Nutrition, Osmoregulation & Excretion (Reference- chapters 41, 44)

Transcription

1 Nutrition, Osmoregulation & Excretion (Reference- chapters 41, 44)

2 The Need to Feed Food is taken in, taken apart, and taken up in the process of animal nutrition In general, animals fall into three categories Herbivores eat mainly plants and algae Carnivores eat other animals Omnivores regularly consume animals as well as plants or algae Most animals are opportunistic feeders

3 Nutrition An animal s diet must provide Chemical energy for cellular processes Organic building blocks for macromolecules Essential nutrients

4 Essential Nutrients Materials that an animal cannot assemble from simpler organic molecules are called essential nutrients, and must be obtained from diet Essential amino acids- meat, eggs, and cheese provide all essential amino acids and are thus complete proteins Essential fatty acids- include certain unsaturated fatty acids; fatty acid deficiencies are rare Vitamins- organic molecules required in the diet in very small amounts Minerals- simple inorganic nutrients, usually required in small amounts

5 Food processing: ingestion, digestion, absorption, and elimination 1 INGESTION Mechanical digestion 2 3 DIGESTION ABSORPTION Chemical digestion (enzymatic hydrolysis) Nutrient molecules enter body cells 4 ELIMINATION Undigested material

6 Suspension Feeding Many aquatic animals are suspension feeders, which sift small food particles from the water Filter feeding Baleen

7 Substrate Feeders Substrate feeders are animals that live in or on their food source Caterpillar Feces

8 Fluid Feeders Fluid feeders suck nutrient-rich fluid from a living host

9 Bulk Feeders Bulk feeders eat relatively large pieces of food

10 Digestion is the process of breaking food down into molecules small enough to absorb Mechanical digestion, such as chewing, increases the surface area of food Chemical digestion splits food into small molecules that can pass through membranes; these are used to build larger molecules In chemical digestion, the process of enzymatic hydrolysis splits bonds in molecules with the addition of water

11 Figure 41.8 Esophagus Crop Gizzard Intestine Pharynx Mouth Anus (a) Earthworm Foregut Midgut Hindgut Rectum Esophagus Anus Mouth Crop Gastric cecae Stomach Gizzard (b) Grasshopper Mouth Intestine Esophagus Crop Anus (c) Bird

12 Digestion in Mammals The mammalian digestive system consists of an alimentary canal and accessory glands that secrete digestive juices through ducts Mammalian accessory glands are the salivary glands, the pancreas, the liver, and the gallbladder Food is pushed along by peristalsis, rhythmic contractions of muscles in the wall of the canal Valves called sphincters regulate the movement of material between compartments

13 Figure 41.9 Tongue Oral cavity Salivary glands Pharynx Esophagus Liver Sphincter Gallbladder Sphincter Pancreas Stomach Small intestine Large intestine Rectum Duodenum of small intestine Anus

14 Absorption in the Small Intestine The small intestine has a huge surface area, due to villi and microvilli that are exposed to the intestinal lumen The enormous microvillar surface creates a brush border that greatly increases the rate of nutrient absorption Transport across the epithelial cells can be passive or active depending on the nutrient

15 Figure 41.14a LUMEN OF SMALL INTESTINE Epithelial cell Triglycerides Fatty acids Monoglycerides 1 Triglycerides are broken down to fatty acids and monoglycerides by lipase. Triglycerides 2 Monoglycerides and fatty acids diffuse into epithelial cells and are reformed into triglycerides.

16 Evolutionary adaptations of vertebrate digestive systems correlate with diet Dentition, an animal s assortment of teeth, is one example of structural variation reflecting diet Carnivore Herbivore Omnivore Incisors Canines Premolars Molars

17 Stomach and Intestinal Adaptations Many carnivores have large, expandable stomachs Small intestine Herbivores and omnivores generally have longer alimentary canals than carnivores, reflecting longer time to digest vegetation Small intestine Carnivore Stomach Cecum Colon (large intestine) Herbivore

18 Mutualistic Adaptations Some intestinal bacteria produce vitamins; intestinal bacteria also regulate the development of the intestinal epithelium and immune function Scientists have found more than 400 bacterial species in the human digestive tract H. pylori

19 Mutualistic Adaptations in Herbivores Many herbivores have fermentation chambers, where mutualistic microorganisms digest cellulose The most elaborate adaptations for an herbivorous diet have evolved in the animals called ruminants Reticulum Rumen Esophagus 3 Intestine 2 Omasum Abomasum 4 1

20 Regulation of Digestion Each step in the digestive system is activated as needed The enteric division of the nervous system helps to regulate the digestive process The endocrine system also regulates digestion through the release and transport of hormones

21 Regulation of Energy Storage The body stores energy-rich molecules that are not needed right away for metabolism In humans, energy is stored first in the liver and muscle cells in the polymer glycogen Excess energy is stored in fat in adipose cells When fewer calories are taken in than expended, the human body expends liver glycogen first, then muscle glycogen and fat

22 Figure 41.UN04 Veins to heart Hepatic portal vein Lymphatic system Liver Mouth Esophagus Stomach Lipids Absorbed food (except lipids) Absorbed water Secretions from salivary glands Secretions from gastric glands Small intestine Secretions from liver Secretions from pancreas Anus Large Rectum intestine

23 Osmoregulation Physiological systems of animals operate in a fluid environment Relative concentrations of water and solutes must be maintained within fairly narrow limits Osmoregulation controls solute concentrations and balances water gain and loss

24 Water enters and leaves cells by osmosis Osmolarity (solute concentration of a solution) determines movement of water across a membrane If two solutions are iso-osmotic, water molecules cross the membrane at equal rates in both directions If two solutions differ in osmolarity, net flow of water is from the hypo-osmotic to the hyper-osmotic solution

25 Figure 44.2 Selectively permeable membrane Solutes Water Hyperosmotic side: Higher solute concentration Lower H 2 O concentration Hypoosmotic side: Lower solute concentration Higher H 2 O concentration Net water flow

26 Osmoregulatory Challenges and Osmoconformers (only some marine animals) are iso-osmotic with their surroundings and do not regulate osmolarity Osmoregulators expend energy to control water uptake and loss in a hyperosmotic or hypoosmotic environment Mechanisms

27 Most animals are stenohaline; they cannot tolerate substantial changes in external osmolarity Euryhaline animals can survive large fluctuations in external osmolarity

28 Marine Animals Most marine invertebrates are osmoconformers Many marine vertebrates and some marine invertebrates are osmoregulators Marine bony fishes are hypo-osmotic to seawater They balance water loss by drinking large amounts of seawater and eliminating the ingested salts through their gills and kidneys

29 Figure 44.4a Osmoregulation in a marine fish Gain of water and salt ions from food Excretion of salt ions from gills Osmotic water loss through gills and other parts of body surface SALT WATER Key Water Salt Gain of water and salt ions from drinking seawater Excretion of salt ions and small amounts of water in scanty urine from kidneys

30 Freshwater Animals Freshwater animals constantly gain water by osmosis from their hypo-osmotic environment Lose salts by diffusion and maintain water balance by drinking almost no water and excreting large amounts of dilute urine Salts lost by diffusion are replaced in foods and by uptake across the gills

31 Figure 44.4b Osmoregulation in a freshwater fish Gain of water and some ions in food Uptake of salt ions by gills Osmotic water gain through gills and other parts of body surface Key Water Salt FRESH WATER Excretion of salt ions and large amounts of water in dilute urine from kidneys

32 Animals That Live in Temporary Waters Some aquatic invertebrates in temporary ponds lose almost all their body water and survive in a dormant state (anhydrobiosis) 50 µm Hydrated tardigrade Dehydrated tardigrade

33 Land Animals Reducing water loss is key to survival on land Body coverings of terrestrial animals limit dehydration Desert animals get water savings behaviors such as a nocturnal lifestyle Land animals maintain water balance by eating moist food and producing water metabolically through cellular respiration

34 Energetics of Osmoregulation Osmoregulators must expend energy to maintain osmotic gradients The amount of energy differs based on How different the animal s osmolarity is from its surroundings How easily water and solutes move across the animal s surface Work required to pump solutes across the membrane

35 Excretion The type and quantity of an animal s waste products can greatly affect water balance Among the most significant wastes are nitrogenous products of protein breakdown Animals excrete nitrogenous wastes in different forms: ammonia, urea, or uric acid (differ in toxicity and the energy costs of producing them)

36 Figure 44.7a Most aquatic animals, including most bony fishes Mammals, most amphibians, sharks, some bony fishes Many reptiles (including birds), insects, land snails Ammonia Urea Uric acid

37 Excretory Processes Most excretory systems produce urine by refining a filtrate derived from body fluids Key functions of most excretory systems Filtration: Filtering of body fluids Reabsorption: Reclaiming valuable solutes Secretion: Adding nonessential solutes and wastes to the filtrate Excretion: Processed filtrate containing nitrogenous wastes is released from the body

38 Excretory systems Flatworms have protonephridia- a network of deadend tubules connected to external openings Each segment of an earthworm has a pair of openended metanephridia In insects and other terrestrial arthropods, Malpighian tubules remove nitrogenous wastes from hemolymph and function in osmoregulation

39 Kidneys Kidneys, the excretory organs of vertebrates, function in both excretion and osmoregulation The many tubules of kidneys are highly organized The vertebrate excretory system also includes ducts and other structures that carry urine from the tubules out of the kidney and out of the body

40 Figure 44.12a Excretory Organs Kidney Structure Nephron Types Renal artery and vein Kidney Renal artery Renal vein Ureter Urinary bladder Urethra Ureter

41 Solute Gradients and Water Conservation The mammalian kidney s ability to conserve water is a key terrestrial adaptation Hyperosmotic urine can be produced only because considerable energy is expended to transport solutes against concentration gradients The two primary solutes affecting osmolarity are NaCl and urea

42 Adaptations of the Vertebrate Kidney to Diverse Environments Variations in nephron structure and function equip the kidneys of different vertebrates for osmoregulation in various habitats

43 Case Study: Kidney Function in the Vampire Bat The South American vampire bat feeds at night on the blood of large birds and mammals, and can alternate rapidly between producing large amounts of dilute urine and small amounts of very hyperosmotic urine

44 Birds and Other Reptiles Birds conserve water by excreting uric acid instead of urea Other reptiles reabsorb water from wastes in the cloaca

45 Freshwater Fishes and Amphibians Freshwater fishes conserve salt and excrete large volumes of very dilute urine Kidney function in amphibians is similar to freshwater fishes Amphibians conserve water on land by reabsorbing water from the urinary bladder

46 Marine Bony Fishes Marine bony fishes are hypoosmotic compared with their environment Kidney filtration rates are low, and very little urine is excreted

47 Hormonal circuits link kidney function, water balance, and blood pressure Mammals control the volume and osmolarity of urine in response to changes in salt intake and water availability A combination of nervous and hormonal controls manages the mammalian kidney, and also contribute to homeostasis for blood pressure and blood volume

48 Antidiuretic Hormone Antidiuretic hormone, ADH, regulates water conservation Osmoreceptor cells in the hypothalamus monitor blood osmolarity and regulate release of ADH from the posterior pituitary When osmolarity rises above its set point, ADH release into the blood stream increases ADH reduces urine volume and lowers blood osmolarity Alcohol is a diuretic as it inhibits the release of ADH

49 Figure 44.UN02 Animal Inflow/Outflow Urine Freshwater fish. Lives in water less concentrated than body fluids; fish tends to gain water, lose salt Does not drink water Salt in H 2 O in (active transport by gills) Large volume of urine Urine is less concentrated than body fluids Marine bony fish. Lives in water more concentrated than body fluids; fish tends to lose water, gain salt Terrestrial vertebrate. Terrestrial environment; tends to lose body water to air Salt out Drinks water Salt in H 2 O out Salt out (active transport by gills) Drinks water Salt in (by mouth) H 2 O and salt out Small volume of urine Urine is slightly less concentrated than body fluids Moderate volume of urine Urine is more concentrated than body fluids