Quiz 32: Digestion and Nutrition


Autotrophic organisms take inorganic compounds from their surroundings to synthesize the compounds they need for growth. They can synthesize their own food. Heterotrophs on the other hand cannot synthesize their own food. They depend on Autotrophs to supply the compounds needed for growth. Phototrophic organisms have chlorophyll pigments which absorb sunlight and use the energy to synthesize necessary compounds. Chemotrophic organisms do not possess chlorophyll and hence cannot absorb sunlight. They gain their energy from inorganic chemical reactions. Herbivores are those animals which feed only on plants while carnivores feed on herbivores and other carnivores. Omnivores eat both plants and animals while insectivores eat mainly insects and worms.

The characteristics of suspension feeders are: • Use ciliated surfaces to produce currents which draw the food particles into their mouths. • Some use mucous sheets to convey food into their digestive system. • Others use sweeping movements of their legs which have setae to create water currents and to trap food. The advantages of suspension feeders are: • Small organisms like phytoplankton and zooplankton can be collected with the help of suspension feeding. • The disintegrating remains of dead organisms also float in the ocean. These particles can also be picked up. The limitation of suspension feeders are: • The plankton growth is not uniform in the seas. These plankton are unevenly distributed in the water. Three different groups of animals that are suspension feeders: • Filter feeders • Deposit feeders • Fluid feeders

The feeding adaptations of carnivores are: • Beaks or tooth-like structures • A muscular pharynx with chitinous jaws • Teeth in fish • Recurved teeth in reptiles • Bills of birds have serrated edges or upper bill is hooked • Mammals have 4 types of teeth -incisors, canines, premolars and molars All these are used for tearing apart the flesh of the prey. Some are used for holding the prey. The 4 types of teeth in mammals have 4 different functions. Incisors are for biting, cutting and stripping. The canines are for seizing, piercing and tearing. Premolars and molars serve the function of grinding and crushing. The feeding adaptations of herbivores are: • Well developed molars with enamel ridges • Well developed self-sharpening incisors • Radula of snails • Mandibles used for grinding and cutting • Wide, corrugated molars for grinding These adaptations in herbivores are used for crushing and cutting plant material. Some are scraping mouthparts. All the above mechanisms are needed to cut out the tough layer of cellulose surrounding the plant cell. This disruption is necessary to accelerate its digestion in the stomach.

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