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50 Cards in this Set
- Front
- Back
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What is nutrition? |
A process by which organisms obtain energy to maintain life functions (biochemical reactions) & matter to create & maintain structure.
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Describe autotrophic nutrition and the 2 types.
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- Synthesis their own complex organic molecules from simple molecules using either light or chemical energy. Photoautotrophic organisms - energy from sunlight to carry out photosynthesis to make organic molecules from the inorganic molecules carbon dioxide (green plants). Chemoautrophic organisms - Use energy from chemical reactions to synthesise organic molecules (organisms are bacteria respiring in deep sea hydrothermal vents). |
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Describe heterotrophic nutrition & list the 3 types of heterotrophic feeders.
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- Cannot produce their own organic molecules - Consume complex organic from other organisms. - They break this material down into smaller, soluble molecules - absorb & assimilate. 3 Types of Heterotrophic Feeders 1. Holozoic Nutrition 2. Saprotrophic Nutrition 3. Parasitic Nutrition
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1. Define holozoic nutrition & give examples.
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- Most animals - Have specialised digestive systems in which they ingest food, digest it & egest any indigestible remains. Carnivores - Eat other animals Herbivores - Plants Omnivores - Both plant & animal material Detritivores - Long dead & decaying matter. |
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2. Define Saprotrophic Nutrition
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- Feed on long dead or decaying organic material (e.g fungi). - Don't have digestive systems. - They carry out extracellular digestion: secrete enzymes outside of body. - Then absorb the soluble products of digestion by diffusion & active transpsort. - Decomposers (microspcopic saprotrophs) play important role in decaying leaf litter & recycling nutrients such as nitrogen.
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3. Define Parasitic Nutrition
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-Parasites are organisms that live in (ectoparasites) or on (endoparasites) the host & gain nutrition from the host & always cause harm to the host (e.g. headlice).
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Describe nutrition in unicellular organisms (e.g. amoeba).
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- Large SA:V ratio. - Obtain nutrients via cell membrane: 1. diffusion 2. facilitated diffusion 3. active transport. - Take in large food molecules via endocytosis: food molecules are surrounded by membrane & form food vacuoles. - Food vacuoles fuse w/ lysosomal enzymes which digest contents. - Products of digestion are then absorbed into cell cytoplasm. - Indigestible remains are egested via exocytosis. |
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Describe Nutrition in Hydra.
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Hydra - animals related to sea anemones. - Cylindrical in shape. - Tentacles @ the top of their head which contain stinging cells. - Have an undifferentiated digestive system. - Live I fresh water w/ sac-like hollow body cavity. - Tentacles used to move paralysed prey into mouth. - Products of digestion are absorbed & indigestible remains are egested through the mouth b/c they only have 1 single opening. |
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Why must food be digested, in humans?
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- Food molecules are too big to cross membranes (polymers to monomers). - Smaller soluble molecules can dissolve into blood & travel to cells where they can be rebuilt into molecules need by blood cells (assimilated). |
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Name the 5 main functions of the human gut.
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1. Ingestion 2. Digestion 3. Absorption 4. Assimilation 5. Egestion |
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Define ingestion.
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- Taking food into body by mouth.
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Define digestion & the 2 types.
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- Breakdown of large insoluble molecules into soluble molecules that are small enough to be absorbed by the blood. 1. Mechanical Digestion: cutting & crushing by teeth & muscle contraction of gut wall - increases SA over which enzymes can work. 2. Chemical Digestion: secretion of digestion enzymes. Bile & stomach acid also contribute to chemical digestion |
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Define Absorption
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Passage of small soluble molecules & ions through the gut wall into the blood.
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Define Assimilation
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Use of products of digestion by the cells for energy or to build bits of the cell.
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Define Egestion
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Elimination of indigestible waste (e.g. cellulose).
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Define Peristalsis
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-Wave of muscular contractions & relaxations of the gut wall which propel contents along the whole length of the gut. - Circular muscles contract behind the bolus of food & relax after food has passed. |
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Structures of the human digestive system & their functions.
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1. Mouth - Ingestion. - Mechanical digestion- crushed by teeth. - Chemical digestion of starch by salivary amylase. 2. Oesophagus - Carriage of food to stomach by peristalsis 3. Stomach - Contractions = churn up food (mechanical digestion - Secretion of hydrochloric acid - Chemical digestion of proteins by enzymes. 4. Duodenum - Receives pancreatic juice from pancreas & bile from gall bladder. - Chemical digestion of carbohydrates, fats & proteins. 5. Ileum - Chemical digestion of carbohydrates, proteins & fats. - Absorption of digested food 6. Colon - Absorption of water 7. Rectum - Storage of faeces 8. Anus - Site of egestion |
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What are the 4 layers of the mammalian gut & their function?
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1. Serosa - Outermost layer. - Contains tough connective tissue = protects the gut wall. - Serosa reduces friction w/ other abdominal organs, during peristalsis. 2. Muscularis - comprises of 2 layers. - Inner = circular muscles & Outer = Longitudinal muscles. - They make waves of contractions (peristalsis). - Circular muscles contract & longitudinal muscles relax pushing bolus along 3. Submucosa - consists of connective tissue - contains blood & lymph vessels = remove absorbed products of digestion. - Lay also contains the nerves which coordinate peristalsis. 4. Mucosa - Innermost layer - Epithelium secretes mucus which lubricates & protects the mucosa. - In some regions, secretes digestive juices & in others, absorbs digested food. |
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How are carbohydrates digested?
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- Starch is broken down by amylase enzyme to produce maltose, which is further broken down by maltase enzyme to produce alpha glucose. - Lactose hydrolysed by lactase - Sucrose hydrolysed by sucrase |
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How are proteins digested?
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Polypeptides broken down to dipeptides, which is further broken down to amino acids. - Endopeptidases: Hydrolyse bonds w/in the protein molecule (pepsin &trypsin). - Exopeptidases: Hydrolyse peptide bonds @ the end of shorter polypeptide chains. |
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How are fats digested?
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- Hydrolysed by lipase to form the products fatty acids & glycerol
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What happens in the buccal cavity (mouth)?
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- Mechanical digestion occurs. - Increases the SA of food for enzymes to work on. - Food is mixed w/ saliva. - Amylase in saliva. -Amylase turns starch to maltose. - HCO(3) & CO(3) (both negative) creates an optimum pH (slightly alkaline). - Mucus lubricates the food. |
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What happens in the oesophagus?
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- Has no role in digestion - Connects the buccal cavity to the stomach. |
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What happens in the Stomach?
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- Bolus of food enters stomach & is kept there by the contraction of 2 Sphincters. - Food remains there for several hours. - Stomach wall muscles contract rhythmically to churn the food w/ gastric juices secreted by glands in the stomach wall (glands in mucosa called gastric pits). - Gastric juice contain mucus & hydrochloric acid. - Mucus secreted by goblet cells which line the mucosa. - Mucus forms a protective lining which protects the stomach wall. - Hydrochloric acid secreted by the oxyntic cells. - It lowers pH to pH2 to create an optimum environment for enzymes & kills bacteria. Pepsin - Inactive = pepsinogen (secreted by chief cells @ base of gastric glands). - Activated by hydrochloric. Trypsin - Inactive = trypsinogen - Activated by enterokinase - pH (7-8).
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What happens @ the Duodenum?
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- 1st section of small intestine. - Receives secretions from the liver & pancreas. - Food from stomach is lubricated by mucus & HCl is neutralised by alkaline secretions from cells in the Brunner's Gland. - Bile passed through to bile duct in duodenum. - Bile contains bile salts which are amphipathic (hydrophilic & hydrophobic). - They emulsify lipids present in the partially digested food by lowering their surface tension& breaking up large globules into smaller globules, thus increasing the surface are for lipase action. |
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Enzymes secreted in the Pancreas & the function
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- Endopeptidase - Hydrolyse protein to peptides. - Trypsinogen - Inactive enzyme converted into the endopeptidase trypsin by enterokinase. - Enterokinase - Converts trypsinogen to trypsin. - Amylase - Chemically digests any remaining starch to maltose. - Lipase - Hydrolyses lipids into fatty acids & glycerol. - Sodium Hydrogen Carbonate - Raises pH to make pancreatic juice more alkaline.
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Structure & function of the ileum.
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- Well adapted for absorption b/c: - very long - Lining is folded - Villi on the surface of the folds. -They have microscopic projections on villi called microvilli = increase SA. |
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What are the specialised cells in the mucosa of the Ileum?
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1. Columnar Epithelial Cells have 2 main adaptations: - Microvilli forming brush border. - Goblet cells 2. Goblet cells - secrete mucus - lubricate & protects the lining of the intestine. |
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Which cells are endopeptidases & exopeptidases secreted from?
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-Cells @ the tip of the villi into the gut lumen & continue the digestion of polypeptides. - Dipeptides are hydrolysed to amino acids by enzymes on the cell membrane. |
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Where are disaccharides absorbed into?
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- Disaccharides are absorbed into epithelial cells. -Carbohydrases in their cell membrane digest them into monosaccharides so the final stage of carbohydrate digestion is intracellular |
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How are certain molecules absorbed & transported? 1. Fatty acids, glycerol 2. Fat-soluble vitamins 3. Glucose & galactose 4. Sodium ions |
1. Diffuses from lumen into epithelial cell & then reassembles into triglycerides. Then diffuses into the blood then carried via lymphatic system to the blood (lacteal). 2. Diffuses from lumen into epithelial cells and then diffuses into the lacteal. 3. Co-transported w/ sodium ions from lumen to epithelial cells and moved into the capillary via facilitated diffusion. 4. Co-transported w/ glucose from the lumen into the epithelial cell and moved into the capillary by facilitated diffusion. |
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How are certain molecules absorbed & transported? 5. Disaccharides 6. Amino acids, di & tri-peptides 7. Minerals 8. water-soluble vitamins 9. Water |
5. Actively transported from the lumen into the epithelial cell & moved into the capillary via facilitated diffusion.
6. Actively transported from the lumen into the epithelial cell and moved into the capillary via facilitated diffusion & then transported to liver via hepatic portal vein. 7. Moved from the lumen into the epithelial cell by facilitated diffusion & into the capillary by facilitated diffusion. 8. Diffuse from the lumen into the epithelial cell & diffuses into the capillary. 9. Moved by osmosis into the epithelial cell & into the capillary by osmosis. |
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What are the uses of the products of digestion? 1. Glucose 2. Lipids 3. Amino Acids |
1. Required for aerobic respiration. - Excess stored as glycogen. 2. Energy storage. - Protection of vital organs. - Thermal insulation under skin. 3. Used for protein synthesis. - Excess deaminated in the liver. |
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Talk about the large intestine.
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- About 1.5m long - Divided into the caecum, the appendix, the colon & the rectum. - By the time it reaches rectum, the indigestible food, sloughed off cells, bacteria & undigested cellulose are egested as faeces. |
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What is absorbed in the large intestine?
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- Water - Mineral ions - Vitamins produced by symbiotic bacteria gut, like Vitamin K & folic acid. |
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How are mammals able to retain food?
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- Have a palate which separates the nasal cavity from the mouth. - Allows food to be retained, rather than swallowed whole between breaths, so can cut up & chew food. - Reptiles & amphibians swallow food immediately when caught. |
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Why are teeth important?
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- Mechanical digestion food. - Chewing makes it easier to swallow food. - Increases SA for enzyme action. |
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Outline 4 different types of teeth, in omnivores, & their function.
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- Human teeth are relatively unspecialised. 1. Incisors - Biting & Cutting food. 2. Canines - Tearing & Ripping meat. 3. Molars / Pre-molars - Grinding & Chewing food. |
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Outline dentition of a herbivore.
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- Cellulose based diet. - Difficult to digest so adapted for grinding to increase SA for bacterial cellulose enzyme action. 1. Incisors & Horny Pad- Horny pad on the top of jaw & the lower incisors then slice through the grass. 2. Canines - None 3. Molars - Interlocking like an M fitting into a W. 4. Diastema -Gap between check & teeth. 5. Horizontal Jaw Movement - Lower jaw moves side to side to make circular grinding action. 6. Open Roots - Unrestricted teeth roots so they can grow, as grinding plant material wears their teeth down. |
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Outline dentition of a carnivore.
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- Teeth adapted for catching & killing prey. 1. Small sharp incisors - Grip & tear flesh from bone. 2. Large Curved Canines - Seize & hold prey. 3. Premolars/molars - Cutting & crushing food. 4. Carnassials - Slide past each other like blades & crush bone. 5. Powerful Jaw Movement - Grip Prey. 6. Vertical Jaw Movement - So jaw can open widely, & can't be dislocated when a prey is struggling in it's grip. |
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Define Mutualism
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A close association between members of 2 different species in which both organisms benefit from the relationship.
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Adaptations of the gut: Ruminant Herbivores
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- Animals such as cows, goat & sheep which mainly eat grass & forage. - This food contains a lot of cellulose (plant cell walls). - These animals are unable to produce the enzyme cellulase needed to break it down. - Ruminants rely on mutualistic microorganisms which live in their gut & secrete cellulase. - Microbes live in 1 of a ruminants stomach chambers called the rumen. - They include bacteria, fungi & Protoctista. |
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Cellulose Digestion in Ruminant Herbivores: Cow.
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1. Grass is chewed mixed w/ saliva & swallowed. 2. Grass passes into rumen & churned & mixed w/ bacteria that secrete cellulase to digest cellulose forming beta glucose. - Beta glucose is fermented (anaerobic conditions) to form organic acids which are absorbed into blood, providing energy. - Waste products = carbon dioxide & methane gas. 3. Fermented grass passes to the reticulum chamber & forms cud. - Cud is regurgitated into the mouth for further chewing. - Process may be repeated several times. - Increases SA of grass to allow for more cellulose digestion to occur. 4. Cud passes into the omasum where water is absorbed into blood. 5. In abomasum bacteria are killed & digested - important source of protein. 6. Other products of digestion pass to the small intestine where they are absorbed. |
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Non-ruminant Herbivores: Rabbits.
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- The caecum is enlarged to accommodate cellulose digesting bacteria. - As bacteria are toward the end of the gut regurgitation isn't possible. - Instead refection occurs - ingests faecal pellets so that the material passes through the gut twice to increase the efficiency of digestion. |
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How does refection (ingesting faecal pellets) increase the efficiency of digestion?
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More time is spent on the cellulose digestion.
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Comparisons between gut of carnivore & herbivore.
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- Carnivore gut s relatively short b/c protein is easily digested. - Large intestine is straight & has a smooth lining. - The gut of a herbivore is longer , as cellulose is much harder to digest. - Large intestine is pouched as it is able to stretch to accommodate the larger volume of faeces produced when digesting plants. - Large intestine is also lined w/ villi where water is absorbed. |
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What are plants & animals parasited by?
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- Bacteria - Fungi - Viruses - Nemotodes - Insects Animals are also parisited by: - Protoctista - Tapeworms - Mites |
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What are the features of a pork tape worm?
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- Tapeworm is ribbon like & can be up to 10 metres long. - Has a scolex (head) made up of circular muscles on which are suckers & hooks. - Body is a linear series of sections called proglottids. - Has 2 hosts: primary host - human & secondary host (pig). - Larval form is found in pigs. Pig becomes infected if it feed on drainage channels contaminated by human faeces containing eggs. - Humans become infected by eating contaminated undercooked pork.
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Problems faced by the tapeworm VS adaptations that the tapeworm has evolved.
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1. Gut is in constant motion (churning & peristalsis) - suckers & hooks 2. Extreme pH, exposure to digestive enzymes & the host's immune response - Thick cuticle & production of inhibitory substance on its surface to prevent digestion. Its body covering protects it from host's immune response. 3. Reproduction (unlikely to find a mate) - Has both male & female reproductive organs so can self-fertilise (hermaphrodite). - Large no. of eggs produced, 40,000. - Eggs have resistant shells to survive being eaten by another host. 4. Host death - If host dies so does the tapeworm 5. Tapeworm has no digestive system - Tapeworm is long & thin = large SA:V ratio. -Lives in small intestine so is surrounded by host's digested food. - Absorbed by diffusion over entire body surface.
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Talk about head lice (pediculus humanus capitis).
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- Wingless insects = unable to fly. - Legs are poorly adapted to jumping & walking. - Eggs hatch after 1-2 weeks. - Eggs hatch into a nymph which after a series of moults becomes an adult. - The adults & nymphs feed on blood, which in the case of head lice is sucked from the scalp of the host.
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