Nutrition Autotroph an organism that produces complex organic

Nutrition • Autotroph – an organism that produces complex organic compounds from simple inorganic molecules, using energy from light or inorganic chemical reactions – The producers in a food web • Heterotroph – an organism that obtains energy by breaking down organic molecules; cannot derive energy from photosynthesis or inorganic chemicals – The consumers in a food web

Nutrition • Autotrophs – Plants – Some Protists – Some Bacteria – Nearly all Archaea • Heterotrophs – Animals – Fungi – Most Protists – Most Bacteria

Plant Nutrition • Plants, like animals, require nutrients • Plants acquire nutrients through photosynthesis and from the soil • Soil – the highly weathered outer layer of the Earth’s crust – A mixture of sand, rocks, clay, silt, minerals an microorganisms – The Earth’s crust include ~92 elements • Most in the form of inorganic compounds called minerals

Plant Nutrition • Soil is composed of minerals, organic matter, water, air, and organisms • Soil is full of microorganisms that break down and recycle organic debris • Most roots of plants are found within the topsoil – Topsoil – a mixture of minerals, living organisms and humus (partly decayed organic matter)

Plant Nutrition

Plant Nutrition • Only minerals that are dissolved in water are available for uptake by roots • Approximately one half of the soil volume is occupied by spaces known as pores, which may be filled with air or water • Water held in small pores is readily available to plants

Plant Nutrition

Plant Nutrition • If topsoil is lost, the water-holding capability and nutrient content of the soil are adversely affected • >50 billion tons of topsoil are lost from fields in the US every year! • The “Dust Bowl” of the 1930 s was a dramatic example of what can happen when the vegetative cover of soil is disrupted

The “Dust Bowl” • Southwestern Great Plains of the U. S. in the 1930’s • Poor farming practices combined with several years of drought enhanced wind erosion dust storms

Plant Nutrition • Acidic (low p. H) and saline (“salty”) soils are challenging habitats for plants • The p. H of a soil affects the release of minerals from weathering rock; at low p. H, toxic elements may “leech” from rocks • Most plants grow best at a neutral p. H (~7) • Saline soils are caused by excess accumulation of salts (Na+, Cl-) • Excess salt makes it more difficult for plant to absorb soil moisture

Plant Nutrition • Plants require 9 macronutrients and 7 micronutrients – Macronutrients – used by plant in large quantities – Micronutrients – used by plant in trace amounts – Carbon, oxygen, hydrogen, nitrogen (essential for amino acids), potassium, calcium, magnesium (the center of the chlorophyll molecule), phosphorus, and sulfur

Plant Nutrition • Plants require ammonia (NH 3) or nitrate (NO 3 -) to build amino acids • Most of the nitrogen in the atmosphere is in the form of Nitrogen gas, N 2 • Plants lack the ability to convert N 2 to ammonia, but some bacteria have this capacity • Symbiotic relationships between some plants and these bacteria have evolved

Plant Nutrition • Nitrogen fixation is very energetically expensive • Rhizohium bacteria require oxygen and carbohydrates to support their energetic demands • Nitrogen-fixing bacteria live in close association with the plant – with roots – Housed in plant tissues (nodules)

Plant Nutrition • Mycorrhizae aid a large portion of terrestrial plants • ~90% of vascular plants have symbiotic relationships with mycorrhizal fungi • Mycorrhizae enhance phosphorus transfer to plant, as well as many micronutrients http: //ecology. botany. ufl. edu/ecologyf 02/Art/CH 08/JPG/figure%2008 -06. jpg

Plant Nutrition • Some plants are able to obtain nitrogen directly from other organisms, as animals do • These carnivorous plants grow in acidic soils, such as bogs, that lack organic nitrogen • By capturing and digesting small animals directly, such plants obtain adequate nitrogen and are able to grow in otherwise unfavorable conditions

Plant Nutrition • Carnivorous plants have modified leaves adapted for luring and trapping prey • Prey is digested with enzymes secreted from specialized glands

Carnivorous Plants • Pitcher plants (common in northeast bogs) – have pitcher-shaped leaves with cavity filled with digestive fluid

Carnivorous Plants • Venus flytrap – (grows in bogs in North and South Carolina) – has 3 sensitive hairs on each side of leaf that, when touched, trigger the two halves of the leaf to snap together – Once the prey is enfolded within a leaf, secreted enzymes from leaf surfaces digest the prey

Venus flytrap

Carnivorous Plants • Sundews – secrete sticky mucilage, which traps small animals, and digestive enzymes

Plant Nutrition • Parasitic plants exploit resources of other plants – Photosynthetic – Non-photosynthetic • 3, 000 species • Adaptations include structures that tap into the vascular tissue of the host plant so that nutrients can be siphoned into the parasitic plant

Parasitic Plants • Mistletoe – grow attached to and within the branches of a tree or shrub • Photosynthetic, uses the host mainly for water and mineral nutrients • Spread by birds; sprout from bird feces deposited on the trunk of trees http: //www. flickr. com/photos/jim-ar/2117900952/

Parasitic Plants • Indian pipe – Lacks chlorophyll – Hooks into host trees through the fungal hyphae of the host’s mycorrhizae – The conspicuous portion (above-ground) of the plant consists of flowering stems

Parasitic Plants • Epiphytes – an organism that grows upon, or attaches to a living plant • Most commonly refers to higher plants, but can also include bacteria, fungi, lichens, mosses, and ferns • “Air plants” – do not root in the soil • Obtain moisture from the air or from dampness (rain and cloud moisture) on the surface of their hosts

Epiphytes http: //www. flickr. com/photos/pierre_pouliquin/74397619/

Animal Nutrition

The human digestive system is a marvel of nutritional storage and acquisition!

Animal Nutrition • Heterotrophs are divided into 3 groups based on their food sources • Herbivores are animals that eat plants exclusively • Carnivores are animals that eat other animals • Omnivores are animals that eat both plants and other animals

Animal Nutrition • Single-celled organisms as well as sponges digest their food intracellularly • Other multicellular animals digest their food extracellularly, within a digestive cavity – In Cnidarians and Flatworms, the digestive cavity called a gastrovascular cavity, has only one opening that serves as both mouth and anus – No specialization; every cell is exposed to all stages of digestion

Animal Nutrition • Specialization occurs when the digestive tract has a separate mouth and anus • The most primitive digestive tract is seen in the phylum Nematoda – A simple tubular gut lined by an epithelial membrane • All more complex animals have a digestive tract specialized in different regions for ingestion, storage, fragmentation, digestion, and absorption of food

Animal Nutrition • The tubular gastrointestinal tract of vertebrates has 4 layers – Mucosa – innermost layer, epithelium that lines the lumen, or interior of the tract – Submucosa – made of connective tissue – Muscularis – consists of a double layer of smooth muscles – Serosa – epithelial layer, covers the external surface of the tract

Animal Nutrition • Ingested food may be stored or first subjected to physical fragmentation • Chemical digestion occurs next, which breaks the food down into subunit molecules • Food particles then pass through the gut’s epithelial lining into the blood (absorption) • Wastes are excreted from the anus

• Mouth and pharynx • Esophagus – a muscular tube that delivers food to stomach – site of preliminary digestion • Small intestine – digestive enzymes continues the digestive process; products of digestion are absorbed across the wall of the small intestine into the bloodstream

• Any food product that remains in small intestine is emptied into the large intestine, where some of the remaining water and minerals are absorbed • From the large intestine, wastes enter the cloaca (nonmammals) or rectum

Animal Nutrition • Accessory digestive organs – Liver – largest organ in body; produces bile which emulsifies fat – Gallbladder – stores and concentrates the bile – Pancreas – produces pancreatic juice which contains digestive enzymes – Bile and pancreatic juice are secreted into the small intestine

Animal Nutrition • Liver – chemically modifies substances absorbed from the digestive tract before they reach the rest of the body – Removes toxins and carcinogens, converting them to less toxic forms – Regulates levels of steroid hormones (makes them more water soluble) – Produces most proteins found in blood plasma

Animal Nutrition • In general, carnivores have shorter intestines for their size than herbivores • Herbivores ingest a large amount of plant cellulose, which resists digestion; these animals have a long, convoluted small intestine

Animal Nutrition • In the mouth, food is physically broken down by teeth (mastication) – Similar in function to the gizzard of birds and worms • Salivary glands excrete saliva – Antibacterial agents, mucin production – Breaks down starch into glucose – Controlled by the nervous system; tasting, smelling, or even thinking about food stimulates salivation

Animal Nutrition • Vertebrate teeth are adapted to their food source • Carnivorous teeth are pointed that lack flat grinding surfaces • Herbivores have large, flat teeth suited for grinding cellulose cell walls of plant tissues • Humans (omnivores) have carnivore-like teeth in the front and herbivore-like teeth in the back

Animal Nutrition • Swallowing is initiated by voluntary action, but is continued under involuntary control • When food is ready to be swallowed, the tongue moves it to the back of the mouth • In mammals, the soft palate elevates, pushing against the back of the wall of the pharynx • Elevation of the soft palate seals off the nasal cavity • Pressure against the pharynx triggers the swallowing reflex

Bolus (food)

The Uvula • The uvula is the projection from the posterior edge of the middle of the soft palate • Not to be confused with the epiglottis • Plays a key role in the articulation of sound • Initiates the gag reflex • Can contribute to snoring

Animal Nutrition • The esophagus actively moves a processed lump of food (bolus) through muscular action • Swallowing stimulates successive, unidirectional waves of contraction that move food along the esophagus into the stomach – peristalsis

The Stomach • The stomach is a sac-like portion of tract • Has convoluted surface, allowing expansion • Stores food (functions as crop of other animals) • Contains an extra layer of smooth muscles for churning food and mixing it with gastric juice – an acidic secretion of the tubular gastric glands of the mucosa

The Stomach • Parietal cells of stomach secrete hydochloric acid (HCl) • Chief cells secrete pepsinogen (inactive), which becomes pepsin (active) at low p. H (~2) • 2 liters of HCl and other secretions is produced by human stomach every day! • The low p. H of the stomach helps denature proteins

The Stomach • Acidity of stomach also kills most bacteria ingested with food • Overproduction of gastric acid can lead to ulcers, a hole through the wall of the stomach • The mixture of partially-digested food and gastric juice is called chyme; chyme leaves the stomach and enters the small intestine

The Stomach

Small Intestine • Site of terminal digestion of carbohydrates, lipids, and proteins • Site of absorption of products of digestion (amino acids, glucose, fatty acids, etc) • Efficient digestion takes time, and so only small amounts of chyme may be introduced into the small intestine at any one time

Small intestine • Longest part of the digestive tract – Up to 6 meters in humans • Consists of duodenum, jejunum, and ileum – Duodenum – first 25 cm; site of most digestion, receives enzymes from the pancreas and bile from the liver and gallbladder – Jejunum and ileum – site of absorption • Very large surface area (3200 ft 2) – folds, villi and microvilli – Similar to function of mycorrhizae

Small intestine

Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Pancreatic islet (of Langerhans) cell From liver cell Common Pancreas bile duct Gallbladder Pancreatic duct Duodenum

Large intestine • The large intestine concentrates and stores wastes • Much shorter than the small intestine, but larger diameter • Small intestine empties directly into the large intestine at a junction where 2 vestigal structures remain – The cecum and appendix

Large intestine • No digestion occurs • Absorption of water, remaining electrolytes and vitamin K (products of bacterial metabolism) • Many bacteria live and reproduce within the large intestine; excess bacteria are incorporated into the feces • Feces are moved along by peristalsis and exit the body through the anus

Variations in Vertebrate Digestive Systems • Animals lack the enzymes necessary to digest cellulose, the structural component of the primary cell wall of green plants • However, the digestive tracts of some animals contain bacteria and protists that convert the otherwise undigestable cellulose into substances that the host can absorb

Variations in Vertebrate Digestive Systems • Ruminants have a four-chambered stomach (“foregut fermenters”) – Rumen – has cellulose-degrading microbes which convert cellulose into simpler compounds; contents regurgitated (“cud”) and re-chewed – Reticulum – Omasum – Abomasum – the true stomach, contents mix with gastric juices

Variations in Vertebrate Digestive Systems • Non-ruminant herbivores, such as horses, deer and rabbits, digest cellulose in the cecum (“hindgut fermenters”) • Cecum – site of microbial digestion of cellulose • Regurgitation of contents is not possible (cecum is located behind the stomach) • Instead, rodents and lagomorphs (rabbits and hares) eat their feces (coprophagy)

Variations in Vertebrate Digestive Systems • The second passage of food through coprophagy allows the animal to absorb the nutrients produced by the organisms in its cecum • Coprophagic animals cannot remain healthy if they are prevented from eating their feces!

Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Nonruminant Herbivore Ruminant Herbivore Simple stomach, large cecum Four-chambered stomach with large rumen; long small and large intestine Esophagus Stomach Small intestine Rumen Abomasum Reticulum Omasum Cecum Small intestine Large intestine Anus Cecum Spiral loop Large intestine Anus Carnivore Insectivore Short intestine and colon, small cecum Short intestine, no cecum Esophagus Small intestine Stomach Esophagus Stomach Small intestine Large intestine Anus Cecum Large intestine

Animal Nutrition • The activities of the gastrointestinal tract are coordinated by the nervous system and the endocrine system • The nervous system stimulates salivary and gastric secretions in response to sight, smell, and consumption of food • When food arrives in the stomach, proteins in the food stimulate the secretion of gastrin, which triggers the release of HCl and pepsinogen from the gastric glands

Animal Nutrition • After a carbohydrate-rich meal, the liver and skeletal muscles remove excess glucose from the blood and store it as glycogen • During fasting or exercise (low levels of glucose), an increased secretion of glucagon by the pancreas promotes the breakdown of glycogen and release glucose (glycogenolysis)

Animal Nutrition • Type 1 diabetes – insulin-dependent diabetes, common in children – Too much glucose, little or no insulin (mutation, no insulin made or non-functional), glucose excreted in urine • Type 2 diabetes – insulin-independent diabetes, adult onset – Normal or elevated levels of insulin, but cells no longer respond to the insulin – Insulin is the only hormone that decreases glucose in the body