Important Questions for Evolution

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Very Short Answer Questions (1 Mark Questions)

Ques. Write any two characteristics of the fossils. 

Ans. The characteristics of fossils are:

• They help in determining the period when they lived.
• Fossils supply a connecting relation between different species.

Ques. How is the age of the tree calculated?

Ans. The age of the tree can be estimated by counting the annual rings on the wood growth. The study of the rings of trees is known as dendrochronology.

Ques. Name the method that helps in estimating the age of a fossil. 

Ans. The carbon dating process determines the fossil’s age.

Ques. Name the period which is known as the ‘age of reptiles.

Ans. The period of the age of reptiles is called the Jurassic period.

Ques. Give one example of adaptive radiation. 

Ans. Examples of adaptive radiation are Darwin's Galapagos finches and honeycreeper birds.

Ques. Can human evolution be called adaptive radiation?

Ans. No, human evolution cannot be called adaptive radiation as human evolution is a slow gradual process making it different from adaptative radiation.

Ques. What were the first mammals like?

Ans. The first mammals were like shrews. They have cylindrical bodies and short and slender limbs.

Ques. Who gave the Big Bang theory?

Ans. Georges Lemaître, a Belgian cosmologist gave the Big Bang theory. He is also known as the father of the Big bang theory. 

Big Bang Theory

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Short Answer Questions (2 Marks Questions)

Ques. What are the steps of human evolution?

Ans. The stages in the human evolution are:

• Dryopithecus
• Ramapithecus
• Australopithecus
• Homo Erectus
• Homo Sapiens Neanderthalensis
• Homo Sapiens Sapiens

Ques. What are the characteristics concerning the Hardy-Weinberg equilibrium?

Ans. The characteristics affecting the Hardy-Weinberg equilibrium are:

• Genetic Recombination
• Gene Flow
• Genetic Drift
• Natural Selection
• Mutation

Ques. What are adaptive radiations?

Ans.  A rapid increase in species with a common ancestor is characterized by great ecological and morphological diversity. 

Example: The growth of mammals after the end of dinosaurs.

Ques. Which group of organisms was responsible for forming unrestricted oxygen in the circumstances of the primitive earth?

Ans. Oxygenic photosynthetic bacteria comparing the present-day blue-green algae or cyanobacteria are responsible for forming unrestricted oxygen in the circumstances of the primitive earth.

Ques. What is the concept of evolution? 

Ans. The transformation in heritable characteristics of biological peoples over consecutive generations is called evolution. 

The key factors of the modern concept of evolution are 

• Variation,
• Inheritance,
• Selection, 
• Time
• Adaptation.

Ques. What is the origin of organic variation?

Ans. The origin of organic variation is Hereditary variations due to mutations, recombination, and polyploidy.

Sources of variation:

• Mutation
• Recombination
• Immigration of genes

Ques. How is the age of rock calculated?

Ans. The generation of the rock is calculated by calculating the amount of specific radioactive components in the rock. The age of the rock is referred to as the absolute age.

Read More: Rock Cycle

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Long Answer Questions (3 Marks Questions)

Ques. What are vestigial organs? Give illustrations and explain the significance of vestigial organs.

Ans. Vestigial organs are non-functional organs in any organism that are functional in corresponding animals and were serviceable in the ancestors. There are 90 vestigial organs in the human body: coccyx (tail bone); nictitating membrane (3rd eyelid); caecum and vermiform appendix; canines; wisdom teeth; body hair; auricular muscles; mammary glands in males; etc. 

Vestigial organs are also available in some animals, e.g. splint bones in the horse; hind-limbs and pelvic girdles in python; wings and feathers in flightless birds; etc. Vestigial organs were available in their ancestral forms but have become non-functional due to shifts in their function and may finally disappear. Thus, the presence of vestigial organs is very convincing evidence of organic evolution which is supported/assisted by Lamarck's theory of use and disuse of organs.

Vestigial Organs in Humans

Read More: Lamarckism

Ques. What are homologous organs? Give similar or different functions and examples. (CBSE 2016) 

Ans. Organs with a common origin, embryonic development, and the same fundamental structure but perform similar or different functions are called homologous organs.

Examples of homologous organs:

• Elephants' tusks and beavers' teeth are homologous structures, though they look pretty different. 
• In plants, the homologous organs may be a thorn of Bougainvillea or a tendril of Cucurbita, both arising in axillary positions. Both of them have different forms in accordance with their function.

Homologous Organs

Ques. Describe the two principal consequences of the experiments performed by Louis Pasteur on the origin of life. (CBSE Delhi 2019)

Ans. The foremost life that appeared on the earth resulted from chemical evolution, i.e. life arose from inorganic molecules that created organic molecules, further forming complex compounds.

Yes, we can set this as energy grows from pre-existent life. Ultimately resulted in uncomplicated partitions and then uncomplicated organisms, where-in complexness developed with time. Nevertheless, once life originated, abiogenesis could not follow, and therefore, energy developed further only via biogenesis, i.e. pre-existent life offered rise to unique life.

Read More: Origin and Evolution of Man

Ques. Describe the antibiotic resistance observed in light of Darwinian selection theory. 

Ans. Antibiotics are considered to be extremely productive against diseases induced by bacteria. But within two or three years of instructing antibiotics, new antibiotic-resistant bacteria occurred in the population. Periodically a bacterial population includes one or a few bacteria having mutations that make them unsusceptible to the antibiotic. Such immune bacteria survive and reproduce quickly as the competing bacteria have broken.

Soon the resistance-providing genes evolve in general, and the bacterial population becomes resistant.

Ques. How does natural selection work according to Darwin's theory of natural selection? 

Ans. Natural selection works in the following ways according to Darwin's theory:

• All plants and animals produce in a geometrical pattern. The number of organisms created is much more than that can survive due to restricted space and food.
• Due to the exact fundamental requirement, competition between organisms occurs, and those better adjusted to the environment survive while the rest fail.
• Someone having reasonable variations overpowers those without such variations. These variations transfer to future generations.

Read More: Types of Natural Selection

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Very Long Answer Questions (5 Marks Questions)

Ques. Explain Hardy-Weinberg's principle. (CBSE Delhi 2019)

Ans. In the given principle, one can discover the frequency of events of alleles of a gene or a locus. This frequency stays specified and stays the same through the years. Hardy-Weinberg's principal said it by using algebraic equations. According to this principle, a population's allele frequencies are steady and consistent from generation to generation. The gene pool remains stable. This is called genetic equilibrium.

For instance, assume the frequency for the allele X in a population is a and that of the allele x is b.

Therefore, the frequency of XX is a², xx is b² and Xx is 2ab. The equation can be expressed as:

a² + b² + 2ab = 1

or

(a+b)² = 1

When the frequency counted differs from expected values, the difference (direction) indicates the extent of evolutionary change.

Disturbance in congenital balance, or Hardy-Weinberg equilibrium, i.e. difference of frequency of alleles in a population, would then be diagnosed as resulting in the evolution.

Ques. How can Hardy-Weinberg equilibrium be affected? Explain giving three reasons. 

Ans. Hardy-Weinberg Principle says that the sum of allelic frequencies in a population is stable and is invariant from generation to generation, i.e. the gene pool in a population remains stable. This is called genetic equilibrium. 

The sum total of all the allelic frequencies is 1.

p² + q² + 2pq = 1

Five factors that impact these values are:

• Genetic drift is unexpected changes in the allele frequencies of a population emerging solely by chance, including genetic drift. The change in allele frequency may become so drastically other that they form a new species.
• Gene migration is when some individuals of a population migrate to different populations or when individuals come into a population; some genes are lost in the first case and counted in the second.
• Natural selection is the most crucial evolutionary process that leads to changes in allele frequencies and turns into transformation due to evolution.
• The mutations are spontaneous and directionless. They are adequate to construct a significant genetic variation for speciation to occur.
• Recombination is when new gene combinations occur due to meiosis crossing over during gametic formation.

Read More: Difference between Gene and Allele

Ques. Describe the present-day conception of evolution. 

Ans. The modern idea of evolution is modified by Darwin's theory of natural selection and is often called Neo-Darwinism. It includes genetic variation, natural selection, and isolation.

Genetic Variation:

• Mutations: Transformation is the ultimate origin of biological transformations and thus the basic material of evolution. The chromosome mutation may be due to structure, number, or gene changes.
• Gene Recombination brings during crossing over in meiosis. The new combinations of genes lead to the production of new phenotypes.
• Hybridisation is intermingling the genes of the details of near corresponding species.
• Genetic importance is the elimination of the genes of some initial parts of a species by an extreme reduction for various motivations.

In Monoparental duplication, only chromosomal and gene mutation are origins of genetic deviation.

Natural Selection:

If differential recurrence continues for many generations, the genes of the individuals who deliver more offspring will become dominant in the population's gene pool. Thus natural preference occurs via differential reproduction in subsequent generations. The migration of someone from one to another inhabitant is an accessory factor for speciation.

Natural Selection

Isolation:

Natural selection guides different populations into different adaptive channels by selecting the most suitable genotypes. The reproductive separateness between the populations due to unavoidable physical obstacles or others leads to the formation of new species. Isolation recreates a meaningful role in evolution.

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