Question 1.
Complete the following diagram.

Answer.

Question 2.
Read the following statements and justify the same in your own words with the help of suitable examples.
a. Human evolution began approximately 7 crore years ago.

1. The earliest fossils of hominins, the group that includes humans and our ancestors, are dated to about 7 million years ago. These fossils were found in East Africa and show that hominins were bipedal, meaning they walked upright on two legs.
2. Over the next few million years, hominins continued to evolve and diversify. Some species became larger and more robust, while others became smaller and more gracile.
3. About 2.5 million years ago, a new species of hominin appeared, called Homo habilis. Homo habilis was the first hominin to make and use tools.
4. About 1.8 million years ago, another new species of hominin appeared, called Homo erectus. Homo erectus was the first hominin to spread out of Africa and into other parts of the world.
5. About 300,000 years ago, a new species of hominin appeared, called Homo sapiens. Homo sapiens is the only surviving species of hominin.
6. Homo sapiens continued to evolve and develop over the next few thousand years. We learned to control fire, develop agriculture, and create art and culture.

 

1. Geographical and reproductive isolation of organisms gradually leads to speciation.

Answer:

1. Speciation is the process by which one species splits into two or more new species.
2. Geographical isolation occurs when a population of organisms is separated from the rest of its species by a physical barrier, such as a mountain range or a body of water.
3. Reproductive isolation occurs when two populations of organisms are unable to interbreed, even if they are not geographically isolated. This can happen due to differences in their breeding behavior, their physical appearance, or their genetic makeup.
4. When a population of organisms is geographically isolated, it can accumulate genetic changes that are not present in the rest of the species. This is because the isolated population is no longer exposed to the same selective pressures as the rest of the species.
5. Over time, the genetic differences between the isolated population and the rest of the species can become so great that the two populations can no longer interbreed. This is when speciation is said to have occurred.
6. There are many examples of speciation that have been caused by geographical and reproductive isolation. One example is the Galapagos finches, which are a group of closely related birds that live on the Galapagos Islands. The finches are thought to have originated from a single species of finch that was blown to the islands by a storm. Over time, the finches have evolved into 13 different species, each with its unique beak shape that is adapted to a particular food source.

 

1. The study of fossils is an important aspect of the study of evolution.
   Answer:
2. Fossils are the preserved remains or traces of organisms that lived in the past. They can be found in rocks all over the world, and they provide scientists with a window into the history of life on Earth.
3. The study of fossils, called paleontology, can help scientists to understand how organisms have changed over time. By comparing the fossils of different organisms, scientists can see how their physical features have evolved.
4. Fossils can also help scientists to understand the environment in which organisms live. For example, the type of rocks in which a fossil is found can tell scientists about the climate and the vegetation of the area at the time the organism lived.
5. Fossils can also help scientists to understand the evolutionary relationships between different organisms. By comparing the fossils of closely related organisms, scientists can see how they are connected.
6. The study of fossils is an essential part of the study of evolution. Without fossils, scientists would have no way to know how organisms have changed over time or how they are related to each other.
7. Fossils are also important for understanding the history of the Earth. By studying the fossils of different organisms, scientists can learn about the changes that have taken place in the Earth’s climate and environment over time.
8. There is evidence of fatal Science among chordates.
   [Please read the above question as: Among different chordates, there are embryological evidence.]
9. The notochord: The notochord is a flexible, rod-shaped structure that is found in the embryonic stage of all chordates. It provides support for the developing embryo and is eventually replaced by the vertebral column in vertebrates.
10. The dorsal hollow nerve cord: The dorsal hollow nerve cord is a neural tube that runs along the back of the embryo. It is the precursor to the central nervous system in all chordates.
11. Gill slits: Gill slits are openings in the pharynx that allow water to pass over the gills for gas exchange. They are present in the embryos of all chordates, but they are only retained in adults of some species, such as fish and amphibians.
12. Apostome: A costume is a small opening at the top of the pharynx that is thought to be the remnant of the pharyngeal slits in the ancestors of chordates. It is only present in the embryos of some chordates, such as lampreys.
13. Caudal fin: The caudal fin is the tail fin that helps to propel the chordate through the water. It is present in the embryos of all chordates, but it is only retained in adults of some species, such as fish and amphibians.
14. Myotomes: Myotomes are blocks of muscle that are arranged along the sides of the embryo. They are responsible for the movement of the chordate.

Question 3.

Question 3.
Complete the statements by choosing the correct options from the bracket.
(Genes, Mutation, Translocation, Transcription, Gradual development, Appendix)
a. The causality behind the sudden changes was understood due to ………… principle of Hugo de Vries.
Answer: Mutation

1. The proof for the fact that protein synthesis occurs through ……….. was given by George Beadle and Edward Tatum.
   Answer: Genes
2. Transfer of information from a molecule of DNA to mRNA is called as …………… process.
   Answer: Transcription

 

d. Evolution means………….
Answer: Gradual development

1. The vestigial organ ……….. present in the human body is proof of evolution.
   Answer: Appendix

Question 4.
Write short notes based on the information known to you.
a. Lamarckism.

1. Lamarckism is a theory of evolution that states that organisms can pass on to their offspring physical characteristics that they acquired during their lifetime.
2. This can happen through the process of use and disuse, whereby an organ or body part that is used a lot becomes stronger and more developed, while an organ or body part that is not used much becomes weaker and less developed.
3. For example, Lamarck believed that the giraffe’s long neck evolved because giraffes had to reach for leaves high up in trees. Over time, the giraffes that reached the highest leaves had more food and were more likely to survive and reproduce. Their offspring inherited the trait of a longer neck, and so on.
4. Lamarck also believed in the inheritance of acquired characteristics, whereby an organism can pass on to its offspring physical characteristics that it acquired through its own experiences, such as scars or muscle memory.
5. For example, Lamarck believed that a blacksmith who developed strong muscles from using a hammer would pass on those strong muscles to his offspring.
6. Lamarckism was a popular theory of evolution in the early 19th century, but it has since been discredited by modern genetics. Scientists now know that acquired characteristics are not inherited.

Here are some additional points about Lamarckism:

• Lamarck’s theory was based on the idea that organisms have a drive to perfection. He believed that organisms are constantly striving to become more complex and sophisticated.
• Lamarck’s theory was also influenced by his belief in teleology, the idea that there is a purpose to evolution. He believed that evolution was guided by a force that was leading organisms toward a higher state of being.
• Lamarck’s theory was challenged by Charles Darwin, who proposed the theory of natural selection. Darwin argued that evolution is driven by the struggle for survival and that organisms that are better adapted to their environment are more likely to survive and reproduce.
• Although Lamarckism is no longer a widely accepted theory of evolution, it remains an important part of the history of science. It was one of the first theories to propose that organisms could change over time, and it helped to pave the way for the development of modern evolutionary theory.

 

1. Darwin’s theory of natural selection.
2. Variation: All organisms within a population vary in their physical characteristics or traits. These variations are caused by mutations, which are changes in the DNA.
3. Inheritance: Traits are passed from parents to offspring through genes.
4. Differential survival and reproduction: Individuals with traits that are better suited to their environment are more likely to survive and reproduce than individuals with less favorable traits.
5. Overproduction: Organisms tend to produce more offspring than can survive.
6. Competition: There is competition for resources such as food, water, and mates.
7. Directional selection: Over time, the traits that are most beneficial for survival and reproduction will become more common in the population.

Here are some additional points about Darwin’s theory of natural selection:

• Natural selection is a slow and gradual process. It takes many generations for even small changes to accumulate.
• Natural selection is not goal-directed. It does not have a specific end in mind. It is simply a process that leads to the adaptation of organisms to their environment.
• Natural selection can lead to speciation, the formation of new species. This happens when a population of organisms becomes isolated from the rest of the species and evolves its own unique set of traits.
• Darwin’s theory of natural selection has been supported by a wide range of evidence, including the fossil record, comparative anatomy, and genetics.

 

1. Embryology.
   Answer:
2. Embryology is the study of the development of an embryo from fertilization to birth.
3. The first stage of embryology is fertilization when a sperm cell fertilizes an egg cell.
4. The fertilized egg cell, called a zygote, then divides into many cells.
5. These cells then form a blastocyst, which implants in the lining of the uterus.
6. The blastocyst then develops into an embryo, which goes through a series of stages, including the gastrula, the neural tube, and the organogenesis.
7. The embryo eventually becomes a fetus, which grows and develops in the uterus until it is born.

Here are some additional points about embryology:

• Embryology is a complex and fascinating field of study. It has helped us to understand how humans and other organisms develop, and it has also led to advances in medicine, such as in the treatment of infertility and birth defects.
• Embryology is divided into two main branches: developmental biology and teratology. Developmental biology studies the normal development of embryos, while teratology studies the development of abnormal embryos.
• Embryology is a rapidly growing field of study. New techniques, such as gene editing and stem cell research, are helping us to learn more about how embryos develop and how to prevent birth defects.

 

(d.)Evolution

1. Evolution is the change in the characteristics of a population of organisms over time.
2. This change is caused by the process of natural selection, whereby organisms with traits that are better suited to their environment are more likely to survive and reproduce.
3. Over time, the traits that are most beneficial for survival and reproduction will become more common in the population.
4. This can lead to the formation of new species, as populations become isolated from each other and evolve their own unique set of traits.
5. Evolution is a slow and gradual process, but it can happen over millions of years.
6. There is a wide range of evidence for evolution, including the fossil record, comparative anatomy, and genetics.

Here are some additional points about evolution:

• Evolution is not random. It is driven by the struggle for survival.
• Evolution is not perfect. There are still many organisms that are not well-adapted to their environment.
• Evolution is not always beneficial. Some changes can lead to the extinction of a species.
• Evolution is still happening today. We can see evidence of evolution in the changing populations of plants and animals

1. Connecting link
2. A connecting link is an organism that has characteristics of two different groups of organisms.
3. Connecting links are often found in the fossil record, and they can help scientists understand the evolutionary relationships between different groups of organisms.
4. Some well-known examples of connecting links include:
   • Archaeopteryx, a bird-like dinosaur with feathers and a long tail.
   • Duck-billed platypus, a mammal that lays eggs and has a duck-like bill.
   • Lungfish, an amphibian that can breathe air and water.
   • Seymouria, an extinct reptile that had features of both amphibians and mammals.
   • Balanoglossus, a marine invertebrate that has features of both chordates and non-chordates.
   • Peripatus, an arthropod that has features of both annelids and arthropods.
5. Connecting links are important evidence for evolution, as they show how different groups of organisms are related.
6. They also help scientists to understand the evolutionary processes that have shaped the diversity of life on Earth.
7. Connecting links are still being discovered, and they continue to provide new insights into the history of life.

Question 5.
Define heredity. Explain the mechanism of hereditary changes.

Heredity is the process by which traits are passed from parents to offspring. These traits can be physical, such as hair color or eye color, or behavioral, such as personality traits. Heredity is controlled by genes, which are segments of DNA that are located on chromosomes.

The mechanism of hereditary changes can be explained by the following:

1. Mutations: Mutations are changes in the DNA that can occur randomly or be caused by environmental factors. Mutations can be harmful, beneficial, or neutral.
2. Genetic recombination: Genetic recombination is the process by which genes are shuffled during meiosis, the process of cell division that produces gametes (eggs and sperm). This shuffling of genes can create new combinations of traits that were not present in the parents.
3. Natural selection: Natural selection is the process by which organisms that are better adapted to their environment are more likely to survive and reproduce. This can lead to the evolution of new traits over time.

Here are some additional points about the mechanism of hereditary changes:

• Hereditary changes can be either genetic or environmental. Genetic changes are caused by changes in the DNA, while environmental changes are caused by factors such as the environment, nutrition, and exposure to toxins.
• Hereditary changes can be beneficial, harmful, or neutral. Beneficial changes can give an organism an advantage in its environment, while harmful changes can give an organism a disadvantage. Neutral changes do not have a significant impact on the organism.
• Hereditary changes can be random or directed. Random changes are caused by chance, while directed changes are caused by specific factors, such as natural selection.
• Hereditary changes can be gradual or rapid. Gradual changes occur over many generations, while rapid changes can occur over a shorter period.

The mechanism of hereditary changes is a complex and fascinating topic that is still being studied by scientists. By understanding how hereditary changes occur, we can better understand the evolution of life on Earth.

Question 6.
Define vestigial organs. Write the names of some vestigial organs in the human body and write the names of those animals in whom the same organs are functional.

Answer. Vestigial organs are organs that have lost their original function in the course of evolution. They are remnants of structures that were once functional in an ancestor.

Here are some examples of vestigial organs in humans:

• Appendix: The appendix is a small, finger-shaped organ that projects from the colon. It is thought to have been involved in the digestion of plant matter in our ancestors, but it is no longer necessary for humans who eat a diet of cooked food.
• Coccix: The coccyx is the small, triangular bone at the end of the spine. It is the remnant of the tailbone that our ancestors had.
• Wisdom teeth: Wisdom teeth are the four molars that grow in the back of the mouth, usually in the late teens or early twenties. They are not necessary for chewing and can often cause problems, such as crowding or impacted teeth.
• Nipples on males: Male nipples are vestigial organs. They are not functional, but they are present because the development of the male and female breast is the same in the early stages of fetal development.
• Plica semilunaris: The plica semilunaris is a fold of tissue in the corner of the eye. It is thought to be a vestigial nictitating membrane, which is a third eyelid that is found in some animals.
• Muscularis mucosae: The muscularis mucosae is a layer of muscle tissue that lines the inside of the digestive tract. It is thought to be a vestigial organ that was once involved in the movement of food through the digestive tract.

The animals in which these organs are functional are:

• Appendix: Some mammals, such as herbivores, have a functional appendix that helps to digest plant matter.
• Coccyx: Some animals, such as monkeys, have a functional coccyx that helps to provide support for the spine.
• Wisdom teeth: Some animals, such as gorillas, have a functional third set of molars that help to chew food.
• Nipples on males: Some animals, such as dogs, have nipples on males, but they are not functional.
• Plica semilunaris: Some animals, such as birds, have a functional nictitating membrane that helps to protect the eye.
• Muscularis mucosae: The muscularis mucosae is a functional layer of muscle tissue in all animals that have a digestive tract.

It is important to note that the presence of a vestigial organ does not mean that the organ is completely useless. Some vestigial organs may still have a minor function, or they may be important for other reasons, such as providing a site for the attachment of muscles or blood vessels.

The existence of vestigial organs is evidence of evolution. Over time, organisms change and adapt to their environment. If a particular organ is no longer needed, it may gradually become vestigial.

Question 7.
Answer the following questions.
a. How are the hereditary changes responsible for evolution?

Hereditary changes, such as mutations, are the raw materials for evolution. These changes can be passed down from parents to offspring, and they can accumulate over time. If a hereditary change is beneficial, it can help an organism survive and reproduce more effectively. This means that the organism is more likely to pass on the change to its offspring. Over time, this process can lead to the evolution of new species.

Natural selection is the process by which beneficial hereditary changes are more likely to be passed on to future generations. This happens because organisms with beneficial traits are more likely to survive and reproduce. For example, if an organism has a mutation that makes it more resistant to disease, it is more likely to survive an epidemic and pass on the mutation to its offspring.

The process of evolution is slow and gradual. It can take millions of years for significant changes to occur. However, there is a wealth of evidence that evolution has occurred, including the fossil record, the geographical distribution of organisms, and the similarities and differences between different species.

The following are some examples of how hereditary changes can lead to evolution:

• A mutation in a bird’s beak can make it better at cracking seeds. This gives the bird an advantage over other birds, and it is more likely to survive and reproduce. Over time, the mutation will become more common in the population.
• A mutation in a plant’s DNA can make it more resistant to a certain type of pest. This gives the plant an advantage over other plants, and it is more likely to survive and reproduce. Over time, the mutation will become more common in the population.
• A group of animals becomes separated from the main population. This can happen due to a natural disaster, such as a flood or a volcanic eruption. The isolated group of animals will be exposed to different environmental conditions, and they may evolve different traits to adapt to these conditions.

Hereditary changes are the fuel that drives evolution. They are the raw materials that can be shaped by natural selection to create new and improved species.

1. Explain the process of formation of complex proteins.
   Answer:

The proteins are synthesized in the following steps:

1. Transcription: This is the process of copying the genetic information from DNA to RNA. The RNA molecule that is produced is called messenger RNA (mRNA).
2. Translation: This is the process of using the mRNA molecule to synthesize a protein. The mRNA molecule is read by ribosomes, which are cellular structures that make proteins.
3. Translocation: This is the process of moving the newly synthesized protein out of the ribosome and into the cell.

The central dogma of protein synthesis is the concept that genetic information flows from DNA to RNA to protein. This means that the sequence of nucleotides in DNA determines the sequence of nucleotides in RNA, which in turn determines the sequence of amino acids in protein.

The central dogma of protein synthesis is a fundamental principle of biology that has been well-established by scientific research. It is the basis for our understanding of how genes control the production of proteins, which are essential for all life processes.

1. Explain the theory of evolution and mention the proof supporting it.
   Answer:

The theory of evolution is the scientific explanation of how life on Earth has changed over time. It states that all living things are related and that they have descended from a common ancestor.

The theory of evolution is supported by a wide range of evidence, including:

• The fossil record, which shows how organisms have changed over time.
• The comparative anatomy of living organisms, which shows that they share common features.
• The study of DNA, which shows that all living things share a common genetic code.
• The experiments of Gregor Mendel, which showed that genes are passed from parents to offspring.

The theory of evolution is a powerful explanation of the diversity of life on Earth. It has helped us to understand how organisms adapt to their environment and how new species arise.

Here are some of the specific proofs of evolution:

• The fossil record: The fossil record shows that organisms have changed over time. For example, the fossil record shows that dinosaurs existed millions of years ago, but they are now extinct.
• Comparative anatomy: Comparative anatomy is the study of the similarities and differences between the anatomy of different organisms. It shows that organisms share common features that are inherited from a common ancestor. For example, all vertebrates have a backbone, which is a shared feature that they inherited from their common ancestor.
• The study of DNA: The study of DNA has shown that all living things share a common genetic code. This is because DNA is the genetic material that is passed from parents to offspring.
• The experiments of Gregor Mendel: Gregor Mendel was an Austrian monk who conducted experiments on pea plants in the 1800s. His experiments showed that genes are passed from parents to offspring in a predictable way. This is known as Mendelian inheritance.

The theory of evolution is a well-supported scientific theory that has been tested and verified by many different scientists. It is the most widely accepted explanation of the diversity of life on Earth

1.Explain with suitable examples importance of anatomical evidences in evolution. 

Anatomical evidence is the study of the similarities and differences in the anatomy of different organisms. It can be used to infer the evolutionary relationships between organisms.

For example, the anatomical similarities between humans and chimpanzees are evidence that we share a common ancestor. We both have a similar skeletal structure, including a backbone, two arms, two legs, and a skull. We also have similar organs, such as the heart, lungs, and liver.

These similarities are not due to coincidence. They are evidence that we inherited these features from our common ancestor. Over time, as our ancestors evolved, these features may have changed slightly, but they have remained largely the same.

Anatomical evidence can also be used to identify vestigial structures. Vestigial structures are structures that no longer have a function. For example, the appendix is a vestigial structure in humans. It is a small, finger-shaped organ that is located in the lower right abdomen. The appendix does not have any known function in humans.

The presence of vestigial structures is evidence that evolution is a gradual process. Over time, structures that are no longer needed may be lost. However, the genes that code for these structures may still be present in the genome. This is why vestigial structures can still be found in organisms today.

Anatomical evidence is a valuable tool for understanding evolution. It can be used to infer the evolutionary relationships between organisms, identify vestigial structures, and learn more about how organisms have changed over time.

Here are some other examples of anatomical evidence that supports the theory of evolution:

• The similarities between the wings of birds and bats.
• The similarities between the flippers of whales and dolphins and the forelimbs of land mammals.
• The similarities between the bones in the forelimbs of humans, whales, bats, and birds.
• The presence of a tailbone in humans.
• The presence of gill slits in embryos of humans and other mammals.

These are just a few examples of the many ways that anatomical evidence can be used to support the theory of evolution. Anatomical evidence is a powerful tool that has helped scientists to understand the history of life on Earth.

1. Define fossil. Explain importance of fossils as proof of evolution.

Answer. A fossil is any preserved remains or traces of an organism that lived in the past. Fossils can be found in rocks, sediments, and other geological formations. They can be made up of the actual remains of the organism, such as bones, teeth, and shells, or they can be made up of impressions of the organism, such as footprints or trackways.

Fossils are important because they provide evidence of the evolution of life on Earth. They show how organisms have changed over time in response to changes in their environment. For example, fossils of dinosaurs show that these animals were once widespread and diverse, but they are now extinct. This is evidence that dinosaurs evolved and changed over time, and that they eventually died out.

Fossils are also important because they can help us to understand the relationships between different organisms. For example, the similarities between the bones of humans and chimpanzees are evidence that we share a common ancestor. This is supported by the fossil record, which shows that humans and chimpanzees shared a common ancestor that lived millions of years ago.

The fossil record is a vast and complex archive of information about the history of life on Earth. It is a valuable tool for understanding evolution and the relationships between different organisms.

Here are some other examples of how fossils can be used to support the theory of evolution:

• The fossil record shows that organisms have become more complex over time.
• The fossil record shows that organisms have adapted to different environments over time.
• The fossil record shows that organisms have gone extinct over time.
• The fossil record shows that new species have arisen over time.

 

1. Write evolutionary history of modern man.
   Answer:

The evolutionary history of modern man is a long and complex one. Scientists believe that modern humans originated in Africa around 200,000 years ago. They then migrated to other parts of the world, eventually replacing the other human species that were living at the time.

The earliest known fossils of modern humans are from Ethiopia. These fossils are about 200,000 years old. They show that early humans had brains that were larger than those of other apes, and that they were bipedal, meaning that they walked upright.

Over time, humans continued to evolve and change. They developed new tools and technologies, and they began to live in larger and more complex societies. About 100,000 years ago, humans began to migrate out of Africa and into other parts of the world.

The migration of humans out of Africa was a slow and gradual process. It took place over many thousands of years. As humans migrated, they encountered different environments and challenges. They adapted to these challenges by developing new ways of living and new technologies.

About 50,000 years ago, humans reached Europe and Asia. They then migrated to Australia and the Americas. By about 15,000 years ago, humans had spread to all parts of the world.

The evolutionary history of modern man is a story of change and adaptation. It is a story of how humans have adapted to different environments and challenges, and how they have become the dominant species on Earth.

Here are some of the key events in the evolutionary history of modern man:

• The evolution of bipedalism: This was a major evolutionary development that allowed humans to walk upright and free up their hands for other tasks.
• The development of language: This was a major turning point in human evolution, as it allowed humans to communicate with each other and share information.
• The development of tools: This allowed humans to manipulate their environment and make their lives easier.
• The migration out of Africa: This was a major event that allowed humans to spread to all parts of the world.
• The development of agriculture: This allowed humans to produce food more efficiently and support larger populations.
• The development of cities: This led to the development of complex societies and cultures.