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Kerala State Syllabus 10th Standard Biology Solutions Chapter 8 The Paths Traversed by Life
The Paths Traversed by Life Text Book Questions and Answers
The Path traversed by life Question 1.
Analyze the following illustration and prepare a note on the theory of chemical evolution.
Gases like hydrogen, ammonia, water vapor and methane which present in the atmosphere of primitive earth reacted together to form simple organic molecules like amino acids. Thunder and lightning ultraviolet radiations, volcanic eruptions are energy sources. Condensation of water vapor present in the atmosphere and the resulting incessant rain led to the formation of oceans. Simple organic molecules are formed first in the primitive ocean. By further reactions, complex molecules were found including genetic material to evolve the first primitive cell.
Urey – Miller Experiment
Which were the conditions of the primitive earth, recreated by Stanley Miller and Harold Urey?
Stanley Miller and Harold Urey re-created the experimental setup, in which the glass flask considered as the primitive atmosphere that contained methane, ammonia, hydrogen and water vapor. Instead of lightning or other energy sources, they passed high voltage electricity through the gaseous mixture. The condensed water from this gaseous mixture was considered as the primitive ocean.
The organic substances synthesized through Urey- Miller experiment?
a) Amino acids
b) Nucleic acids
a) Amino acids.
Observe the illustration and answer the questions that follow:
a) Name the scientists who set up this experiment.
b) What was the aim of their experiment?
c) Name the gases which are filled within the ‘A’ of the figure.
d) Which type of organic molecules did they synthesize through this experiment?
a) Stanley Miller and Harold Urey.
b) To prove the theory of chemical evolution (Oparin- Haldane hypotheses) scientifically.
c) Methane, ammonia, hydrogen and water vapor.
d) Amino acids
Analyze the major events related to the origin of life?
Eukaryotes are originated from primitive prokaryotic cell. Gradually colonies of membrane-bound eukaryotic cells are formed. This led to the emergence of multicellular organisms.
Evolution – Through Theories
Mutation Accumulation Theory Question 6.
Explain the ideas of J.B. Lamarck about organic evolution.
Theory of Inheritance of Acquired Characters. Continuous use or disuse of an organ results variations to develop changes in the structure of that organ (Acquired characters). These will be transmitted to the next generation to form new species.
Syllabus 10th Class Question 7.
Why did scientists criticize Lamarck’s view?
The changes in the body (Acquired characters) that occur in the lifetime of an organism do not affect its genetic constitution and hence not possible to transmit to the next generation.
comparative morphology Question 8.
The items given in the box indicates a scientist.
a) Identify the scientist.
b) What idea did he put forward in the field of evolution?
1. The origin of species
2. HMS Beagle
3. Galapagos Islands
4. Survival of the favorable ones.
a) Charles Darwin.
b) Theory of Natural Selection
Given below is the illustration of the ‘Darwin’s finches’ on the basis of indicators, analyze illustration.
a) Which peculiarity of the finches attracted Darwin.
b) How do these peculiarities help finches in their survival?
The differences in the beaks of finches attracted Darwin.
The finches of Darwin’s had beaks adapted to their feeding habits insectivore finches have small beaks, cactus feeding finches have long and sharp beaks, woodpecker finches feed on worms in tree trunks have sharp beaks and ground finches feed on seeds have large beaks.
Complete the table of Darwin finches which showed differences in food and food habits.
|Type of finches||Food||Diversity of the beaks|
|Insectivorous finch||Insects||Small beaks|
|Cactus eating finch||Cactus plant||Long sharp beaks|
|Woodpecker Finch||worms||Sharp beak|
Compare the ideas of Thomas Robert Malthus and main concepts of Theory of Natural Selection’ put forward by Darwin.
|Theory of Robert Malthus||Theory of Darwin|
|Rate of food production is not proportionate to the growth of human population and when scarcity of food led to diseases starvation and struggle for existence||Every species produce more number of offsprings than that can survive on earth. They compete with one another for food, space, and mate.|
The Theory Of Natural Selection
Describe the theory of Natural Selection proposed by Charles Darwin.
Variations develop in each species. Only those variations, which are favorable to that nature, survive and those which are unfavorable get eliminated, According to Darwin, organisms of one kind, when produced in large numbers (Over Production), compete for food, space, mate, and other limited resources (Struggle for Existence). In this struggle, only organisms with favorable variations survive in that nature (Survival of the Fittest). Over a long period, the favorable variations accumulate, resulting the formation of new species.
What was the limitation in Darwin’s theory? Who gave sufficient explanations to this?
Darwin could not explain the reasons for continuous variations in organisms. However, Hugo deVries explained that one of the reasons for variations in organisms is mutation (sudden changes that occur in genes).
Describe Neo Darwinism.
Neo Darwinism is the modified version of Darwin’s theory in the light of new information from the branches of genetics, cytology, geology, and paleontology about the reasons of variations occurred in organisms. Hugo deVries first supported Darwin by his theory of mutation.
Sudden changes that occur in genes are called mutation.
Mutation theory explains that new species are formed by the inheritances of sudden changes that occur in genes. This theory formulated by a Dutch scientist Hugo de Vries.
Evidence Of Evolution
Mention the branches of science which provide evidence to organic evolution.
- Paleontology (fossil study)
- Comparative morphological studies
- Molecular biology
Fossils are remnants of primitive organisms preserved in earth crust.
Analyze the following illustration.
The study of fossils reveals that complex structured organisms are evolved from primitive simple organisms.
Certain linking fossils reveal the evolution of one form of organisms from another form.
Extinction of some species as well as the emergence of new species.
Comparative Morphological Studies
‘Comparative study of structure gives evidence to evolution’. Evaluate this statement.
Though there are differences in the external structure (morphology) among different organisms, there are certain similarities in their internal structure (anatomy). The evidence from the comparative morphological studies justifies the inferences that all organisms were evolved from a common ancestor.
The morphological and anatomical structure of forelimbs in lizard, bat and sea cow are shown here. Observe the illustration and answer to the following questions.
a) Are these forelimbs differ morphologically or anatomically or both? What is the reason behind this difference?
b) What is the term used for such organs that are similar in structure but different in function?
a) Only morphological differences are there among these organs. Reason for these differences are their adaptations to live their own habitats.
b) Homologous organs.
Homologous organs are seen among reptiles, birds, and mammals. What do you mean by homologous organs?
Organs that are similar in structure but perform different functions are called homologous organs.
Biochemistry And Physiology
Observe the illustration and write the inference.
All organisms are made up of cells with protoplasm. There are similarities among the cell organelles and cellular activities. Enzymes control chemical reactions and energy is stored in ATP molecules in all organisms. Hereditary factors are gene , seen in DNA and the structure of DNA is alike in all. Carbohydrates, proteins, and fats are the basic substances. There are similarities in growth, excretion, etc.
What evolutionary interference can be arrived from the evidence from the comparative morphological, Biochemical and physiological studies?
The evidence from the comparative morphological, Biochemical and physiological studies justify the inferences that all organisms were evolved from a common ancestor.
What evidences of organic evolution do the study of molecular biology provide us?
Through a comparative study of protein molecules in different species, the evolutionary relationship (similarity/difference) among organisms can be identified. For instance, we can analyze the similarities or differences in the sequence of amino acids in the beta chain of hemoglobin molecules of different mammals and thereby we can understand about the evolutionary relationship among them.
The differences of the sequential arrangement of amino acids in the beta chain of hemoglobin of man with other animals are given below.
|Gorilla||Difference of 1 amino acid|
|Rat||Difference of 31 amino acids|
Which animal is so close to human beings? What is the reason for this?
There is no difference in the sequential arrangement of amino acids in the beta chain of hemoglobin in man and chimpanzee.
How molecular studies can infer the period of separation of different groups from their ancestors?
Mutations are the main reason for evolutionary changes. Through the molecular studies, we can find out how mutation occurs in the genes that determine amino acid sequences in protein molecules. From this, we can infer the period of separation of different group of organisms from their ancestors.
Evolution Of Human Beings
An evolutionary tree relating to certain organisms including humans is given below. Analyze and prepare a note.
Which organisms is the closest to humans in specific characters?
Do you agree with the statement that man is evolved from monkeys? What is your opinion?
This statement is wrong. Man come under the group Hominoidea while monkeys are included in Cercopithecoidea. It is believed that both the ancestors of man and monkeys are evolved from a common ancestor.
Name of a few animals are given in the box. Out of these which one is more similar to man? Mention any two peculiarities of the other animals.
Baboons, Chimpanzees, Monkeys
Analyze the following illustration which shows the evolutionary history of modern man.
|a) Ardipithecus ramidus||Most primitive human race|
|b) Australopithecus Afarensis||Slender body|
|c) Homo habilis||Made weapons from stones and bones|
|d) Homo erectus||Thick chin and large teeth, ability to stand erect|
|e) Homo neanderthalensis||Contemporary to modern man|
|f) Homo sapiens||Modern man|
The primitive man might be lived in African continent Do you agree this statement? What is your opinion?
This statement might be right, because, fossils of Ardipithecus ramidus, Australopithecus afarensis, Homo habilis, and Homo erectus were discovered ” from African continent.
How do modern men differ from the other groups of human beings?
Modern man have developed brains and equipped with advanced technologies.
Do the interventions of modern man cause any change to natural evolutionary process? How?
Yes. Biodiversity is on a dangerous decline due to the interference of human beings in nature and natural resources. By human interventions, climatic changes brought in as well as the extinction of many organisms.
Here is an incomplete illustration of human evolutionary tree. Find out the missing links.
B: Homo habilis
C: Homo neanderthalensis.
Let Us Assess
Which concept is put forward by the theory of natural selection?
a) Origin of life
b) Origin of species
c) Origin of eukaryotes
d) Chemical evolution of life
b) Origin of species
List the main concepts that indicate how the biodiversity seen today has been developed from prokaryotes.
Origin of prokaryotes 3500 million years ago
Origin of eukaryotes 1500 million years ago
Origin of multicellular organisms 1000 million years ago
How does the interference of human beings in nature influence the process of evolution? How do these affect the existence of other organisms?
Biodiversity is on a dangerous decline due to the interference of human beings in nature and natural resources. By human interventions, climatic changes brought in as well as the extinction of many organisms.
Prepare and exhibit a model of the experimental set up constructed by Urey-Millerto scientifically prove the theory of chemical evolution.
Prepare a chart illustrating the evolutionary tree of man. (See Question 70)
The Paths Traversed by Life More Questions And Answers
The hypothesis which explain how do the evolution occur in living beings is illustrated below:
a) Write the name of scientist who proposed this hypothesis.
b) This hypothesis was not fully accepted. Give reason. (Model 2014)
b) variations affect genetic constitution only transferred to next generation
Rearrange the following based on the relationship between different Primates. Chimpanzee – Gorilla – Gibbon – Orangutan (March 2014)
Gibbon → Orange → Orangutan → Gorilla → Chimpanzee
DDT was sprayed on some insects as an experiment. Among them some died and some 3 survived A second generation was created by mating the survived ones. Again DDT sprayed. This process was repeated on five generations. The result is given in the table. Analyze it arid answer the following questions.
|Generations||Percentage of survived insects|
a) Interpret the result given in the table.
b) What scientific explanation can you give for this result?
c) What may be the result if the experiment is continued? (March 2014)
a) After each generation’s resistance to DDT increases, ie. variation increases.
b) It is an example for Darwin’s theory of Natural selection. Due to struggle existence variations will arises and transmitted into next generations.
c) The total population becomes resistant to DDT / Evolution of DDT resistant species.
Name of certain animals belong to primates is given below.
i) Which among them is closest to human beings according to the theory of evolution.
ii) Write down any two characteristics of the others. (March 2013)
i) b) Gibbon
2. Colonial life
Even though chemicals are used continuously, mosquitoes can’t be destructed completely. Write down scientific explanations for this statement on the basis of the theory of evolution. (March 2013)
Mosquitoes develop resistant power in them against the chemicals. This is the survival of the fittest. Those mosquitoes which have the ability to resist the action of the chemicals survive, the others die.
Rearrange the following animals according to the evolutionary series.
b) List out any two evidences of organic evolution.
c) Man is involved in the evolution of other living beings. Substantiate your answer. (Model 2012)
a) Gibbon, Orang-utan, Gorilla, Chimpanzee, Man.
b) Morphological similarities among animals and similar biochemical reactions indicate about a common ancestor/Different type of fossils are available / Scientific classification or taxonomy and molecular biology indicate that organisms are evolved from common ancestor and how they are interrelated or different, (any 2 points)
c) Yes. The involvement of man in his environment altered the natural evolutionary processes. Human influence may lead to mutation and other natural calamities which lead to evolution or extinction of certain species. Genetic engineering processes caused the production of new species, (any 2 points)
The Paths Traversed by Life Questions & Answers
Identify the odd one from those given below, and write the feature common to others. (Question Pool – 2017)
a) Monkey, gibbon, orangutan, gorilla.
b) acquired characters, overproduction, struggle for existence, favorable variations.
a) 1. Monkey
2. Others belong to Hominoidea
b) 1. Acquired characters
2. Others are related to the theory of natural section
Analyze the word pair relationship and fill in the blanks.
a) Monkey: Cercopithecoidea
b) Theory of Natural Selection: Charles Darwin
b) Hugo deVries
The stages related to the origin of life are given below, b Analyse and arrange them correctly. (Question Pool – 2017)
a) Organic compounds
b) Prokaryotic cells
c) Chemical evolution
d) eukaryotic cells
e) Multicellular organism
f) Colonies of eukaryotic cells.
(c) → (a) → (b) → (d) → (f) → (e)
Match the following
|a) Lamarck||i) Natural selection|
|b) Darwin||ii) Chemical evolution|
|c) Oparin||iii) Acquired characters|
An illustration related to chemical evolution is given below. Complete the illustration using the information given in the box. (Question Pool – 2017)
i) RNA, DNA
ii) polysaccharides, peptides, fats
iii) Presence of H2, N2, CO2
iv) Monosaccharides, aminoacids
A – (iii)
B – (i)
C – (iv)
D – (ii)
Identify the statements that are related to chemical evolution:
i) Life originated in some other planets in the universe and accidentally reached the earth.
ii) Life originated as a result of the changes that occurred in the chemical substances in water, under specific conditions of primitive earth.
iii) The theory is supported by the organic substances found in the meteors that fell on earth.
iv) A.I.Oparin and J.B.S.Haldane are the proponents of the theory.
ii) Life originated as a result of the changes that occurred in the chemical substances in water, under specific conditions of primitive earth.
iv) A.I.Oparin and J.B.S.Haldane are the proponents of the theory.
Tabulate the data appropriately in the box given below.
i) Chemical evolution
ii) Natural selection
iii) Panspermia theory
iv) Mutation theory
Origin of life i) Chemical evolution and iii) Panspermia theory
Evolution – ii) Natural selection and iv) Mutation theory
Complete the illustration related to the evolution of human beings appropriately. (Question Pool – 2017)
c) Small brain
Complete the table using the data given in the box. (Question Pool – 2017)
Most primitive members of the human race, cranial capacity is 460cm3, made weapons from stones and bone pieces, cranial capacity is 1000 cm3, thick chin, and large teeth, cranial capacity is 1700cm3, slender body, cranial capacity 610cm3, cranial capacity 325cm3, contemporary of modem man.
|Homo erectus||1000cm3||thick chin and large teeth|
|Homo habilis||610 cm3||made weapons from stones and bone pieces.|
|Ardipithecus||325 cm3||most primitive members of the human race.|
Given below is an illustration of the differences observed by Darwin in the beaks of the finches in the Galapagos island. (Question Pool-2017)
Finches with different beaks emerged from the ancestor finch. Substantiate the statement.
Though the finches were similar in sound and nesting habits, only they showed differences in food and food habits. (Insectivore finches have small beaks, cactus feeding finches have long and sharp beaks, woodpecker finches feed on worms in tree trunks have sharp beaks and ground finches feed on seeds have latg beaks, etc.) So, Darwin thought that they were evolved from a common ancestor.
The links in the evolutionary history of modern man are given in the box. Complete the illustration choosing the appropriate ones from the box. (Question Pool – 2017)
Ardipithecus ramidus, Homo neanderthalensis, Homohabilis, Homo erectus, Homo sapiens, Australopithecus afarensis
a) Australopithecus afarensis
‘The constant use of antibiotics develops resistance in bacteria”. (Question Pool-2017)
Substantiate the above statement on the basis of the theory of natural selection.
The constant use of antibiotics develops resistance in bacteria. It is an example for Darwin’s theory of natural selection. Due to struggle for existence variations will arise and transmitted to next generation. So bacteria become resistant to antibiotic.
Complete the illustration given below, related to the evidences that support the evolution of new species. (Question Pool – 2017)
B – Comparative morphology
D – Molecular biology
Scientific study of the remnants, body parts and imprints of primitive organisms are evidences on evolution.
a) What inferences do we arrive at, through such scientific studies?
b) How will you explain these inferences as evidences on evolution?
a) 1. Primitive fossils have simple structure
2. Recently formed fossils have complex structure
3. Certain fossils are connecting links between different species.
b) 1. Organisms with complex structures are formed from those with simple structures.
2. Certain fossils indicate the evolution of one species from another species.
The forelimbs of the organisms shown in the picture below, do not show any similarity. Hence they do not have any evolutionary relationship. (Question Pool-2017)
How will you respond to this statement? Substantiate
Do not agree
- The similarity in blood vessels, nerves, muscles and bones.
- Such anatomical resemblances indicate that they evolved from a common ancestor
- Differences in their external appearance are their adaptations to like in different habitats
Arrange the following links in human evolution in the ascending order of their cranial capacity. (Question Pool-2017)
Homo sapiens, Ardipithecus,
Homo erectus. Homo habilis
Ardipithecus → Homo habilis → Homo erectus → Homo sapiens
Arrange the links in human evolution appropriately: (Question Pool – 2017)
C- Homo erectus
There is a common ancestor for all the different species that exist today.
Explain how Biochemical and Physiological studies substantiate the above statement?
All organisms are made up of cells with protoplasm, There are similarities among the cell organelles and cellular activities. Enzymes control chemical reactions and energy is stored in ATP molecules in all organisms. Hereditary factors are gene, seen in DNA and the structure of DNA is alike in all. Carbohydrates, proteins, and fats are the basic substances. There are similarities in growth, excretion, etc.
An excerpt from the article “Darwin view of evolution” is given below. (Question Pool – 2017)
Variations often occur in organisms. New species arise when these variations are subjected to natural selection. But Darwin could not explain the reason for these variations.
a) Explain the reason for variations on the basis of Genetics.
b) How was Darwinism revised later?
a) Mutations taking place in gene, chromosome; This brings about variations,
b) Darwinism was revised as Neodarwinism in the light of new information form the branches of genetics, cytology, geology, and paleontology.
The table given below shows the difference in amino acids obtained from a comparative study of the (3 chains of hemoglobin of different organisms Analyse the table and answer the questions. (Qn. Pool-2017)
|Organism||Difference from the aminoacids in the p chain of hemoglobin in man|
a) Which organism is more closely related to man on the basis of evolution? Substantiate your observation.
b) Explain the reason for the difference in amino acids of hemoglobin of the organisms listed in the table on biochemical basis.
a) 1. Chimpanzee
2. No difference in the amino acid sequence in the Beta-chain of hemoglobin
b) 1. Mutations may occur in the genes that determine amino acid sequence
2. This causes changes in amino acid sequence.
A few concepts of scientists like Darwin and Malthus are given below. Classify them in the table given below. (Question Pool – 2017)
a) Selection by nature leads to the diversity of species.
b) Rate of food production does not increase proportionately to the increase in population.
c) Those organisms that overcome the unfavourable situations will survive.
d) Scarcity of food and starvation leads to struggle for existence.
Concepts of Darwin – a, c
Concepts of Malthus – b, d
An excerpt from the science article. ‘Man and Evolution’ is given below. Analyze the excerpt and answer the questions. (Question Pool -2017)
Certain evolutionary features make man different from other animals included in evolutionary history. This helped him in his dominance over nature and other organisms. His interference had created a negative impact on the existence of other organisms.
a) What are the features that make man different from other animals?
b) Has man’s interference led to Biodiversity deterioration as mentioned in the excerpt? Evaluate.
a) High cranial capacity, ability to stand erect, ability to walk in two legs, ability to make and use machines and tools, cultural development
b) Yes, Climate changes, deteriorating habitats, extinction.
Observe the illustration and answer the questions given below. (Orukkam – 2017)
a) What are the characteristic features of Cercopithecidae group?
b) Name the group which includes man and gorilla. What are the characteristics features of this group?
c) Which organism is close to man from the evolutionary point of view?
Give explanation for this on the basis of molecular biology?
a) Small brain, Longtail
c) Developed brain, free moving hands
The amino acid sequencing in the beta chain of hemoglobin in both chimpanzees and man is almost same.
There exist certain scientific proofs about the formation of different species by evolution. Justify this statement. (Orukkam – 2017)
(Hints – Fossils, Comparative morphological studies, Molecular biology)
a) Evidence from fossil studies-Agradual change from simple structure to complex structure, Linking between two groups of organisms.
b) Comparative study of homologous organs Reveals the existence of a common ancestor.
c) Molecular biology proves the evolutionary relationship among different groups of organism.
The different views regarding the evolution of species are given below. (Orukkam – 2017)
a) Name the scientists who proposed those views.
b) Name the view which was not accepted by scientific world. Why?
a) A – Gene Lamarck,
B – Hugo devices
C – Charles Darwin
b) Theory of Lamarck was not accepted. The acquired characters described by him, make no change in genes, to affect evolutionary change.
Fill in the blanks by observing the relationship in the first pair. (Orukkam – 2017)
a) Cranial capacity 610 cu.cm: Homo habilis
Cranial capacity 1430 cu.cm : ……………………
b) Gibbon: Hominoidea
What do you mean by homologous organs? What evidences do they give for evolution? (Orukkam – 2017)
Organs which are different in external structure and function, but similar in internal structure are called homologous organs. The comparative study of homologous organs reveals the possibility of a common ancestor to such animals.