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.

In the context of evolution, the use of feathers by birds for flying means that birds have evolved from reptiles. Dinosaurs have feathers but could not fly using them. Birds, later adapted the feathers for flight. Since, dinosaurs were reptiles, this means that birds have evolved from them.

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

When pure bred tall plant with phenotype (TT) crossed with short plant with phenotype (tt), the possible progeny in F2 generation: TT (1), tt (1) and Tt (2). Thus the ratio of pure tall (TT) to pure short (tt) is 1:1.

Evolution is a sequence of gradual changes which take place in the primitive organisms over millions of years in which new species are produced. Since the evolution is of the living organisms, so it is also called “organic evolution”. All the plants and animals or organisms which we see today around us have evolved from some or the other ancestors that live on this earth long, long ago.

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.

The acquired traits of organisms cannot be passed on to their future generations. If we breed some mice, all the progeny of mice will have tails, just like their parents. Now, if we cut the tails of these first-generation mice surgical and breed them, we will get new mice, all with full details. It has been observed that even after cutting the tails of mice for a number of generations, a tail-less mouse is never born. Actually, the cut tail of mice is an acquired trait which is never passed on to their progeny. This is because cutting the tails of mice does not change the genes of their reproductive cells or gametes.

The genotype of the tall parent can be depicted as TtWW. It is because T is the gene for tallness, t for dwarfness; W is the gene for violet flowers, while w is for white flowers. Thus, T and W are dominant genes, whereas t and w are recessive genes.

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.

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.

Wings of birds and wings of bat are “Homologous”. Since they have some basic design however their origin is different.

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 weight reduction due to starvation will not change the DNA of the germ cells, because low weight is not a trait that is genetically controlled or inherited. Thus, low weight parents may have heavy weight progeny. Traits which are not inherited, i.e. the acquired traits are simply changes in non-reproductive tissues, so, cannot be passed on to DNA of germ cell. Evolution results from change in frequency of genes in a population over several generations.

A zygote that has an X-chromosome inherited from father will develop into a girl. All children weather boys or girls inherited an X-chromosomes from their mother. Thus, sex is determined by what they inherited from their father. A child who inherits X-chromosome from her father will be a girl, and one who inherits a Y-chromosome from him will be a boy.

In human males, one pair called the “Sex chromosomes” are unpaired. Here, one is a normal sized X-chromosome while other is a short Y-chromosome. Women have a perfect pair of sex chromosomes, both called X.

The cross between RRyy and rrYY seeds will produce RrYy (round and yellow) seeds in F1 generation, because round and yellow are dominant traits.

In F1 generation, the cross between “TT” and “tt” will result into all tall plants. Thus, tallness is the dominant trait or character. Whenever the two traits of a character are crossed, the F1 plants show only one of the traits. This trait is called the dominant trait. The other trait (dwarfness in this case) that does not express itself in F1 generation is called the recessive trait.

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.