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Domains and Kingdoms The broadest category in the classification used by most biologists is the domain The most widely used biological classification system has six kingdoms and three domains The three domains are Bacteria, Archaea, and Eukarya The six kingdoms are Bacteria, Archaea, Protists, Fungi, Plantae, and Animalia • rRNA (ribosomal RNA) indicates archaea are more closely related to eukaryotes than bacteria-share a more recent common ancestor Domains and Kingdoms Domain Archaea Archaea are thought to be more ancient than bacteria Archaea are diverse in shape and nutrition requirements They are called extremophiles because they can live in extreme environments Archaea • • • • No peptidoglycan in cell walls Introns Unusual lipids in cell membranes Genes and rRNA that resembles eukaryote genes and rRNA Archaea Thermoacidophiles live in hot, acidic environments-hot springs, thermal vents Halophiles live in very salty environmentsGreat Salt Lake & Dead Sea Methanogens cannot live in the presence of O2-convert H gas and CO2 into methane Archaea Photosynthetic bacteria bacteria 9560x 3000x Domain Bacteria Prokaryotes whose cell walls contain peptidoglycan No introns Diverse group-can survive in many different environments Lipids in cell membranes Genes and rRNA unlike eukaryotes Gram Stain Bacteria are divided into 2 major groups Gram-negative-more complex cell wall, less peptidoglycan Gram-positive-simpler cell wall, more peptidoglycan Identifying Prokaryotes 3 main shapes Spherical = Cocci (chains-strepto, grape-like clusters-staphylo) Rod-shaped = Bacilli Spiral-shaped = Spirochetes Spirochetes Bacilli Cocci 400x 5460x 2000x Ecology of Bacteria Nutrient cycling Bacteria can be decomposers, returning vital nutrients to the environment. Nitrogen-fixing bacteria live in a symbiotic relationship in the root nodules of plants such as soybeans, clover, and alfalfa. Normal Flora Most of the bacteria that live in or on you are harmless and are called normal flora. 21,674x E. coli Foods and Medicines Some foods are made with the aid of bacteria. cheese yogurt buttermilk pickles vitamins Disease-causing Bacteria A small percentage of bacteria cause disease. Bacteria multiply quickly at the site of infection. Some bacteria secrete a toxin. Viruses A nonliving strand of genetic material within a protein coat No organelles to take in nutrients or use energy Cannot make proteins Cannot move Cannot replicate on their own Most viruses range in size from 5 to 300 nanometers. Viruses—An Exception Viruses do not possess cells, nor are they cells, and are not considered to be living. Because they are nonliving, they usually are not placed in the biological classification system. Viruses Domain Eukarya All eukaryotes are classified in Domain Eukarya. Domain Eukarya contains Kingdom Protista, Kingdom Fungi, Kingdom Plantae, and Kingdom Animalia. Kingdom Protista Protists are eukaryotic organisms that can be unicellular, colonial, or multicellular. Protists are classified into three different groups— plantlike, animallike, and funguslike. Protists All protists are eukaryotes. Some reproduce asexually by mitosis while others exchange genetic material during meiosis. Animal-like Protists Protozoans are heterotrophs and usually ingest bacteria, algae, or other protozoans. Introduction to Protists Plantlike Protists Plantlike protists make their own food through photosynthesis. Algae Funguslike Protists Funguslike protists absorb their nutrients from other organisms. Kingdom Fungi A fungus is a unicellular or multicellular eukaryote that absorbs nutrients from organic materials in its environment. Member of Kingdom Fungi are heterotrophic, lack motility, and have cell walls. Major Features of Fungi Cell wall composed of chitin Hyphae form a netlike mass called a mycelium. Hyphae provide a larger surface area for nutrient absorption. Major Features of Fungi Hyphae are divided into cells by cross-walls called septa. Septa allow nutrients, cytoplasm, and organelles to flow between cells. Some fungi are aseptate. Lichens Provide a symbiotic relationship between a fungus and an alga or a photosynthetic partner. A green algae or cyanobacterium provides food for both organisms. The fungus provides a web of hyphae in which the algae or cyanobacterium can grow. Lichens The fungus provides hyphae where the algae or cyanobacterium can grow. Kingdom Plantae Members of Kingdom Plantae form the base of all terrestrial habitats. All plants are multicellular and have cell walls composed of cellulose. Most plants are autotrophs, but some are heterotrophic. Kingdom Animalia All animals are heterotrophic, multicellular eukaryotes. Animal organs often are organized into complex organ systems. They live in the water, on land, and in the air.