Lecture 17 biology 2

Lecture 17 biology 2 - Osmoregulation and the Excretory...

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Osmoregulation and the Excretory System Osmotic equilibrium 1. Gain ions from the outside environment Hypertonic environment 2. Lose water to the outside environment “Dry out” in water Excretory system I. Maintaining homeostasis I. Osmoregulation —controlling water and ionic balance II. Nitrogenous wastes III. Excretory system I. Components II. Kidneys I. Structure II. How they work III. Urine
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What does the excretory system do? • FUNDAMENTAL CHALLENGES – Homeostasis (steady state physiological condition) : maintaining desired water and ion balance • Movement of water and solutes (substances dissolved in water) – Keep the good stuff, get rid of the bad stuff • Water, nutrients, vitamins, salts, nitrogenous waste • Varies by habitat: fresh- vs. saltwater; land vs. water • How do efficiently? Dealing with water • Marine environments – Hypertonic for most vertebrates • Concentrated urine with lots of salt, little water • Freshwater environments – Hypotonic (dilute urine with few salts) • Terrestrial environments – Desiccation • Skin, exoskeleton, waxy cuticle, shells, etc.
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Excretion of Nitrogenous Wastes (= compounds containing nitrogen) Are the by-products of breaking down of proteins and amino acids. These are excreted as different chemicals depending on the habitat of the animals -- Ammonia -- Urea -- Uric acid Classes of compounds used to excrete nitrogenous wastes 1. —a very small and toxic molecule (NH 4 ) Soluble in water Because of its toxicity it can
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Lecture 17 biology 2 - Osmoregulation and the Excretory...

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