II. Digestion & Nutrition

• DIGESTION - process by which the body breaks down food into smaller, absorbable components that can be used for energy, growth, and repair
• AUTOTROPH - Producer

  • organisms that use energy from the sun to produce food
• HETEROTROPH - Consumer

  • organisms that cannot make their own food; must obtain energy from outside sources
• PLANTS: DIGESTION AND NUTRITION

  A) Photosynthesis

  B) Root Absorption

  C) Transport

  D) Assimilation

  
• Plant Nutrients

  • Photosynthesis is major source of plant nutrition via the fixation of CO2 into sugar using solar energy
• Macronutrients – used in relatively large amounts.

  • Nine = C, O, H, N, K, Ca, Mg, P, and S.
• Micronutrients – used in minute amounts.

  • Seven = Cl, Fe, Mn, Zn, B, Cu, and Mo.
• Mineral deficiencies

  • Mg - yellowing between veins; leaves are raised and bumpy
  • Cu - curled leaves
  • N - light yellow leaves
  • Zn - brown spots between veins
  • K - brown spots at the tip
• Identifying Nutritional Requirements: Hydroponics

  • A method of growing plants without soil, where nutrient-rich water is used to deliver essential minerals and nutrients directly to the plant roots
  • Allows plants to grow well if they are supplied with all the nutrients they need
• Special Nutritional Strategies: Rhizobium

  • Plants need ammonia (NH3 ) or nitrate (NO3 ) to build amino acids
  • However, they lack the biochemical pathways necessary to convert N2 in the atmosphere into NH3 .
  • Symbiotic relationships have evolved between plants and nitrogen-fixing bacteria
  • Legumes form nodules that house the bacterium Rhizobium.
• Special Nutritional Strategies: Mycorrhizae

  • Symbiotic associations with mycorrhizal fungi are found in about 90% of vascular plants Substantially expand the surface area available for nutrient uptake.
  • Play a significant role in enhancing phosphate transfer to the plant
  • Uptake of some micronutrients is also facilitated
• Special Nutritional Strategies: Carnivorous Plants

  • Often grow in acidic soils that lack nitrogen
  • Prey is digested with enzymes secreted from specialized glands
  • Ex. Asian pitcher plant (Nepenthes)
• Special Nutritional Strategies: Carnivorous Plants

  • Often grow in acidic soils that lack nitrogen
  • Trap and digest small animals, primarily insects, to obtain adequate nitrogen supplies.
  • Ex. Venus Flytrap
• Special Nutritional Strategies: Carnivorous Plants

  • Often grow in acidic soils that lack nitrogen
  • Have modified leaves adapted for luring and trapping prey
  • Ex. Sundew (Drosera)
• Special Nutritional Strategies: Parasitic Plants

  • May be photosynthetic or non-photosynthetic
  • At least 3,000 types of plants Tap into the nutrient resources of other plants
  • Adaptations include structures that are inserted into the vascular tissue of the host plant so that nutrients can be siphoned into the parasite
  • Examples include dodder and Indian pipe
• DIGESTIVE SYSTEM

  • Includes all the organs, tissues, and cells involved in ingesting food and breaking it down into smaller components.
  • Contributes to homeostasis by providing body with nutrients needed to sustain life of cells.
• Digestive System

  A) Absorbs nutrients molecules

  B) Ingest food

  
• INCOMPLETE DIGESTIVE TRACT

  • An incomplete digestive tract has a single opening used as an entrance for food and exit for wastes.


  Planarians

  • Food enters through the mouth and muscular pharynx.
  • Gastrovascular cavity branches throughout the body.
  • Wastes exit through the mouth and muscular pharynx.
  • It lacks specialized parts.
• COMPLETE DIGESTIVE TRACT

  • A complete digestive tract has two openings


  Example: Earthworm.

  • Food enters through the mouth.
  • Wastes exit through the anus.
  • Specialization of parts is obvious because the pharynx, crop, gizzard, and intestine have their own functions.
• INGESTION

  • Process by which an organism takes in food or other substances into its body for various purposes, such as obtaining nutrients, energy, or even for defensive mechanisms
  • Heterotrophs are divided into three groups based on their food sources
• Ingestion

  A) Herbivores

  B) Carnivores

  C) Omnivores

  
• Ingestion - Herbivores (ADAPTATIONS TO DIET - Dentition differs with mode of nutrition)

  • Eat only plants.
  • Incisors for clipping.
  • Premolars and molars for grinding.
  • Land snails and some insects are herbivores.
  • Koalas, which are mammals, eat only eucalyptus leaves.
  • Grazers, like horses, feed on grasses.
  • Ruminants, like cattle, goats, and sheep, have a four-chambered stomach which allows them to regurgitate solid material for complete digestion.

  A) Herbivores

  
• INGESTION - Carnivores

  • Eat only other animals.
  • Pointed incisors and enlarged canines.
  • Shear off pieces small enough to swallow.
  • Spiders and sea stars are carnivores.
  • Dogs, lions, and dolphins are carnivores.
  • The lion’s pointed canine teeth are used for killing, sharp incisors for scraping bones, and pointed molars for slicing flesh.

  A) Carnivores

  
• INGESTION - Omnivores

  • Variety of specializations to accommodate both vegetation and meat.
  • Clams and tube worms are invertebrate omnivores.
  • Humans, pigs, raccoons, and most bears are omnivores.
  • Dentition of the above is specialized to accommodate vegetable and meat diet.
  • Better ability to adapt to different food sources

  A) Omnivores

  
• INGESTION - Mouth and Teeth

  • Many vertebrates have teeth used for chewing or mastication
  • Birds - Lack teeth and Break up food in a two-chambered stomach
  • Gizzard – muscular chamber that uses ingested pebbles to pulverize food
• MECHANICAL DIGESTION - grinding, chewing, and swallowing of food (bolus)
• PARTIAL CHEMICAL DIGESTION - secretion of saliva and amylase by salivary glands
• CHEMICAL DIGESTION

  • enzyme-mediated and hydrolytic process of breaking large food molecules into smaller units enough for the body to absorb
  • occurs in the stomach and small intestine
• ABSORPTION - The complete digestion and absorption of nutrients occurs in the small intestine.

  A) Duodenum

  
• ELIMINATION

  • Feces composed of water, undigested and unabsorbed matter, and bacteria are formed in the large intestine.
  • These move through the colon, stored in the rectum, and eliminated in the anus.
• MONOGASTRIC DIGESTIVE SYSTEM

  • Example: Humans, dogs, etc.
  • Characteristics:

  1. Have a single-chambered stomach
  2. Digestion primarily occurs in the stomach, where gastric juices break down food.
  3. Nutrient absorption occurs in the small intestine.
• RUMINANT DIGESTIVE SYSTEM

  • Example: cows, sheep, and deer,
  • Characteristics:

  1. have a complex stomach with four compartments: rumen, reticulum, omasum, and abomasum.
  2. foregut fermentation, where microbes in the rumen break down fibrous plant material before it enters the true stomach (abomasum) for further digestion and absorption.
• NONRUMINANT DIGESTIVE SYSTEM

  • Example: horses, rabbits, guinea pigs, and elephants, etc.
  • Characteristics:

  1. single-chambered stomach, similar to that of humans.
  2. Enlarged cecum and colon
  3. sites for microbial fermentation of fibrous plant materials
  4. results in the production of volatile fatty acids (VFAs), which can serve as an energy source for the animal.
  5. involves enzymatic breakdown of carbohydrates, proteins, and fats
• AVIAN DIGESTIVE SYSTEM

  • Example: birds
  • Characteristics: beak of birds is adapted for various feeding habits
• AVIAN DIGESTIVE SYSTEM

  • The crop is a storage pouch that temporarily store ingested food before it moves to the stomach for digestion.
  • The proventriculus, also known as the glandular stomach, that secretes gastric juices and enzymes to initiate the chemical breakdown of food.
• AVIAN DIGESTIVE SYSTEM

  • The gizzard is a muscular organ that acts as a powerful grinding chamber, breaking down tough food particles, such as seeds and grains, with the help of ingested grit (small, hard particles like stones).
  • The cloaca is the common chamber into which the digestive, urinary, and reproductive systems empty