Adaptations For Nutriton


Methods of Nutriton

  • autotrophic
    • green plants make complex organic molecules from simple inorganic raw materials CO2 and water via photosynthesis and sunlight
    • also known as producers and provide foord for all other life forms
  • heterotrophic
    • consume food materials from the autotrophs
    • known as consumers and depend on producers
    • holozoic
      • nearly all animals take food into their body and break it down via digestion using a specialised digestion system
      • feeding solely on plants= herbivores solely on meat= carnivores bi of both= omnivores 
      • detrivores feed on dead and decaying materials
    • saprophytes
      • feed on dead and decaying matter without a digestive system
      • secrete enzymes onto their food and then absorb the products made
      • these are decomposers and feed extracellularly
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  • feed off another living organism known as a host
  • can live inside or on surface
  • host suffers harm and potentially death from highly specialised parasites
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Processing in the Digestive System

  • digestion and absorbtion take place in the gut (long hollow muscular tube) optimised to allow movement in one direction
  • advanced organisms have specialised guts divided to deal with specific steps in mechanical and chemical digestion and absorption
  • food is propelled along by peristalsis
  • human gut has 4  functions
    • ingestion of food via mouth
    • digestion breakdown of large insoluble food molecules via enzymes using mechanical strength of the teeth and rhythmical contractions
    • absorption of digested food into the blood through gut wal
    • egestion eliminates food that is indigestible 
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Human Digestive System

  • gut wall consists of four layers of tissues surrounding the lumen
  • outer serosa has tough connective tissue protecting the wall of the gut reducing friction of other organs
  • muscle layer consists of two layers of muscle in different directions, inner circular muscle and outer longitudinal muscle
  • these cause waves of muscular contractions (peristalsis) propelling food along, behind the food ball circular muscles contract when lonitudinal muscles relax
  • sub mucosa has connective tissue with blood and lymph vessels to remove absorbed food products and contain the nerves coordinating the muscuar contractions involved in peristalsis
  • mucosa lines the wall of the gut secreting mucus for lubrication and protection, and also smetimes secreting digestive juices or absorbs digested food
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  • absorption of nutrients by gut epithelial cells after large molecules are broken down via enzymes
  • carbohydrates are broken to disaccharides then monosaccharides. starch is hydrolised by amylase to disaccharide maltose then broken down by maltase to the monosaccharide glucose
  • proteins break down to polypeptides then dipeptides then amino acids via peptidase
  • endopeptidases hydrolyse peptide bonds
  • fats are broken to fatty acids and glycerol by lipase
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Regional Specialisation

  • the mouth
    • beginning of mechanical digestion via chewing of the teeth
    • mixing of food with saliva containing mucus and amylase beginning carbohydrate digestion
  • the stomach
    • food enters stomach and kept by contraction of muscles at entrance and exit
    • muscles contract rhythmically and peptidase begins the digestion of protein
    • optima pH of 2 via gastric juices
  • the small intestine
    • food passes into the duodenum a little at a time and recieves secretions from the liver and pancreas such as bile
    • bile salts emulsify the lipids so fat digestion begins so large globs break into tiny droplets enabing lipase action, bile also neutralises acidity of food
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Pancreas & the Small Intestine

  • pancreatic juice secreted from exocrine glands ad enters duodenum 
  • contains endopeptidases for digestion of protein
  • amylase for starch
  • lipase for lipid
  • duodenum secretes alkaline juice and mucus to keep the pH constant and for lubrication and protection
  • small intestine has villi which secrete enzymes
  • maltase for maltose
  • endopeptides and exopeptidases completing the digestion of polypeptides to amino acids
    • endopeptises hydrolyse the chain, exopeptises hydrolyse the ends
  • carbohydrate digestion is completed inside a cell
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  • the ileum at the end of the small intestine is folded and long for large surface area with villi and microvilli to increase surface area further
  • energy is required for active absorption so epithelial cells have large numbers of mitochondria
  • glucose and amino acids absorb across the epithelium by diffusion and active transport 
    • pass into capillaries 
    • carbs are continually digested so greater conc in the intestine than the blood allowing glucose to diffuse in, glucose is constantly needed for respiration and as diffusion is too slow active transport also assists
    • fatty acid are passed into lacteal lymph
    • fatty acids, glycerol, glucose and vitamins pass through membrane of epithelium by diffusion
    • disaccharides, amino acids and dipeptides require energy of ATP for active transport
    • dipeptides and disaccharides are digested intracellularly
    • glucose and amino acids diffuse from epithelium to blood
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Large Intestine & Fate after Absorption

  • 1.5 metres long 
  • caecum, appendix, colon & rectum
  • water and minerals absorbed from the colon with vitamins from bacteria resonsible for vitamin K and folic acid
  • at the rectum indigestible food is in a semi solid condition of cellulose bacteria and dead cells to be egested in defication
  • after digestion and absorption are completed. soluble foods are carried in the blood to tissues for assimilation/energy
  • glucose is used in respiration
  • amino acids are used in protein synthesis, excess is unstorable so amino groups are converted to urea and the rest to carbs and stored
  • lipids are used in membranes and hormones and for fat
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Adaptation for Diet

  • reptiles and amphibians swallow food whole whereas mammals cut it up and chew
  • mammals have a palate to separate the nasal cavity from the mouth for breathing to occur seperate from chewing and swallowing
  • carnivore guts are short as protein is easily digested but herbivore guts are long as digestion of plant material is difficult
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  • humans are omnivores with incisors, canines, premolars and molars whch arent particuarly specialised
  • herbivores have incisiors on the lower jaw cutting against a horny pad, the canines are indistiguishable. a gap called the diastema allows the tongue to operate and move the food about, behind this are the premolars and molars which interlock top and bottom as the jaw moves in a circular grinding motion. the teeth are worn to sharp edges and have unrestricted roots for continual growth. plants are a tough material and needs to be fully ground up before swallowing.
  • carnivores have sharp incisors to tear fleash from bone with good grip. canines are large and curves with sharp points for seizing, killing and tearing. premolars and molars are used to cut and crush. carnassials are specialised teeth that slide past eachother like shears as the jaw moves up and down for wider opening of the mouth aided by powerful jaw muscles for holding onto prey.
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  • symbosis involves close association between members of two different species so both recieve a benefit from the relationship
  • herbivorous animals lack the ability to make enzymes to digest cellulose, cellulase
  • as a large proportion of plant material is cellulose cell walls all of this would be wasted without the relationship between cellulose digesting bacteria that can live in their stomach
  • the animal can recieve the products of cellulose digestion where the bacteria get a place to live and feed
  • theres a region of the gut separate from the main digestive region for the bacteria so that food is kept there long enough for the bacteria to work, the bacteria arent digested and are at an optimum pH
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Cellulose Digestion

  • grass chopped by teeth, mixed with saliva, swallowed as a cud
  • rumen hold the first chamber where food is mixed with the bacteria to make glucose whch ferments to organic acids absorbed into the blood
  • CO2 and methane pass out as waste
  • fermented grass passes into next chamber and forms a cud, regurgitated for further chewing
  • cud passes back into third chamber for water reabsorption
  • last chamber is where normal stomach functions happen and protein is digested
  • digested food passes to next region for absorption in small intestine
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  • organisms that live on a host and obatin nourishment at their expense
  • often cause harm and death
  • tapeworm 
  • parasites have specialised to survive inside a host
  • tapeworms are like ribbons can be up to 10m long with a muscle head of suckers and hooks with a body of segmented linear parts
  • primary host is the human and the secondary host is the pig
  • pig is infected from eating faeces and humans are infected from eating undercooked infected pork
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Parasite Problems

  • surrounded by digestive juices and mucus
  • everything is in constant motion
  • extremes of pH 
  • hosts immune system
  • death of the host means death of the parasite
  • needs a way of penetrating host
  • needs to be able to attach itself
  • protection from immune responses
  • develop only essential organs
  • produce many eggs
  • have an intermediate host
  • resistant stages when not involved with a host
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Tapeworm Adaptations

  • suckers and double row of hooks for attachment
  • body covering to protect from immune responses
  • thick cuticle and inhibitory substances on segement to prevent digestion
  • no sensory system as dont move about, simple excretory and nervous system
  • thin with large surface area to volume ratio for simple digestive system as predigested food is absorbed over whole body
  • each segement has male and female reproductive organs as gut cant hold two tapeworms
  • vast gamete production passed out in segments in faeces
  • eggs have resistant shells to survive until eaten by secondary host 
  • further development takes place to form embryos that hatch and move into pigs muscles and then remain dormant until eaten by a human
  • adult worms cause little discomfort but dormant egg embryos form cysts in various organs and damage surrounding tissue
  • adults can be treated with drugs 
  • public health measures and frequent inspection of meat are essential measures
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