Science [2 Mark Questions]

a. Ray diagram of the defect

Myopic eye
b. In a myopic eye, rather than at the retina itself, the image of a distant object is created in front of the retina. This flaw may result from (i) an excessively curved eye lens or (ii) an elongated eyeball. With the use of a concave lens of the appropriate power, this flaw can be fixed. The flaw is fixed by returning the picture to the retina with a concave lens of the proper power.

Correction for myopic

i. Decomposers are essential in a biosphere as they return nutrients back to the environment by breaking down dead complex organic matter into recyclable simpler compounds.
ii. The flow of energy through different steps in the food chain is unidirectional as the food chain progress the energy passes from lower trophic level to upper but never vice versa.

Grass → grasshopper → frog → snake → hawk.
A food chain always start with producers and ends with top consumers.

Anaerobic respiration occurs in man when there is deficiency of oxygen during cellular respiration. In such situation, pyruvic acid is reduced to lactic acid by the lactate dehydrogenase. In yeast also, anaerobic respiration occurs in the condition of absence of oxygen.

i. A circulatory system in which the blood travels twice through the heart in one complete cycle is known as double circulation. It is commonly seen in amphibians, reptiles, birds, and mammals.
ii. The separation of the right side and the left side of the heart is useful to keep oxygenated and deoxygenated blood from mixing. This type of separation allows a highly efficient supply of oxygen to the body. This is useful in animals that have high energy needs, such as birds and mammals, which constantly use energy to maintain their body temperature. In animals that do not use energy there body temperature depends on the temperature in the environment. Animals, like amphibians and reptiles have three-chambered hearts, and tolerate some mixing of the oxygenated and de-oxygenated blood streams.

a. Amoeba reproduces through simple binary fission. Amoeba reproduces asexually through binary fission. In this process of reproduction, a single Amoeba is divided into two similar daughter cells. It grows larger and one nucleus in the Amoeba splits and forms two nuclei. The amoeba is produced by the single parent.
In Leishmania, binary fission occurs in a definite orientation due to the presence of flagellum at the end of the cell. Hence, there is a specific plane in which the fission occurs, while Amoeba can undergo binary fission in any plane.


b. Malarial parasite or Plasmodium reproduces by multiple fission. Each Plasmodium cell divides its nucleus into many small nuclei followed by the division of the cell body to form many daughter cells with each cell obtaining one nucleus. This type of reproduction is called multiple fission.

a. x is 2 and y is 4
b. A is Ethyne and B is propyne