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The origin of life is considered to be a unique event in the universe's history, leading to the beginning of life and the evolution of humans. This chapter explores interesting facts about the origin and the first organisms that came into existence, and the theories and evidence to prove these facts. By studying the Evolution of organisms in NCERT Solutions for Class 12 Biology, students can easily understand each principle and process, as they are explained in detail, step by step by the subject experts.
The Miller-Urey experiment explains the origin of life on Earth. This explanation is supported by evidence from paleontology, morphology, embryology, and genetics, which suggest that complex organisms evolved from simpler ones. In the Evolution in organisms NCERT Solutions, students will also learn about Darwin's theory of natural selection and Lamarckism, which have made the basis for explaining evolution. The diversity of life on Earth has continuously changed over millions of years.
Regular practice of the solved exercises provided in the article offers you a deeper understanding of important principles like Hardy-Weinberg, adaptive radiation, and the ancestral characteristics of humans and horses. It also explores how humans evolved from their early ancestors. The Class 12 Evolution in organisms NCERT Solutions cover all topics necessary to understand human evolution and the origin of life on Earth millions of years ago.
The free PDF is given below. Going through this gives you a clear understanding of how life evolves.
From here students can have detailed and clear solutions for the exercise questions given in the textbook to have more knowledge about the topic.
Q1. Explain antibiotic resistance observed in bacteria in light of Darwinian selection theory.
Answer:
Darwinian selection theory indicates that organisms with variations have high chances of surviving and reproducing in a changing environment. A classic example of this can be seen with antibiotic resistance in bacteria. In this experiment, bacteria grown in an environment containing penicillin were mostly killed, but those having genetic variations survived. These surviving bacteria then multiplied and reproduced, passing down their resistance genes. As time passed, the population evolved to be more resistant to penicillin, indicating how environmental factors can influence evolutionary outcomes.
Answer:
In September 2015 in the newspapers, we heard the discovery of 100 million-year-old pieces of a skeleton of Homo naledi.
This was a newly discovered human species represented by a jawbone found in South Africa by John Hawks.
It is said that the fossil filled a gap in the early evolution of man, and it is believed that this human ancestor buried its death.
Q3. Attempt to give a clear definition of the term species.
Answer:
A species represents the lowest taxonomic group that has similar structural and functional features and is capable of breeding true among themselves.
A species consists of all individuals that share a common gene pool.
The study of these species plays an important role in evolutionary research, ecology, and conservation biology.
Answer:
There are several components associated with human evolution, such as brain size, function, skeletal structure, diet, posture, etc.
Below is the table of different features:
Genus/species | Brain size | Posture | Diet | Features |
Dryopithecus | - | Knuckle walker | Soft fruits and leaves | Frontally broadened jaws, large canines, arms, and legs of equal size |
Ramapithecus | - | Semi-erect posture | Seeds and nuts | Small and delicate jaws, small canines, and flattened molars |
Australopithecus afarensis | 600cm3 | Fully erect | Fruits and leaves (herbivores) | Large jaws, small canines, and incisors lived in caves |
Homo habilis(Handyman) | 680cm3 | Fully erect, around 1.5m tall | Carnivorous | Jaws lightly built, small canines and capable of making tools of stone |
Homo erectus | 900cm3 | Fully erect, around 1.5m tall | omnivorous | Large canines make use of fire for hunting and cooking and live in caves |
Homo sapiens neanderthalnsis | 1450cm3 | 1.5 m tall, heavily built | omnivorous | Heavy jaw and small canines bury their dead bodies |
Homo sapiens fossilis | 1660cm3 | Completely erect,1.5m tall | omnivorous | Shorter skulls and reduced jaws lived in caves and made cave paintings. |
Homo sapiens sapiens | 1200cm3 to 1600cm3 | Completely erect, posture, around.8m tall | omnivorous | Possess the high intelligence, developed language, speech, and cultivation of crops observed. |
Answer:
Self-consciousness is an acute sense of self-awareness. Several animals are self-aware and are of great intelligence like dolphins. All great apes(orangutans, gorillas, and chimpanzees) and elephants are some examples that can evaluate their knowledge and work according to situations.
Answer:
Some modern animals and fossils to which they can be linked are as follows:
Name of the animal | Name of the fossils | |
1. | Human(Homo sapiens) | Ramapithecus |
2. | Giraffe | Palaeotragus |
3. | Tetrapods | Ichthyostega |
4. | Fish | Arandaspis |
5. | Dog | Leptocyon |
6. | Horse | Eohippus |
7. | Whale | Protocetus |
8. | Bat | Archaeonycteris |
9. | Elephant | Moerithers |
10. | Camel | Protylopus |
Q7. Practise drawing various animals and plants.
Answer:
By practicing the various plants and animals, you can understand the main characteristic features of that species. Students can take the help of teachers and parents, to gain more suggestions about the labeled drawings.
Q8. Describe one example of adaptive radiation.
Answer:
The process of evolution of different species in a given geographical area, starting from a point and radiating to other areas of geography, is called adaptive radiation.
Darwin’s finches represent one of the best examples of this phenomenon. From the original seed-eating features, many other forms with different beak structures and different food habits, such as herbivores and carnivores
Several marsupials, each different from the other evolved from an ancestral stock, but all within the Australian Island continent.
Q9. Can we call human evolution adaptive radiation?
Answer:
The evolution of man is an example of directional evolution and not an example of adaptive radiation, as adaptive radiation is the process of diversification of species starting from one point at a particular time and then radiating to other areas of habitats. Darwin’s finches are the best example of adaptive radiation, as is the phenomenon of Australian marsupials. Diversification, which is the main characteristic of adaptive radiation, is not a part of human evolution.
Answer:
There are 5 evolutionary stages of horses, which are given below:
Period | Name of the evolutionary stage | Features of the animal |
Eocene | Eohippus | 4 digits in forelimbs, the size of a fox, lived on soft ground |
Oligocene | Mesohippus | 3 digits in toes, live in dry conditions |
Miocene | Merychippus | It was 100 cm tall with 3 toes on each foot, taller with a longer neck |
Pliocene | Pilohippus | It had a single functional toe and was about 108 cm tall. |
Pleistocene | Equus | They have one toe on each foot. Premolars replaced by molars, well adapted for running. |
Also Check NCERT Books and NCERT Syllabus here:
Given below is a list of all the essential topics from this chapter:
6.1 | Origin of life |
6.2 | Evolution of life forms |
6.3 | What is the Evidence for Evolution? |
6.4 | What is Adaptive Radiation |
6.5 | Biological evolution |
6.6 | Mechanism of evolution |
6.7 | Hardy-Weinberg Principle |
6.8 | A Brief Account of Evolution |
6.9 | Origin and Evolution of Man |
The origin of life is the most complex state of organization that occurs in the history of the universe. Several theories have been proposed to explain it. The most accepted one is the Miller-Urey Experiment.
They recreated the probable conditions of the primitive earth in the laboratory.
This experiment proved that life originally arose from the inorganic molecules on the primitive earth.
Some evidence proves that life forms evolved on this earth a million years ago.
Evidence from Palaeontology- The relics of living life plants or animals that are embedded in the rocks. Fossils are mostly found in sedimentary rocks.
Embryological evidence- The study of the development of an organism from egg to adult also provides evidence for organic evolution.
Divergent Evolution- Organs though different in functions but of the same origin and development known as Homologous organs. For example, the arm of a man, the leg of a horse, and the wing of a bat show similarities in the pattern of the forelimb.
Convergent evolution- Organs that perform the same function but are of different origin are called analogous organs.Example- The fins of fish and the flippers of whales perform the same function but are structurally different.
The process of evolution of different species in a given geographical area, starting from a point and radiating to other areas of habitats, is called adaptive radiation.
Darwin’s Finches represent one of the best examples of adaptive radiation.
Hardy-Weinberg Principle in Class 12 Chapter 6 Biology Solutions
This principle provides a simple mathematical model of how genetic equilibrium can be maintained in a gene pool.
Five factors affect the Hardy-Weinberg equilibrium:
Genetic recombination
Theories related to evolution
Two main theories have explained the concept of evolution which are:-
1- Theory of inheritance of acquired characters(Lamarckism)
2-Theory of natural selection(Darwinism)
Class 12 Biology in Evolution Organisms NCERT Solutions helps you deeply understand how life began billions of years ago and also the evidence of evolution that supports the theories of famous scientists. Completing all the solved exercises, students can improve their exam performance and gain clarity on complex topics like natural selection, adaptive radiation with examples, and the Hardy-Weinberg principle. Simply explaining everything by our experts allows students to easily learn about our ancestors and how they evolved.
NCERT solutions for Class 12 Maths |
NCERT solutions for Class 12 Chemistry |
NCERT solutions for Class 12 Physics |
Below are the necessary diagrams of Evolution that make students understand concepts clearly and easily:
Hardy-Weinberg Principle
Adaptive Radiation
Evolution of Human
Question 1: The similarity of bone structure in the forelimbs of many vertebrates is an example of
Answer:
Organs that look different and perform different functions but have similar basic structures, topographies, and embryonic origins are known as homologous organs. In homology, in different vertebrates, bones of forelimbs are similar, but their forelimbs are adapted in different ways as per their adaptation.
Hence, option(3) is correct.
Question 2: State two postulates of Oparin and Haldane with reference to origin of life.
Answer:
(i) First form of life could have come from pre-existing non - living organic molecules RNA and protein.
(ii) Formation of life was precedded by chemical evolution / formation of diverse organic molecules from inorganic constituents.
Question 3: Write the characteristics of Ramapithecus, Dryopithecus, and Neanderthal man.
Answer:
Ramapithecus- hairy, walked like gorillas and chimpanzees, more man-like.
Dryopithecus - hairy, walked like gorillas and chimpanzees, more ape-like.
Neanderthal man - brain size is 1400cc, used hides to protect their body, buried their dead.
Question 4: Difference between sympatric and allopatric speciation with an example.
Answer:
Allopatric speciation occurs when populations of a species are separated by a physical barrier - this could be a river for animals that cannot swim, for example. Separation of the populations means that there is very low or no gene flow between them - the proportion of different genotypes in each population is therefore able to change independently of the other (there's no mixing up of genes between the two populations).
Sympatric speciation occurs without a physical barrier to gene flow. This is more common in plant species - plants can mutate in a way that results in them producing offspring with double or even quadruple the number of chromosomes they normally do. The sex cells (sperm and eggs) produced by these individuals cannot fuse with sex cells from a "normal" plant - the plants with unusually high numbers of chromosomes, therefore, become isolated genetically from the "normal" plants, even though they may be growing right next to each other. This genetic isolation results in the two types of plants developing into species due to lack of gene flow and independent changes in the genotypes of plant populations.
Question 5: What are the differences between Lamarckism and Darwinism?
Answer:
Lamarckism: Lamarck (1744 –1829) was one of the most brilliant stars on the horizon of the history of evolution. He was the first naturalist to put forward a general theory of evolution in his famous book. Philosophic Zoologique, published in 1809.
(1) The theory lays stress on internal force and the use and disuse of organs.
(2) It believes that changes in environment bring about a conscious reaction in animals.
(3) According to Lamarckism, the acquired characters are passed on to the next generation.
Darwinism: Charles Robert Darwin was undoubtedly the first naturalist who put the idea of organic evolution on sound footing. His statements and theories were based upon practical experiences and a large number of proofs that he collected directly from nature.
(1) According to this theory, the accumulation of continuous variations causes changes in individuals to form new species.
(2) It believes in the selection of individuals based on the accumulation of variation.
(3) Darwinism does not believe in isolation.
(4) It can explain the origin of new characters.
(5) Darwinism cannot explain the persistence of certain forms in the unchanged condition.
Question 6: What is adaptive and parallel evolution?
Answer:
Adaptive evolution refers to evolutionary changes that are adaptive to the given environment. Such changes increase survivorship or reproduction by addressing some specific challenge or opportunity presented by the environment. Adaptive evolution is produced by natural selection.
Adaptive evolution is the reason different species appear to be designed to live in their particular environments. It also explains why some species appear to have been designed at cross purposes to others. For instance, human adaptations include a complicated immune system, large brains, and dextrous hands capable of producing medicines and health programs to kill off infectious agents.
Parallel evolution refers to the evolutionary process wherein two or more species in the same environment develop similar adaptations or characteristics. An example of parallel evolution is the North American cactus and the African euphorbia that developed similar adaptations, which are their thick stems and sharp quills to survive the hot, arid climates. These two plant species are of different plant families but live in the same type of environment.
Given below are the chapter-wise links:
We hope Class 12 students will ace your Board examinations with the help of NCERT Solutions for Class 12 Biology Chapter 6 Evolution.
The important topics of evolution ncert class 12 are:
Darwin’s theory of natural selection is based on the following five fundamental principles:
Enormous fertility in living beings
Struggle for existence
Variations under nature
Natural selection or survival of the fittest
Origin of species
Lamarckism | Darwinism |
The growth of living organisms and their parts continuously | Enormous fertility in living beings |
New organs are formed as the result of need | Struggle for existence |
Use and disuse | Variations under nature |
Inheritance of acquired characters | Survival of the fittest |
Example- Feet of modern horse | Example- Giraffe’s neck |
The Hardy-Weinberg principle provides a simple mathematical model of how genetic equilibrium is maintained in a gene pool. Five factors are known to affect the Hardy-Weinberg equilibrium.
There are three types of natural selection, which are given below:
Directional selection- It favors one extreme of a trait, due to which the population shifts to one side. Example- Giraffe neck
Stabilizing selection only favors the intermediate trait of one character; thus, it reduces the variation in a population. Example - Human birth weight.
Disruptive selection- This type of selection favors both the extremes of a trait and leads to the formation of two different groups. Example- Beaks of birds.
Fossils are relics of former living plants or animals that are embedded in the dugout of rock in past geological periods. They are mostly found in sedimentary rocks.
Fossil records provide a complete history of certain organisms that indicate that evolution has taken place for several years.
Genetic drift describes changes in gene frequency, and these changes are due to events that are unrelated to the inherited traits.
Genetic drift tends to reduce the amount of genetic variation within the population, mainly as a result of the loss of the alleles, and thus plays an important role in evolution.
Homologous organs | Analogous organs |
Organs that are different in function but of similar origin and development are known as homologous organs. | Analogous organs are those that perform the same function but are of different origin. |
Homologous organs are a result of divergent evolution. | Analogous organs are a result of convergent evolution. |
Example- the arm of a man, the leg of a horse, and the wing of a bird | Example: Tendrils of vine and pea |
Speciation is the process by which new species are formed. Each species is a gene pool that is adjusted in the given environment.
Two types of evolution exist in the environment:
Convergent evolution- This evolution is the result of analogous organs, and the phenomenon is known as analogy.
Divergent evolution- Divergent evolution occurs due to the result of homologous organs, and the process is known as homology.
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