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Life Processes in Animals - Nutrition in Animals

Grade 7CBSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Animal nutrition includes nutrient requirement, mode of intake of food, and its utilization in the body. It is a heterotrophicheterotrophic mode of nutrition.

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The process of digestion in humans involves five main steps: Ingestion→Digestion→Absorption→Assimilation→EgestionIngestion \rightarrow Digestion \rightarrow Absorption \rightarrow Assimilation \rightarrow Egestion.

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The human digestive tract or alimentary canal consists of the buccal cavity, oesophagus, stomach, small intestine, large intestine ending in rectum, and the anus. The total length of the alimentary canal is approximately 99 meters.

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Complex food substances like CarbohydratesCarbohydrates are broken down into simpler substances like GlucoseGlucose during digestion.

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The stomach secretes mucous, hydrochloric acid (HClHCl), and digestive juices. HClHCl kills bacteria and provides an acidic medium for protein digestion.

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The small intestine receives secretions from the liver (bile) and the pancreas (pancreatic juice). The inner walls have finger-like outgrowths called villivilli that increase the surface area for absorption of digested food.

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Ruminants (grass-eating animals like cows) have a specialized stomach with a chamber called the rumenrumen. They perform 'rumination' where partially digested food called cudcud returns to the mouth for chewing.

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Amoeba is a microscopic single-celled organism that captures food using pseudopodiapseudopodia (false feet) and digests it inside a food vacuolefood\ vacuole.

📐Formulae

Starch→Salivary AmylaseSugarStarch \xrightarrow{Salivary\ Amylase} Sugar

Proteins→Pepsin/TrypsinAmino AcidsProteins \xrightarrow{Pepsin/Trypsin} Amino\ Acids

Fats→Bile Juice (Emulsification)Fat DropletsFats \xrightarrow{Bile\ Juice\ (Emulsification)} Fat\ Droplets

Fats/Lipids→LipaseFatty Acids+GlycerolFats/Lipids \xrightarrow{Lipase} Fatty\ Acids + Glycerol

Complex Carbohydrates→Digestive JuicesGlucoseComplex\ Carbohydrates \xrightarrow{Digestive\ Juices} Glucose

💡Examples

Problem 1:

A student consumes 20002000 calories in a day. If 20%20\% of these calories are derived from proteins, how many calories come from proteins? Use vertical multiplication to show the calculation of 2000×202000 \times 20.

Solution:

The calories from protein are calculated as 20100×2000=400\frac{20}{100} \times 2000 = 400 calories.

Explanation:

To find 20%20\% of 20002000, we first multiply 20002000 by 2020: 2000×2040000\begin{array}{r} 2000 \\ \times 20 \\ \hline 40000 \end{array} Then, we divide by 100100: 40000100=400\frac{40000}{100} = 400. Thus, 400400 calories are from proteins.

Problem 2:

If the surface area of a smooth small intestine wall is S=0.5 m2S = 0.5\text{ m}^2, and the presence of villivilli increases the surface area by a factor of 3030, what is the total effective surface area StotalS_{total} for absorption?

Solution:

Stotal=15 m2S_{total} = 15\text{ m}^2

Explanation:

The effective surface area is calculated by multiplying the initial area by the increase factor: Stotal=S×30S_{total} = S \times 30 Stotal=0.5×30=15 m2S_{total} = 0.5 \times 30 = 15\text{ m}^2