Current Affairs 3rd Class

     Living Things Respond to Changes to their Surrounding   All living things respond to changes in their external environment. Organisms have sense organs like eyes, ear, nose, tongue and skin to detect these changes. Human respond to heat and cold in the surroundings by wearing cotton, light clothes and woolen clothes respectively. There is coordination between the brain and the sense organs to respond to changes in the surrounding. Sense organs receive the changes called the stimulus, which then reaches to brain through nerves. Brain interprets it and sends the message through the nerves to sense organs for respond. Removing hand on touching hot plate is an example of respond to the changes in the environment. Plants also respond to changes in their surroundings. Sunflower bends towards light. Light is stimulus and bending is response. Movement of root under the ground and stem away from it, Mimosa pudica (touch me not) unfurls its leaves on touching, etc. are the examples of plants reasons to the changes in the surroundings. Look at the following picture to understand the plants respond to change according to their surroundings:     Insects like ants, cockroaches, and butterflies grasshoppers have a pair of feelers as sense organs. Feelers respond to touch and smell stimulus. Non living things do not respond to any kind of changes in the surrounding.                   How do we respond if there is too cold in the surrounding? (a) By wearing silk clothes (b) By wearing cotton clothes (c) By wearing woolen clothes (d) By wearing rain coat (e) All of these   Answer: (c) Explanation Cold is a stimulus and wearing woolen clothes is response. Woolen clothes keep our body warm in cold temperature. Therefore, option (c) is correct and rest of the options is incorrect.         Which one of the following sense organs has largest-surface area? (a) Eye (b) Nose (c) Tongue (d) Ear (e) None of these   Answer: (c) Explanation The surface area of tongue is largest as compare to above given sense organs. Therefore, option (c) is correct and rest of the options is incorrect.

    Source of Food for Plant and Animal   Food is essential because it gives energy for growth and to do various activities of day to day life. Plants prepare its own food with the help of water, carbon dioxide and sunlight. Leaves of plant are green in colour because of the presence of chlorophyll. Plants prepare food for itself by trapping sun's light in the presence of water and carbon dioxide. Plants need little amount of food prepared by them for immediate consumption, remaining food is stored in other parts of plants like root, stem etc. Animals are dependent on plants for their food. Animals also eat the flesh of other animals. Hence animals are directly or indirectly dependent on plants. The process of food obtained by living things is best described by a chain called food chain.   Look at the following picture of the process of photosynthesis:     Look at the following picture of food chain:                Which one of the following performs photosynthesis? (a) Green Plants (b) Elephants (c) Sun (d) All of these (e) None of these   Answer: (a) Explanation All the green plants make their food by photosynthesis. Therefore, option (a) is correct and rest of the options is incorrect.         Leaves of plant are green in color because of _____? (a) Carbon dioxide (b) Oxygen (c) Chlorophyll (d) All of these (e) None of these   Answer: (c) Explanation Leaves of plant are green because of the presence of Chlorophyll. Therefore, option (c) is correct and rest of the options is incorrect.

    Food of Living Things         Different Animals have Different Feeding Habits On the basis of kinds of food eaten by the animals, they can be broadly classified into three groups.        Plant Eating Animals Animals like horse, cow, goat, buffaloes like to eat grasses whereas rabbits, rats and squirrels love to eat seeds, nuts and fruits. These animals are also called herbivores because they eat only plants or plant products.        Flesh Eating Animals Animals like lion, tiger, etc. eat the flesh of other animals. They are called carnivores.         Flesh and Plant Eating Animals Some animals eat plants and flesh both. Human beings, as well as few animals like crow, bear and some birds like to eat both. The organisms which eat both plant and flesh of animal or animal product are called omnivores. For example: human beings eat rice, fruits, wheat, and vegetables pulses etc. which are plant products. They also eat eggs, fishes, meat etc. which are obtained from animals.        First Feeding Mechanism (Mouth) of Living Thing Herbivores have flat broad teeth to cut leaves and grasses and strong grinding teeth to grind. Herbivores like cattle swallow the food first, then they bring it again into the mouth and chew. This is called chewing the cud.   Look at the following picture of internal structure of mouth of a goat (Herbivores): Carnivores like tigers, lions, dogs have sharp front teeth to tear the flesh. Rodents like rat/mouse, squirrel and rabbits have sharp front teeth to gnaw nuts, fruits and seeds. Birds of prey like vulture, eagle, hawk, kite and owl have sharp, strong, and hooked beaks to hold and tear the flesh of prey.   Look at the following pictures of teeth of a lion (Carnivorous) and beak of a vulture:          Sharp lion teeth                     Sharp Beak Reptiles like snakes swallow their food as they do not have chewing teeth. Butterflies suck the nectar from the flowers with the help of long thin tube. Similar mechanism is found in other insects also like mosquitoes, honey bees etc. Frog uses its long rolling sticky tongue to catch insects. After catching it rolls back its tongue into the month. Elephant uses its long tubular trunk to put food and water into its mouth. Giraffe has long neck to obtain leaves and other plant products from tall trees.            Which one of the following animals eats flesh of other animals? (a) Tiger (b) Elephant (c) Parrot (d) Camel (e) more...

   Breathing in Living Things   In breathing process, living organism, takes in oxygen and gives out carbon dioxide gas. There are special organs in the living body which perform these functions. These organs are called breathing organs. Different types of organisms have different kinds of breathing organs. The following table shows the organisms and their breathing organs.   Look at the following flow chart of breathing organs in different living organism:   Animals obtain oxygen through breathing process, which produces energy by oxidizing digested food. Like animals, plants also take in oxygen for breathing and give out carbon dioxide all the time.                                                      Which one of the following doesn't breathe?                                                                                         (a)                                                (b)                                         (c)                                               (d)                                      (e) None of these   Answer: (d) Explanation All living organisms, plants and animals breathe in oxygen and breathe out carbon dioxide. Book is non living thing, hence does not breathe. Therefore, option (d) is correct and rest of the options is incorrect.          Which one of the following animals has two types of respiratory organs? (a) Human (b) Insects (c) Tiger (d) Frog (e) Dolphin   Answer: (d) Explanation Frog is an amphibian which can live both on the land and in water. It breathes through its lungs when it is outside the water and with moist skin when it is inside water. Therefore, option (d) is correct and rest of the options is incorrect.

    Growth in Living Things   All living things, plants and animals, grow with time. Pattern of growth is different in different animals. Babies of all animals grow into adult with the passage of time. A seed grows into plant and plant grows into tree.   Look at the following flow chart of the growth in living things:      Look at the following pictures of growth in living things:                  Growth is one of the main characteristics features in living things. A non living thing does not have the characteristics as discussed above. For example, pen and pencil cannot grow because these are non living things.                Match the following: