How do Organisms Reproduce?: Class 10 Science Q&A · Page 4
112 free answers on How do Organisms Reproduce? (Science) for Class 10 students, across CBSE, ICSE and State boards.
Question & Answer
Questions
- ScienceClass 10CBSE
Does geographical isolation of individuals of a species lead to the formation of a new species? Provide a suitable explanation.
Soln: The geographical isolation of individuals of a species leads to genetic drift. This limits the sexual reproduction of the separated population. This results in separated individuals reproducing among themselves. This leads to the formation of a new variation. Accumulation and transfer of these variations through generation will lead to the formation of new species.
- ScienceClass 10CBSE
A woman has only daughters. Analyse the situation genetically and provide a suitable explanation.
Soln: A woman has only daughters: It means the egg always received X chromosomes from the sperm. If sperm donates X chromosomes, the resultant child will be female, and if sperm donates Y chromosome, the baby will be male.
- ScienceClass 10CBSE
Why did Mendel choose the pea plant for his experiments?
Soln: Mendel chose the pea plant for his experiments for the following reasons: Pea plants are easy to grow They have a short lifespan They have larger size flower Pea plants are self-pollinated Easily identified characters
- ScienceClass 10CBSE
1. Give the pair of contrasting traits of the following characters in the pea plant and mention which is dominant and recessive. (i) yellow seed (ii) round seed
Soln: Yellow-dominant Green-recessive Round-dominant Wrinkled-recessive
- ScienceClass 10CBSE
1. Does the occurrence of the diversity of animals on earth suggest their diverse ancestry also? Discuss this point in the light of evolution.
Soln: In spite of the fact that animals have a different variety of structures, they do not have a common ancestry. This is because common ancestry may greatly limit the extent of diversity. Many of the animals inhabit the same habitat; their evolution by geographical isolation and speciation is also not likely. Hence, common ancestry for all animals is not the likely theory.
- ScienceClass 10CBSE
1. What are homologous structures? Give an example. Is it necessary that homologous structures always have a common ancestor?
Soln: Homologous structures are those which have a common basic structure but may perform different functions. For example, the forelimbs of reptiles, amphibians and mammals. They have common ancestry, but are modified and adapted to carry out various functions.
- ScienceClass 10CBSE
1. A very small population of a species faces a greater threat of extinction than a larger population. Provide a suitable genetic explanation.
Soln: A very small population of a species faces a greater threat of extinction than a larger population because of the following reasons: Inbreeding depression: Small population promotes inbreeding. It results in lesser variations. Genetic drift: A small population is vulnerable to a sudden change in the environment. Because of genetic drift there is more chance that the species with a small population
- ScienceClass 10CBSE
In human beings, the statistical probability of getting either a male or female child is 50:50. Give a suitable explanation
Soln: The sex of the offspring is determined by the gamete donated by the male. Males possess X and Y chromosomes in their 23rd pair. The ratio between X and Y is 1:1. Hence, the probability of getting either a male or female child is 50:50.
- ScienceClass 10CBSE
Why do all the gametes formed in human females have an X chromosome?
Soln: Females possess XX in their 23rd chromosome pair. During meiosis, one X chromosome enters each gamete; hence all female gametes possess X chromosomes.
- ScienceClass 10CBSE
Mention three important features of fossils which help in the study of evolution.
Soln: Fossils are the preserved ancient Fossils help determine evolutionary differences between organisms and their Fossils determine the living period of specific
- ScienceClass 10CBSE
Do the genetic combination of mothers play a significant role in determining the sex of a newborn?
Soln: No, the sex of a newborn will be determined by the chromosome contributed by the father. Mothers have XX in their 23rd chromosome pair, and they always contribute one X chromosome. But fathers have X And Y in their 23rd chromosome pair. If the father inherits X, the child will be a girl, and if the father inherits Y, the child will be a boy.
- ScienceClass 10CBSE
How is the sex of a newborn determined in humans?
Soln: The sex of the individual is determined by the genes inherited from the parents. If a newborn acquires X chromosomes from the father, the child will be a female, and if the newborn receives a Y chromosome from the father, it will be a male.
- ScienceClass 10CBSE
1. Some dinosaurs had feathers, although they could not fly; birds have feathers that help them to fly. In the context of evolution, this means that (a) reptiles have evolved from birds (b) there is no evolutionary connection between reptiles and birds (c) feathers are homologous structures in both organisms birds have evolved from reptiles
Soln: The answer is (d) birds have evolved from reptiles Explanation: Dinosaurs were reptiles. Some dinosaurs had feathers, but they could not use them to fly. Feathers in dinosaurs started as providing insulation in cold weather, and later, birds adapted them to flight. So, in the context of evolution, this means that birds have evolved from reptiles.
- ScienceClass 10CBSE
1. The theory of the evolution of species by natural selection was given by (a) Mendel (b) Darwin (c) Morgan Lamarck
Soln: The answer is (b) Darwin Explanation: Mendel proposed laws of heredity. Morgan discovered a mutation in drosophila. Lamarck proposed the use and disuse theory.
- ScienceClass 10CBSE
1. Select the statements that describe the characteristics of genes (i) genes are a specific sequence of bases in a DNA molecule (ii) a gene does not code for proteins (iii) in individuals of a given species, a specific gene is located on a particular chromosome (iv) each chromosome has only one gene (a) (i) and (ii) (b) (i) and (iii) (c) (i) and (iv) (d) (ii) and (iv)
Soln: The answer is (b) (i) and (iii) Explanation: Statement ii) is wrong because genes code for specific proteins. Statement 4 is wrong because chromosomes have any number of genes.
- ScienceClass 10CBSE
1. The two versions of a trait (character) which are brought in by the male and female gametes are situated on (a) copies of the same chromosome (b) two different chromosomes (c) sex chromosomes any chromosome
Soln: The answer is (a) copies of the same chromosome Explanation: Each diploid individual inherits two copies of a chromosome, one from each parent. Hence the two versions of a trait or alleles of a gene, which are contributed by the male and female gametes are present on a pair of homologous chromosomes.
- ScienceClass 10CBSE
1. From the list given below, select the character which can be acquired but not inherited (a) colour of eye (b) colour of skin (c) size of body nature of hair
Soln: The answer is (c) size of body Explanation: A person’s food habits decide the nature of the body. Regular exercise helps in building a muscular body. Body nature is not transferred to offspring; hence, the size of the body is not inherited.
- ScienceClass 10CBSE
1. According to the evolutionary theory, the formation of a new species is generally due to (a) sudden creation by nature (b) accumulation of variations over several generations (c) clones formed during asexual reproduction movement of individuals from one habitat to another
Soln: The answer is (b) accumulation of variations over several generations Explanation: New species are formed due to variations in the DNA for several generations. Asexual reproduction will not result in variation as there are no gametes involved. The movement of individuals from one habitat to another will not affect DNA change; hence it cannot be the right answer.
- ScienceClass 10CBSE
1. Select the group which shares the maximum number of common characters (a) two individuals of a species (b) two species of a genus (c) two genera of a family two genera of two families
Soln: The answer is (a) two individuals of a species Explanation: Species is the lowest taxon hence members of the same species share a maximum number of common characteristics.
- ScienceClass 10CBSE
1. A trait in an organism is influenced by (a) paternal DNA only (b) maternal DNA only (c) both maternal and paternal DNA neither by paternal nor by maternal DNA
Soln: The answer is (c) both maternal and paternal DNA Explanation: DNA is contributed to an offspring by both parents hence traits are influenced by both parents.