Heredity and Evolution: Class 10 Science Q&A
47 free answers on Heredity and Evolution (Science) for Class 10 students, across CBSE, ICSE and State boards. Includes questions such as “Differentiate between acquired and inherited traits, providing an example for each.”, “How is the equal genetic contribution of male and female parents ensured in the progeny?”
Question & Answer
Questions
- ScienceClass 10CBSE
While humans have chromosomal sex determination, some organisms exhibit environmental sex determination. Give an example of an organism where sex is determined by environmental factors and briefly explain how it works.
An example of an organism where sex is determined by environmental factors is the green sea turtle (and many other reptile species like crocodiles and alligators). In green sea turtles, the sex of the hatchlings is determined by the temperature at which the eggs are incubated during a critical period of embryonic development. This phenomenon is known as Temperature-Dependent Sex Determination (TSD). High Incubation Temperatures: Typically produce female offspring.
- ScienceClass 10CBSE
In a dihybrid cross, if the F1 generation has genotype RrYy, what proportion of gametes produced by this F1 individual will carry the alleles 'RY'? Justify your answer based on Mendel's laws.
The F1 individual has the genotype RrYy. According to Mendel's Law of Independent Assortment, the alleles for different genes (in this case, R/r for seed shape and Y/y for seed color) assort independently of each other during gamete formation. This means that the segregation of R and r is independent of the segregation of Y and y. For the 'R' gene, the individual Rr will produce gametes with 'R' and 'r' alleles in equal proportions (1/2 R, 1/2 r). For the 'Y' gene, the individual Yy will prod
- ScienceClass 10CBSE
Compare the amount of variation generated in a population through asexual reproduction versus sexual reproduction. Which mode of reproduction is more advantageous for evolution and why?
Variation in Asexual Reproduction: Asexual reproduction typically involves a single parent producing genetically identical offspring (clones). Variations in asexually reproducing organisms arise primarily due to random mutations during DNA replication. The rate of mutation is generally low, so the amount of variation generated in a population through asexual reproduction is very limited. Variation in Sexual Reproduction: Sexual reproduction involv
- ScienceClass 10CBSE
Mendel used several contrasting characters in his pea plant experiments. List any four such contrasting characters and explain why pea plants were a good choice for his experiments.
Four contrasting characters Mendel studied in pea plants: 1. Stem Height: Tall vs. Dwarf 2. Seed Shape: Round vs. Wrinkled 3. Seed Color: Yellow vs. Green 4. Pod Shape: Inflated vs. Constricted 5. Pod Color: Green vs. Yellow 6. Flower Color: Purple vs. White 7. Flower Position: Axial vs. Terminal Reasons why pea plants were a good choice for Mendel's experiments: 1. Easily Cultivat
- ScienceClass 10CBSE
Why is variation important for the survival of a species, especially in changing environmental conditions? Illustrate with an example.
Variation is crucial for the survival of a species because it provides the raw material for natural selection to act upon, allowing populations to adapt to changing environmental conditions.If all individuals in a population were genetically identical, a sudden change in the environment (e.g., a new disease, climate change, or a new predator) could potentially wipe out the entire species if no individual possessed a trait that allowed them to survive the change. With variation, some in
- ScienceClass 10CBSE
Distinguish between acquired and inherited traits with two examples for each. Why are acquired traits generally not passed on to the next generation?
Acquired Traits: These are characteristics that an individual develops during its lifetime due to environmental influences, experiences, or lifestyle choices. They are not encoded in the organism's DNA and therefore cannot be passed on to offspring. Examples: 1. A person developing strong muscles through weightlifting. 2. A scar resulting from an injury. 3. Learning to play a musical instrument. 4. A
- ScienceClass 10CBSE
Describe the chromosomal mechanism of sex determination in humans. What are the possible combinations of chromosomes in the gametes produced by males and females, and how do these combinations lead to male or female offspring?
In humans, sex determination is primarily chromosomal, involving two sex chromosomes: X and Y. Females have two X chromosomes (XX), while males have one X and one Y chromosome (XY). Gamete Production: Females (XX): During meiosis, females produce only one type of gamete (egg) with respect to sex chromosomes, which always carries an X chromosome. Males (XY): During meiosis, males produce two types of gametes
- ScienceClass 10CBSE
Differentiate between Mendel's Law of Segregation and Law of Independent Assortment. Explain each law with a suitable example from pea plant crosses.
Mendel's Law of Segregation states that during the formation of gametes, the two alleles for a heritable character separate (segregate) from each other such that each gamete carries only one allele for that character. When the egg and sperm unite, they bring together two alleles for each character.For example, in a monohybrid cross involving pea plants for stem height (Tall 'T' and dwarf 't'), a heterozygous parent (Tt) will produce gametes where 50% carry the 'T' allele and 50% carry
- ScienceClass 10CBSE
Explain the concept of 'accumulation of variations' in a population during sexual reproduction, and how it contributes to evolution. Provide an example.
Accumulation of variations refers to the gradual build-up of small differences in traits within a population over generations. In sexual reproduction, variations arise due to processes like crossing over during meiosis, independent assortment of chromosomes, and random fertilization. Each new offspring inherits a unique combination of genes from its parents, leading to slight variations in their characteristics. These small, individual variations, when passed down and compounded o
- ScienceClass 10CBSE
Discuss the significance of the 'Law of Independent Assortment' in understanding genetic diversity. Provide an example to illustrate this law.
The Law of Independent Assortment states that alleles for different genes assort independently of one another during gamete formation. This means that the inheritance of one trait does not influence the inheritance of another trait, as long as the genes are located on different chromosomes or are far apart on the same chromosome. This law is crucial for understanding genetic diversity because it explains how new combinations of traits can arise in offspring that are not present in
- ScienceClass 10CBSE
A genetic cross involves a true-breeding plant with red flowers (RR) and a true-breeding plant with white flowers (rr). If red is dominant over white, what is the probability of obtaining white-flowered plants in the F2 generation?
First, the cross between RR and rr will produce an F1 generation that is entirely Rr (red flowers). When two F1 plants (Rr x Rr) are crossed, the F2 generation will have genotypes RR, Rr, and rr in a 1:2:1 ratio. The phenotypes will be 3 red (RR, Rr) : 1 white (rr). Therefore, the probability of obtaining white-flowered plants in the F2 generation is 1/4 or 25%.
- ScienceClass 10CBSE
How does the environment sometimes influence sex determination in certain organisms, contrasting with the chromosomal mechanism in humans?
While humans and many other organisms use a chromosomal mechanism for sex determination, some species exhibit environmental sex determination. In these cases, external factors like temperature, pH, or social cues during development can influence whether an individual develops as male or female. For example, in many reptiles like crocodiles and turtles, the temperature at which eggs are incubated determines the sex of the hatchlings. Higher temperatures might lead to one sex, while
- ScienceClass 10CBSE
Explain the Law of Segregation using an example of a monohybrid cross involving flower color in pea plants (Purple is dominant over white).
The Law of Segregation states that during the formation of gametes, the two alleles for a heritable character segregate (separate) from each other such that each gamete receives only one allele. For example, if we cross a pure-breeding purple-flowered pea plant (PP) with a pure-breeding white-flowered pea plant (pp), the F1 generation will all be heterozygous purple (Pp). When these F1 plants form gametes, the 'P' allele and the 'p' allele segregate, so that half the g
- ScienceClass 10CBSE
Consider a monohybrid cross between a homozygous dominant tall pea plant (TT) and a homozygous recessive dwarf pea plant (tt). What will be the genotype and phenotype of the F1 generation?
The homozygous dominant tall pea plant has genotype TT, and the homozygous recessive dwarf pea plant has genotype tt. The gametes produced by the tall plant will all carry the 'T' allele, and the gametes produced by the dwarf plant will all carry the 't' allele. When these are crossed, all offspring in the F1 generation will have the genotype Tt. Since 'T' (tallness) is dominant over 't' (dwarfness), the phenotype of all F1 offspring will be tall.
- ScienceClass 10CBSE
Explain the concept of 'sex determination' in humans. What role do the X and Y chromosomes play in this process?
In humans, sex determination is primarily chromosomal. Females typically have two X chromosomes (XX), while males typically have one X and one Y chromosome (XY). During reproduction, the mother always contributes an X chromosome to the offspring. The father, however, can contribute either an X or a Y chromosome. If the father contributes an X chromosome, the offspring will be XX (female). If the father contributes a Y chromosome, the offspring will be XY (male). The presence or ab
- ScienceClass 10CBSE
Differentiate between acquired and inherited traits, providing an example for each.
Acquired traits are characteristics that an organism develops during its lifetime in response to environmental influences or experiences. These traits are not encoded in the organism's DNA and therefore cannot be passed on to offspring. An example is a person developing strong muscles through exercise or learning to play a musical instrument. Inherited traits, on the other hand, are characteristics determined by an organism's genes, which are passed down from parents to offspring.
- ScienceClass 10CBSE
Describe Gregor Mendel's experiment with pea plants that led to the formulation of the Law of Dominance. What specific observations supported this law?
Mendel's experiment for the Law of Dominance involved crossing pure-breeding tall pea plants with pure-breeding dwarf pea plants (P generation). He observed that all the offspring in the first filial (F1) generation were tall. When he self-pollinated these F1 tall plants, the second filial (F2) generation produced both tall and dwarf plants in a 3:1 ratio. The specific observation that supported the Law of Dominance was that in the F1 generation, only one of the parent
- ScienceClass 10CBSE
Explain the concept of 'accumulation of variations' in sexually reproducing organisms. How does this differ from variations observed in asexually reproducing organisms?
In sexually reproducing organisms, variations accumulate over generations due to the shuffling of genes during meiosis and fertilization. Each parent contributes a unique set of genes, and the combination of these genes in the offspring creates new variations. This continuous mixing leads to a wider range of phenotypic differences within a population. In contrast, asexually reproducing organisms produce offspring that are genetically identical to the parent (clones), with variatio
- ScienceClass 10CBSE
Only variations that confer an advantage to an individual organism will survive in a population. Do you agree with this statement? Why or why not?
Solution: The statement holds true – only variations provide an advantage to individual organisms that will survive in a population. For example, variations that lead to the increase in heat resistance in bacteria are very useful for survival if they find themselves in an environment where there is a sudden increase in ambient temperature. This will determine the difference between life and death for the bacteria.
- ScienceClass 10CBSE
How is the equal genetic contribution of male and female parents ensured in the progeny?
Solution: Equal genetic contribution of male and female parents is ensured in progeny through the inheritance of equal numbers of chromosomes from both parents. There are 23 pairs of chromosomes, but not all are paired. The 22 pairs are called autosomes, while the remaining 1 pair is called the sex chromosomes (represented as X and Y.) Females have two sets of X-chromosomes, while males have one X-chromosome and one Y-chromosome. During the process of reproduction, fer