Class 10 Science 2 Lesson no.1 Heredity and Evolution Exercise | Question Answers | Maharashtra Board
1.Heredity and Evolution
Heredity and Evolution – Exercise
In this exercise, we have provided simple and easy-to-understand answers to all the important questions from Heredity and Evolution – Class 10 Science 2. These answers are prepared according to the Maharashtra State Board pattern and are useful for exam preparation.
Students can use these question answers, short notes and diagrams for quick revision and better understanding of the chapter.
Let’s start the exercise. 📚✍️
Q.1. Complete the following diagram
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.b. Geographical and reproductive isolation of organisms gradually leads to speciation.c. Study of fossils is an important aspect of study of evolution.d. There is evidence of fatal science among chordates.
(A) Human evolution began approximately 7 crore years ago.
Answer:
Approximately 7 crore years ago, dinosaurs disappeared completely. At that time, monkey-like animals appeared which were more or less similar to modern lemurs.
About 4 crore years ago, their tails disappeared. Due to the enlargement of their brain and improvement in their hands, ape-like animals evolved. Later, gibbon and orangutan evolved from these ape-like animals.
Thus, the evolutionary history of humans can be traced back to about 7 crore years ago. Hence, the statement “Human evolution began approximately 7 crore years ago” is justified.
(B) Geographical and reproductive isolation of organisms gradually leads to speciation.
Answer:
Speciation is the process by which new species are formed from an existing species.
A species is a group of organisms that can reproduce among themselves and produce fertile offspring.
Sometimes, some individuals of a species become separated from the others due to a geographical barrier such as a mountain, river or sea. This is called geographical isolation.
Due to this separation, the two groups cannot reproduce with each other. Over many generations, they undergo different changes and follow their own evolutionary path. This may lead to reproductive isolation and finally, two different species are formed.
Thus, geographical and reproductive isolation gradually lead to speciation.
(C) Study of fossils is an important aspect of study of evolution.
Answer:
Many plants and animals get buried under the earth due to natural calamities such as earthquakes, volcanic eruptions and floods.
The preserved remains and impressions of such organisms are called fossils. Examples are bones, shells, exoskeletons and stone impressions of animals.
The age of a fossil can be found by measuring the amount of radioactive carbon (C-14) present in it. By knowing the age of fossils, we can get information about the organisms that lived in the past.
This information helps us to understand the gradual changes in organisms and the process of evolution.
Therefore, the study of fossils is an important aspect of the study of evolution.
(D) There is evidence of embryological similarity among chordates.
Answer:
Von Baer studied the development of embryos in different vertebrates such as fish, frog, tortoise, pigeon, chimpanzee and man.
In the early stages, the embryos of these animals are very similar to each other. It is difficult to identify them separately if they are mixed.
As the embryos develop, they become different because special characters develop in them.
The similarity in the early stages of embryos shows that these animals may have common ancestors.
Thus, embryological similarities provide evidence for evolution among chordates.
Q.3.Complete the statements by choosing the correct options from the bracket.
(Gene, Mutation, Translocation, Transcription, Gradual development, Appendix)
a. The causality behind the sudden changes was understood due to Mutation principle of Hugo de Vries.
b. The proof for the fact that protein synthesis occurs through Gene was given by George Beadle and Edward Tatum.
c. Transfer of information from molecule of DNA to mRNA is called as Transcription process.
d. Evolution means Gradual development.
e. Vestigial organ Appendix present in human body is proof of evolution.
Answers in one place:
(a) Mutation | (b) Gene | (c) Transcription | (d) Gradual development | (e) Appendix
Q. 4. Write a short note on
(A). Lamarckism.
Answer:
Lamarckism is the first theory of evolution. It was proposed by Jean Baptiste de Lamarck.
According to this theory, a change in the environment causes changes in the external characters of organisms. Due to the use and disuse of organs, some organs become more developed while others become less developed.
The characters acquired by organisms during their lifetime are passed on to the next generation.
Example:
The neck of a giraffe became long because it continuously stretched its neck to feed on the leaves of tall trees for many generations.
Thus, Lamarck explained evolution on the basis of use and disuse of organs and inheritance of acquired characters.
(B) Darwin’s theory of natural selection.
Answer:
Darwin’s theory of natural selection states that all organisms have a great capacity to reproduce. Therefore, the number of organisms increases rapidly.
As a result, organisms compete with each other for food, space and other resources. Only those organisms which are better adapted to the environment can survive.
Nature selects the organisms that are fit to survive, while the others may disappear. The organisms that survive reproduce and pass their useful characters to the next generation.
Over many generations, these changes may lead to the formation of new species with specific characters.
In simple words:
Variation → Competition → Survival of the fittest → Reproduction → New species
(C). Embryology.
Answer:
Embryology is the study of the formation and development of an embryo and foetus.
All multicellular organisms begin their life from a single cell called a zygote. The zygote undergoes repeated mitotic divisions and forms a morula.
The morula develops into a blastula and then into a gastrula. The gastrula further develops into an embryo and finally a mature foetus.
Easy sequence to remember:
Zygote → Morula → Blastula → Gastrula → Embryo → Foetus.
(D). Evolution.
Answer:
Evolution is the gradual change that takes place in living organisms over a very long period of time.
These changes are very slow and take place over many generations. Changes in the specific characters of organisms may lead to the formation of new species. Nature selects the organisms that are better suited to their environment.
Thus, evolution explains the gradual development and changes in living organisms over a long period of time.
(E). Connecting link.
Answer:
The plants or animals which have characteristics of two different groups are called connecting links.
For example, lungfish has some characteristics of fish and some characteristics of amphibians. It has paired fins, gills and scales like fish. But it breathes through lungs like amphibians.
Therefore, lungfish is a connecting link between fish and amphibians.
Q6.Define vestigial organs. Write names of some vestigial organs in human body and write the names of those animals in whom the same organs are functional.
The organs which are underdeveloped and have little or no function in humans are called vestigial organs.
Examples of vestigial organs:
| Vestigial organ in humans | Functional in |
|---|---|
| Appendix | Cattle, Rabbit |
| Ear pinna muscles | Monkeys |
| Coccyx (tail bone) | Monkeys and other tailed mammals |
| Nictitating membrane (third eyelid) | Birds |
Thus, vestigial organs provide evidence of evolution.
7. Answer the following questions.
Answer:
Heredity is the transfer of genes from one generation to another generation. However, sometimes sudden changes in genes occur due to a process called mutation. These are hereditary changes. Evolution is the gradual change occurring in living organisms over a long period of time. New species are formed due to changes in specific characters over several generations and are selected by nature for survival. Thus, hereditary changes are responsible for evolution
(b) Explain the process of formation of complex proteins.
Answer:
DNA forms mRNA and mRNA forms protein. This process is called Central Dogma.
mRNA is formed from DNA by a process called transcription. The sequence of mRNA is complementary to the DNA strand.
The mRNA comes into the cytoplasm with the coded message from DNA.
The message on mRNA contains codes for amino acids. Each code consists of three nucleotides and is called a triplet codon.
tRNA brings the required amino acids according to the message on mRNA. The complementary sequence on tRNA is called an anticodon. This process is called translation.
The amino acids are joined together by peptide bonds with the help of ribosomes (rRNA).
The ribosome moves along the mRNA, and more amino acids are joined to form a polypeptide chain. Many such chains together form a complex protein.
Easy sequence to remember:
DNA → mRNA → Amino acids → Polypeptide chain → Complex protein
(C) Explain the theory of evolution and mention the proofs supporting it.
Answer:
According to the theory of evolution, protoplasm, the first living material, was formed in the ocean. After that, unicellular organisms were formed. Gradually, due to changes in these organisms, multicellular and complex organisms were formed. These changes were slow and gradual and took millions of years. The gradual development of plants and animals from their ancestors is called evolution. There are many proofs supporting the theory of evolution.
1. Morphological evidences:
Similarities in the external structure of organisms show that they may have a common origin and common ancestors. For example, the structure of the mouth, position of nostrils, ear pinnae and hair on the body are similar in animals like dog, goat and sheep.
2. Anatomical evidences:
Different animals may have organs which perform different functions but have similar bone structures. This shows that they may have common ancestors. For example, the human hand, cat's foreleg, bat's patagium and whale's flipper have different functions but their bones are similar.
3. Vestigial organs:
Underdeveloped organs which have little or no function in some organisms are called vestigial organs. For example, the appendix in humans and ear pinna muscles in humans are considered vestigial.
4. Paleontological evidences:
The preserved remains and impressions of organisms buried under the ground are called fossils. The study of fossils provides important evidence for evolution.
5. Connecting links:
Some organisms have characteristics of two different groups and are called connecting links. For example, lungfish has fins, gills and scales like fish, but it breathes through lungs like amphibians. Therefore, lungfish is a connecting link between fish and amphibians.
(d) Explain with suitable examples the importance of anatomical evidences in evolution.
Answer:
Some organs of different animals perform different functions, but their bones and bony joints are similar in structure.
For example, the human hand, cat’s foreleg, patagium of bat and flipper of whale perform different functions. The human hand is used for holding, cat’s foreleg for walking, patagium of bat for flying and flipper of whale for swimming.
Although their functions are different, the basic arrangement of their bones is similar. This shows that these animals may have evolved from a common ancestor.
(e) Define fossil. Explain the importance of fossils as proof of evolution.
Answer:
A fossil is any preserved remains, impression or trace of organisms that lived in the past. Examples include bones, shells, exoskeletons and stone imprints of animals.
The age of a fossil can be determined by measuring the radioactivity of C-14 and the ratio of C-14 to C-12 present in it. This method of determining the age of a fossil is called carbon dating.
After determining the age of fossils, we can get information about organisms that lived in the past. The study of fossils gives evidence about the gradual changes in organisms during evolution. It also helps us understand that vertebrates originated gradually from invertebrates.
Thus, fossils are important evidence for the study of evolution.
 |
Answer:
The evolutionary history of modern man is as follows:
1. Approximately 7 crore years ago, dinosaurs disappeared completely.
2. At that time, monkey-like animals appeared, which were more or less similar to modern lemurs.
3. About 4 crore years ago, their tails disappeared. Due to enlargement of the brain and improvement in their hands, ape-like animals evolved.
4. Later, these ape-like animals evolved into gibbon and orangutan.
5. About 2.5 crore years ago, gorilla and chimpanzee evolved.
6. About 2 crore years ago, the first human-like animals evolved. They had an erect posture and were able to use their hands.
7. Ramapithecus was recorded as the first human-like animal. Later, it became larger in size and more intelligent.
8. About 20 lakh years ago, skilled humans developed, and about 15 lakh years ago, humans with an erect posture and ability to walk evolved.
9. Neanderthal man was considered to be the first wise man.
10. About 50,000 years ago, Cro-Magnon man evolved. Afterwards, human evolution became faster than before.
Comments
Post a Comment