Methods of Nutrition
Autotrophic nutrition e.g. plants
Autotrophic organisms make there own complex organic molecules by chemical processes such as photosynthesis, using just single molecules CO2 and H2O. They are the producers for all energy in the food chain.
Bring food/ complex molecules from the organisms into the body for digestion e.g. animalia
Secrete digestive juice/enzymes onto complex molecules/food source outside the body, then absorb digested products by diffusion. This is called extracellular digestion. e.g. decomposers that are involved in the nitrogen cycle.
Parasitic: Organisms that live on or in another organism, consuming their complex organic molecules. They usually cause some degree of harm or even death to the host e.g. the pork tapeworm.
Movement in the digestive system
Unspecialised guts e.g. worms
The gut is consistent through its length, all carrying out the same function.
Specialised guts e.g. mammals
The gut has diffrentiated regions, that carry out different functions e.g. stomach mixes, ileum absorbs.
Digestive system functions
Ingestion- food is brought into the body by the mouth.
Digestion- food is broken into its simple soluble molecules by enzymes in the stomach and duodenum. It is also assisted by the muscular movement and chewing, which increases SA.
Absorption- digested food molecules are absorbed by the villi in the ileum, and transported to cells by the blood.
Egestion- the removal of undigestable food, such as cellulose, as faeces.
The Human digestive system: Gut structure
This consists of thick connective tissue that protects the gut and reduces friction from other organs.
consists of longitudinal and circular muscle. These deliver waves of muscular contraction during peristalsis to push food along the gut.
Contains blood and lymph vessels to carry away the products of digestion. Also contains nerves that coordinate the muscles in peristalsis.
This secretes mucus to lubricate the gut and protects it from digestive enzymes. In some areas it releases digestive juices, and in others it has many villi to absorb food moelcules.
The Human digestive system: The mouth, stomach and
This takes in food, and cuts it up with the teeth. It alsos secretes saliva, to lubricate the bolus. The saliva also has salivary amylase that begins hydrolysing starch into maltose.
This hold food between two muscular rings. It mixes food up with rythmic contractions. Epithelial cells are with goblet cells that release gastric juices that have a pH of 2.0. This helps kill most bacteria that were ingested with the food, as well as providing optimum conditions for peptidases. Epithelial cells also secrete mucus that protects the lining of the stomach from the acid.
This is the first region of the small instestine. It recieves secretions from the liver and the pancreas. The pancreatic juices contain many enzymes e.g. lipases and amylase. The gallbladder releases bile that emulsifies fats, increasing the surface area that lipase can work on.
The walls of the duodenum secrete alkaline juices and mucus.
The Human digestive system: Ileum, colon and rectu
The ileum- This is the main bulk of the small instestine. It has a large surface area due to folding and the microvilli on the epithelial cells on the villi. The villi also have great blood supply and lacteal vessels. These help create a concentration gradient to aid diffusion. Epithelial cells also contain many mitochondria for the active transport of food molecules into blood vessels. (Blood carries amino acids and glucose; lacteal carries lipids.)
- Fatty acids and glycerol diffuse passively through epithelial membrane into the lacteal.
- Glucose, dipeptides and amino acids need ATP for absoprtion.
- Dipeptides are digested intracellularly into amino acids.
- Glucose and amino acids then diffuse from epithelial cell and into the blood.
The Colon- absorbs excess water from digested food, as well as mineral ions and vitamins produced by microrganisms e.g. folic acid and Vitamin K.
Rectum- defication of undigestable materials including cellulose, sloughed cells and bacteria as faeces.
Fate for digested molecules
Absorbed from blood into cells for use as energy in respiration.
- Amino acids
Used for protein synthesis. Excess is deanimated (removal of amine group) and stored as carbohydrate.
Used for hormones and membranes. Excess stored as fat.
Adaptations to different diets: DENTITION
- Incisors cut up against a horny pad.
- Canines are indistinguishable from incisors.
- Tongue works in diastema, moving freshly cut grass to the molars.
- Molars interlock in a W/M way, and grind food down. The grinding erodes the teeth, exposing sharp edged enamel ridges= better at grinding.
- Unrestricted roots of the molars ensure the teeth can keep growing.
- Jaw works in a circular motion.
- Sharp incisors for cutting meat.
- Large, curved sharp canine teeth used for catching and killing prey.
- No diastema
- Molars are specialised into carnaissals which work as garden shears (jagged and slide past eachother) to tear meat.
- The jaw works in a vertical motion, allowing it to open wider to catch prey.
Adaptations for diet: The ruminant
Ruminants diet mainly consists of plant material and cellulose. They do not produce the enzymes to digest this, so have developed a symbiotic relationship with bacteria that produce cellulase. This digests cellulose to produce methane and CO2.
The bacteria live a separate chamber of the stomach, to avoid digestion themselves, and the acidic conditions. They get shelter and food from the relationship, and the ruminant gets cellulose digested for its own use.
ROUTE THROUGH THE STOMACH
- Cud is formed in the mouth and swallowed
- Passes into the first chamber (the rumen), where cellulose is fermented by the bacteria, and glucose produced and used for energy.
- Cud is regurgitated for extra chewing, swallowed, and bypasses the first chamber.
- The third chamber reabsorbs water, and then the next act as a normal stomach where proteins and fats are digested, then absorbed.
Adaptation for diet: the Parasite
The Pork Tapeworm
Adaptations to problems:
- Hooks and suckers- these help lodge the worm onto the gut, to avoid movement by peristalsis.
- Body covering to protect it from the hosts immune system.
- Thick cuticle and inhibitory substances secretion- this protects the worm from digestive enzymes.
- Thin skin and large surface area- this shortens diffusion paths so the worm can easily absorb digestive products from the small instestine.
- Very basicorgans- no digestive system as the food around it is already ready for use, no sensory organs as a very stable environment.
- Hermaphrodite- there isn't enough room for two tapeworms, so the one has male and female reproductive systems. Each segment of the worm can produce up to 40,000 eggs.
- Eggs have resistant shells- these prevent harm until ingested by the secondary host, where the embryo is then hatched and remains dormant in pig muscle untileaten by a primary host-human.
Problems the tapeworm causes
- Adult tapeworms cause relatively little discomfort, apart form a lack of nutrition.
- If the eggs are eaten, dormant embryos can form cysts in various organs and damage tissues.
- Adults can be treated easily with drugs.
- Public health and meat inspection are essential measures to avoid infection.