Class 10 Science Chapter 8 MCQ

British scientist J.B.S. Haldane suggested in 1929 that life must have developed from the simple inorganic molecules (such as methane, ammonia, hydrogen Sulphide etc.) which were present on the earth soon after it was formed. He said that the condition on earth at that time could have converted simple inorganic molecules into complex or organic molecules which were necessary for life. The theory of origin of life on earth proposed by Haldane was confirmed by experiments conducted by Stanley L. Miller and Harold C. in 1953.

Here, all the statements are correct. Hence, your answer will be option [D].

The theory of evolution of species by natural selection was given by “Charles Darwin”. “Mendel” gave the laws of inheritance of traits. “Morgan” worked on “Drosophila Melanogaster” and gave concept of linked genes. “Lamarck” gave the theory of inheritance of acquired characteristics.

The number of sex chromosomes in the zygote of humans is one pair. It is not always a perfect pair. In females, it is perfect with two X-chromosomes. However, in males, there is one X-chromosome and one Y-chromosome.

Here, all the statements are correct. Hence, your answer will be option [D].

Genes are stretches of DNA found on chromosomes of a cell. A gene contains information for making proteins in a “Cell”. A specific gene is located on a particular chromosome in individuals of a given species.

Acquired traits developed in response to the environment. The size of the body is an acquired trait because it can be changed on the availability of less or more food. The other three colour of eye and skin and nature of hair are inherited characters from the parents.

Accumulation of variation over several generation forms new species. Genetic drift accumulates different changes in sub-populations of a species. Also, natural selection may also operate differently in the different geographic location. Eventually different groups of new species will be formed.

Father is responsible for the sex of the baby boy or girl which is born. If the husband contributes a “Y sex chromosome” at fertilization through his sperm, then the baby born will be a boy. This means that it is the sex chromosome contributed by husband which decides the sex of the baby which the wife will give birth to. Thus, husband is responsible for the sex of the baby (boy or girl) which is born.

Two individuals of a species share maximum number of common characters. A species is a population of organisms consisting of similar individuals which can breed together and produce fertile offspring.

All variations in a species do not have equal changes of survival. Some of the variations may be so drastic that the new DNA copy cannot work with the cellular apparatus it inherits. Such a newborn cell dies soon. Depending on the nature of variations, different individual will have different kinds of advantage. Variations results from changes in genetic composition. Advantages of variations are selected by environmental factors. This leads to evolution and speciation. In asexual reproduction, there is minimum variation that is due to small errors in DNA copy.

Fossils refer to the petrified remains of organisms that live in the past and get preserved in rocks. The fossil position in the layer of earth related to the time of extinction of organisms. If the fossils of an organism is found in the deeper layers of earth, then it is predicted that extinction of organism has occurred thousands of years ago. Whereas the fossils found closer to the surface are more recent.

Radish and carrot represent homologous structures as they have the same structure or basic design through they are different species.

The new combination in F2 progeny will be round yellow and wrinkled green. The phenotype ratio of 9 : 3 : 3 : 1 is obtained. Round yellow : Round green : Wrinkled yellow : Wrinkle green = 9 : 3 : 3 : 1

New species may be formed if the DNA changes are severe enough, such as a change in the number of chromosomes. This leads to new variations.

The maleness of a child is determined by the Y-chromosome in zygote inherited from the father. If X-chromosome is inherited from the father, the zygote will develop into girl.

The incorrect statement is [D] as fat molecules are not related to genes. On the other hand, genes contain information for making proteins in a cell. The proteins synthesized may be enzymes that catalyses biochemical reaction. The enzymes also control the process of making hormones. This explains why A, B and C are correct.

The nature of the cross will be cross fertilization. Fertilizing a plant using pollen from another plant of the same species is cross fertilization. Double fertilization is a complex fertilization mechanism of flowering plants. It involves fusion of a male and female gamete. Self-pollination is a form of pollination that occur in a flower that has both stamen and carpel.

Exchange of genetic material take place in sexual reproduction as genes of two parents are involved. In asexual reproduction, no exchange of genetic material take place as a single parent is involved. Budding and vegetative reproduction are types of “Asexual Reproduction”. So, there is no exchange of genetic material.

The sex of a child is determined by the Y chromosome that is present in a sperm.

F2 generation can be obtained by allowing flowers on the plants of F1 generation to be self-pollinated.

Mendel ensured that he used pure breeding plants for his experiments by letting each variety self-pollinate for several generations

The accumulation of “heat resistant variation” or trait in some bacteria will ensure its survival, even when the temperature in its environment rises to much due to a heat wave or some other reasons. On the other hand, the bacteria which did not have these variations to withstand heat would not survive under these circumstances and die.

Here, all the statements are correct. Hence, your answer will be option [D].

Here, all the statements are correct. Hence, your answer will be option [D]. tors that live on this earth long, long ago.