Short & Long Question Answers with Solution: Evolution | Biology Class 12 - NEET PDF Download

Short Answer Type Questions

Q1: How does genetic variation help in evolution?
Ans: Genetic diversity plays a crucial role in the process of evolution by enabling natural selection to modify the prevalence of existing alleles within a population. These genetic variations provide some individuals with the capacity to better suit themselves to their surroundings.

Q2: Explain the evolution of birds from reptiles and give one piece of evidence.
Ans: The compelling evidence supporting the idea that birds have evolved from reptiles is found in a transitional species known as Archaeopteryx. This species exhibits traits characteristic of both birds and reptiles.

Q3: Bring out differences between De Vrie’s mutations Darwinian Variations?
Ans: 

• Mutations are abrupt, significant hereditary alterations in a population's traits that can lead to speciation in a single occurrence. In contrast, Darwinian evolution is a gradual process that results from small variations accumulating over numerous generations.
• Mutations occur randomly and lack a specific direction, while variations are typically small and have a specific direction.

Q4: How is convergent evolution different from divergent evolution?
Ans: Convergent evolution occurs when two or more species, originating from different ancestors, develop similar characteristics as an adaptation to a specific environment. In contrast, divergent evolution takes place when species with a common ancestor develop different traits due to environmental changes, eventually giving rise to new species.

Q5: Life originated from the earth’s inorganic atmosphere in the past, but this no longer happens today. State two suitable reasons.
Ans: The origin of life from Earth's inorganic atmosphere is unlikely due to the following reasons:

• The present-day atmosphere has lower temperatures compared to the primitive atmosphere.
• The current atmosphere contains oxygen, making it oxidizing and unsuitable for the formation of life.

Q6: Define natural selection. Who else along with Charles Darwin proposed it as the mechanism of evolution?
Ans: Natural selection is a mechanism where nature favors individuals with advantageous traits that enhance their survival in natural environments, leading them to outcompete those with less favorable traits. Alfred Wallace also proposed a similar concept, known as the "survival of the fittest."

Q7: Explain adaptive radiation. Give examples in support of your answer.
Ans: Adaptive radiation is a phenomenon where a single ancestral organism diversifies into multiple new forms as a result of environmental changes. An example of this is Darwin's Finches, which are found on the Galapagos Islands and have developed various beak shapes adapted to their specific diets. Over time, these finches, originating from a single species, adapted to different environmental and dietary conditions, resulting in the development of distinct beak types.

Q8: Write a note on genetic drift.
Ans: Genetic drift is an evolutionary process where allele frequencies change randomly over generations, primarily affecting small populations. It occurs in situations like the bottleneck effect or founder effect. Importantly, genetic drift doesn't discriminate based on whether an allele is advantageous or harmful to the individual. There's a chance that a beneficial allele may be lost, while a detrimental one could persist.

Q9: Would you consider wings of butterfly & a bat as homologous or Analogous & why?
Ans: Butterfly and bat wings are considered analogous because they have evolved from different structures – for example, butterfly wings originate from skin and feathers, while bat wings originate from forelimbs. However, both types of wings serve the same purpose, which is flying.

Q10: Comment on the statement with reference to industrial melanism, “Evolution is apparently reversible”.
Ans: The peppered moth originally lived on lichens and used camouflage to protect itself from predators. However, during the industrialization of Europe, emissions from coal-based industries turned the lichens black, making the moths more visible to predators. As a result, the moth population declined, and a mutant black variant of the moth thrived because it was not easily seen by predators.
In 1956, clean air legislation was introduced in Europe, leading to a decrease in smoke emissions. With cleaner air, the lichens and non-melanic (light-colored) peppered moths started reappearing. This observation suggests that evolution can be reversed, as the non-melanic moths are making a comeback in response to changing environmental conditions.

Long Answer Type Questions

Q1: What are the types of evolution
Ans: There are various types of evolution:

• Convergent evolution: This is a process where different species independently evolve similar traits in response to similar environmental pressures. For instance, flying insects, birds, and other flying creatures have all separately developed the ability to fly.
• Coevolution: This process involves two or more species evolving together as they exert selective pressures on each other. Examples include the coevolution of host-parasite relationships, predator-prey interactions, the relationship between flowering plants and pollinating insects, and mutualistic or symbiotic interactions.
• Adaptive radiation: In this process, a species diverges into multiple new forms when changes in the environment provide new resources or present new challenges. An example is the adaptive radiation of finches on the Galapagos Islands, where different beak shapes evolved to exploit various food sources on different islands.

Q2: Chemical insecticides remain useful only for a limited time. Explain the process of evolution with an example.
Ans: Many crop-damaging pests and insects in agricultural fields can be effectively controlled through the use of chemical pesticides. These pesticides target specific metabolic processes in pests, ultimately leading to their demise. However, it's important to note that pests can develop resistance to these chemicals over time due to genetic mutations. As a result, the continued use of these insecticides may become ineffective in the long run, raising questions about their utility.

Q3: By taking industrial melanism as on example, explain the concept of natural selection by evolution?
Ans: 

• The theory of natural selection posits that species undergo change over time as a result of the survival of the fittest individuals, who possess advantageous variations that are preserved and passed on to subsequent generations, ultimately leading to the emergence of new forms.
• For example, in the 1850s, observations of moth populations showed that there were more moths with white wings than dark wings. However, with the onset of industrialization, trees' trunks became darkened due to industrial pollution. In this altered environment, white-winged moths became more vulnerable to predators and did not survive as well as dark-winged moths. Before industrialization, when trees were covered in thick white lichen, white-winged moths had an advantage, while dark-colored moths were more easily spotted by predators. In this way, nature selects which species is better suited to its changing environment.

Q4: If the industries were removed, what impact would it have on the population of moths in England?
Ans: 

• The population of peppered moths before industrialization consisted of two variants: black and grey. These moths lived on the surface of lichens. Prior to industrialization, the grey moths had an advantage because their coloration provided effective camouflage, making them less visible to predators. In contrast, the black moths were more easily spotted and preyed upon by their natural predators.
• If the industrial pollution and associated environmental changes were reversed, the population of black moths would likely have decreased significantly. This reduction would be due to the fact that the black moths were at a disadvantage in the pre-industrial environment, and their increased visibility would have made them more vulnerable to predation. As a result, the population of grey moths, which were better adapted to the pre-industrial environment, would have become more predominant.

Q5: What does Biogeography mean? Explain how Darwin’s finches give biogeographical evidence in favour of evolution.
Ans: 

• Biogeography is a field within geography that focuses on examining how plants and animals are distributed across different regions.
• For instance, during Charles Darwin's expedition to the Galapagos Islands, he observed that the animal species on these islands were similar to those found on nearby South American islands. Additionally, he noted that the bird species on the Galapagos Islands, known as Darwin's finches, were distinct from their counterparts in South America. Darwin proposed that these finches originated from a common ancestor that had migrated from the mainland to the islands and had undergone various adaptations in response to the unique environmental conditions found there.

Q6: What is adaptive radiation? Explain with an example.
Ans: Adaptive radiation is an evolutionary process driven by natural selection, leading to the emergence of multiple new species from a single lineage that diversifies rapidly. An illustrative example of adaptive radiation can be seen in the case of the Darwin's finches on the Galapagos Islands. These islands are home to a diverse array of finch species that originated from a single ancestral species, which initially arrived on the islands by chance. Over time, these finches underwent significant evolutionary changes, adapting to various new habitats and developing distinct feeding behaviors. As a result, they evolved different types of beaks to match their specific dietary preferences, leading to the development of insect-eating, blood-sucking, and other finch species with a wide range of dietary habits, all originating from a common seed-eating ancestor.

Q7: State the facts that assist Darwin’s Theory of Natural selection.
Ans: These facts indeed provide support for Charles Darwin's Theory of Natural Selection, which is a fundamental concept in the field of evolutionary biology.
Let's elaborate on how each of these facts aligns with the theory:

• Overproduction: Organisms tend to produce more offspring than the environment can support. This concept is in line with the idea that species have the potential to reproduce at a high rate, but not all of their offspring will survive and reproduce. This surplus of offspring sets the stage for competition and selection.
• Struggle for Survival: In any given environment, there are limited resources such as food, space, and other necessities for survival. As a result, there is fierce competition among individuals, not only within a species but also between different species, for access to these resources. This struggle for existence is a crucial element of natural selection because it leads to the differential survival and reproduction of individuals with advantageous traits.
• Variations: Even among individuals of the same species, there is inherent variability. No two individuals are exactly alike, and this variation is partly due to genetic diversity. Darwin recognized that these variations can be heritable and that they play a critical role in the process of natural selection. Some variations may confer advantages in the struggle for survival, while others may be less beneficial or even detrimental.
• Survival of the Fittest: This is the central concept of Darwin's theory. In a competitive environment, individuals with variations that better suit them to their specific circumstances are more likely to survive and reproduce. Over time, these advantageous traits become more common in the population because they are passed on to the next generation. This process, often referred to as "survival of the fittest," leads to the gradual adaptation and evolution of species.

In summary, these facts provide empirical support for Darwin's Theory of Natural Selection, which posits that over time, the process of differential survival and reproduction of individuals with advantageous variations leads to the adaptation and evolution of species, resulting in a better fit between organisms and their environments.

Q8: Enumerate the key concepts in the evolution theory of Darwin.
Ans: The fundamental principles of Darwin's theory of evolution are:

• Divergent Evolution:
  • Divergent evolution involves the emergence of new species from a common ancestor, and this occurs as they adapt to their new environment through reproductive isolation. An example of this process is observed in Darwin's finches, which evolved from a single species of seed-eating bird.
• Natural Selection:
  • Natural selection is a mechanism where variations within individuals contribute to the survival and reproduction of a species. Those with advantageous variations tend to reproduce more, passing on their traits to future generations, allowing them to better adapt to changing environmental conditions. For instance, in the case of giraffes, some have long necks and others have short necks. If the low-lying shrubs are reduced for some reason, giraffes with longer necks have a better chance of survival and reproduction, eventually leading to a shift in the population's characteristics.

Q9:  Distinguish between convergent and divergent evolution giving one example of each.
Ans: 

• Divergent Evolution: Divergent evolution refers to the process where distinct functional structures evolve from a shared ancestral form. This is exemplified by homologous organs, which are indicative of divergent evolution. Notable examples include Darwin's Finches, Australian Marsupials, and variations in mammalian locomotion.
• Convergent Evolution: Convergent evolution involves the development of similar adaptive functional structures in unrelated groups of organisms. This is characterized by analogous organs, demonstrating convergent evolution. Examples include the similarities between Australian Marsupials and Placental mammals, as well as the development of various aquatic vertebrate adaptations and wings in insects, birds, and bats.

Q10: Explain the terms:

• Race
• Breed
• Cultivars
• Variety

Ans: 

• Race: Races are phenotypic populations within the same species, and they are categorized at a level higher than strains but lower than species. Examples of races include Mongoloid and Negroid.
• Breed: Breeds are distinct sub-groups within a race that exhibit morphological and physiological differences. These sub-groups maintain their individuality through controlled breeding within the same group. For example, breeds like Rhode Island Red and Plymouth Red are cultivated within the larger race.
• Cultivars: Cultivars refer to groups of plants that have been selected by plant breeders for specific desirable characteristics. These characteristics can be maintained through propagation methods. Common examples include cultivated varieties of flowers like roses and daffodils.
• Variety: Varieties are sub-groups of a species that are distinguishable by their unique morphological, physiological, and genetic characteristics. Examples of varieties include different types of vegetables like cauliflower and cabbage.