Heredity

Q1. A student observes that in a field of sugarcane plants (asexual reproduction), almost all plants look identical, but in a nearby goat herd (sexual reproduction), every goat looks distinctly different. Which of the following best explains this observation based on the chapter content?

• A. Sexual reproduction shuffles genetic material from two parents, creating greater diversity than asexual reproduction which copies DNA with only minor errors ✓
• B. Asexual reproduction produces identical copies while sexual reproduction causes intentional mutations in DNA to create variation
• C. Sugarcane plants are genetically programmed not to vary, while goats are programmed to vary maximally
• D. The environmental conditions in the sugarcane field prevent variation, but the goat herd environment promotes it

Answer: A — The chapter explicitly states that sexual reproduction generates greater diversity than asexual reproduction due to the combination of genetic material from two parents, while asexual reproduction shows only minor variations from DNA copying errors; option B wrongly claims mutations are intentional, and C-D misattribute the cause to genes or environment rather than reproductive mechanism.

Q2. In Activity 8.1, a student finds that both parents have attached earlobes, yet their child has free earlobes. Based on Mendel's principles discussed in the chapter, what does this observation suggest?

• A. Both parents must be carrying a hidden version (allele) for free earlobes, which appeared in the child ✓
• B. The child acquired free earlobes from environmental exposure during development
• C. Free earlobes are a new mutation that arose spontaneously in the child
• D. One parent must actually have free earlobes, but it was not visible due to surgery

Answer: A — Mendel's principle states that each trait has two versions in sexually reproducing organisms; if both parents show attached earlobes but carry the hidden recessive allele for free earlobes, this trait can appear in the child—option B incorrectly attributes it to environment, C to spontaneous mutation, and D to surgery rather than inheritance.

Q3. A farmer notices that a trait appears in 5% of a wild plant population while another trait appears in 85% of the same population. Which trait most likely arose earlier in the species' history?

• A. The trait appearing in 85% of the population, as it has had more time to spread through the population ✓
• B. The trait appearing in 5% of the population, as rare traits are always older
• C. Both traits arose at the same time since they coexist in the population
• D. The question cannot be answered without knowing the reproduction method

Answer: A — The chapter's Question 1 and concept of accumulation of variation indicate that older traits have had more generations to become established and common in the population, while newer traits remain rarer; option B incorrectly assumes rarity indicates age, and C ignores the principle that trait frequency reflects historical prevalence.

Q4. During a biology lesson, a student crosses two tall pea plants from Mendel's F1 generation (which were produced by crossing a tall and short parent). The student expects all offspring to be tall, but instead finds a 3:1 ratio of tall to short plants. What does this result demonstrate?

• A. Both F1 tall plants carried a hidden version of the shortness trait that was inherited from their short parent ✓
• B. The tall F1 plants mutated during self-pollination to produce short offspring
• C. The soil conditions caused some tall plants to become short in the F2 generation
• D. One of the F1 tall plants was actually heterozygous and the other was homozygous

Answer: A — The chapter explains that F1 plants inherit both tallness and shortness traits from their parents but express only tallness, and when self-pollinated produce the 3:1 F2 ratio—this proves both alleles were present but hidden; option D partially describes this but uses technical terminology beyond the chapter scope, while B and C wrongly attribute it to mutation and environment.

Q5. A breeder wants to understand why crossing two healthy, normal-looking rabbits occasionally produces offspring with a rare genetic condition. Using Mendel's principles, which explanation best fits this observation?

• A. Both parents are carriers of recessive alleles for the condition; when each parent contributes their recessive allele, the condition appears in the offspring ✓
• B. The condition is caused by environmental stress during pregnancy, not inheritance
• C. The rare condition is a new mutation that occurs randomly during reproduction
• D. One parent must have had the condition but it was not visible due to camouflage or medical treatment

Answer: A — Mendel's work shows that organisms inherit two versions of each trait, and a recessive condition appears only when both alleles are recessive—both normal-looking parents can carry hidden recessive alleles; B and D attribute it to environment and hidden phenotypes, while C ignores the hereditary pattern demonstrated by repeated occurrence.

Q6. Assertion (A): In sexually reproducing organisms, each trait is influenced by genetic material from both the mother and the father. Reason (R): Sexual reproduction involves the combination of genetic material from two different parents, which is why greater variation is produced compared to asexual reproduction. Choose the correct option:

• A. Both A and R are true and R is the correct explanation of A ✓
• B. Both A and R are true but R is not the correct explanation of A
• C. A is true but R is false
• D. A is false but R is true

Answer: A — The chapter explicitly states that both parents contribute equal amounts of genetic material and that sexual reproduction creates greater diversity due to combining genetic material from two parents; R correctly explains why A is true, making option A correct.

Q7. Assertion (A): All variations that appear in a population have equal chances of surviving in the environment. Reason (R): Environmental conditions select for certain variations, forming the basis for evolutionary processes. Choose the correct option:

• A. Both A and R are true and R is the correct explanation of A
• B. Both A and R are true but R is not the correct explanation of A
• C. A is true but R is false
• D. A is false but R is true ✓

Answer: D — The chapter states that variations do NOT have equal chances of survival and that environmental selection occurs—A is explicitly contradicted by the text which asks 'Do all these variations have equal chances? Obviously not,' while R is the correct principle explaining differential survival.

Q8. Assertion (A): In Mendel's F2 generation from self-pollination of F1 tall pea plants, approximately 75% of plants are tall and 25% are short. Reason (R): The F1 tall plants are homozygous for the tallness allele and produce only tall offspring when self-pollinated. Choose the correct option:

• A. Both A and R are true and R is the correct explanation of A
• B. Both A and R are true but R is not the correct explanation of A
• C. A is true but R is false ✓
• D. A is false but R is true

Answer: C — The chapter clearly demonstrates that F1 tall plants produce the 3:1 ratio in F2 generation (A is correct), but this occurs because F1 plants are heterozygous (not homozygous as stated in R)—they carry both alleles but express only tallness; R's explanation is factually incorrect.

Q9. A scientist examines a population of beetles and finds that 92% have black shells while 8% have red shells. Based on the principle of trait accumulation during reproduction, which inference is most reasonable?

• A. The black shell trait likely arose earlier in the population's history and has become more prevalent through successive generations ✓
• B. The red shell trait is older because it is rarer and has been diluted over time
• C. Both traits arose in the current generation and will stabilize at different frequencies
• D. The frequency of traits has no relationship to when they first appeared in the population

Answer: A — The chapter's principle of accumulation of variation indicates that traits appearing in higher percentages have had more time to spread through successive generations; option B reverses this logic incorrectly, C assumes both are recent, and D contradicts the mechanism of inheritance over time.

Q10. A gardener observes that in a hybrid tomato plant variety (from sexual reproduction), individual plants show significant variation in fruit size, colour, and shape, while in an experimental line created through tissue culture (asexual reproduction), all plants are virtually identical. What is the most scientifically accurate explanation for this observation?

• A. Sexual reproduction generates variation through recombination of genetic material from two parents, while asexual reproduction produces clones with only minor DNA copying errors ✓
• B. Hybrid plants are inherently unstable and decompose more easily, causing visible variation
• C. Tissue culture deliberately introduces mutations to increase variation in plants
• D. Sexual reproduction creates variation due to environmental stress, while asexual reproduction is protected from environmental effects

Answer: A — The chapter explains that sexual reproduction shuffles genetic material from two parents creating diversity, while asexual reproduction copies DNA with only minor copying errors—option A directly matches chapter principles; B incorrectly claims instability, C wrongly states mutations are deliberate, and D misattributes variation to environment rather than reproductive mechanism.