kingdom monera.... classification of living things

Kingdom Monera

Characteristics

All organisms in the Kingdom Monera are prokaryotes. They lack nuclei (don’t have nucleus membrane)  and organelles and most of their cell walls are made of peptidoglycan. Most utilize flagella for movement.

Digestion is extracellular (outside the cell) and nutrients are absorbed into the cell. Many prokaryotes are organized by how the metabolize resources.

Classification based on obtaining food:

·        Autotrophs- make their own food

·        Heterotrophs- obtain their energy by feeding on other organic substances.

REPRODUCTION

Most organisms in the Kingdom Monera reproduce through

·        binary fission (asexual) 

·        conjugation (sexual)

This Kingdom is divided into:

o   Bacteria

o   Cyanophyta (Blue-green algae)

Bacteria:
Bacteria belong to group Eubacteria are small, relatively simple, single-celled organisms. Some bacteria can be photosynthetic, using H₂S rather than H₂O, as a source of electrons, but most are heterotrophic, absorbing nutrients from the surrounding environment.

Bacteria do not have chromosomes. Instead, their genetic material is a single circular loop of DNA (Figure 1).

They reproduce by the process of "binary fission", where the cell duplicates its components and divides into two cells (Figure 2). In other words, the cell pinches into two without the complex movement of chromosomes seen in mitosis. Newly produced cells usually become independent, but they may remain attached in linear chains or grapelike clusters. In favourable environments, individual bacterial cells rapidly proliferate, forming colonies consisting of millions of cells.

 Figure 1: Typical prokaryotic cell (non-photosynthetic bacterial cell).

Figure 2: Binary fission in bacteria.

Microscopic examination of bacterial cells reveals that most bacteria can be classified according to three basic shapes:

·         bacilli (rods), is divided into:

-          Monobacilli – single rod

-          Diplobacilli – pair of rods

-          Streptobacilli- Join together to form a structure resembling a chain

·         cocci (spheres), is divided into:

-          Monococcus – single spheres

-          Diplococcus – pair of spheres

-          Sarcina – spherical bacteria which make a group of 4 to form a cube

-          Streptococcus – a long structure resembling a chain

-          Staphylococcus – a colony to form a structure resembling grapes.

·         spirilla (spiral), is divided into:

-          Spiral

-          Vibro / comma

-          Spirochetes – have a spiral shape that can move

Figure 3: Bacterial types.

Most bacteria in this group are heterotrophic, which means that they derive their energy from organic molecules made by other organisms. Many heterotrophic bacteria are important in the ecosystem as decomposers because they feed on dead organic matter and release nutrients locked in dead tissues. Other heterotrophs are parasites, often referred to as pathogens. They cause many of the diseases of plants and animals, including those of humans.

·        Example of Useful and Pathogenic Bacteria

·        Useful bacteria:

Acetobacter xylinum – making nata de coco

Acetobacter sp – making alcohol into vinegar acid

·        Pathogenic bacteria:

Salmonella typhii – typhoid disease

Vibrio comma – cholera disease

Cyanobacteria

Cyanobacteria are commonly known as blue-green algae. They are autotrophic, which means that they derive their energy from photosynthesis or the oxidation of inorganic molecules. In addition to chlorophyll, they contain phycocyanin (blue) and phycoerythrin (red). Because of various proportions of these pigments, only about half of cyanobacteria are actually blue-green in color; many range in color from brown to olive green. They live in aquatic environments and moist soil.. As far as is known, reproduction in the cyanobacteria is by fission only.

The cells of the cyanobacteria are prokaryotic but reveal a considerable level of complexity (see Figure 4). Their chlorophyll is integrated into thylakoids, extensions of the cell membrane. Actually, the entire photosynthetic cell is comparable to a eukaryotic chloroplast. Photosynthesis in the cyanobacteria is nearly identical, biochemically, to that of the algae and the green plants. Like the algae and plants, their photosynthetic pigments include chlorophyll a and the accessory pigment beta-carotene, although they lack chlorophyll. The glucose produced by the cyanobacteria in the process of photosynthesis is stored in their own form of starch, which is similar to animal glycogen. These characteristics make cyanobacteria predecessors of the eukaryotic chloroplasts.

Figure 4: Typical cell of cyanobacteria.

A number of cyanobacteria produce specialized, nitrogen-fixing cells called heterocysts. Their role is to incorporate atmospheric nitrogen into a form useful for producing amino acids and other nitrogen containing molecules. Some cyanobacteria also produce spores (akinetes) that are resistant to drying. These spores allow cyanobacteria to survive unfavorable environmental conditions. 

Example of Cyanophyta:     Spirulina

                                                Anabaena