CH:1 Heredity and Evolution Class 10th Solutions | Heredity and Evolution SSC Class 10 Questions And Answers
Complete the following chart:
Solution
Read the following statement and justify the same in your own words with the help of a suitable example.
Human evolution began approximately 7 crore years ago.
Solution 1: Scientific and Written Exam Answer
The process of human evolution began approximately 7 crore years ago. It started with primates, and through gradual evolutionary changes, modern humans evolved. This process is known as biological evolution.
The major stages of human evolution are as follows:
| Stage | Scientific Name | Years Ago |
|---|---|---|
| Early Primates | Dryopithecus | 7 - 10 crore years ago |
| First Hominids | Australopithecus | 40 lakh years ago |
| Early Humans | Homo habilis | 25 lakh years ago |
| Advanced Humans | Homo erectus | 15 lakh years ago |
| Neanderthals | Homo neanderthalensis | 4 lakh years ago |
| Modern Humans | Homo sapiens | 50,000 years ago |
Example: Fossil evidence of early human species like Australopithecus and Homo habilis shows that human beings have evolved from ape-like ancestors through gradual changes over millions of years.
Solution 2: Simple and Understandable Answer
Human evolution started around 7 crore years ago. At first, early primates lived on trees. Slowly, they started walking on two legs, making tools, and developing intelligence.
Here is a simple timeline of human evolution:
- 7 - 10 crore years ago: Early apes (Dryopithecus) appeared.
- 40 lakh years ago: The first human-like species (Australopithecus) developed.
- 15 lakh years ago: Humans started walking straight and using fire.
- 50,000 years ago: Modern humans (Homo sapiens) appeared.
Example: Scientists have found old fossils of human ancestors that show how humans have changed from ape-like creatures to modern people over millions of years.
Read the following statement and justify the same in your own words with the help of a suitable example.
Geographical and reproductive isolation of organisms gradually leads to speciation.
Solution 1: Scientific and Written Exam Answer
Speciation is the formation of new species due to geographical and reproductive isolation. When a group of organisms becomes separated from the main population, they adapt to their new environment over time. As a result, they develop different characteristics and eventually become a new species.
There are two main types of isolation that lead to speciation:
- Geographical Isolation: A physical barrier such as a river, mountain, or ocean separates a species, preventing them from interbreeding.
- Reproductive Isolation: Due to genetic, behavioral, or structural changes, the separated organisms can no longer reproduce with the original group.
Example: The Darwin’s finches of the Galápagos Islands provide a classic example of speciation. These birds were once part of a single species but became isolated on different islands. Over time, they adapted to different food sources, which led to changes in their beak sizes and shapes. Eventually, they evolved into different species.
Solution 2: Simple and Understandable Answer
Sometimes, a group of animals or plants gets separated from others because of natural barriers like rivers, mountains, or climate changes. Since they no longer mix with the original group, they change and adapt to their new environment. Over many generations, they become so different that they turn into a new species.
Types of Isolation:
- Geographical Isolation: A group is physically separated by mountains, rivers, or long distances.
- Reproductive Isolation: They stop reproducing with the original group due to changes in their bodies or behaviors.
Example: Long ago, birds of the same species in the Galápagos Islands got separated on different islands. Over time, they developed different beak shapes based on the type of food available. Now, they are completely different species.
Read the following statement and justify the same in your own words with the help of suitable examples.
Study of fossils is an important aspect of the study of evolution.
Solution 1: Scientific and Written Exam Answer
The study of fossils is known as Paleontology. Fossils are the preserved remains or traces of ancient organisms found in layers of the Earth’s crust. They provide crucial evidence about the evolution of life on Earth.
How Fossils Help in Evolutionary Studies:
- Evidence of Ancestral Species: Fossils show how ancient species looked and help us trace their changes over millions of years.
- Transitional Forms: Some fossils act as a link between ancient and modern species, proving gradual evolution. For example, Archaeopteryx is a fossil that shows both reptilian and avian features, proving the link between reptiles and birds.
- Age Determination: The deeper the fossil is buried, the older it is. This helps scientists create a timeline of evolution.
Example: Fossils of whales show that they evolved from land-dwelling mammals. The discovery of fossilized remains of Ambulocetus, an early whale ancestor with legs, confirms this evolutionary transition.
Solution 2: Simple and Understandable Answer
Fossils are the remains of ancient plants and animals that got buried under layers of soil and rock. They help us understand how living things have changed over time.
Why Fossils Are Important in Evolution:
- Show Old Life Forms: Fossils tell us about animals and plants that lived millions of years ago.
- Prove Changes Over Time: Some fossils show features of both old and new species, proving how they changed.
- Help in Dating Life Forms: The deeper a fossil is found, the older it is.
Example: Scientists found fossils of Archaeopteryx, an ancient bird-like reptile, which proves that birds evolved from reptiles.
Read the following statement and justify the same in your own words with the help of a suitable example.
There is evidence of fetal science among chordates.
Solution 1: Scientific and Written Exam Answer
Chordates show strong evidence of fetal science, which means that during early stages of development, embryos of different chordates (such as fish, amphibians, reptiles, birds, and mammals) appear very similar. This suggests that all these animals share a common ancestor.
Key Evidence:
- Similar Embryonic Stages: In the early stages, embryos of different chordates have common features like a notochord, gill slits, and a tail.
- Gradual Differentiation: As embryos develop further, they start showing characteristics of their respective species.
- Common Ancestry: These similarities in embryonic development provide evidence that all chordates evolved from a single ancestral species.
Example: The early-stage embryos of a fish, a chicken, and a human look nearly identical, having gill slits and a tail, even though they develop into completely different species later.
Solution 2: Simple and Understandable Answer
All chordates, like fish, frogs, birds, and humans, look very similar as embryos. This means they are related and share a common ancestor.
Why This is Important:
- Same Early Features: In the beginning, all chordate embryos have a tail and gill-like structures.
- They Change Later: As they grow, they develop into different animals.
- Proves Evolution: The similarity in embryos shows that all chordates evolved from one common ancestor.
Example: A human baby in the womb looks like a fish embryo at one stage, but later develops into a human. This proves that humans and fish had a common ancestor long ago.
Complete the statement by choosing the correct option from below.
The causality behind the sudden changes was understood due to -- -- principle of Hugo de Vries.
Options:
- Gene
- Mutation
- Translocation
- Transcription
- Gradual development
- Appendix
Solution:
The causality behind the sudden changes was understood due to Mutation principle of Hugo de Vries.
Complete the statement by choosing the correct option from below.
The proof for the fact that protein synthesis occurs through -- --- was given by George Beadle and Edward Tatum.
Options:
- Gene
- Mutation
- Translocation
- Transcription
- Gradual development
- Appendix
Solution:
The proof for the fact that protein synthesis occurs through Transcription was given by George Beadle and Edward Tatum.
Complete the statement by choosing the correct option from below.
Transfer of information from molecules of DNA to mRNA is called as ______ process.
Options:
- Gene
- Mutation
- Translocation
- Transcription
- Gradual development
- Appendix
Solution:
Transfer of information from molecules of DNA to mRNA is called as Transcription process.
Complete the statement by choosing the correct option from below.
Evolution means -- -- -- --.
Options:
- Gene
- Mutation
- Translocation
- Transcription
- Gradual development
- Appendix
Solution:
Evolution means Gradual development.
Complete the statement by choosing the correct option from below.
Vestigial organ ______ present in the human body is proof of evolution.
Options:
- Human hand
- Appendix
- Ear muscles
- Tail-bone
- Gradual development
- Mutation
- Gene
- Transcription
- Translocation
Solution:
Vestigial organ Appendix present in the human body is proof of evolution.
Write short notes based upon the information known to you.
Lamarckism
Solution:
Lamarckism is the theory of evolution proposed by the French biologist Jean-Baptiste Lamarck in the early 19th century. This theory states that organisms develop new characteristics based on their needs and pass them on to their offspring. It is also known as the Theory of Inheritance of Acquired Characteristics.
Key Points of Lamarckism:
- Organisms develop new traits due to environmental changes.
- These acquired characteristics are passed to the next generation.
- Example: Giraffes developed long necks by stretching to reach high leaves.
Although Lamarck’s theory was later disproved by modern genetics, it played a significant role in early evolutionary studies.
Write short notes based upon the information known to you.
Darwin’s Theory of Natural Selection
Solution:
Charles Darwin proposed the Theory of Natural Selection in his book “On the Origin of Species” in 1859. This theory explains how species evolve over time through a process where individuals with favorable traits survive and reproduce.
Key Points of Darwin’s Theory:
- There is variation among individuals of a species.
- Organisms with beneficial traits have a higher chance of survival.
- These advantageous traits are passed on to future generations.
- Over time, this leads to the evolution of new species.
Example: The evolution of long-necked giraffes because they could reach higher leaves for food, giving them a survival advantage.
Darwin’s theory remains a fundamental concept in modern evolutionary biology.
Write short notes based upon the information known to you.
Embryology
Solution:
Embryology is the branch of biology that studies the development of embryos from fertilization to birth. It provides important evidence for evolution by showing similarities in the early developmental stages of different organisms.
Key Points:
- Many vertebrate embryos (e.g., fish, birds, and humans) look similar in early stages.
- This suggests that they share a common ancestor.
- As development progresses, differences become more noticeable.
Example: The embryos of humans and fish have gill slits in early stages, which disappear in humans but remain in fish, showing evolutionary links.
Write short notes based upon the information known to you.
Evolution
Solution:
Evolution is the gradual process of change in living organisms over generations. It explains how species develop and adapt to their environments over time.
Key Points:
- Evolution occurs due to genetic variations and natural selection.
- It leads to the formation of new species from existing ones.
- It is supported by evidence from fossils, anatomy, and molecular biology.
Example: The evolution of modern horses from small, multi-toed ancestors over millions of years.
Write short notes based upon the information known to you.
Connecting Link
Solution:
A connecting link is an organism that shows characteristics of two different groups of organisms, proving evolutionary relationships.
Key Points:
- It provides evidence of gradual evolution.
- Such organisms show traits of both their ancestors and modern species.
- They help scientists understand the transition between major evolutionary groups.
Example: Archaeopteryx is a connecting link between reptiles and birds as it had feathers like birds but teeth and claws like reptiles.
Define heredity.
Solution 1: Scientific and Written Exam Answer
Heredity is the process by which characteristics are transmitted from parents to their offspring through genes. It occurs due to the inheritance of genetic material, primarily DNA, from one generation to another. The units of heredity are called genes, which are located on chromosomes. This process ensures continuity of traits within a species.
Solution 2: Simple and Understandable Answer
Heredity is the passing of traits like eye color, height, and hair type from parents to children. It happens because of genes, which carry information from one generation to the next. For example, if a child has curly hair like their mother, it is due to heredity.
Explain the mechanism of hereditary changes.
Solution 1: Scientific and Written Exam Answer
The mechanism of hereditary changes involves genetic variations caused by mutations, recombination, and crossing over. These changes occur due to alterations in the DNA sequence, leading to differences in traits among individuals. The key processes involved in hereditary changes include:
- Mutation: Sudden changes in genes that alter the genetic code.
- Genetic Recombination: Exchange of genetic material during meiosis that increases diversity.
- Natural Selection: Traits beneficial for survival are passed on to the next generation.
These mechanisms contribute to evolution and variation in species over time.
Solution 2: Simple and Understandable Answer
Hereditary changes happen when small differences occur in genes. This can happen due to natural processes like mutations (small changes in DNA) or when parents pass mixed traits to their children. For example, if a child has a unique eye color different from both parents, it may be due to a genetic change.
Define vestigial organs. Write names of any two vestigial organs in the human body. Write name of those animals in which these vestigial organs are functional.
Solution 1: Scientific and Written Exam Answer
Vestigial organs are those structures in an organism that have lost their original function due to evolution. These organs may have been fully functional in ancestral species but are now reduced or non-functional in modern organisms.
Examples of Vestigial Organs in Humans:
- Appendix: A small pouch attached to the large intestine, which was once useful in digesting plant material.
- Coccyx (Tailbone): The remnant of a tail found in human ancestors.
Animals Where These Organs are Functional:
- Appendix: Functional in herbivorous animals like rabbits, where it helps in digesting cellulose.
- Tailbone: Functional in animals like monkeys and other primates that have tails for balance and movement.
Solution 2: Simple and Understandable Answer
Vestigial organs are body parts that do not have an important function in humans but were useful to our ancestors. Over time, evolution made these organs less useful.
Examples in Humans:
- Appendix: A small organ near the stomach that has no major role today.
- Tailbone: The lower part of our spine, which was once part of a tail in early human ancestors.
Where These Organs Work Properly:
- Appendix: Helps in digestion in animals like rabbits.
- Tailbone: Used for balance in monkeys and other animals with tails.
Write names of some vestigial organs in the human body.
Solution 1: Scientific and Written Exam Answer
The following are some vestigial organs in the human body:
- Appendix: A remnant of the large intestine with no significant function.
- Tailbone (Coccyx): A leftover structure from ancestors who had tails.
- Wisdom Teeth: Extra molars that were used for chewing tough food in early humans.
- Ear Muscles: Small muscles that were used to move ears in ancient species but are now non-functional in humans.
Solution 2: Simple and Understandable Answer
Vestigial organs are parts of our body that do not have any major function. Some examples are:
- Appendix: A small organ in the stomach area.
- Tailbone: The last part of the backbone.
- Wisdom Teeth: Extra teeth that many people get removed.
- Ear Muscles: Tiny muscles in the ears that do not help us hear better.
Write the names of those animals in whom the human body organs are functioning.
Solution 1: Scientific and Written Exam Answer
Some organs in the human body are vestigial but are fully functional in other animals. These animals include:
- Appendix: Functional in herbivorous animals like rabbits, where it helps digest cellulose.
- Tailbone (Coccyx): Functional in monkeys and other primates that use their tails for movement and balance.
- Wisdom Teeth: Useful in herbivorous mammals like gorillas, where they help chew tough plant material.
- Ear Muscles: Functional in cats, dogs, and horses, helping them move their ears toward sound sources.
Solution 2: Simple and Understandable Answer
Some organs in humans do not work much but are important in other animals. Here are a few examples:
- Appendix: Helps rabbits digest plant food.
- Tailbone: Works as a tail in monkeys and helps them balance.
- Wisdom Teeth: Useful for gorillas to chew hard plants.
- Ear Muscles: Help dogs and cats move their ears to hear better.
How are the hereditary changes responsible for evolution?
Solution 1: Scientific and Written Exam Answer
Hereditary changes, also called genetic mutations, are the primary driving force behind evolution. These changes occur in the DNA of organisms and are passed from one generation to another. If a genetic variation provides an advantage in survival and reproduction, it becomes more common in a population over time. This process is known as natural selection.
Example: The evolution of long-necked giraffes from short-necked ancestors due to mutations that favored reaching higher leaves for food.
Formula for Evolutionary Change:
$$ P = P_0 e^{rt} $$
Where:
- P = Final population with advantageous traits
- P₀ = Initial population
- r = Rate of selection
- t = Number of generations
Solution 2: Simple and Understandable Answer
Heredity is how traits are passed from parents to children. Sometimes, small changes (mutations) happen in genes. If these changes help an organism survive, they are passed on to the next generation. Over time, this leads to evolution.
Example: Giraffes once had short necks, but some were born with slightly longer necks. They could reach more food, survived better, and passed their long-neck genes to their babies. Slowly, all giraffes evolved to have long necks.
Explain the process of formation of complex proteins.
Solution 1: Scientific and Written Exam Answer
The formation of complex proteins occurs through a multi-step process called protein synthesis. This process involves two main stages: Transcription and Translation.
1. Transcription:
- Occurs in the nucleus.
- DNA is used as a template to produce mRNA (messenger RNA).
- The enzyme RNA polymerase helps in the synthesis of mRNA.
Equation for Transcription:
$$ DNA \to mRNA $$
2. Translation:
- Occurs in the ribosome.
- mRNA carries the genetic code to ribosomes where tRNA (transfer RNA) brings amino acids.
- These amino acids are linked together by peptide bonds to form a polypeptide chain.
Equation for Translation:
$$ mRNA + tRNA + Ribosome \to Protein $$
After translation, the protein undergoes folding and modifications to achieve its final complex structure.
Solution 2: Simple and Understandable Answer
Proteins are made in cells through two steps:
1. Transcription (Copying the Code):
- The cell reads DNA and makes a small copy called mRNA.
- This happens inside the nucleus.
2. Translation (Building the Protein):
- The mRNA moves to the ribosome, where tRNA brings small pieces (amino acids).
- These amino acids join together like beads to form a protein.
Example: Just like following a recipe to cook a dish, cells follow DNA instructions to make proteins that help the body work.
Explain the theory of evolution and mention the proof supporting it.
Solution 1: Scientific and Written Exam Answer
The theory of evolution explains how organisms change over generations due to variations, natural selection, and environmental adaptation. It was proposed by Charles Darwin in his book "On the Origin of Species" in 1859.
Key Points of Darwin’s Theory:
- Variation: Organisms show differences in traits due to genetic variations.
- Struggle for existence: Due to limited resources, organisms compete for survival.
- Natural selection: Only the fittest organisms survive and reproduce.
- Survival of the fittest: Organisms with beneficial traits are more likely to pass them to the next generation.
- Speciation: Over time, changes lead to the formation of new species.
Proof Supporting Evolution:
1. Fossil Evidence:
- Fossils of extinct species show a gradual development of present-day organisms.
- Example: Fossils of Archaeopteryx show features of both reptiles and birds.
2. Embryological Evidence:
- Embryos of different animals (e.g., fish, reptiles, birds, humans) look similar in early stages.
- Example: Human embryos have gill slits like fish embryos, which later disappear.
3. Anatomical Evidence:
- Similar bone structures in different species suggest a common ancestor.
- Example: The forelimbs of humans, bats, and whales have the same bone structure but different functions.
4. Vestigial Organ Evidence:
- Some organs, once useful in ancestors, are now reduced or non-functional.
- Example: The appendix in humans is a vestigial organ, while it is functional in herbivores.
5. Molecular Evidence:
- DNA similarities between different species prove common ancestry.
- Example: Humans share about 98.5% of DNA with chimpanzees.
Solution 2: Simple and Understandable Answer
The theory of evolution explains how living things slowly change over time to adapt to their environment. This happens because of small differences (variations) that help them survive and reproduce better.
Main Points of Evolution:
- Living things change over many generations.
- Nature selects the strongest and best-adapted individuals.
- New species are formed over time.
Proof of Evolution:
- Fossils: Old bones and remains of animals found in rocks show how life changed.
- Embryos: The early stage of development looks similar in different animals.
- Body Structures: Humans, bats, and whales have similar arm bones.
- Vestigial Organs: Some organs (like the appendix) are no longer needed.
- DNA Evidence: Humans and monkeys have very similar genes.
Example: Just like a mobile phone has changed from simple models to smartphones over time, living beings also change to become better suited to their surroundings.
Explain with suitable examples the importance of anatomical evidence in evolution.
Solution 1: Scientific and Written Exam Answer
Anatomical evidence refers to the similarities in body structures of different organisms, which suggest that they share a common ancestor. The study of such structures helps scientists understand evolutionary relationships.
Types of Anatomical Evidence:
1. Homologous Organs:
- These organs have a similar structure but perform different functions in different species.
- Example: The forelimbs of humans, bats, whales, and birds have the same bone arrangement but are used for different purposes (grasping, flying, swimming, and perching, respectively).
2. Analogous Organs:
- These organs perform the same function but have different structures and evolutionary origins.
- Example: The wings of birds and insects help in flying but have different structures.
3. Vestigial Organs:
- These are organs that were functional in ancestors but are now reduced or non-functional in present-day organisms.
- Example: The appendix in humans is a vestigial organ, while it is functional in herbivores for digesting cellulose.
Importance of Anatomical Evidence in Evolution:
- It shows how different species have evolved from a common ancestor.
- It helps in classifying organisms based on their evolutionary relationships.
- It supports the concept of gradual development of life over millions of years.
Solution 2: Simple and Understandable Answer
Anatomical evidence helps us understand how different living things are related. By studying body structures, scientists can find out which animals had common ancestors.
Examples of Anatomical Evidence:
- Same Structure, Different Use: The arms of humans, wings of bats, and flippers of whales look similar inside but are used for different purposes.
- Same Function, Different Structure: The wings of birds and insects help them fly, but their body parts are very different.
- Leftover Body Parts: Humans have an appendix, which is no longer useful but was once important in ancient ancestors.
Why is this important?
- It helps scientists understand how living things have changed over time.
- It proves that animals and humans evolved from common ancestors.
- It explains why some body parts are similar even in different animals.
Example: Just like different types of vehicles (cars, trucks, and buses) have wheels but are used differently, animals also have similar body parts that work in different ways!
Define fossil.
Solution 1: Scientific and Written Exam Answer
A fossil is the preserved remains, impressions, or traces of ancient organisms found in sedimentary rocks. Fossils help scientists study extinct species and understand evolutionary history.
Examples of Fossils:
- The fossilized skeleton of dinosaurs found in rock formations.
- The Archaeopteryx fossil, which provides evidence of the transition between reptiles and birds.
Formation of Fossils: Fossils form when organisms are buried under sediments, and their hard parts (bones, shells, teeth) are preserved over millions of years.
Solution 2: Simple and Understandable Answer
Fossils are the remains or marks of animals and plants that lived long ago. They are found in rocks and help us learn about extinct creatures.
Examples:
- Dinosaur bones found in the ground.
- Footprints of ancient animals preserved in stone.
Think of it like this: Fossils are like old photographs of ancient life, preserved in the earth for scientists to study!
Explain the importance of fossils as proof of evolution.
Solution 1: Scientific and Written Exam Answer
Fossils provide crucial evidence for evolution by showing how species have changed over time. They help scientists understand the development of life on Earth.
Importance of Fossils in Evolution:
- Evidence of Extinct Species: Fossils of dinosaurs show that many species once existed but later disappeared.
- Transitional Links: The fossil of Archaeopteryx shows characteristics of both reptiles and birds, proving evolutionary transitions.
- Age Determination: Fossils help in dating the Earth’s history and understanding ancient ecosystems.
Fossils act as historical records, confirming the gradual changes in species over millions of years.
Solution 2: Simple and Understandable Answer
Fossils help us understand how animals and plants have changed over time. They are like nature’s history book, showing what life was like millions of years ago.
Why are fossils important?
- They show that some animals and plants have become extinct.
- They prove that new species evolved from older ones.
- They help scientists know how old the Earth is.
Example: Just like we look at old family photos to see how people have changed, fossils help scientists see how living things have evolved!
Write evolutionary history of modern man.
Solution 1: Scientific and Written Exam Answer
The evolutionary history of modern humans (Homo sapiens) is traced through a process known as human evolution. This process involved gradual biological and cultural development over millions of years.
Stages of Human Evolution:
- Australopithecus (4 - 2 million years ago): Early hominins that walked upright but had small brain sizes.
- Homo habilis (2.4 - 1.4 million years ago): The first tool-making species, also known as "Handy Man."
- Homo erectus (1.9 million - 110,000 years ago): Discovered fire, developed hunting skills, and migrated from Africa.
- Neanderthals (400,000 - 40,000 years ago): Intelligent early humans who lived in Europe and Asia.
- Homo sapiens (300,000 years ago - present): Modern humans who developed language, agriculture, and technology.
Modern humans evolved around 300,000 years ago in Africa and spread across the world, developing civilizations and advanced societies.
Solution 2: Simple and Understandable Answer
Humans evolved over millions of years from ape-like ancestors. Our early relatives started walking on two legs, using tools, and discovering fire.
Major Stages:
- First Humans: Walked on two legs but had small brains.
- Tool Makers: Learned to use stones for hunting and survival.
- Fire Discoverers: Started cooking food and staying warm.
- Early Humans: Lived in caves and hunted for food.
- Modern Humans: Created language, farming, and technology.
Example: Just like how we learn and improve over time, humans have also changed and developed new skills throughout history!
State Mendel's first law of inheritance.
Solution 1: Scientific and Written Exam Answer
Mendel’s First Law of Inheritance is known as the Law of Segregation. It states that:
"During gamete formation, the two alleles for a gene separate so that each gamete receives only one allele from each pair."
Mathematical Representation:
If a gene has two alleles, say "A" and "a", then the possible gametes will be:
$$ A, a $$This law ensures that offspring inherit one allele from each parent.
Example:
- In pea plants, the tall (T) and short (t) traits segregate during reproduction, resulting in different combinations like TT, Tt, or tt.
Solution 2: Simple and Understandable Answer
Mendel’s first law says that parents pass only one of their two genes for each trait to their children.
Example:
- If a father has a tall (T) and a short (t) gene, he can pass either T or t to his child.
- The mother does the same, and their child’s height depends on the combination (TT, Tt, or tt).
Think of it like this: It’s like flipping a coin! Each parent gives one gene, and the combination decides the trait.