Science M.C.Q

Lack of oxygen in muscles causes accumulation of lactic acid, due to anaerobic respiration. Accumulation of lactic acid leads to cramps in the legs of sprinters.

The food is ingested through the mouth. It is then digested in the mouth, the stomach and the small intestine. Then, it is absorbed and assimilated in the small intestine, the reabsorption of water takes place in the large intestine and the undigested waste is egested through the anus.

In biology, ATP is known as the energy currency of a cell. It is a high energy molecule that stores the energy.

Capillaries do not have valves, while heart, arteries and veins have valves to prevent the back - flow of blood.

During anaerobic respiration in human beings, pyruvic acid is converted into lactic acid in the mitochondria of the muscle cells.

The blood leaving the tissues becomes richer in carbon-dioxide, i.e. it becomes deoxygenated.

In insects (such as cockroaches, grasshoppers), the tiny holes called spiracles are present on the body. Air enters the body through these holes.

In the muscle cells that lack oxygen, concentration of lactic acid is increased. This is because, here, anaerobic respiration takes place in which glucose is converted into lactic acid with the release of a small amount of energy.

White blood cells or WBCs destroy the disease causing germs. They are like soldiers that protect the body from various infections.

In Pisces, the heart does not pump oxygenated blood to different parts of the body. This is because Pisces have two - chambered heart with one auricle and one ventricle.
Since, Both the auricle and ventricle remain undivided, only deoxygenated blood passes through it. The deoxygenated blood then enters the gills for oxygenation from the ventricle.

The digestion of proteins begins in the stomach by pepsin.

In earthworm, the main excretory organs are nephridia. It functions like a kidney.

Rate of breathing in aquatic animals is much faster than terrestrial animals. This is because a faster rate of breathing provides more oxygen to the aquatic animals.

During contraction, valves prevent the back - flow of blood inside the heart.

When guard cells have water, stomatal pores open and when water moves out of the guard cells, these pores close.

Parakeet and Paramecium feed on solid food.
Therefore, they have holozoic mode of nutrition.

Prawn is an aquatic animal that respires through gills. The gills extract oxygen dissolved in water and take away carbon-dioxide from the body.

Transpiration is the loss of water through the stomata of leaves and other aerial parts of the plants in the form of water vapour. It provides a transpirational pull, which is responsible for the upward movement of water and dissolved minerals from the roots to the leaves through the stem.

Veins carry carbon-dioxide rich blood from the various tissues of the body to the heart.

Pulse is the expansion of the artery each time the blood is forced into it.

Leech and earthworm breathe only through their moist skin. Fish breathe through gills, while frogs breathe through lungs and skin.

Fungi (yeast, mushroom, bread mould) are saprophytes. They obtain their food by breaking it outside the body and then absorbing it.

The main excretory unit in the human excretory system is called nephron. It produces urine and maintains the homeostasis of the body.

This is because herbivores mainly eat plants.Plants contain cellulose, which is difficult to digest.
Hence, they have the longest small intestine.

White blood cells make chemicals known as antibodies that help to fight against infection and protect the body from foreign particles.

During blood circulation, blood passes through the kidneys. This blood contains both useful and waste materials. The kidneys filter the wastes from the blood and produce urine. From the kidneys, the urine goes into the urinary bladder through two narrow tubes called ureters. The urinary bladder stores the urine until it is forced out of the body, through an opening known as the urethra.

Water absorption through roots can be increased by keeping the potted plants under the fan.

During daytime, the carbon-dioxide produced through respiration is used up in photosynthesis by leaves. In fact, more carbon-dioxide is taken in from the air for this purpose.
So, oxygen is diffused out and carbon-dioxide is diffused in.
Hence, if a plant is releasing carbon-dioxide during the daytime, then photosynthesis is not taking place.

The length of small intestine in a human adult is around 6.5 m.

The process of digestion begins in the mouth with the help of the enzymes present in the saliva.

Veins transport deoxygenated blood from various organs of the body towards the heart. Only pulmonary vein carries the oxygenated blood from the lungs to the heart.

Red blood cells do not have nuclei.

In plants, the phloem tissue is responsible for the transport of food (in the form of sugar) from the leaves to different parts of the body.

Amoebae obtain food by the process called phagocytosis, which means cell feeding.

Mucus protects the inner lining of the stomach from erosion, which can be caused by hydrochloric acid.

The device used for measuring blood pressure is called sphygmomanometer.

Tracheids are the only conducting tissue in non - flowering plants.

Carbohydrates are digested by amylases that are present in the saliva and the pancreatic juice.

The autotrophs, like plants, store energy in the form of starch.