gets attached to the new molecule of DNA, the cell wall and cell membrane start growing inwards from near the middle of the dividing cell and cell is divided into two, each with one daughter nucleoid.
Sexual Reproduction: Conjugation is the process by which one bacterium transfers genetic material to another through direct contact. During conjugation, one bacterium serves as the donor of the genetic material, and the other serves as the recipient.