Class 10 Science Chapter 8 MCQ

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.

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

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.

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.

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.

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.

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.

A trait of an organism is influenced by both maternal and paternal DNA. It is passed down from one generation to another through genes found on the chromosomes. During sexual reproduction, both mother and father passed their genes to their children, thus determining their traits or characteristic features.

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.

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 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.

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.

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 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.

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.