Inheritance

Correct answer: A. Independent assortment

A dihybrid cross follows two pairs of contrasting traits at the same time. Mendel’s principle of independent assortment states that, during gamete formation, the allele pair for one trait is distributed independently of the allele pair for another trait, when the relevant conditions apply. This produces combinations not seen in the original parents. Therefore option A is correct; blending, acquired-trait inheritance and chromosome destruction do not explain the result.

Correct answer: A. Because evolution needs the trait to pass through generations

Natural selection can influence evolution only when a beneficial difference is heritable. A trait may help one individual survive, but if it is not transmitted to offspring, it will not become more common through reproduction. Evolutionary change requires inherited variation to persist and alter the composition of a population over generations. Option A is correct. Survival is relevant, but without inheritance its advantage generally ends with that individual rather than spreading through the lineage.

Correct answer: A. Independent assortment of alleles for different traits.

When offspring display combinations of traits that were not present together in the parents, the hereditary factors for the two traits are not being transmitted as one inseparable package. During gamete formation, allele pairs for different traits can assort independently and then recombine during fertilisation. This is Mendel’s law of independent assortment, so option A is correct. The other choices concern unrelated or scientifically unsupported ideas.

Correct answer: A. It must be inherited and provide a survival or reproductive advantage

For a useful variation to become common, it generally must be heritable so that it can pass to offspring, and it must improve survival or reproductive success under the relevant conditions. Natural selection can then increase its frequency over generations, although chance and population structure also matter. Option A gives the essential requirements. B ignores inheritance and selection, C is false because variations may be beneficial, neutral or harmful, and D contradicts heredity.

Correct answer: A. Because evolution is linked with inherited changes across generations

Evolution is a population-level change that becomes visible across generations. A useful characteristic can help one individual survive, but it can influence the future of a population only if the genetic basis of that characteristic is transmitted to offspring. Without inheritance, the change usually ends with the individual and cannot accumulate through reproduction. Thus option A is correct. B is false because usefulness does not guarantee inheritance, while C and D contradict basic evolutionary biology.

Correct answer: A. Inherited changes accumulate over generations and guide evolution

Heredity transmits genetic information from parents to offspring, allowing particular variations to persist in a population. When heritable variations affect survival or reproduction, natural selection can change their frequency over many generations. This population-level, long-term change is evolution. Therefore option A correctly connects heredity with evolution. Acquired traits are not automatically inherited, heredity does not always prevent change, and evolution is not completed within the lifetime of one organism.

Correct answer: A. It can pass to the next generation

The governing concept is inheritance through germ cells. Reproductive cells, such as sperm and ova, contribute genetic material to offspring during sexual reproduction. Therefore, a gene present in such a cell has a route to enter the next generation and influence an inherited trait. It is not restricted to digestion, destined to become a fossil, or unable to pass on. Hence option A correctly states its importance.

Correct answer: A. Independent assortment of different traits

A dihybrid cross follows two pairs of contrasting traits at the same time. During gamete formation, the allele pair for one trait can separate independently of the allele pair for the other, producing parental and non-parental combinations. This observation supports Mendel’s law of independent assortment. It does not support acquired inheritance, chromosome destruction, or permanent blending of traits.

Correct answer: B. When it occurs in a reproductive cell and can pass to offspring

A mutation is a change in genetic material, but it can influence evolution only when its effect is heritable. A mutation in a germ cell or an early cell giving rise to gametes may enter the next generation. If it occurs only in a body cell, it usually affects the individual but is not inherited. Thus option B is correct; the other choices describe injury, no mutation, or non-reproductive lethality.

Correct answer: A. Because it will not regularly pass to offspring

Natural selection changes population frequencies when advantageous variations are inherited and passed through reproduction. A non-heritable useful trait may help one individual, but its offspring will not consistently receive the genetic basis for that trait. Consequently, the trait cannot reliably increase across generations, even if it improves survival temporarily. Therefore option A is correct; the other options are unrelated or biologically unsupported.