Inheritance

The governing concept is the distinction between acquired and inherited traits. Exercise can enlarge muscles during an individual’s lifetime, but this body change normally does not alter the DNA of the reproductive cells. Since evolution across generations depends on heritable genetic variation, the exercised muscles are not transmitted as a programmed trait to offspring. Thus A is correct; B, C and D confuse acquired changes with genes or fossils.

The governing distinction is between somatic changes acquired during life and hereditary information carried by reproductive cells. Exercise, scars or learned abilities may alter body cells or behaviour, but they usually do not change the genes in sperm or eggs. Without a change in reproductive-cell DNA, the trait is not transmitted genetically. Option B is correct; usefulness, fossils and dominance do not explain inheritance.

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.

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.

Heredity transmits genetic information and traits from parents to offspring, whereas variation creates differences among offspring. Evolution requires both: variation provides alternative traits, and heredity preserves and passes advantageous heritable traits to later generations. Natural selection can therefore change the frequency of traits in a population. Heredity alone would copy traits, and acquired traits alone do not adequately explain genetic evolution.

DNA stands for Deoxyribonucleic Acid. It stores genetic information in cells and plays an important role in the transmission of traits from one generation to the next. Dinucleic Acid is not the standard scientific expansion of DNA. Exam tip: Memorise the full forms and correct spellings of common abbreviations such as DNA, RNA and ATP.

A gene is the basic unit of heredity. It is a specific segment of DNA that carries genetic information for a trait and can be passed from parents to offspring. A chromosome is a structure made of DNA and proteins that contains many genes, so it is not the basic unit itself. Exam tip: For the phrase “basic unit of heredity,” choose gene.

DNA stores an organism’s genetic information. During cell division and reproduction, this information is passed to offspring, enabling the inheritance of traits. Oxygen is transported mainly by haemoglobin, not DNA. Exam tip: Remember DNA as the storehouse of genetic information.