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Hierarchy in Biology

Hierarchy in Biology. Atom  Molecule  Organelle  Cell  Tissue  Organ  Organ System Ex. H  H 2 O  Mitochondrion  Muscle Cell  Muscle  Heart  Circulatory System. Tissue ~ group of cells that perform similar fxns

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Hierarchy in Biology

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  1. Hierarchy in Biology • Atom  Molecule  Organelle  Cell  Tissue  Organ  Organ System • Ex. H  H2O  Mitochondrion  Muscle Cell  Muscle  Heart  Circulatory System

  2. Tissue ~ group of cells that perform similar fxns • Organ ~ several types of tissues that work together to perform one fxn • Organ System ~ a group of organs that work together to perform a vital body fxn

  3. Digestive System • Must accomplish the following tasks: • Ingestion – food intake • Digestion – food  nutrients • Absorption – nutrients  blood • Egestion – waste eliminated from the body • Simple animals – gastrovascular cavity • Food enters and exists though one cavity • Complex animals – digestive tract • Two opening cavity – food enters and exists seperately • Humans – gastrointestinal (GI) tract • 7 m – 9 m long!!!

  4. Human Digestive Tract • Tube that is open at both ends (mouth to anus) • Inner surface of the tract is continuous with the outer surface of the body •  contents are still technically part of the external environment! • Primary Structures: mouth, pharynx, esophagus, stomach, small/large intestines, and anus.

  5. Mouth and Stomach MOUTH • Food is acquired through ingestion. • Mouth is involved in both mechanical and chemical digestion. • Teeth chew food (mechanical) and mix it with saliva (chemical)

  6. TEETH Incisors – blade-like teeth, biting Canines – shredding and tearing Pre-molars and molars - grinding

  7. Saliva contains amylase (an enzyme that breaks down starch into simple sugars) • The bolus of food passes through the pharynx - a cavity that connects the mouth to the esophagus, nose, and trachea (wind pipe). • The bolus is prevented from entering the trachea by the epiglottis (trap door).

  8. The esophagus, is a muscular tube that takes food from the throat and pushes it down into the stomach. • It moves food by peristalsis – a wave of muscle contractions and relaxations

  9. STOMACH • Has a thick muscular wall that contracts to mash the food into a sloppy soup called chyme ("kime"). (mechanical) • Stomach lining produces strong digestive juices that chemically attack the food to break it down and dissolve its nutrients. (chemical) • Hydrochloric acid, and a protein called pepsinogen, are secreted • HCl gives the stomach a pH of about 2 • which also kills any ingested microbes that may be harmful! • Pepsinogen is activated by the acid to become pepsin ~an enzyme that breaks down proteins into polypeptides)

  10. Two valves control passage of food into and out of the stomach: • Pyloric Sphincter - opening to the small intestine • Gastroesophageal Sphincter - opening b/w esophagus and stomach • Damage can cause "heartburn“ – where acidic contents move back into esophagus • A layer of mucus lines the stomach to protect if from the acidity.

  11. Ulcers: ~ Occur when the mucus barrier of the stomach breaks down and the acid erodes a hole in the stomach. • Smoking and stress may be increase likeliness of getting ulcers. • A bacteria (Heliobacterpylori) is present in many people with ulcers. Thus, antibiotics often help eliminate ulcers. • Treatment can also include antacids.

  12. HWK • Sketch a diagram to explain how ingested food is really still part of the outside world. • What are two fxns of HCl in the stomach? • Page 411 # 1 - 5

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