Evolution

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CBSE Learning Objectives – Key Concepts & Skills You Must Know

Understand the origin of life and its connection to the evolution of the universe.
Explain the concept of chemical evolution and its role in the formation of biomolecules.
Describe the process of natural selection and its impact on species variation and evolution.
Analyze the evidence for evolution through comparative anatomy, fossils, and biochemistry.
Discuss the significance of adaptive radiation in the evolution of species.
Apply the Hardy-Weinberg principle to determine allele frequencies in populations.
Trace the evolutionary history of modern humans and their ancestors.

CBSE Revision Notes & Quick Summary for Last-Minute Study

Chapter 6: Evolution

6.1 Origin of Life

The origin of life on Earth is linked to the origin of the universe and Earth itself.
Chemical evolution, or the formation of biomolecules, is believed to have preceded the first cellular forms of life.
The first cellular life forms likely originated around 2000 million years ago, primarily in water environments.
The theory of biogenesis suggests that life arose from non-living molecules through evolutionary forces.

6.2 Evolution of Life Forms - A Theory

Evolution is the study of the history of life forms on Earth.
Charles Darwin's observations during his voyage on the H.M.S. Beagle led to the conclusion that existing life forms share similarities with ancient life forms.
Extinctions and the emergence of new life forms have occurred throughout Earth's history.

6.3 What are the Evidences for Evolution?

Evidence for evolution includes comparative anatomy, fossils, and comparative biochemistry.
Homology is explained through branching descent, while analogy results from convergent evolution.

6.4 What is Adaptive Radiation?

Adaptive radiation refers to the diversification of a group of organisms into forms filling different ecological niches.

6.5 Biological Evolution

Biological evolution encompasses the changes in species over time through mechanisms such as natural selection.

6.6 Mechanism of Evolution

The Hardy-Weinberg principle states that allele frequencies in a population remain constant from generation to generation, indicating genetic equilibrium.

6.7 Hardy - Weinberg Principle

The principle can be summarized as:
- Allele frequencies are stable.
- The sum of all allelic frequencies is 1.

6.8 A Brief Account of Evolution

Evolutionary history includes the development of modern Homo sapiens from earlier hominids, with significant milestones such as the development of agriculture.

6.9 Origin and Evolution of Man

The evolution of modern humans includes significant developments in brain size, skeletal structure, and cultural practices.

Exercises

Explain antibiotic resistance in bacteria using Darwinian selection theory.
Research recent fossil discoveries or controversies about evolution.
Define the term species clearly.
Trace the components of human evolution, including brain size and dietary preferences.
Investigate self-consciousness in animals other than humans.
List modern-day animals and link them to corresponding ancient fossils.
Practice drawing various animals and plants.
Provide an example of adaptive radiation.
Discuss whether human evolution can be classified as adaptive radiation.
Trace the evolutionary stages of a specific animal, such as the horse.

CBSE Exam Tips, Important Questions & Common Mistakes to Avoid

Common Mistakes and Exam Tips

Common Pitfalls

Misunderstanding Evolutionary Concepts: Students often confuse homology and analogy. Homologous structures arise from divergent evolution, while analogous structures result from convergent evolution.
Ignoring Evidence for Evolution: Failing to recognize the importance of comparative anatomy, fossils, and biochemical similarities in supporting evolutionary theory.
Overlooking the Role of Natural Selection: Many students do not fully grasp how natural selection operates on phenotypic variations within populations.
Confusing Theories of Origin: Mixing up the theories of special creation and chemical evolution can lead to misunderstandings about the origin of life.

Tips for Success

Clarify Definitions: Make sure to clearly define terms such as species, homology, and analogy before exams.
Use Diagrams: Practice drawing and labeling diagrams that illustrate evolutionary concepts, such as the Hardy-Weinberg principle and modes of natural selection.
Connect Concepts: Relate different topics within evolution, such as linking the evolution of modern species to their ancient counterparts.
Stay Updated: Keep abreast of recent discoveries in evolutionary biology, such as fossil finds, to enhance your understanding and examples.
Practice Application: Work on exercises that require you to apply Darwinian selection theory to real-world examples, like antibiotic resistance in bacteria.

CBSE Quiz & Practice Test – MCQs, True/False Questions with Solutions

Multiple Choice Questions

Gene flow

Genetic drift

Natural selection

Founder effect

Correct Answer: C

Solution:

Natural selection is at work here, as the mutation confers an advantage in survival and reproduction in the presence of the pesticide, leading to an increase in the frequency of resistant individuals.

Wings of bats and birds evolving independently to perform flight.

The development of antibiotic resistance in bacteria.

A single species of fish evolving into two distinct species.

The evolution of different beak shapes in Darwin's finches.

Correct Answer: A

Solution:

Convergent evolution occurs when different species develop similar traits independently, often due to similar environmental pressures. The wings of bats and birds are an example of convergent evolution.

Random mating within a large population.

No migration between populations.

Natural selection favoring certain alleles.

Stable allele frequencies over generations.

Correct Answer: C

Solution:

Natural selection disrupts Hardy-Weinberg equilibrium by favoring certain alleles that confer a survival or reproductive advantage, leading to changes in allele frequencies over time.

Genetic drift

Natural selection

Gene flow

Mutations

Correct Answer: B

Solution:

The development of longer proboscises in the insect population is an example of natural selection. Insects with longer proboscises are better adapted to feeding on the plant's nectar, increasing their chances of survival and reproduction.

Different species of finches on the Galapagos Islands evolving from a common ancestor.

A single species of moth changing color due to industrial pollution.

A population of bacteria developing antibiotic resistance.

A species of lizard developing a new color morph to blend into its environment.

Correct Answer: A

Solution:

Adaptive radiation refers to the diversification of a group of organisms into forms filling different ecological niches. The finches on the Galapagos Islands are a classic example of adaptive radiation.

The evolution of Darwin's finches

The development of antibiotic resistance

The formation of coal deposits

The extinction of dinosaurs

Correct Answer: A

Solution:

Adaptive radiation refers to the process where organisms diversify rapidly into a multitude of new forms, such as Darwin's finches on the Galapagos Islands.

The consistent survival of certain species over time.

The appearance of resistant organisms due to chance mutations.

The predictable patterns of species development.

The uniformity of species across different habitats.

Correct Answer: B

Solution:

The appearance of resistant organisms due to chance mutations supports the idea that evolution is a stochastic process.

They needed to escape predators on land.

They adapted to a new aquatic habitat over time.

They were forced into the water due to food scarcity on land.

They were naturally buoyant and preferred water.

Correct Answer: B

Solution:

Some land reptiles evolved into fish-like reptiles as they adapted to living in aquatic environments.

Convergent evolution

Common ancestry

Random mutations

Environmental adaptation

Correct Answer: B

Solution:

Homologous structures indicate common ancestry, as they result from divergent evolution.

Stabilizing selection

Directional selection

Disruptive selection

Genetic drift

Correct Answer: C

Solution:

Disruptive selection occurs when extreme values for a trait are favored over intermediate values, leading to two or more contrasting phenotypes in the population.

Mammals evolved from birds due to environmental changes.

Mammals were the first organisms to appear on Earth.

Mammals evolved from reptiles and were more intelligent in sensing and avoiding danger.

Mammals evolved independently from all other life forms.

Correct Answer: C

Solution:

Mammals evolved from reptiles and were more intelligent in sensing and avoiding danger, which helped them survive.

Gene flow

Genetic drift

Natural selection

Mutation

Correct Answer: B

Solution:

Genetic drift refers to changes in allele frequencies due to random events. The volcanic eruption likely caused a random change in the population, affecting allele frequencies.

Stabilizing selection

Directional selection

Disruptive selection

Balancing selection

Correct Answer: B

Solution:

Directional selection is likely occurring as the environment favors the green morph, leading to an increase in its frequency over time while the brown morph is selected against.

Stabilizing selection

Directional selection

Disruptive selection

Balancing selection

Correct Answer: C

Solution:

Disruptive selection would favor birds with either very small or very large beaks, as these would be most efficient at accessing the available food resources, leading to a bimodal distribution of beak sizes.

It leads to the extinction of all variants except the most fit.

It results in the survival of organisms that can adapt to their environment.

It is a random process that does not affect allele frequencies.

It guarantees the evolution of new species.

Correct Answer: B

Solution:

Natural selection results in the survival and reproduction of organisms that are best adapted to their environment.

A large population of insects migrating to a new area, maintaining genetic diversity.

A small group of birds colonizing a new island, leading to a limited gene pool.

A stable population of mammals experiencing no significant migration or mutation.

A population of plants undergoing frequent mutations due to environmental stress.

Correct Answer: B

Solution:

The founder effect occurs when a small group of individuals establishes a new population, leading to reduced genetic diversity compared to the original population. In this scenario, the small group of birds colonizing a new island exemplifies the founder effect.

The evolution of different species from a common ancestor due to adaptation to different environments.

The process by which unrelated organisms independently evolve similarities when adapting to similar environments.

The gradual change in species over time due to natural selection.

The sudden appearance of new species due to large mutations.

Correct Answer: A

Solution:

Adaptive radiation refers to the evolution of various species from a common ancestor, adapting to different environments.

Genetic drift

Natural selection

Gene flow

Mutation

Correct Answer: B

Solution:

Natural selection is the process where organisms better adapted to their environment tend to survive and produce more offspring. In this case, the bacteria that survive the antibiotic have traits that confer resistance, allowing them to reproduce.

Mutation

Natural selection

Random mating

Gene flow

Correct Answer: C

Solution:

Random mating is one of the conditions required to maintain Hardy-Weinberg equilibrium. Mutation, natural selection, and gene flow are factors that can disrupt it.

Stabilizing selection

Directional selection

Disruptive selection

Balancing selection

Correct Answer: C

Solution:

Disruptive selection is occurring, as it favors individuals at both extremes of the beak size distribution, leading to a reduction in the frequency of medium-sized beaks.

Stabilizing selection

Directional selection

Disruptive selection

Artificial selection

Correct Answer: B

Solution:

Directional selection is responsible for this change as it favors one extreme phenotype over others, leading to a shift in the population's trait distribution towards larger ears.

Adaptive radiation

Convergent evolution

Divergent evolution

Stabilizing selection

Correct Answer: C

Solution:

The scenario describes divergent evolution, where two groups of the same species evolve different traits due to adaptation to different environments.

Stabilizing selection

Directional selection

Disruptive selection

Sexual selection

Correct Answer: C

Solution:

Disruptive selection is at play as it favors individuals at both extremes of the color spectrum, leading to a bimodal distribution of traits.

The wings of bats and the wings of insects, both used for flying.

The forelimbs of whales and the forelimbs of humans, both having similar bone structures.

The eyes of octopuses and the eyes of mammals, both used for vision.

The thorns of roses and the tendrils of peas, both used for protection.

Correct Answer: B

Solution:

Homology refers to similarities in structures due to common ancestry. The forelimbs of whales and humans have similar bone structures due to their evolutionary origin from a common ancestor, illustrating homology.

It increases genetic variation by introducing new alleles.

It decreases genetic variation by random changes in allele frequencies.

It stabilizes allele frequencies over time.

It is a directed process that favors advantageous traits.

Correct Answer: B

Solution:

Genetic drift refers to random changes in allele frequencies, which can decrease genetic variation in a population.

They fluctuate randomly over time.

They remain constant from generation to generation.

They increase steadily over time.

They decrease due to natural selection.

Correct Answer: B

Solution:

The Hardy-Weinberg principle states that allele frequencies in a population remain constant from generation to generation, assuming no evolutionary influences.

A case of convergent evolution

A transitional form in evolutionary history

A result of artificial selection

A species that evolved through adaptive radiation

Correct Answer: B

Solution:

The presence of intermediate traits suggests that the fossil represents a transitional form, providing evidence of evolutionary change between two species.

Water

Amino acids

Carbon dioxide

Oxygen

Correct Answer: B

Solution:

The experiment described is similar to the Miller-Urey experiment, which demonstrated that amino acids could be synthesized from simple gases under conditions simulating early Earth.

Mutations are always harmful and decrease the survival of organisms.

Mutations provide genetic variation that can lead to evolutionary changes.

Mutations occur in response to environmental changes.

Mutations are the only source of genetic variation in populations.

Correct Answer: B

Solution:

Mutations introduce genetic variation, which is essential for evolution. While not all mutations are beneficial, they can provide the raw material for natural selection to act upon.

Genetic drift

Gene flow

Natural selection

Mutation

Correct Answer: C

Solution:

Natural selection favors the survival and reproduction of individuals with advantageous traits, such as antibiotic resistance, leading to an increase in the frequency of these traits in the population.

Stabilizing selection

Directional selection

Disruptive selection

Balancing selection

Correct Answer: C

Solution:

Disruptive selection is likely occurring as it favors individuals at both extremes of the trait distribution, leading to an increase in the frequency of both very large and very small fins.

Genetic drift

Natural selection

Gene flow

Mutation

Correct Answer: B

Solution:

The change in moth population, where dark-winged moths became more common due to industrial pollution, is an example of natural selection.

Ability to fly

Viviparous reproduction

Cold-blooded nature

Larger body size

Correct Answer: B

Solution:

Mammals are viviparous, which means they give birth to live young and protect them inside the mother's body, increasing their chances of survival.

Genetic drift

Gene flow

Natural selection

Mutation

Correct Answer: C

Solution:

Natural selection is the most likely factor, as the introduced allele may confer a survival advantage, leading to its increased frequency in the population.

It is a process where individuals with advantageous traits reproduce more successfully.

It is the random change in allele frequencies in a population.

It is the process of acquiring traits during an organism's lifetime.

It is the creation of new species through large mutations.

Correct Answer: A

Solution:

Natural selection is a process where heritable traits that enhance survival and reproduction become more common in successive generations.

Natural selection due to better camouflage in shaded areas.

Genetic drift resulting from random changes in allele frequencies.

Gene flow from a neighboring island with predominantly dark brown furred mammals.

Artificial selection by humans introducing dark brown furred mammals.

Correct Answer: A

Solution:

Natural selection is the most likely mechanism in this scenario. The increase in vegetation cover provides more shaded areas, where dark brown furred mammals would be better camouflaged from predators. This would increase their survival and reproductive success, leading to an increase in their population over generations.

Stabilizing selection

Directional selection

Disruptive selection

Balancing selection

Correct Answer: B

Solution:

Directional selection occurs when one extreme phenotype is favored over others, leading to a shift in the population's trait distribution. In this case, thicker fur is favored due to the colder climate.

Wings of birds and bats

Thorns of Bougainvillea and tendrils of Cucurbita

Flippers of penguins and dolphins

Sweet potato and potato

Correct Answer: C

Solution:

Convergent evolution occurs when different structures evolve for the same function, such as the flippers of penguins and dolphins.

Wings of a butterfly and wings of a bird

Thorns of Bougainvillea and tendrils of Cucurbita

Flippers of penguins and dolphins

Eyes of octopus and mammals

Correct Answer: B

Solution:

Thorns of Bougainvillea and tendrils of Cucurbita are examples of homology, as they are structurally similar but serve different functions.

They had a genetic mutation that made them invincible to predators.

They were better camouflaged against the darkened tree trunks.

They migrated to areas with fewer predators.

They reproduced at a much faster rate than other moths.

Correct Answer: B

Solution:

Dark-winged moths were better camouflaged against the soot-darkened tree trunks, making them less visible to predators.

Evolution into birds

Climatic changes

Competition with mammals

A massive volcanic eruption

Correct Answer: B

Solution:

The disappearance of dinosaurs is often attributed to climatic changes, although some theories suggest they evolved into birds.

Divergent evolution

Convergent evolution

Adaptive radiation

Genetic drift

Correct Answer: B

Solution:

Analogous structures arise from convergent evolution, where different species develop similar traits independently, often due to similar environmental pressures.

Genetic drift

Gene flow

Natural selection

Mutation

Correct Answer: C

Solution:

The increase in frequency of the mutation is likely due to natural selection, as the mutation provides a fitness advantage by allowing better digestion of a specific seed type, leading to better survival and reproduction.

The evolution of new species

The stability of allele frequencies in a population

The process of natural selection

The mutation rate in a population

Correct Answer: B

Solution:

The Hardy-Weinberg principle states that allele frequencies in a population remain constant from generation to generation under certain conditions.

A small group of birds is blown off course during migration and establishes a new population on an isolated island.

A population of rabbits develops resistance to a new virus through natural selection.

A species of fish evolves larger fins due to increased predation pressure.

A plant species develops a new flower color due to a mutation.

Correct Answer: A

Solution:

Genetic drift is a change in allele frequencies due to random events. The scenario of birds establishing a new population on an isolated island represents a founder effect, a type of genetic drift.

Oxygen, nitrogen, carbon dioxide

Methane, ammonia, hydrogen

Carbon monoxide, sulfur dioxide, helium

Nitrogen, oxygen, argon

Correct Answer: B

Solution:

The Miller-Urey experiment used a mixture of methane (CH4), ammonia (NH3), hydrogen (H2), and water vapor (H2O) to simulate early Earth conditions and successfully produced amino acids.

Convergent evolution

Co-evolution

Genetic drift

Artificial selection

Correct Answer: B

Solution:

Co-evolution is the process where two or more species reciprocally affect each other's evolution. In this case, the plant and its pollinator evolve traits that benefit each other.

They had better camouflage abilities.

They were more intelligent.

They required fewer resources to survive.

They evolved into birds.

Correct Answer: C

Solution:

Small-sized reptiles survived because they required fewer resources, allowing them to endure environmental changes.

Genetic drift

Gene flow

Natural selection

Artificial selection

Correct Answer: C

Solution:

Natural selection is the process where organisms with favorable traits are more likely to survive and reproduce, leading to an increase in the frequency of those traits in the population.

0.21

0.42

0.49

0.09

Correct Answer: B

Solution:

According to the Hardy-Weinberg principle, the frequency of heterozygous individuals (Aa) is given by 2pq, where p is the frequency of allele A and q is the frequency of allele a. Given p = 0.7, q = 1 - p = 0.3, therefore 2pq = 2 * 0.7 * 0.3 = 0.42.

A population of birds where medium-sized beaks are favored due to stable seed availability.

A population of moths where darker coloration becomes more common due to industrial pollution.

A population of rabbits where both very large and very small sizes are favored due to varying predator threats.

A population of fish where the average size remains constant over generations.

Correct Answer: B

Solution:

Directional selection occurs when one extreme phenotype is favored over others, leading to a shift in the population's trait distribution. In this case, the darker moths are favored due to their better camouflage in polluted environments, demonstrating directional selection.

It describes the process of natural selection.

It predicts the frequency of alleles in a population will remain constant in the absence of evolutionary influences.

It explains the mechanism of genetic drift.

It provides evidence for the theory of adaptive radiation.

Correct Answer: B

Solution:

The Hardy-Weinberg principle states that allele frequencies in a population remain constant from generation to generation in the absence of evolutionary influences.

Miller-Urey experiment; chemical evolution

Pasteur's experiment; spontaneous generation

Griffith's experiment; transformation

Hershey-Chase experiment; DNA as genetic material

Correct Answer: A

Solution:

The scenario resembles the Miller-Urey experiment, which demonstrated that organic compounds such as amino acids could form under prebiotic conditions, supporting the theory of chemical evolution.

Their ability to fly

Their burrowing behavior

Their large size

Their aquatic lifestyle

Correct Answer: B

Solution:

The burrowing behavior of the small mammals likely provided them with protection from environmental changes, such as temperature fluctuations and predators.

Increased genetic diversity within a population due to new mutations.

Formation of new species as isolated populations adapt to different environments.

Stabilization of allele frequencies due to large population size.

Decreased competition among species due to resource abundance.

Correct Answer: B

Solution:

Habitat fragmentation can lead to isolated populations that adapt to different environments, potentially resulting in the formation of new species. This process is known as allopatric speciation.

Adaptive radiation

Founder effect

Convergent evolution

Genetic recombination

Correct Answer: B

Solution:

The founder effect is a form of genetic drift that occurs when a new population is established by a very small number of individuals. This can lead to significant genetic differences from the original population, potentially resulting in speciation.

True or False

Correct Answer: True

Solution:

Dinosaurs disappeared from the earth about 65 million years ago, though the exact reason is unknown.

Correct Answer: False

Solution:

The excerpt mentions that the first mammals were viviparous and protected their unborn young inside the mother's body.

Correct Answer: True

Solution:

The first mammals were viviparous, meaning they gave birth to live young and protected them inside the mother's body.

Correct Answer: False

Solution:

The excerpt mentions that the true reason for the disappearance of dinosaurs is unknown, with some attributing it to climatic changes and others to evolution into birds.

Correct Answer: True

Solution:

Most scientists believe that chemical evolution, which involves the formation of biomolecules, preceded the appearance of the first cellular forms of life.

Correct Answer: False

Solution:

Darwinian evolution suggests that variations are small, heritable, and directional, contributing gradually to evolution. In contrast, mutations, as proposed by Hugo deVries, are random and directionless.

Correct Answer: True

Solution:

The excerpt describes Darwin's observation of the diversity of finches on the Galapagos Islands as an example of adaptive radiation.

Correct Answer: False

Solution:

The excerpts indicate that the evolution of life forms is a conjectured story and not fully understood.

Correct Answer: True

Solution:

Natural selection can indeed lead to stabilization, directional change, or disruption, as described in the excerpt.

Correct Answer: False

Solution:

Homologous structures are based on divergent evolution, not convergent evolution.

Correct Answer: True

Solution:

The excerpt states that about 2000 million years ago, the first cellular forms of life appeared on Earth.

Correct Answer: False

Solution:

Homology is based on divergent evolution, not convergent evolution.

Correct Answer: False

Solution:

The exact cause of the dinosaurs' extinction is not definitively known. While some theories suggest climatic changes, others propose that many dinosaurs evolved into birds.

Correct Answer: True

Solution:

The excerpt mentions that the story of the evolution of modern man is most interesting.

Correct Answer: True

Solution:

Genetic drift can cause allele frequencies to change significantly in a population, potentially leading to the formation of a new species.

Correct Answer: True

Solution:

The excerpt states that the story of evolution of modern man appears to parallel the evolution of the human brain and language.

Correct Answer: False

Solution:

The chemical evolution, i.e., formation of biomolecules, is believed to have preceded the appearance of the first cellular forms of life.

Correct Answer: False

Solution:

The Hardy-Weinberg principle states that allele frequencies in a population remain stable and constant from generation to generation, assuming no evolutionary influences.

Correct Answer: False

Solution:

Homology is based on divergent evolution, where species with a common ancestor develop different structures. Convergent evolution leads to analogous structures, not homologous ones.

Correct Answer: False

Solution:

The first mammals were viviparous, meaning they gave birth to live young and protected them inside the mother's body.

Correct Answer: False

Solution:

Darwin believed in gradual evolution through small, heritable variations, not large mutations.

Correct Answer: True

Solution:

According to the Hardy-Weinberg principle, allele frequencies in a population are stable and remain constant from generation to generation.

Correct Answer: True

Solution:

Adaptive radiation refers to the rapid evolution of diversely adapted species from a common ancestor when new environmental niches become available.

Correct Answer: True

Solution:

The origin of life is indeed considered a unique event in the history of the universe, as stated in the provided excerpts.

Correct Answer: False

Solution:

The excerpt mentions that the evolution of modern man appears to parallel the evolution of the human brain and language.

Correct Answer: False

Solution:

The excerpts suggest that the disappearance of dinosaurs is not definitively known and could be due to climatic changes or evolution into birds.

Correct Answer: True

Solution:

Darwinian evolution suggests that heritable variations that improve an organism's ability to utilize resources and survive are more likely to be passed on, leading to evolutionary change over time.

Correct Answer: True

Solution:

Darwin observed adaptive radiation in the Galapagos Islands, particularly noting the diversity of finches.

Correct Answer: True

Solution:

The first mammals were viviparous, meaning they gave birth to live young and protected them inside the mother's body, unlike the earlier reptiles.

Correct Answer: False

Solution:

Evolutionary theory, supported by examples such as the peppered moth, indicates that variations within a population are not completely wiped out but are subject to selection pressures, which can lead to changes in population characteristics over time.

Correct Answer: True

Solution:

The excerpt states that most scientists believe chemical evolution, i.e., the formation of biomolecules, preceded the appearance of the first cellular forms of life, supporting the statement as true.

Correct Answer: True

Solution:

The excerpt states that the first mammals were like shrews and were viviparous.

Correct Answer: True

Solution:

The excerpt mentions that the most successful story is the evolution of man with language skills and self-consciousness.

Correct Answer: False

Solution:

The excerpt explains that homology is accounted for by the idea of branching descent, not convergent evolution.

Correct Answer: True

Solution:

The diagram description outlines the Miller-Urey experiment setup aimed at simulating early Earth conditions.

Correct Answer: False

Solution:

The Hardy-Weinberg principle states that allele frequencies in a population are stable and remain constant from generation to generation.

Correct Answer: True

Solution:

Fossil evidence from Ethiopia and Tanzania shows man-like primates that walked upright, supporting the evolution of hominids in East Africa.

Correct Answer: True

Solution:

The disappearance of dinosaurs around 65 million years ago is believed by some to be due to their evolution into birds, among other theories.

Correct Answer: False

Solution:

The true reason for the disappearance of dinosaurs is not known; some theories suggest climatic changes, while others propose evolution into birds.

Evolution

AI Learning Assistant

CBSE Learning Objectives – Key Concepts & Skills You Must Know

CBSE Revision Notes & Quick Summary for Last-Minute Study

Chapter 6: Evolution

6.1 Origin of Life

6.2 Evolution of Life Forms - A Theory

6.3 What are the Evidences for Evolution?

6.4 What is Adaptive Radiation?

6.5 Biological Evolution

6.6 Mechanism of Evolution

6.7 Hardy - Weinberg Principle

6.8 A Brief Account of Evolution

6.9 Origin and Evolution of Man

Exercises

CBSE Exam Tips, Important Questions & Common Mistakes to Avoid

Common Mistakes and Exam Tips

Common Pitfalls

Tips for Success

Multiple Choice Questions

Q1.Consider a population of insects where a mutation causes some individuals to develop resistance to a new pesticide. Over time, these resistant insects become more prevalent. Which evolutionary mechanism is primarily at work in this scenario?

Correct Answer: C

Q2.Which of the following best describes convergent evolution?

Correct Answer: A

Q3.In the study of evolutionary biology, which of the following is a key factor that disrupts Hardy-Weinberg equilibrium?

Correct Answer: C

Correct Answer: B

Q5.In the context of adaptive radiation, which of the following examples is most accurate?

Correct Answer: A

Q6.What is an example of adaptive radiation?

Correct Answer: A

Q7.What evidence supports the idea that evolution is a stochastic process?

Correct Answer: B

Q8.Which of the following statements best explains why some land reptiles evolved into fish-like reptiles?

Correct Answer: B

Q9.What does the presence of homologous structures in different species indicate?

Correct Answer: B

Correct Answer: C

Q11.Which of the following statements about the evolution of mammals is true?

Correct Answer: C

Q12.A scientist observes that in a population of moths, the frequency of a particular allele changes significantly after a volcanic eruption. Which evolutionary process is most likely responsible for this change?

Correct Answer: B

Q13.In a certain region, a species of lizards displays two distinct color morphs: green and brown. If green lizards are more camouflaged in the lush vegetation and brown lizards are more visible to predators, what type of natural selection is likely occurring?

Correct Answer: B

Q14.A population of birds on an island shows a wide range of beak sizes, from very small to very large. If the island's environment changes such that only very small seeds and very large seeds are available, which evolutionary outcome is most likely?

Correct Answer: C

Q15.Which of the following statements about natural selection is true?

Correct Answer: B

Q16.Considering the concept of genetic drift, which of the following scenarios is most likely to lead to the founder effect?

Correct Answer: B

Q17.Which of the following best describes the process of adaptive radiation?

Correct Answer: A

Q18.In a laboratory experiment, a population of bacteria is exposed to a new antibiotic. After several generations, a small percentage of the bacteria survive and reproduce. Which evolutionary mechanism is primarily responsible for this outcome?

Correct Answer: B

Q19.Which factor is NOT known to disrupt Hardy-Weinberg equilibrium?

Correct Answer: C

Q20.During a study on a population of birds, researchers observe that individuals with medium-sized beaks are less common than those with either very large or very small beaks. Which type of selection is likely occurring in this population?

Correct Answer: C

Correct Answer: B

Correct Answer: C

Q23.A study finds that a species of fish in a lake has developed two distinct color patterns, each adapted to different parts of the lake environment. This is an example of which type of natural selection?

Correct Answer: C

Q24.Which of the following best illustrates the concept of homology in evolutionary biology?

Correct Answer: B

Q25.Which of the following best describes the role of genetic drift in evolution?

Correct Answer: B

Q26.What does the Hardy-Weinberg principle state about allele frequencies in a population?

Correct Answer: B

Q27.During a paleontological dig, scientists discover fossils of a species with traits that are intermediate between two known species. What does this discovery most likely indicate?

Correct Answer: B

Q28.In an experiment, scientists simulate early Earth conditions to study the formation of organic compounds. They introduce a mixture of gases including methane, ammonia, and hydrogen into a closed system with electrical sparks. Which compound is most likely to be synthesized in this experiment?

Correct Answer: B

Q29.Which statement best describes the role of mutations in evolution?

Correct Answer: B

Q30.A new antibiotic is introduced to a bacterial population, and after several generations, a resistant strain becomes predominant. Which evolutionary mechanism best explains this observation?

Correct Answer: C

Q31.During a study on a population of fish, researchers observe that individuals with either very large or very small fins are more common than those with medium-sized fins. What type of selection is most likely occurring in this population?

Correct Answer: C

Q32.Which evolutionary concept is demonstrated by the change in moth population during the industrial revolution?

Correct Answer: B