All questions of Building a Timeline for Grade 8 Exam

Answer A is correct. why don't you go through the ncert once.

Correct answer is a because according to Darwin the who leaves more Number of reproducing individuals are more successful

Sedimentary rocks are mostly involved in forming fossils, owing to the way in which they are formed.

Believers of spontaneous generation believed that life originated only spontaneously. Let's understand this statement in detail.

Explanation:
Spontaneous generation is the theory that proposed that living organisms could arise from non-living matter under certain conditions. This theory was widely accepted for many centuries, until it was disproven by Louis Pasteur in the mid-19th century.

a) Life originated from other similar organisms or spontaneously:
According to the theory of spontaneous generation, life could arise either from other similar organisms or spontaneously from non-living matter. However, this is not the correct answer as the believers of spontaneous generation did not consider the possibility of life originating from other similar organisms.

b) Life originated only spontaneously:
This is the correct answer. The believers of spontaneous generation argued that life could only originate spontaneously from non-living matter. They believed that under certain conditions, such as the presence of air, moisture, and organic material, life could arise spontaneously.

c) Life originated from similar organisms:
This is not the correct answer. The believers of spontaneous generation did not consider the possibility of life originating from similar organisms. They believed that life could only arise from non-living matter.

d) Life originated from air:
While air was considered to be one of the necessary conditions for spontaneous generation, it was not believed to be the source of life. The believers of spontaneous generation thought that life could originate from the combination of non-living matter, air, and other environmental factors.

In conclusion, the correct answer is option 'B' - the believers of spontaneous generation believed that life originated only spontaneously from non-living matter under certain conditions. However, it's important to note that this theory has been disproven by scientific experiments and observations, and the modern understanding of life's origin is based on the principles of biogenesis, which states that life only arises from pre-existing life.

Phylogenetic trees are diagrams that show the evolutionary relationships between different organisms. They are used to display the branching pattern of evolutionary relationships between organisms. The diagram looks like a tree with branches that represent different groups of organisms. These branches are called clades, and they represent groups of organisms that have descended from a common ancestor.

Phylogenetic trees are constructed based on a variety of data, including:

1. Morphological characteristics: The physical features of organisms, such as their shape, size, and structure.

2. Molecular data: DNA and RNA sequences are used to compare the genetic makeup of different organisms.

3. Fossil records: The study of fossils provides evidence of the evolutionary history of organisms.

Phylogenetic trees are an important tool for understanding the relationships between organisms and how they have evolved over time. They can be used to answer questions about the origins of different species and how they are related to one another.

In conclusion, phylogenetic trees are diagrams that show the branching pattern of evolutionary relationships between organisms. They are constructed based on a variety of data, including morphological characteristics, molecular data, and fossil records. They are an important tool for understanding the evolutionary history of organisms.

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The correct answer for the given question is option 'D' - Camouflage. A praying mantis is a perfect example of an organism that uses camouflage as a defense mechanism. Camouflage refers to the ability of an organism to blend in with its surroundings, making it difficult for predators to detect or capture it. Praying mantises have evolved unique adaptations that allow them to effectively camouflage in their environment, making them highly successful predators themselves.

Adaptations for Camouflage

Praying mantises have several physical adaptations that help them camouflage effectively:

1. Body Shape: Praying mantises have an elongated body shape that resembles sticks or plant stems, allowing them to blend in with the surrounding vegetation. Their thin bodies and elongated legs further aid in mimicking plant structures.

2. Coloration: Praying mantises come in a range of colors including green, brown, and even pink. These colors help them match the color of their surroundings, whether it be leaves, twigs, or flowers. Some species can even change their coloration to match their environment.

3. Texture: The texture of a praying mantis' exoskeleton also contributes to its camouflage. The rough and uneven surface helps break up its outline, making it harder for predators to spot them.

Benefits of Camouflage

Camouflage provides several benefits to praying mantises, including:

1. Predator Avoidance: By blending in with their surroundings, praying mantises can avoid being detected by predators such as birds, lizards, and even other insects. This allows them to hide in plain sight and increases their chances of survival.

2. Ambush Predation: Praying mantises are ambush predators, relying on their camouflage to remain undetected by their prey. They patiently wait for unsuspecting insects to come within striking distance, using their cryptic coloration and immobility to remain hidden until the opportune moment.

3. Reproductive Success: Camouflage also plays a role in the reproductive success of praying mantises. Females, in particular, benefit from their camouflage as it allows them to hide from males after mating, reducing the risk of cannibalism.

In conclusion, the praying mantis is an excellent example of an organism that utilizes camouflage as a defense mechanism. Its unique adaptations in body shape, coloration, and texture allow it to blend seamlessly with its surroundings, providing benefits such as predator avoidance and successful predation.

Adaptive Radiation:

Adaptive radiation is the evolution of different species in a given area starting from a point and spreading to other geographical areas. It is a type of divergent evolution that occurs when a single ancestral species evolves into many different species to adapt to different ecological niches. The term "adaptive radiation" was coined by the American evolutionary biologist Henry Fairfield Osborn in 1897.

Factors that contribute to adaptive radiation:

1. Ecological opportunity: When new habitats or resources become available, organisms can exploit them and evolve to fill new niches.

2. Morphological innovation: Morphological innovation can allow organisms to exploit new resources or habitats.

3. Competition: Competition for resources can drive organisms to evolve different adaptations, leading to adaptive radiation.

Examples of adaptive radiation:

1. Darwin's finches: The Galápagos Islands are home to a number of different finch species that evolved from a common ancestor. Each species has a specialized beak that allows it to feed on different types of food.

2. Hawaiian honeycreepers: The Hawaiian Islands are home to a diverse group of birds known as honeycreepers. These birds evolved from a single ancestral species and have adapted to different ecological niches on the islands.

3. Australian marsupials: Australia is home to a number of different marsupial species that evolved from a common ancestor. These marsupials have adapted to different ecological niches, such as the kangaroo, koala, and Tasmanian devil.

Conclusion:

Adaptive radiation is an important process in the evolution of new species. It allows organisms to adapt to new environments and resources and can lead to the development of new ecological niches. The study of adaptive radiation can provide insights into the mechanisms of evolution and the factors that contribute to biodiversity.

Darwin's Observations on the H.M.S. Beagle
Charles Darwin's voyage on the H.M.S. Beagle (1831-1836) was a pivotal moment in the development of his theory of evolution. His extensive observations led him to conclude that:
Evolutionary Change
- Darwin noted that various species exhibited adaptations to their environments, suggesting they were not static but rather dynamic.
- He observed diverse life forms in different geographical locations, particularly in the Galápagos Islands, where he found unique species that were closely related to mainland species but adapted to their specific habitats.
Common Ancestry
- The similarities between species suggested that they shared common ancestors, indicating that life forms have evolved over millions of years through gradual changes.
- Fossils he examined showed a progression of life forms, supporting the idea that living organisms have evolved from earlier ones.
Natural Selection
- Darwin proposed that natural selection is a mechanism driving evolution, where individuals with advantageous traits are more likely to survive and reproduce.
- This led to the gradual adaptation of species over time, as those traits become more common in a population.
Conclusion
- The conclusion that existing living forms share similarities with ancient life forms and have evolved gradually encapsulates the essence of Darwin’s findings.
- This perspective laid the groundwork for modern evolutionary biology, highlighting the interconnectedness of life and the processes that shape it.
In summary, Darwin’s observations during his voyage led him to understand that species evolve over time, influenced by their environment and through natural selection, fundamentally reshaping our understanding of life on Earth.

From ramapithicus to homosapiens all have 46 chromosomes except the person who suffers from down's syndrome and klintifer syndrome

Evolution is a stochastic process.

Definition of Evolution
Evolution refers to the gradual change in the inherited characteristics of biological populations over successive generations. It is a fundamental process in biology that drives the diversity of life on Earth. The theory of evolution, proposed by Charles Darwin, explains how species adapt and change over time through the mechanisms of natural selection, genetic mutation, and genetic drift.

The Stochastic Nature of Evolution
Evolution is considered a stochastic process. Stochastic refers to a process that involves randomness or probability. In the context of evolution, this means that the changes that occur in a population's genetic makeup are not predetermined or predictable, but rather influenced by random events and chance.

Natural Selection and Stochasticity
Natural selection is one of the main driving forces of evolution. It acts on the variation present in a population and favors individuals with traits that increase their chances of survival and reproduction. While natural selection is a deterministic process, the variation on which it acts is largely stochastic.

Genetic Mutation and Stochasticity
Genetic mutation is another important mechanism of evolution. Mutations are random changes in the DNA sequence of an organism's genome. These mutations can introduce new genetic variation into a population, which can then be subjected to natural selection. The occurrence of mutations is random and unpredictable, making it a stochastic process.

Genetic Drift and Stochasticity
Genetic drift is a stochastic process that occurs due to random fluctuations in the frequencies of different genotypes within a population. It is particularly pronounced in small populations, where chance events can have a significant impact on the genetic makeup of the population over time. Genetic drift can lead to the loss of genetic diversity or the fixation of certain alleles within a population.

Conclusion
In conclusion, evolution is a stochastic process because it involves random events and chance. Natural selection, genetic mutation, and genetic drift are all stochastic mechanisms that contribute to the evolution of species. Understanding the stochastic nature of evolution is crucial for comprehending the complexity and diversity of life on Earth.

Industrial Melanism in Biston Betularia

Industrial melanism is a phenomenon observed in certain species where the frequency of dark-colored individuals increases dramatically in response to environmental changes. One of the most well-known examples of industrial melanism is seen in the moth species Biston betularia.

Background
Before the industrial revolution, Biston betularia moths in England were predominantly light-colored, with a small proportion of dark-colored individuals. These light-colored moths were able to blend in with the lichen-covered tree trunks, which provided camouflage against predation by birds. However, with the advent of industrialization, the landscape underwent significant changes due to pollution.

Impact of Pollution
Industrial pollution led to the accumulation of soot and other dark particles on tree trunks and other surfaces. As a result, the lichen cover on the trees decreased, exposing the darkened bark. This change in the environment created a selective pressure favoring dark-colored individuals of Biston betularia.

Natural Selection
Dark-colored moths had a better chance of survival in the polluted environment as they were able to blend in with the darkened tree trunks, making them less visible to predatory birds. On the other hand, the light-colored moths stood out against the dark background and became more vulnerable to predation. Consequently, the frequency of dark-colored individuals increased significantly over time.

Observations and Studies
The phenomenon of industrial melanism in Biston betularia was first observed and documented by British geneticist Bernard Kettlewell in the 1950s. Kettlewell conducted experiments to investigate the role of natural selection in the evolution of moth coloration. He released moths in both polluted and unpolluted environments and observed that the survival rates of the moths were influenced by their coloration, with dark-colored moths faring better in polluted areas.

Conclusion
The case of industrial melanism in Biston betularia serves as a remarkable example of natural selection in response to environmental changes. It demonstrates how human activities, such as industrialization and pollution, can exert selective pressures on organisms, leading to evolutionary changes within relatively short periods of time. This phenomenon has been extensively studied and has contributed to our understanding of adaptation and evolution.

Statement (1) is as it is given in Ncert , means when to adaptive radiation occurs simultaneously in an isolated geographical area it becomes convergent evolution.for eg.adaptive radiation in placental mammals divergent evolution and adaptI've radiation in marsupoals is divergent evolution , but together , it show convergent evolution
and in option (3) these all are examples of adaptive radiation in marsupials
but 2nd is wrong

The ape that is closely related to man is the chimpanzee.

Chimpanzees, scientifically known as Pan troglodytes, are the closest living relatives to humans. They share a common ancestor with humans, with whom they have a high degree of genetic similarity. Here is an explanation of why chimpanzees are considered to be closely related to humans:

1. Genetic Similarity:
- Humans and chimpanzees share approximately 98.7% of their DNA.
- This high degree of genetic similarity indicates a close evolutionary relationship between the two species.

2. Common Ancestor:
- Humans and chimpanzees diverged from a common ancestor around 6 to 7 million years ago.
- Over time, this common ancestor gave rise to two distinct lineages, one leading to humans and the other to chimpanzees.

3. Physical Similarities:
- Chimpanzees and humans share several physical characteristics, such as opposable thumbs, forward-facing eyes, and complex social behaviors.
- These similarities suggest a common evolutionary history and a close relationship.

4. Behavioral Similarities:
- Chimpanzees exhibit complex behaviors, including tool use, hunting, and communication.
- These behaviors are similar to those observed in early human ancestors, providing further evidence of a shared ancestry.

5. Social Structure:
- Chimpanzees live in social groups, similar to human societies.
- They form complex social hierarchies, maintain social bonds, and engage in cooperative activities.
- These social behaviors parallel many aspects of human social organization.

In conclusion, the chimpanzee is closely related to humans due to the high degree of genetic similarity, shared ancestry, physical and behavioral similarities, and similar social structures. Studying chimpanzees helps scientists gain insights into human evolution, behavior, and biology.

Factors affecting the Hardy-Weinberg principle:

1. Mutation: Mutations introduce new alleles into a population, which can disrupt the equilibrium predicted by the Hardy-Weinberg principle.



2. Gene flow: The movement of alleles between populations can alter allele frequencies and disrupt the genetic equilibrium.



3. Genetic drift: Random changes in allele frequencies due to chance events can lead to deviations from Hardy-Weinberg equilibrium.



4. Non-random mating: If individuals preferentially choose mates with specific traits, it can lead to changes in allele frequencies and disrupt the principle.



5. Natural selection: Differential survival and reproduction of individuals with certain genotypes can also cause deviations from Hardy-Weinberg equilibrium.

Each of these factors plays a role in shaping the genetic composition of populations and can lead to deviations from the predictions of the Hardy-Weinberg principle. Understanding and considering these factors is crucial in studying population genetics and evolution.

Gene migration or gene flow (1) involves the movement of genes between populations, affecting gene frequencies.
Genetic drift (2) refers to random changes in gene frequencies due to chance events, especially in small populations.
Mutation (3) introduces new genetic variations that can alter gene frequencies.
Genetic recombination (4) during gametogenesis creates new combinations of alleles, influencing genetic diversity.
Natural selection (5) acts on heritable traits, enhancing reproductive success and influencing the frequency of advantageous alleles in future generations.
All these factors contribute to changes in allele frequencies and can lead to speciation over time.

The correct answer is option 'D': The size of their brain of Homo erectus was smaller than that of Homo sapiens.

Explanation:
Homo sapiens and Homo erectus are two distinct species of hominins that lived during different periods of human evolution. There are several differences between these two species, but one of the most significant differences lies in the size of their brains.

1. Homo erectus:
- Homo erectus is an extinct species of hominin that lived from about 1.9 million years ago to about 143,000 years ago.
- They had a relatively larger cranial capacity compared to earlier hominins, but their brain size was still smaller than that of Homo sapiens.
- The average cranial capacity of Homo erectus was about 900 to 1100 cubic centimeters.
- Homo erectus is known for its robust physical features, including a thick skull, prominent brow ridges, and a long, low skull shape.

2. Homo sapiens:
- Homo sapiens, also known as anatomically modern humans, emerged around 300,000 years ago and are the only surviving species of hominins.
- They have a significantly larger brain size compared to Homo erectus.
- The average cranial capacity of Homo sapiens is about 1200 to 1600 cubic centimeters.
- Homo sapiens have a more rounded skull shape and less pronounced brow ridges compared to earlier hominins.

Importance of brain size:
- The size of the brain is often correlated with cognitive abilities, such as problem-solving, language, and complex social interactions.
- A larger brain size generally indicates a higher level of cognitive development and intelligence.
- The increase in brain size throughout human evolution is believed to be associated with the development of complex behaviors and cultural advancements.

In summary, the main difference between Homo sapiens and Homo erectus is that the size of the brain of Homo erectus was smaller compared to that of Homo sapiens.

Introduction to the Theory of Saltations
The Theory of Saltations, proposed by Hugo de Vries, significantly contributed to the understanding of evolution and genetic variation. De Vries introduced this concept in the early 20th century, challenging the gradualism of Darwinian evolution.
Key Concepts of Saltation Theory
- Definition of Saltation:
Saltation refers to sudden and large evolutionary changes, as opposed to gradual changes over time.
- Mutation as a Driver:
De Vries emphasized mutations as the primary mechanism of saltation, suggesting that new species can arise rapidly due to significant genetic changes.
- Experiments with Evening Primrose:
De Vries conducted experiments on *Oenothera lamarckiana* (evening primrose) to observe how mutations could lead to new forms, supporting his theory.
Impact on Evolutionary Biology
- Revolutionized Understanding:
Saltation theory provided an alternative view to Darwin's gradualism, leading to discussions about the pace of evolutionary change.
- Foundation for Modern Genetics:
De Vries' work laid the groundwork for the field of genetics, influencing later researchers like J.B.S. Haldane and others who explored genetic variations in populations.
Conclusion
Hugo de Vries' Theory of Saltations highlights the importance of mutations in the evolutionary process, offering a perspective that complements traditional evolutionary theories. Understanding this theory is crucial for comprehending the mechanisms of evolution, especially in the context of genetic diversity and speciation.

Refer ncert u'll get the explanation

Melanised moths and natural selection:
The statement (i) is correct. The increase in melanised moths after industrialisation in Great Britain is indeed a proof for natural selection. Before industrialisation, the majority of moths in Britain were light-colored (non-melanised) because they blended well with the lichen-covered trees. However, with the onset of industrial pollution, the lichens died out, and the trees became darkened with soot. This led to an increase in the number of melanised (dark-colored) moths as they were better camouflaged against the new background. This change in the moth population over time is an example of natural selection, where individuals with advantageous traits are more likely to survive and reproduce.

Mean character value and disruption:
The statement (ii) is incorrect. The term "disruption" refers to a type of natural selection where individuals with extreme or divergent traits have higher fitness than those with intermediate traits. This can lead to the splitting of a population into two distinct groups or the formation of multiple phenotypic clusters. It does not involve the acquisition of a mean character value by more individuals.

Allelic frequency and Hardy-Weinberg equilibrium:
The statement (iii) is incorrect. Changes in allelic frequency in a population do not necessarily lead to Hardy-Weinberg equilibrium. The Hardy-Weinberg equilibrium describes a theoretical population in which the allelic frequencies remain constant from generation to generation in the absence of evolutionary forces like mutation, migration, selection, and genetic drift. Any change in allelic frequency indicates that the population is not in Hardy-Weinberg equilibrium.

Genetic drift and gene frequency:
The statement (iv) is correct. Genetic drift refers to the random fluctuations in gene frequencies within a population due to chance events, particularly in small populations. These chance events can lead to the loss or fixation of certain alleles over time, resulting in changes in the existing gene or allelic frequencies in future generations. Genetic drift is one of the mechanisms of evolution and can have significant effects on the genetic diversity of populations.

Therefore, the correct option is (c) both (i) and (iv) are correct.

The correct answer is option 'A' - Neanderthal human.

Explanation:

Neanderthals were a species of extinct humans who lived from approximately 100,000 to 40,000 years ago in Europe, Asia, and parts of Africa. They are known for their distinct physical features and characteristics.

Physical Features:
1. Short Stature: Neanderthals had a relatively short average height compared to modern humans, with males averaging around 5'5" and females around 5'1".
2. Heavy Eye Brows: They had prominent brow ridges and heavy eyebrows, giving them a unique facial appearance.
3. Retreating Foreheads: Neanderthals had low and sloping foreheads.
4. Large Jaws with Heavy Teeth: They had robust jaws and large teeth, which were adapted for a diet that included tough and coarse foods.
5. Stocky Bodies: Neanderthals had a robust and stocky body build, with strong bones and muscles.
6. Lumbering Gait and Stooped Posture: Due to their body structure, Neanderthals had a distinctive gait and posture, often described as stooped or hunched.

Differences from Modern Humans:
Despite some similarities to modern humans, Neanderthals had several distinct features that set them apart:
1. Cranial Capacity: Neanderthals had a larger cranial capacity than modern humans, suggesting a different pattern of brain development.
2. Tool Use: Neanderthals were skilled toolmakers and used a variety of stone tools for hunting and other activities.
3. Cultural Behavior: They had their own unique cultural behaviors, including burying their dead and creating symbolic objects.
4. Genetic Differences: Genetic studies have shown that Neanderthals interbred with early modern humans, and some individuals of non-African descent today carry a small percentage of Neanderthal DNA.

Conclusion:
Neanderthals were an extinct human species that lived in Europe, Asia, and parts of Africa. They had distinct physical features such as short stature, heavy eyebrows, retreating foreheads, large jaws with heavy teeth, stocky bodies, a lumbering gait, and a stooped posture. Neanderthals had their own unique cultural behaviors and interbred with early modern humans.

Correct answer is B because, as you know, lamarck in his theory talked only about the inheritance of the acquired characters from the parents to progeny. He told that, giraffes has acquired the long neck from the ancestors in which the long neck was not present at the time of birth, but aquired during their course of development.