Evolution - Class 12 Medical Biology - Extra Questions

Australopithecus, group of extinct primates closely related to, if not actually ancestors of, modern human beings and known from a series of fossils found at numerous sites in eastern, north-central, and southern Africa. For a time in the 1960s and ’70s, Ramapithecus was thought to be a distinct genus that was the first direct ancestor of modern humans (Homo sapiens). 

Answer is "0.6"
Total number of individuals = 1000
Genotype AA has 360 individuals i.e. the frequency of allele A in AA = 360
Genotype Aa has 480 individuals i.e. frequency of allele A in Aa = 1/2 *480 = 280
Genotype aa does not contain allele A. So frequency is zero
So total frequency of allele A =360+240/1000 = 0.6

Hardy-Weinberg equation states that the frequency of occurrence of alleles of a gene is constant. The gene pool remains constant. The total sum of allelic frequencies is 1.

UV radiations, electric energy produced during lightning, heat of the earth.

Fossils can show distribution of organisms in the rocks, disparity between past and present organisms, ancestry of organisms and missing links between groups of organisms.

Homologous structures : These are the structures which bear common basic structure but perform different functions. Examples : Forelimbs of reptiles, amphibians and mammals. Homologous structures bear common ancestory but get differently modified to carry on different activities.

Maintenance of constant internal conditions by organisms for survival. This is achieved by regulating metabolic processes.

The differences shown by the individuals of the same species and also by their offsprings are termed variations.

Extinct organisms having characters of two different groups of organisms e.g. Archaeoptery.

Image shows adaptive radiation of marsupials in Australia. Continental drift separated Australia from other continents. The Australian monotremes and marsupials continued to thrive and diversify. Geographical isolation of Australia served as barrier for placental mammals, which arose elsewhere at a later time, from competing with its monotremes and marsupials. Placental mammals evolved in other areas of the world where most monotremes and marsupials became extinct.

Convergent evolution occurs when two groups of largely unrelated organisms are exposed to very similar environments and develop similar adaptations to survive. The examples of convergent evolution from the above-given examples are:
(i) Flippers of penguins and dolphins
(ii) Eyes of octopus and mammals

The process of evolution in which new species are produced from a single point and radiate in different directions is known as adaptive radiation. This is possible due to natural selection. One of the most common examples of adaptive radiation is that of Darwin's finches which he found on Galapagos islands. He observed a variety of birds on the island, all of which were formed from a single seed-eating species which landed there accidentally. Thus due to the different feeding habits, birds with a variety of beaks developed. Different birds with a difference in the availability of food developed different eating habits which helped them all to survive in that environment. 

Charles Darwin went on a voyage to Galapagos islands for 5 years in his ship H.M.S beagle. There he observed a variety of birds with different beaks which are known as Darwin's finches. While studying these birds he gave his theory of natural selection. According to his theory, there is a rapid multiplication of species in the environment. But due to limited food and space, there is always an interspecific or intraspecific struggle for existence. Therefore, only those individuals which are fit to survive in the existing environment are selected by nature. These organisms reproduce while others die. This variation which exists in the surviving individuals are passed to next generation and ultimately lead to evolution. 

If the giant cell possess photosynthesis evolved into the plants and those that was not able to capture sunlight for photosynthesis evolved into the animals. In plants, first tracheophytes formed and from which bryophytes, pteridophytes, gymnosperms and highly evolved is angiosperm. Like that only animal are evolved reptiles to the mammals. 

Diversification of ancestral line into different forms which in turn occupy diverse ecological niche is referred to as adaptive radiation. For example, the ancestral seed-eating stock of Darwin’s finches diversified based on different types of food that were (plants, seeds, insects, cactus etc) available The of beak adapted to that food and got modified accordingly. The geographical isolation led reproductive isolation and thus, the evolution of new species of finches from the parental stock.

Diversification of ancestral line into different forms which in turn occupy diverse ecological niche is referred to as adaptive radiation. It is a quick process. Human evolution is a slow gradual process making it different from adaptative radiation. Therefore, human evolution can not be called as adaptive radiation.

(i) The Hardy-Weinberg's principle states that allele and genotype frequencies in a population will remain constant from generation to generation in the absence of other evolutionary influences.
(ii) Theory of recapitulation states that ontogeny recapitulates phylogeny. It means that embryos, in their development repeat the evolutionary history of their ancestors in a short and abbreviated form.

Genetic equilibrium describes the condition of an allele or genotype in a gene pool (such as a population) where the frequency does not change from generation to generation. It is also called as Hardy-Weinberg equilibrium. Any factor which can disturb the alleles in a population is likely to affect the Hardy-Weinberg equilibrium. 

a) The principle mentioned here is Hardy-Weinberg principle.

Evolution is caused due to the fluctuating environmental conditions which create variations and this help in better adaptation. In Divergent evolution organs with similar structural plan evolve along different lines. In Convergent evolution, widely different organisms evolve similar structures due to similar environmental habitat.

Hardy–Weinberg principle states that allele and gene frequencies in a population will remain constant from one generation to the next if certain conditions are kept constant. These conditions are- 

The first modern Homo sapiens appeared in Africa nearly 2.4 million years ago.

Discovered in 1868, Cro-Magnon 1 was among the first fossils to be recognized as belonging to our own species—Homo sapiens. This famous fossil skull is from one of several modern human skeletons found at the famous rock shelter site at Cro-Magnon, near the village of Les Eyzies, France.

The phrase "Ontogeny recapitulates phylogeny" was coined by Ernst Haeckel. It states that the development of an organism (ontogeny) expresses evolutionary history and all the intermediate forms of its ancestors (phylogeny). Recapitulation means the development of an embryo followed the evolutionary history of organism. This is based on the comparative study of the embryos of related groups of animals.

The industry could have polluted the nearby water body from which the birds drank water or it may have polluted the air by the liberation of harmful gases in the atmosphere which made their environment uncomfortable to survive.

 Haldane theory of chemical evolution states that life originated from pre-existing, non-living organic molecules. In 1953, S.L. Miller observed the formation of amino acids from hydrogen and water vapour at 800-degree centigrade.

A protocell (or protobiont) is a self-organized, endogenously ordered, spherical collection of lipids proposed as a stepping-stone toward the origin of life.

In 1924, Oparin put forward his influential theory that life on earth developed through gradual chemical evolution of carbon-based molecules in a 'primordial soup', at just about the same time Haldane proposed a similar theory.

Such energy can be provided by sources such as Lightening or Volcanic heat.

Biogeographic map show distribution of species in a map. Organisms and biological communities often vary in a regular fashion along geographic gradients of latitude, elevation, isolation and habitat area.

The forelimbs of all vertebrates are built upon the same pattern as they all have the same bones namely humerus, radius, ulna carpels. These bones differ in different animals because they are modified and specialized according to different modes of life, such as swimming, walking, jumping, flying, climbing, digging, etc. Such structures are said to be homologous organs. They show that once all different vertebrates shared a common ancestor which diverged into different species as per requirement of adaptation with different geographical conditions and lifestyles. Hence, it supports evolution. 

The activity of the cambium ring is influenced by the climatic changes. In woody species, the period of growth and reproduction alternate with the period of inactivity during winter. Reactivation of cambium takes place during the spring season. However, the cambium becomes more active during this season and forms plenty of xylem vessels with wider cavities called as Springwood or early wood. In winter, however, the cambial activity slows down and gives rise to narrower xylem elements. The wood thus, formed in winter is called autumn wood or latewood. As growth continues, these two types of wood are produced year after year and appear together as a concentric ring in the transverse section. This concentric ring is known as the annual ring or growth ring. 

For evolution to take place, a population must have both Variations and Heredity. The differences between the characters or traits among the individuals of the same species are called variations. Heredity is responsible for the transmission of better-adapted characters to the offsprings.

Darwin's finches were one of the examples of adaptive variation. On Galapagos islands, we can observe the total 15 types of finches species. The beaks of finches were evolved according to the surrounding and there eating habits. The differences were acted upon by natural selection and resulted in the evolution of the finch species, which led Darwin to his theory.

In ancient time, many events occurring in nature were used to count intervals of time as these events repeat after a particular interval of time. Everyday, sun rises in the morning. Hence, the time interval between 2 sunrise was called as day. Similarly, every month, full moon is observed. Hence, the time interval between 2 full moon was considered as a month.

The very fine blood capillaries in bat's wings were discovered by paleontologists. These allow the dispersal of heat generated during the flight.

Adaptive radiation is an evolutionary process that produces new species from a single, rapidly diversifying lineage. This process occurs due to natural selection. Adaptive radiation generally occurs when an organism enters a new area and different traits affect its survival.   this divergence happens in a relatively short interval of geological time.  

The experiment conducted by two eminent biochemists, Stanley L. Miller and Harold C. Urey, in 1953, provided an evidence to the fact that the life on earth has originated from inanimate matter.

The Hardy-Weinberg balance guideline depicts the constant recurrence of alleles and genotypes in a steady, glorified populace. In this populace, we accept there are arbitrary mating and sexual multiplication without typical developmental powers, for example, transformation or hereditary float. 

• Human development is the process of growth to maturity. The process begins with fertilisation, where an egg released from the ovary of a female is penetrated by sperm. 
  
• The egg then lodges in the uterus, where an embryo and later fetus develop until birth. Growth and development occur after birth and include both physical and psychological development, influenced by genetic, hormonal, environmental and other factors. 
• Development and growth continue throughout life, through childhood, adolescence, and through adulthood to senility, and are referred to as the process of ageing. 
  
• The entire process can be divided into distinctive phases as follows : 
  

• Increase in cranial capacity is regarded as the most significant change as it leads to the expan­sion in the cere­bel­lum and neo­cor­tex, areas which are asso­ci­at­ed with learn­ing, con­scious thought and reasoning.
  
• The devel­op­ment of the brain enabled hominids to make and use tools and fire, com­mu­ni­cate using lan­guage, devel­op cul­ture and soci­ety, adapt to new envi­ron­ments and, final­ly, to become self-aware and creative.

• Anatomical evolution mainly focuses on similarities and differences in the body structures of different species.
  
• The study of comparative anatomy forms the basics for modern study of evolution. Organisms with similar structures must have common ancestor which serves the subject for determining the relatedness of species.
• When species have same structure but different functions according to their needs and adaptions, this process is called Divergent Evolution and structures are homologous (Common Ancestry).
  Examples-  Vertebrate hearts or brains, All mammals share similarity in their forelimbs.
• When species have different structure but similar functions according to their environmental changes and adaptations, this process is called Convergent Evolution and structures are analogous (Different Ancestry).
  Examples-  Wings of insects, birds, bats

Tools that are responsible for tracing evolutionary relationships among species are-

Analogus structure are the different looking structure evolve from a common ancestor.

Human evolution is the evolutionary process that led to the emergence of anatomically modern humans like that of plants and other animals, beginning with the evolutionary history of primates – in particular genus Homo – and leading to the emergence of Homo sapiens as a distinct species of the hominid family, the great apes. This process involved the gradual development of traits such as human bipedalism and language,. as well as interbreeding with other hominins. The most important stages in the chronological order are as follow :

The homologous organs are similar in form (or are embryologically same), but perform different functions in different organisms. These provide strong evidence in the favour of evolution. 

Lateral meristems appear in the mature tissues of roots and shoots. It is called the secondary meristem as it appears later in a plant’s life. It helps in adding secondary tissues to the plant body and in increasing the girth of plants, and therefore called lateral meristem. Examples include fascicular cambium, interfascicular cambium, and cork cambium.

A small mantispid and a preying mantis, an example of convergent evolution. Cladograms showing four different hypotheses for the monophyletic origin of flowering. level, then their continued use is not justified and can even be misleading. flying phalanger is remarkably similar to the North American flying squirrel.

Peking Man is categorized as a member of the hominid species Homo erectus as is Java Man. However, Cro- Magnon or modern man are early Homo-sapiens that lived about 40,000 years ago. The odd one out will be Cro-Magnon man. So, the correct option is 'cro- Magnon man'.

When two or more different species develop similar characteristics due to adaptation to the particular environment, but they do not belong to the same ancestors, are kept under Convergent Evolution. While divergent evolution is the phenomenon in which two species have common ancestors, but develop different characteristics due to changes in the environment which they adapt slowly and hence give rise to new species.

Two main propositions of Oparin and Haldane were
(i) The primitive atmosphere was reducing, i.e.free oxygen was absent.
(ii) There was high temperature, high methane, ammonia and hydrogen gas in the atmosphere.

Hardy – Weinberg Principle mathematically explains the occurrence and consistency of gene frequency for a particular gene. The principle states that the allelic frequency remains constant through generations and the gene pool remains constant. This phenomenon is called genetic equilibrium. Also, all the allelic frequencies sum up to 1.

Let us assume, the frequency for the allele X in a population is a and that of the allele x is b.
Thus, the frequency of XX is $$a^2$$, xx is $$b^2$$ and Xx is $$2ab$$. The equation can thus be represented as:
$$a^2$$ + $$b^2$$ + $$2ab$$ = 1
or
$$(a + b)^2$$ = 1

Factors affecting the Hardy-Weinberg principle:

• Mutation
• Genetic drift
• Natural selection
• Genetic recombination
• Gene flow
  

All these factors contribute to the change in gene frequency of a species in an area. If a few individuals from a species migrate to another place, the gene frequency changes again. It decreases from the place from where the individuals migrate and increase in the place they migrate to. If the frequency of the genes is high enough in the newly migrated land to start a new species, the migrated individuals become the founder species, and the effect is called founder effect. Thus, all these mechanisms contribute to the process of evolution.

• Adaptive radiation is the evolutionary process in which different species starting from a common point.
  
• Adaptive radiation generally occurs when an organism enters a new area and different traits affect its survival. 
  
• An example of adaptive radiation is the development of mammals after the extinction of dinosaurs.
  

Genetic mutations and natural selection forms the basis of evolution

(d) wings of housefly 

A similar evolution in species of different lineage is called convergent evolution. Convergent evolution happens in an isolated geographical area. Flippers of dolphins and penguins are examples of convergent evolution. In both animals; flippers have different origins but serve a similar purpose.

The age of a fossil is computed by using carbon dating. The relative presence of $$14_{C} $$ (a radioactive carbon) is calculated to compute the age of a fossil.

The theory about the extinction of dinosaurs suggests that a natural disaster can be the cause of the extinction of species. A majority of scientists agree that a meteor hit the earth which led to large scale destruction and eventual extinction of dinosaurs.

Paul Steinhardt of Princeton University has proposed Ekpyrotic Model and has said that the universe came into existence as a result of collision of two three-dimensional universes in fourth dimension. This theory also accepts the expansion of the universe but this expansion is quite different than the one as proposed in Big Bang theory. The universe is expanding like a rubber membrane. The structures in the universe are going away from each other but there is no locus of this ever expanding distance. 

Life has evolved from complex combination of chemical substances. Presence of methane on various celestial bodies indicates that the primitive atmosphere on earth was highly reducing in nature because of presence of methane, ammonia, hydrogen and water vapor. Compounds formed after combination of these elements underwent further combinations to form complex compounds. Different forms of those complex compounds had laid the foundation of life. In due course of time, primitive life forms went through a prolonged phase of struggle and competition to create the living world which we witness today. 

Ramapithecus is more like man than Dryopithecus.

Among the five factors that are known to affect Hardy Weinberg equilibrium, three factors are gene flow, genetic drift, and genetic recombination, Mutation, and Natural Selection are the other two factors.

The age of a rock is computed by using carbon dating. The relative presence of $$14_C$$ (a radioactive carbon) is calculated to compute the age of a rock.

A body plan or design is a group of structural and developmental characteristics that can be used to identify a group of animals. A better body design is one that gives the animal a better chance at survival. It is obvious that out of the four (bacteria, spiders, fish, and chimpanzee) chimpanzee has a much more organized and elaborate body design in evolutionary terms. However, since body design is meant for the competitive survival of a particular organism in its particular environment, all the four species given above have a body design that is well suited to their respective environment.

(a) The process of evolution of different species in a given geographical area starting from a point and literally radiating to other areas or habitat is called an adaptive radiation.
For example, alterations in beaks of finches on Galapagos island.

Natural Selection:

• It is a process in which heritable variations help in the survival of an organism, enabling it to reproduce and give rise to a large number of offspring.
  
• There may be changes in the frequency of genes and alleles in future generations.
  
• It leads to the formation of new species.
  

The process of evolution of different species in a geographical area starts from a point and literally radiates to other geographical areas. This is a form of adaptive radiation. Darwin explained this process with the help of an example of finches. The finches have different types of the beak. There were different varieties of finches found on the Galapagos island. The ancestor of this finches was the bird which feeds on the seeds. These birds have evolved and adapted to the different type of beak to feed on insects. This is a type of adaptive radiation where there are many different species which have evolved from the same species. 

a) Neanderthal man ( 1450 BC) 

Following are similarities in the structures of embryos of all vertebrates:-

Phylogeny is the history of the evolution of a species or group, especially in reference to lines of descent and relationships among broad groups of organisms. This is done using fossils available and establishing common links, their divergence point in time and understanding changes that occurred with time for adaptation. 

To prove abiotic origin of biomolecules; recreated the probable conditions on the primitive earth in the laboratory.

Similarities in chromosome number, banding pattern of chromosomes and DNA content of great apes (orangutan, chimpanzee, and gorilla) and man support the idea of their common ancestry. Each human cell contains 46 chromosomes, of these 44 are autosomes and 2 are sex chromosomes. However, the chromosome number is 48 for orangutan, chimpanzee and gorilla. Chromosomes are treated with specific stains to study the banding pattern. It is interesting to note that the banding pattern of the human chromosome is very similar and in a few cases identical to the banding pattern of apparently homologous chromosomes in great apes.

Biochemical investigations helped us in establishing molecular homology. Homology is also seen amongst the molecules. For example, the proteins found in the blood of man and ape are similar. Following are other shreds of evidence of evolution from biochemical investigations:- 

Locomotion Walks semi-erect on outer edges of feet and knucles of hands/Walks fully erect after infancy on the soles of the feet.

(a) Palaeontology is the study of the history of life on Earth as based on fossils. Fossils are the remains of plants, animals that have been replaced by rock material or impressions of organisms preserved in rock.

Biogeography involves the study of the geographic distribution of species throughout the world. Study of geographical distribution of plants and animals has added further evidence in favour of the theory of organic evolution or common descent. 

Convergent evolution is the result of analogous structures which develop in organisms as a result of independent development of similar form and feature by the unrelated organism as an adaptation to a similar environment. 

Explanation: 

• According to Hardy-Weinberg equilibrium, the dominant genotype is P and recessive is q. 

• The formula is p + 2pq + q = 1 

• We have about 1000 individuals, out of which 360 belong to genotype AA.

• So here AA is the dominant allele.

•  That means AA is 360.

• And frequency is 360/1000 = 0.36

• Then A is= root of 0.36 that will be 0.6.

So the frequency of allele A is 0.6

Oparin, in 1924 and Haldane in 1928 suggested the biochemical theory for the origin of life. They suggested that the primitive earth conditions were reducing in nature due to the absence of the oxygen. There was a constant supply of energy in the form of lightning and this resulted in the accumulation of inorganic molecules to form organic molecules. Several organic molecules like polypeptides, polysaccharides, polynucleotides and fats gathered to form a coacervate. These coacervates were capable of dividing by budding. A layer of water and fats surrounded them. They were present in hot sea water, which provided conditions for their metabolism. This led to the appearance of the first cell.

Since a lot is known about the metabolic processes today, life can be created in the lab. Urey and Miller successfully demonstrated the precipitation of coacervate-like structure in their famous lightning experiment. Hence, life can be created in lab today.

In a population, the frequency of heterozygous individual is 42%. It means 2pq = 0.42. Hence, pq = 0.21 = 0.7 x 0.3.

Convergent evolution	Divergent evolution
Development of similar adaptive functional structures in unrelated groups of organisms is called convergent evolution.	Development of different functional structures from a common ancestral form is called divergent evolution.
Example - Analogous organs like nature of the flight/wings of insects, birds, pterosaurs, and bats. All four serve the same function and are similar in structure, but each evolved independently.	Example - Darwin's finches. Darwin's finches are a group of about 15 different species of finches that live on the Galapagos Islands. Each separate species of finch adapted to a different diet, causing variation in their beak shape and/or size. All of them evolved from one species of finch that was a common ancestor.

Abiogenesis theory proposes the idea that life arose from non-living matter more than 3.5 billion years ago on Earth. Abiogenesis proposes that the first life-forms generated were very simple and through a gradual process became increasingly complex. Biogenesis, in which life is derived from the reproduction of other life, was presumably preceded by abiogenesis, which became impossible once Earth’s atmosphere assumed its present composition. 

The equation p2 + 2pq + q2 = 1 is a binomial expansion of (p+q)2. It mathematically represents the Hardy-Weinberg’s principle which is used to calculate the genetic variation of a population at equilibrium. This principle states that “Allele frequencies in a population are stable and remain constant from generation to generation”. 

Here, p represents the frequency of allele A, q represents the frequency of allele a, p2 represents the frequency of AA (homozygous) individuals in a population, q2 represents the frequency of aa (homozygous) individuals and 2pq represents the frequency of Aa (heterozygous) individuals Also, the sum of all the allelic frequencies is equal to 1. If p and q are known values, then the frequencies of the three genotypes can be calculated using the Hardy-Weinberg equation.

Homo erectus represents a significant transformation from previous hominins, like the Australopiths, to a species much more similar to modern humans. Homo erected were considered more advanced because :-

Yes, I agree. With the human genome project turning into a reality; it is now possible to understand gene flow in different populations of the world. This can help us in assessing and predicting human migratory patterns in pre-history and history.

Hardy Weinberg's principle states that gene frequencies remain the same from generation to generation unless disturbed by factors like mutation, non-random mating genetic drift, etc.