Biology By2 Revision

Topics: Digestion, Gamete, Pancreas Pages: 10 (2218 words) Published: January 8, 2012
Parasitic Nutrition
21 May 2011 10:43

= organisms that live on or in another organism obtaining nourishment at the expense of the host and causing harm. Gut parasite (Taenia solium) = tapeworm Primary host = human (eat uncooked infected pork) Secondary host = pig (drainage channels contaminated by human faeces) Adaptations… - Suckers & hookers (attachment) - Body covering (immune responses) - Thick cuticle (inhibitory substances = enzymes) - Simple body systems (reproduction) - Very thin & large surface area (food absorbed over whole body surface = diffusion) - Male & female sex organs (gut can only accommodate 1 tapeworm) - Number of eggs produced (increase chance of survival) - Eggs have resistant shells (survive until eaten) Dormant embryos can form cysts in organs - damage surrounding tissue

BY2 revision Page 1

Adaptions to different diets
21 May 2011 10:53

Reptiles & Amphibians = swallow food whole Mammals = cut up and chew (palate separates nasal cavity & mouth - kept in mouth longer) Carnivore = short gut (easily digest protein) Herbivore = long gut (plant digestion difficult)

Dentition Mechanical digestion = easier to swallow & increases surface area for enzyme action Herbivore Incisors Canines Lower jaw, cuts against horny pad (upper jaw) Indistinguishable from incisors Carnivore Sharp (tear flesh from bone) Large, curved, pointed = seizing prey, killing & tearing flesh Carnassial (slide past each other = garden shears) molars = cutting/crushing) Vertical (open wide to capture & kill prey) Not horizontal (dislocation) Jaw muscles = well developed/powerful (grip firmly on prey/crush bones)

Cheek teeth Interlock. (W into M) Worn down = sharp enamel ridges (efficiency). Open roots (grinding) Jaw movement Other Circular grinding. Horizontal plane Diastema = gap between front & side teeth. Tongue moves cut grass to grinding surfaces (cheek teeth)

Ruminants Produce most protein eaten by humans eg. Cows/sheep

Mutualism/Symbiosis = close association between members of 2 species, both derive some benefit from the relationship. - Can't digest cellulose (no cellulose enzymes) - Cellulose-digesting bacteria live in gut of cow - Separated = food left long enough for digestion, bacteria isolated (optimum pH & conditions)

Cellulose digestion… - Grass chopped (teeth), saliva, cud formed, swallowed - 1st stomach = cellulose digesting bacteria (glucose = fermented - organic acids into blood. Waste = co2 & methane - Cud into next region, regurgitated & chewed again - 3rd stomach = water absorption - 4th stomach ('normal' stomach) = protein digestion - Small intestine = absorption Rumen = greater variety of mutualistic organisms than in caecum More efficient = more complete breakdown of cellulose Bacteria = source of protein when dead

BY2 revision Page 2

21 May 2011 11:35

= the break down of large insoluble molecules into smaller soluble molecules. Physical & chemical. Food passes through alimentary canal where it is digested & absorbed into the body. Digestive enzymes = hydrolases (catalyse hydrolysis of substrate - addition of water) - Carbohydrates (polysaccharides) → disaccharides → monosaccharides (Amylase = maltose →glucose) - Proteins →polypeptides →dipeptides →amino-acids (peptidase = endo/exo) - Fats → fatty acids & glycerol (lipase)

Mouth (buccal cavity) - Mechanical digestion (teeth) - Saliva = salivary glands (mucus, salivary amylase & mineral ions = optimum pH - slightly alkaline) = lubrication & some protein digestion (amylase = starch → maltose) - Swallowed as bolus Oesophagus - Peristaltic contractions (longitudinal & circular muscles = not under conscious control) - Occurs all way through alimentary canal Stomach = muscular sac (2 sphincter muscles = cardiac & pyloric keep food in stomach) - Muscles in stomach wall contract rhythmically (mix food with gastric juice = secreted by stomach wall) - Gastric juice = optimum pH of enzymes (pH2.0), kills most bacteria,...
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