Evolution

Lepidoptera are insects that include butterflies and moths.

Lichen is a composite organism that arises from algae or cyanobacteria living among filaments of multiple fungi species in a mutualistic relationship. Lichens grow in area which is not polluted, as lichens do not possess roots and air is their primary source for most elements. Hence Lichens are used as an atmospheric pollution indicator.

Lycopersicon is a genus in flowering plant family and contains 13 species of tomato groups.

Lycopodium is a genus of club mosses.

Hence the correct answer is option (b).

According to the theory of Spontaneous generation the life of living organisms came from decaying and rotting matters like straw, mud, etc.

Life arose non-living things only according to theory of Spontaneous generation.

Hence the correct answer is option (c).

Animal husbandry programmes are concerned with raising animal for meat, fibre, milk, eggs, etc. They involve selective breeding of the animals.

Plant breeding programmes are concerned with altering the genetic pattern of the plant to increase their value and utility.

So for both animal husbandry and plant breeding programmes desirable characters need to be introduced in the plants or animals. This is done only by artificial selection.

Hence the correct answer is option (b).

Palaeontology means study of fossils. Hence Paleontological evidences for evolution refer to the fossils.

Hence the correct answer is option (c).

The bones of forelimbs of whale, bat, cheetah and man are similar in structure but get developed into different direction to adapt to different needs. This is called as Divergent evolution. And these structures which are similar anatomically but perform different functions are known as Homologous structures. And homology shows these living organisms have common ancestor.

Hence the correct answer is option (b).

Analogous organs refer to those organs that are not anatomically similar but perform similar functions i.e., they evolved from different ancestors. Such analogous organs result into convergent evolution.

That is different structures evolving for the same function and hence having similarity.

Hence the correct answer is option (d).

Hardy-Weinberg principle stated that in a given population the frequency of occurrence of alleles of a gene is supposed to remain fixed and same through generations.

This principle says that allele frequencies in a population are stable and is constant from generation to generation. The gene pool (total genes and their alleles in a population) remains a constant. This is called genetic equilibrium. Sum total of all the allelic frequencies is 1.

He represented it using algebraic equation (p+q)² = p² + 2pq + q² = 1, where p and q are individual frequencies of two different types of alleles.

So this equation represents population genetics.

Hence the correct answer is option (a).

Adaptive radiation – This is evolution of different species for a single organ depending on the geographical area in which they live.

Transduction – This refers to transfer of different viral or bacterial genetic materials.

Divergent evolution – This refers to homologous organs which are similar anatomically but perform different functions.

The appearance of antibiotic-resistant bacteria is an example of pre-existing variation in the population. So when a bacterial population encounters a particular antibiotic, those sensitive to it die. But some bacteria having mutations become resistant to the antibiotic. Soon, the resistance providing genes become widespread and the entire population becomes resistant.

Hence the correct answer is option (c).

We can observe that most of the ancient organisms, i.e., primitive organisms like amoeba lived in water. And when compared with present organisms most of the complex organisms like apes lived on land.

So, evolution of life shows that life forms had a trend of moving from water to land.

Hence the correct answer is option (d).

Viviparous are one that protect their young ones inside the mother’s body. And after-giving birth the new born are taken care leading to more chances of survival. And these mammals are more intelligent in terms of sensing danger and avoiding it. So, Viviparity is considered to be more evolved.

Hence the correct answer is option (c).

Fossils are generally found in different aged sedimentary rocks. Sedimentary rocks are formed by deposition of sediments.

Igneous rocks are formed from lava, so fossils cannot be present in these types of rocks.

Metamorphic are formed either from igneous rocks or sedimentary rocks.

Hence the correct answer is option (a).

Hardy-Weinberg principle stated that in a given population the frequency of occurrence of alleles of a gene is supposed to remain fixed and even remain the same through generations. He represented it using algebraic equation (p+q)² = p² + 2pq + q² = 1, where p and q are individual frequencies of two different types of alleles.

So the expected frequency can be calculated using this equation.

For MN-blood group system:

Let frequencies of M be p, and from question p = 0.7

Let frequencies of N be q, and from question p = 0.3

Substituting these values in the above equation, we get

(p + q)² = p² + 2pq + q² = 1

(p + q)² = (0.7)² + 2(0.7)(0.3) + (0.3)² = 1

(p + q)² = 0.49+0.42+0.09 = 1

So from the above equation we can see that frequency of MN-blood group organism is 2pq = 0.42, or 42%.

So, the expected frequency of MN-blood group bearing organisms is likely to be 42%.

Hence the correct answer is option (a).

Industrial melanism means evolution of dark-coloured varieties of animals (especially moths) in industrial areas where they are better camouflaged than paler forms.

Stabilising changes in which individual acquire mean characters.

Directional changes in which individual acquire value other than the mean character value.

Disruptive changes in which individual acquire peripheral character value at both ends of the distribution curve.

So industrial melanism is not a character but rather is acquired trait by most of the animals.

So it is an example of directional change.

Hence the correct answer is option (b).

Human evolution started from primates called Dryopithecus and Ramapithecus.

Followed by Australopithecines, this creature was called the first human-like being the hominid and was called Homo habilis.

The next stage is Homo erectus, followed by Homo sapiens.

So the most accepted line of descent in human evolution is Ramapithecus → Homo habilis → Homo erectus → Homo sapiens.

Hence the correct answer is option (c).

Lobe fish – shows characters from cartilaginous fishes and from amphibians. They belong to bony fishes.

Dodo bird – is extinct flightless bird.

Sea weed - is multicellular benthic marine algae.

Chimpanzee – are relatives to humans.

Lobe fish show characters from two groups of animals (cartilaginous fishes and amphibians).

Hence the correct answer is option (a).

Darwin – stated theory about evolution by natural selection.

Oparin – with Haldane proposed that the first form of life could have come from pre-existing non-living organic molecules called a biogenesis.

Lamarck - said that evolution of life forms had occurred but driven by use and disuse of organs.

Wagner – related to continental drift theory.

Hence the correct answer is option (b).

The primitive conditions on earth were – high temperature, volcanic storms, reducing atmosphere containing CH₄ (Methane), NH₃ (Ammonia), H₂ (hydrogen) and water.

Hence the correct answer is option (d).

Variations during mutations of meiotic recombination are random and directionless.

Hugo de Vries stated the Mutation Theory. He stated that mutations are random and directionless contradicting Darwinian variations are small and directional.

Hence the correct answer is option (d).

The characteristic of life forms that had been fossilised are as follows:

i. The early fossils were simple life forms which evolved into complex life forms later.

ii. Fossilised organisms hard body surface which allowed them to get preserved and fossilised.

Yes many aquatic life forms did get fossilised.

The remains of aquatic life forms get fossilised in the sediments of the water bodies. Later, sediments form the part of sedimentary rocks in which fossils, are deposited. Such fossils of sea creatures are found in mountains as opposed to deep-sea beds.

This is because the rocks in which the fossils are found used to be al the bottom of the water bodies. Due to the changes in the crustal plates over time, the ocean sediments were pushed up to form mountains.

The terms ‘Simple organisms’ and ‘complex organisms’ are used to classify the organisms based on the period of their evolution.

‘Simple Organisms’ are primitive organisms whereas ‘complex organisms’ are advanced organisms.

‘Simple Organisms’ have simple structural and functional organisation whereas ‘complex organisms’ have complex structural and functional organisations.

‘Complex organisms’ evolved from ‘Simple Organisms’.

These terms are used to refer to the complexity of the division of labour.

These terms are also used to refer to the relative level of organisation in the organisms.

The age of a living tree is calculated by either counting the number of rings present in the trunk of the tree or by comparing the diameter of the trunk of the tree with average growth factor of that tree (which is found from records).

The method of calculating the age of the tree by counting the number of annual growth rings of the tree is known as Dendro-Chronology.

The diameter of the tree is found by dividing the circumference of the tree trunk by 3.14. Then the diameter is multiplied with the tree’s average growth factor to find the approximate age of the tree in years.

The growth factor of the tree is the annual gain in width of the trunk. This growth factor is available from records. Or this can also be found by measuring the rings of a dead tree from the same species.

Convergent evolution refers to the appearance of similar features in species of different lineages.

Convergent evolution forms analogous structures.

Analogous organs refer to those organs that are not anatomically similar but perform similar functions i.e., they evolved from different ancestors.

Example of convergent evolution is –

Wings of birds and butterflies, they perform similar function of flying but have different anatomically, i.e., different bone structures, different wing coverings, different shape and size.

The age of a fossil can be calculated by radioactive dating.

In this technique a comparison is done between the naturally occurring radioactive isotopes with that of the decay product, using known decay rates.

Some of the techniques used are radio-carbon dating, potassium-argon dating, uranium lead dating, etc.

Adaptive radiation is a process in which organisms diversify rapidly from an ancestral species into various new forms when a change in the environment makes new resources available or new environmental niches open.

The most important pre-condition for adaptive radiation is geographic barrier or an isolated habitat.

The age of a rock can be computed by natural radio-active decay of certain elements.

The radio-active half-life (the amount of time required for one half of the parent atoms to be converted to daughter atoms) is used to calculate the age of the rock.

Functional macromolecules are evolving towards the creation of a complex organism.

The proof for this comes from the fact that there are various evidences which are common to simple as well as complex life forms.

For example, if we look at the genetic code for any life form, it is found to be identical, whether we talk about bacteria or plants or even animals.

The likely frequency of B alleles is sum total of all of BB alleles frequency plus half of the combined frequency of Bb alleles.

i.e., Frequency of B = all of BB + of Bb

⇒ Frequency of B = 22% +

⇒ Frequency of B = 22% + 31% = 53%

Similarly the likely frequency of b alleles can be calculated as

Frequency of b = all of bb + of Bb

⇒ Frequency of b = 16% +

⇒ Frequency of b = 16% + 31% = 47%

Hence the likely frequency of B and b alleles is 53% and 47% respectively.

Five factors are known to affect Hardy-Weinberg equilibrium. These are gene migration or gene flow, genetic drift, mutation, genetic recombination and natural selection.

So the other two factors are mutation and natural selection.

Mutation – is the large difference arising suddenly in a population.

Natural Selection – is a process in which heritable variations enabling better survival are enabled to reproduce and leave greater number of progeny.

It is the phenomenon that occurs when a small group of organisms becomes isolated from a larger population and becomes so genetically different from the original population that they become a new population altogether.

The smaller the population higher are the chances of the founder effect.

Ramapithecus was more man-like while Dryopithecus was more ape-like with same length of arms and legs.

Both Dryopithecus and Ramapithecus were hairy and walked like gorillas and chimpanzees.

Ramapithecus walked erect on its hind legs, ate hard nuts and seeds, had jaws and teeth similar to humans.

The Latin name for the first known hominid is Homo habilis.

Homo habilis are the oldest known species of our genus. They were man-like primates.

They hunted with stone weapons and ate fruits.

Among Ramapithecus, Australopithecines and Homo habilis – Homo habilis did not eat meat.

Homo habilis were first human-like being with brain capacities between 650-800cc.

Louis Pasteur by careful experimentation demonstrated that life comes only from pre-existing life.

He performed the following experiment:

He took a pre-sterilised flasks and concluded life did not come from killed yeast. While in another flask open to air, new living organisms arose from ‘killed yeast’.

This experiment of Louis Pasteur dismissed the Spontaneous generation theory once and for all.

However, the experiment of Louis Pasteur did not answer how the first life form came on earth.

Next Oparin of Russia and Haldane of England proposed that the first form of life could have come from pre-existing non-living organic molecules (e.g. RNA, protein, etc.) when primitive atmosphere was present (i.e., high temperature, volcanic storms, reducing atmosphere containing CH₄, NH₃, etc).

The experiment by S. L. Miller showed that organic molecules could develop from inorganic molecules leading to origin of life.

So Louis Pasteur’s observation can be corrected by Miller’s

Yes, natural disasters can be a cause for extinction of species.

Sudden, abrupt and group-specific extinction have occurred in nature because:

i. Changes in the environmental conditions like excessive cooling or warming, drought or rains.

ii. Natural disasters like floods, earthquakes, volcanoes, tsunamis, etc.

iii. Meteor hitting the earth led to large scale destruction.

There have been five major mass extinction events. The third mass extinction occurred during the End Permian. 96% of the total species were lost due to acid rain following a massive release of volcanic gases.

Nascent oxygen is a highly reactive substance; it is a permanent oxidising agent. It can easily react with various kinds of molecules like DNA, proteins present in the aerobic life forms.

This reaction will lead to unwanted mutation which may threaten the aerobic life forms.

Like if it reacts with DNA it can lead to mutation and defective proteins. Similarly if it reacts with proteins and enzymes they are degraded and many metabolic pathways may be impaired.

So, nascent oxygen supported to be toxic to aerobic life forms.

Variations occur randomly and spontaneously in each subsequent generation. These variations may be passed to next generation or may not be. The variation is not passed to next generation when the variation is not supported by the environment. So creation and presence of variation is directionless.

Now when a variation passes the natural selection test it is passed on to next generation. So natural selection is directional as it is in the context of adaptation. Natural selection is called so because it leads to only one path that is selection of better adapted individuals.

Natural selection leads to survival of fittest which survive in the prevailing conditions.

In the evolutionary story of moths in England, before industrialisation, it was observed that more white-winged moths on trees than dark-winged or melanised moths. But after industrialisation, there were more dark-winged moths in the same area, i.e., the proportion was reversed.

Before industrialisation period, the white moths survived because the tree bark was covered with white lichens, so they were unnoticed by predators.

In Post industrialisation period, the tree trunks became dark due to industrial smoke and soot. Under this condition the white-winged moth did not survive due to predators, dark-winged or melanised moth survived.

Hence 'evolution is apparently reversible'.

It is an ongoing debate whether to call evolution and natural selection as an end result or a process.

When we talk about the world and the different organisms that we see today, we refer to evolution as being a process that result in all these changes. But, when we talk about life itself we say that evolution is a consequence of natural selection.

Five factors are known to affect allele frequency in populations i.e., Hardy-Weinberg equilibrium. These are gene migration or gene flow, genetic drift, mutation, genetic recombination and natural selection.

Gene migration or gene flow – it is movement of alleles into a gene pool or out of a gene pool. When this movement of alleles takes place gene frequencies change in the original as well as in the new population. New genes/alleles are added to the new population and these are lost from the old population. This will lead to a gene flow if this gene migration, happens multiple times.

Genetic drift – If the movement of alleles into a gene pool or out of a gene pool takes place by chance it is called Genetic Drift. This always influences frequencies of alleles and s inversely proportional to the size of the population. It sometimes result into founder effect i.e., when a small group of individuals get isolated from a larger population to form a new population. Genetic drift may result into reduced genetic variation.

Mutation – is the large difference arising suddenly in a population, they are random and occur in all directions.

Natural Selection – is a process in which heritable variations enabling better survival are enabled to reproduce and leave greater number of progeny. That is nature selects only those traits which help an organism to survive in the changed conditions. Those that are not fit for survival perish in the long run leading to evolution of new species.

Genetic recombination – Production of new offspring with traits which differ from parents is called Genetic recombination.

Yes gene flow occurs through generations.

As gene flow occur thorough various barriers like language over generations, by studying specific allele frequencies in different population of the world we can predict human migratory patterns in pre-history and history.

Nowadays there are many projects like human genographics project which uses previous studies data on specific genes to trace evolutionary history and migratory patterns of humans.

Race – it is a classification system used to categories human into many groups or populations. Race is an informal taxon and is kept below the species. This means that members from different races of the same species can be interbreed.

Breed – It is a specific group of domestic animals or plants having homogenous appearance, characteristics or behaviours that distinguish it from other animals or plants of the same species. This homogeneity is through selective breeding.

Cultivators – A selected group of plants selected for desirable characteristics which can be raised through vegetative propagation.

Variety – Variety is similar to race but is used for the plants. Thus variety is informal taxon which is kept below the species in the plant kingdom. A variety arises naturally in the plant kingdom and plant grown from its seeds will typically come out true to type.

Survival of the fittest means those who survive are fit.

In the struggle for existence, the individuals who have more favourable variations will enjoy an advantage over others. They are fit and survive and reproduce.

Natural Selection – is a process in which heritable variations enabling better survival are enabled to reproduce and leave greater number of progeny. That is nature selects only those traits which help an organism to survive in the changed conditions. Those that are not fit for survival perish in the long run leading to evolution of new species.

The characteristic criteria for designating a Mendelian population are as follows:

i. Population must be sufficiently large. The population to be selected as Mendelian’s population should be very large so that experiments can be done easily.

ii. Population should have potential for free flow of genetic materials is ensured through sexual reproduction. Here genetic material should be present among the individuals of the population to be considered as Mendelian’s population.

iii. There should be negligible or nil migration in the population.

Migration is movement of individuals from one place to another.

When movement of alleles takes place, gene frequencies change in the original as well as in the new population. New genes/alleles are added to the new population and these are lost from the old population. This will lead to a gene flow if this migration happens multiple times.

Immigration brings in those alleles which confer the traits that are not selected by nature. And emigration may lead to removal of alleles that confer better adaptations.

Hence "Migration may enhance or blur the effects of selection".

• The law that states that the sum of allelic frequencies in a population remains constant is Hardy-Weinberg principle.

• It states that in a given population the frequency of occurrence of alleles of a gene is supposed to remain fixed and the same through generations.

• He represented it using the algebraic equation (p+q)² = p² + 2pq + q² = 1.

• Five factors are known to affect allele frequency in populations i.e., Hardy-Weinberg equilibrium.

• These are gene migration or gene flow, genetic drift, mutation, genetic recombination and natural selection.

• Gene migration or gene flow – it is movement of alleles into a gene pool or out of a gene pool that allows gene frequencies to change in the original as well as in the new population.

• Genetic drift – If the movement of alleles into a gene pool or out of a gene pool takes place by chance it is called Genetic Drift. This always influences frequencies of alleles and is inversely proportional to the size of the population. It sometimes result in the founder effect i.e., when a small group of individuals get isolated from a larger population to form a new population.

• Mutation – Amutationis a change in the sequence of an organism's DNA. They are random and occur in all directions.

• Natural Selection – is a process in which heritable variations enabling better survival are selected and passed onto the progeny. That is nature selects only those traits which help an organism to survive in the changed conditions. Those that are not fit for survival perish (die off) in the long run leading to evolution of new species.

• Genetic recombination – Production of offspring with traits which differ from parents because of gene reshuffling or combination is called genetic recombination. This phenomenon occurs during gamete formation when chromosomes are passed from parents to progeny.

• In Divergent evolution two species have common ancestors, but they develop different characteristics because of changes in the environment to which they adapt slowly and giving rise to new species.

• For example: The bones of forelimbs of whale, bat, cheetah and man are similar in structure but serve different functions. The similarity in structure points towards a common ancestry but because their environments were different, they adapted accordingly.

• Forelimbs of a whale are for swimming, forelimbs of bat are for flying and forelimbs of cheetah are for walking/running. But all these forelimbs have the same anatomy: humerus, radius, ulna, carpals, metacarpals and phalanges.

• Divergent evolution can occur due to changes in abiotic factors (temperature, pH, sunlight level etc) or biotic factors (living components of the ecosystem).

• The driving force behind the divergent evolution is adaptations to a new habitat and changed environmental conditions.

• Pepper moths had two variants– dark and light coloured moths.

• In England, before industrialisation, it was observed that there were more white-winged moths than dark-winged or melanised moths. This was because the tree bark was covered with white lichens and white wings of the moth helped them in camouflaging. So they went unnoticed by predators and survived whereas dark-winged moths were easily visible to the predators that ate them.

• But after industrialisation, there were more dark-winged moths in the same area.

• This happened because in the post industrialisation period, the lichens did not survive due to increased pollution.

• Soot covered the tree trunks making them dark.

• This made the white-winged moth more visible to the predators that now picked them up instead of the dark moths. The dark moths were now able to camouflage because of the dark tree drunks.

• Now, had the industries be removed, the pollution level would have gone down, allowing lichen to grow back and the number of white winged moths would have gone up again.

• Branching descent and natural selection are the two key concepts of Darwinian Theory of Evolution.

• Branching descent – It is defined as a process by which new species originate from a single commondescendant. Hence the various life forms can be represented as branches coming out of the same tree.

Example of branching descent

• Natural Selection is a process in which heritable variations enabling better survival are selected and passed on from parent to progeny over generations. That is nature selects only those traits which help an organism to survive changed conditions.

• Other important concepts in Darwin Theory are: Over-production of living beings, struggle for existence, survival of fittest.

• Two organisms occupying the same areas would show convergent evolution.

• This means that would try to adapt to the environment in a way that would benefit them.

For example: (let us consider the example taken, of a desert)

i. A desert has several types of drought resistant plants. Examples include Orchids, Agaves, Bryophyllum, Aloes, etc. All of them store mucilage and water but they’re different from each other morphologically.

ii. Similarly, wings of birds and butterflies, they perform similar function of flying but have different anatomically, i.e., different bone structures, different wing coverings, different shape and size. So in a similar habitat they are grouped due to similar adaptive features but have different ancestors.

• Evolution is a dynamic process. This means that it is constantly happening.

• Humans are evolving. Evolutionary changes appear after hundreds and thousands of years so they aren’t visible to us as they are happening.

• Some examples of human evolution that has taken places are:

• Appearance of mutation in the lactose tolerance gene. Earlier humans were unable to digest lactose containing products like milk and cheese. But now half of the world’s population can now consume lactose containing products. This development of lactose tolerance took about 20,000 years — which is like a minute in evolutionary time.

• People living at extremely high altitude places have evolved in such a way that their red blood cells are able to carry more oxygen, preventing them from suffering from hypoxia. (body doesn’t get enough oxygen)

• Another evolutionary change that happened can be observed in the population living in malaria prone regions.

• People in these areas developed sickle cell anaemia to fight off the malaria causing protozoa (Plasmodium). E

• Darwin is credited with the theory of natural selection.

• He talked about variations that occurred in organisms and these variations accumulated over time, giving rise to new organisms.

• However, Darwin did not know about the source of these variations. (We now know that mutation, recombination, and immigration of genes are responsible for variations in a population.)

• Mendel on the other hand was trying to find out what was causing the genetic and physical changes in the pea plants he was crossing.

• He said that there were “factors” that were being passed down from generation to generation through gametes. (We now know that these “factors” are none other than genes.)

• In both Mendel’s and Darwin’s theories, genes were playing a role but they remained unaware of it.

• Were they aware of each other’s work, it is possible that Darwin could have explained the origin of variation.

• Mendel’s work talked of “factors” being passed down and Darwin believed that changes were occurring and accumulating, so the possibility of Darwin explaining the source of variation is high.