Thursday, April 2, 2015

Obtaining and Utilization Food Class 7 Science Solved question (Basic Science Questions answers)

A. Answer these questions

1. Name the three life process help living being to procure energy from food?

Answer: Three life processes that help living organisms to procure energy from food are:

(i) Digestion (Nutrition)

(ii) Respiration

(iii) Transportation

2. What are Autotrophs? Name an organism other than other than green plant that is an autotroph.

Answer: Autotrophs are organisms that can prepare their own food.

Chlamydomonas is a type of green algae which is an example of an autotroph, other than green plants.

Cyanobacteria are also an example of autotroph.

3. Name three type of heterotrophic nutrition

Answer: Three types of heterotrophic nutrition are:

(i) Saprophytic nutrition (ii) Parasitic nutrition (iii) Holozoic nutrition

4. What are enzymes?

Answer: Enzymes are chemical substances that act as biological catalysts and are important for carrying out biochemical processes, such as digestion, in our body

5. Name the steps involve in holozoic nutrition.

Answer: Holozoic nutrition involves the following steps:

(i) Ingestion (ii) Digestion (iii) Absorption (iv) Assimilation (v) Egestion

6. Name the three things green plant need in order to photosynthesize.

Answer: Green plants require the following three things to prepare their food:

(i) Carbon dioxide (CO2) (ii) Water (H2O) and (iii) Sunlight

7. What is the juice secreted by liver called? What does it do?

Answer: Juice secreted by the liver is called bile. It helps in digestion of fats by breaking them down into small droplets

8. Name a parasitic plant, and a parasite that live in our intestine?

Answer: Cuscuta is a parasitic plant. Tapeworm ( Ascaris) is a parasite that lives in our intestines.

9. What is digestion?

Answer: Digestion is the process of breaking down complex food material into simpler form so that they could be absorbed into the watery blood plasma.

10. Name the Holozoic animal that not a herbivore or a carnivore or an omnivore?

Answer: Spider (also earthworm, mushroom is a Holozoic organism but not a herbivore or a carnivore or an omnivore

B. Answer these questions

1. What are saprophytes and parasites?

Answer: Saprophytes: Saprophytes are the organisms that feed on dead and decaying organic matter. Example: Bread mould (a fungi)

Parasites: Parasites are organisms that derive their nutrition from other animals or plants by living inside their body or on it. Example: Round worm

2. Write two special feature related to the teeth of herbivore?

Answer: Herbivores feed on green plants, which are difficult to chew and digest due to cellulose in them. Herbivores have large, dull, flat teeth. These teeth are excellent for chewing and breaking down tough plant material. They also have sharp - edged incisors in the front to help them cut the grass.

3. Write briefly about the process of nutrition in amoeba?

Answer: Amoeba use fingers like projections called pseudopodia to engulfing the food. Then food reach the food vacuole, where it gets digested by the action of enzymes.

4. Why do carnivores plant trap insects? Explain how such plant trap insect?

Answer: Carnivore plants are found at places where there is lack of nitrogen in soil. Therefore they trap insects and digest them to fulfil their nitrogen requirement for making protein. For example, sundews and pitcher plants.

Leaves of these of plants are modified to secrete sticky substance that attract and capture insects.

5. What are Symbionts? Explain with an example.

Answer: Symbionts are organisms that live together for mutual benefits.

An example of symbiont is nitrogen fixing bacteria. They live in the root nodules of plants to get food and fix atmospheric nitrogen into soluble form, which is useful for plants. They fix nitrogen for plants and plants provide them food and protection.

6. What is digestive juice in mouth called? What enzymes does it contain and what does it do?

Answer: Digestive juice in the mouth is called saliva.

Saliva contains enzyme called amylase. This enzyme acts upon complex carbohydrates starch to convert them into simpler carbohydrates such as sugar (maltose) . Thus, saliva helps in partial digestion of carbohydrates.

7. What is peristalsis? Does it occur only in the oesophagus?

Answer: The alternate relaxation and contraction of organs made of smooth muscles in our body is called peristalsis. For example food pushed down the oesophagus by peristalsis.

No, it occurs in the whole alimentary canal and not just in oesophagus.

8. The juice produced in stomach contain an acid and as well as enzymes. Name the enzymes. What do the acids and enzyme do?

Answer: The juice produced in the stomach contains hydrochloric acid and pepsin enzyme. Hydrochloric acid kills the bacteria and other pathogens, and pepsin helps in the digestion of proteins.

9. What happen to the undigested food that remains in large intestine?

Answer: At first some water is absorbed from the undigested food and remaining are thrown out of the body via the anus in the form of semi­solid waste (faeces) .

C. Answer these questions

1. How would you show that chlorophyll is needed for photosynthesis?

Answer: Take a leaf and put it in a test tube, half filled with alcohol. The leaf should be submerged in the alcohol in such a way that half of it remains outside. Put the test tube in a beaker filled with water and heat it.

Direct heating of the test tube containing alcohol should be avoided as it may catch fire.

The part of leaf submerged in the alcohol will start losing colour, as alcohol destroys its green pigment, chlorophyll. When this half leaf loses its colour completely, pull out the leaf and wash it gently to remove alcohol. After a few minutes, put some drops of iodine on the green and non ­ green halves.

Observation: It is observed that the green part changes its colour to blue­black on dropping iodine. This indicates the presence of starch. The green pigment synthesises starch by trapping energy and gives blue­black colour on reaction with iodine. The colourless part of the leaf gives no such result.

Thus, it is confirmed that presence of chlorophyll is a must for photosynthesis to take place.

2. What happen to the food in the small intestine? 

 Answer: Complete digestion and absorption of food occur in the small intestine. As the food enters the small intestine, it is acted upon by a number of digestive juices secreted by the liver, pancreas and walls of small intestine.

Bile juice is secreted by the liver that breaks fat into smaller pieces to make it easily digestible.

Pancreatic juice secreted by pancreas act upon carbohydrates and proteins to digest them completely.

Walls of small intestine have many fingers like projections called villi, which help in increasing the surface area of the small intestine. This in turn helps in efficient absorption of digested food.

3. How many teeth an adult have ? Describe different types of teeth?

Answer: An adult human has 32 teeth arranged in the upper and lower jaws.

We have four kinds of teeth in our oral cavity or mouth. They are:

(i) Incisors : They are flat teeth that act like scissors. They help in cutting food.

(ii) Canines: These are sharp teeth and are very prominent in carnivores. They are pointed and help

in tearing food. They function like knives in carnivores and help them capture their prey.

(iii) Premolars: These are teeth having broad surface. They help in grinding and chewing food.

(iv) Molars : They also help in grinding the food and chewing it. They are larger than premolars

4. How did Dr. Beaumont study the function of the stomach?

Answer: see book page: 90

5. Explain how digestion occurs in ruminants?

Answer: The stomach of a ruminant (grass eating herbivores) is divided into four chambers and is capable of digesting cellulose. The four parts of the stomach are the rumen, reticulum, omasum, and abomasum.

Ruminants chew the grass partially before swallowing it. This half or partially chewed food goes to the first chamber of the stomach called rumen, where bacteria and other micro organism act on it . Then it is sent to reticulum. This half digested food is sent back to the mouth for re­chewing. This re­ chewing of half digested food is called cud chewing or rumination.

Now, complete chewed food goes to the omasum where some water gets absorbed. At last food reach to abomasums where final digestion occur b the action of enzymes.

D. Fill in the blanks

1. The tubelike mouthpart of a butterfly is called a proboscis.

2. The process by which digested food enters the blood is called absorption.

3. Chemical substances produced in the body of an organism to help in the process of digestion are called enzymes.

4. The tube, starting from the mouth and ending in the anus, through which food passes is called the alimentary canal.

5. Digestion begins in the mouth.

6. The finger like folds in the wall of the small intestine are called villi

E. Choose the correct options

1. Heterotrophs are organism which (c) depend on sources other than themselves for food

2. Iodine makes starch turn (a) blue­black

3. The wall of the large intestine absorb (a) water

4. Assimilation is the process by which (c) digested food is utilised by the body5.

5.Cellulose forms a large part of the undigested matter we egest. It is

(d) undigested sugar

6. Plants store food as (d) starch


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