Tema 2 Moneras, Protoctistas, Hongos PDF

# TEMA 2 MONERAS, PROTOCTISTAS, HONGOS The kingdom of moneras, protists and fungi includes the simplest living organisms that were the first to appear on Earth. ## 1. THE KINGDOM OF MONERAS * **Bacteria** belong to this kingdom. * Bacteria are microscopic, unicellular organisms with **prokaryotic...

# TEMA 2 MONERAS, PROTOCTISTAS, HONGOS The kingdom of moneras, protists and fungi includes the simplest living organisms that were the first to appear on Earth. ## 1. THE KINGDOM OF MONERAS * **Bacteria** belong to this kingdom. * Bacteria are microscopic, unicellular organisms with **prokaryotic cells** (without a nucleus). * Bacteria were the first living organisms to appear on Earth. * Bacteria can live in all places on the planet and in very harsh conditions. * Bacteria usually live alone, but sometimes they can form colonies. * The resistance of bacteria to all types of environments is due to their structure. Bacteria have many protective layers. ### 1.1. Structure of bacteria A bacterium is a very simple prokaryotic cell. It does not have a nucleus or organelles. It is composed of: * **Plasma membrane:** Similar to the eukaryotic cell membrane, it delimits the interior of the cell and allows the passage of substances to the interior. * **Bacterial cell wall:** It is a rigid layer that surrounds the membrane. It gives shape and protects the bacterium. * **Bacterial capsule:** Not all bacteria have it. It is a thin layer that surrounds the cell wall. It is composed of sugars and water. * **Cytoplasm:** It is the liquid content of the cell. It contains water and dissolved substances. Vital processes of the cell occur in it. * **Genetic material:** It is DNA, a long molecule that is coiled up and stores the information of the cell. The DNA is free in the cytoplasm, so there is no nucleus encapsulating it. * **Flagella:** Some bacteria have extensions called flagella that help them move. **There are 4 types of bacteria classified by their shape:** * **Cocci** * **Bacilli** * **Spirilla** * **Vibrios** ### 1.2. Nutrition of bacteria Bacteria can be: * **Heterotrophic:** They feed on other living organisms. There are 3 types of heterotrophic bacteria: * **Parasites:** They feed on a living organism, causing it damage. Example: Cholera bacterium. * **Decomposers:** They feed on remains of living organisms, decomposing them. * **Symbionts:** They live associated with another living organism, benefiting mutually. For example, the bacteria that form the gut microbiota. They feed on our food and in return, they help us digest and produce vitamins. * **Autotrophic:** They carry out photosynthesis. Example: Blue-green bacteria or cyanobacteria. ### 1.3. Reproduction and relationships of bacteria * Bacteria reproduce by **binary fission**, meaning they split in half to form two daughter bacteria. * They grow until they reach the proper size to divide again. * The process is so fast that bacteria can divide every 30 minutes. * In terms of relationships with other bacteria, they can perceive harmful or beneficial substances and approach or flee from them. * Some bacteria can form **resistance spores** when environmental conditions are unfavorable. They are surrounded by a thick wall and remain "hibernating" until conditions improve. ## 2. KINGDOM OF PROTISTS Prototists are formed by eukaryotic cells. * Most of them are unicellular. Multicellular prototists form groups of independent cells called colonies. * They do not have tissues. * They are classified into two groups: protozoa and algae. ### a. Protozoa * Protozoa are formed by eukaryotic cells similar to those of animals, which is why it is thought that the animal kingdom originated from protozoa. * They are heterotrophic and live in aquatic environments, both fresh and salt water. * Some live freely and others are parasites. * The set of protozoa that live floating in the water form the **zooplankton**, which is food for fish and other marine animals. **There are 4 groups of protozoa, classified according to their mode of movement:** * **Flagellates:** They have a long extension called a flagellum to move. * **Ciliates:** They have many short extensions, cilia, which they use as oars to move. * **Rhizopods:** They move by extensions of their cytoplasm called pseudopods. * **Sporozoans:** They do not move, because they do not have flagella, cilia or pseudopods. They are parasites. Example: Plasmodium causes malaria ### b. Algae. * Algae are also eukaryotes. * Their cells are similar to those of plants, as they have cell walls and chloroplasts. * If protozoa originated the animal kingdom, algae originated the plant kingdom. * Algae are autotrophic, as they carry out photosynthesis. * They can be unicellular or multicellular, but they lack tissues. * All algae are aquatic, both marine and freshwater. * Unicellular algae that float in the water form the **phytoplankton**, the base of the food chain in aquatic environments. * According to the pigments they have to carry out photosynthesis, there are green, brown and red algae. ## 3. Importance of micro-organisms Micro-organisms, whether protists or moneras, live everywhere and carry out very important functions. They can be: * **Beneficial microorganisms:** * **Decomposers:** They decompose remains of living organisms, converting them into mineral salts that return to the soil. Thanks to them, the soil regains its inorganic nutrients and plants can absorb them to carry out photosynthesis. * **Plankton:** Formed by zooplankton and phytoplankton. It is the base of the food chain in aquatic environments: oceans, lakes, rivers, etc. * **Intestinal microbiota:** They are beneficial bacteria that live in our intestines. They help us digest and produce vitamins. * **Microorganisms used to make food**, such as yogurt bacteria. * **Harmful microorganisms:** * They are also called **pathogens** because they cause diseases. Example: bacteria that causes pneumonia, meningitis, measles virus, AIDS, etc. ## 4. The Kingdom of Fungi Fungi have their own characteristics: * **Heterotrophic:** Unlike plants, they feed on other organisms. If they feed on remains of dead organisms, they are called **saprophytes**. If they feed on a living organism, causing it damage, they are called **parasites**. * **Unicellular or multicellular:** But they never have true tissues. * **Eukaryotic cells:** With a nucleus. * **They have a cell wall:** However, it is not made of cellulose, as in plant cells. * **Their body is formed by filaments of joined cells:** These filaments are called **hyphae**. A fungus is formed by many hyphae. The set is called **mycelium**, and it is usually buried in the ground. * **They reproduce by spores.**