Evolution

Fore limbs of whales and bats are examples of divergent evolution that show homology.

About 65 mya - The dinosaurs suddenly disappeared from the earth.

About 500 mya - Invertebrates were formed and became active.

About 350 mya - Jawless fish probably evolved.

About 320 mya - Seaweeds and few plants probably existed.

Evolution of human appears parallel to the progressive development of brain and language skills.

• The correct chronological order in which human evolution took place is :

Ramapithecus → Australopithecines → Homo habilis → Homo erectus → Neanderthalensis → Homo sapiens

When more than one adaptive radiation appeared to have occurred in an isolated geographical area (representing different habitats), one can call this convergent evolution.

Placental mammals in Australia also exhibit adaptive radiation in evolving into varieties of such placental mammals each of which appears to be 'similar' to a corresponding marsupial.

Homo sapiens arose in Africa and moved across continents and developed into distinct races. During ice age, between 75,000-10,000 years ago, modern Homo sapiens arose.

The frequency of allele $A(p)=0.1$

As per the Hardy-Weinberg equilibrium,

Frequency of $A A=p^2=(0.1)^2=0.01$

Forelimbs of bats and humans share similarities in the pattern of bone arrangement.

Though their forelimbs perform different functions, they have similar anatomical structure, as all of them have humerus, radius, ulna, carpals, metacarpals and phalanges in their forelimbs.

Hence, in these animals, the same structure developed along different directions due to adaptation to different needs. This is divergent evolution, and these structures are homologous.

Natural selection can lead to stabilization, directional change or disruption. Natural selection is a process in which heritable variations enabling better survival enabled to reproduce and leave greater number of progeny. A critical analysis makes us believe that variation due to mutation or recombination during gametogenesis , or due to gene flow or genetic drift results in changed frequency of genes and alleles in future generation.

Sweet potatoes and regular potatoes are an example of a certain type of evolutionary relationship. Both have a similar function but are anatomically different—sweet potatoes are root modifications, whereas potatoes are stem modifications.

These types of structures, which serve similar functions but are not anatomically similar, are known as analogous structures. Analogous structures arise through a process known as convergent evolution, where different species evolve similar traits independently, often because they adapt to similar environments or ecological niches.

In contrast, homologous structures are anatomically similar due to shared ancestry but may serve different functions. This variation arises from divergent evolution, where related species evolve different traits.

The correct answer is Option B: A-IV, B-II, C-III, D-I.

Here's the breakdown of each term and its corresponding definition:

(A) Gene pool: This refers to the total number of genes and their alleles within a population. So, the correct match for gene pool is (IV) Total number of genes and their alleles.

(B) Genetic drift: It's a random change in the frequency of alleles within a population due to chance events like natural disasters or small population size. Therefore, the correct match for genetic drift is (II) Change in gene frequency by chance.

(C) Gene flow: This involves the movement of genes between populations. It can occur through migration or the exchange of genetic material. So, the correct match for gene flow is (III) Transfer of genes into or out of population.

(D) Gene frequency: It represents the relative proportion of a specific allele within a population. Gene frequencies tend to remain stable within a generation unless acted upon by evolutionary forces. Therefore, the correct match for gene frequency is (I) Stable within a generation.

The correct answer is option (D), because the evolutionary phenomenon depicted in the sketch is adaptive radiation as from the original seed-eating features, many other forms of finches with altered beaks arose, enabling them to become insectivorous and vegetarian finches.

Option (A) is incorrect because artificial selection is anthropogenic, where man breeds selected plants and animals for different uses.

Option (B) is incorrect because genetic drift is change in gene frequency by chance.

Option (C) is incorrect because convergent evolution is when different structures, with different origins evolve for the same function due to same habitat and hence have similarity. Darwin’s finches are the example of divergent evolution.

Convergent evolution refers to the process where organisms not closely related independently evolve similar traits as a result of having to adapt to similar environments or ecological niches. Let's match List-I with List-II based on the principle of convergent evolution:

Here's the matching based on some understanding of convergent evolution species:

• Lemur (A) matches with Spotted cuscus (III) - both are arboreal and have similar ecological roles in their environments.
• Bobcat (B) matches with Tasmanian tiger cat (IV) - both are predatory and adapt similarly to their environments.
• Anteater (C) matches with Numbat (II) - both have adapted to eating ants and termites.
• Flying squirrels (D) matches with Flying phalanger (I) - both have developed the ability to glide.

So, the correct answer is:

Option A

A-III, B-IV, C-II, D-I

Let's understand each term in the lists and then match them correctly.

List I:

1. Living Fossil: Organisms that have remained virtually unchanged over millions of years. They are often considered evolutionary "relics" and provide valuable insights into past ecosystems.
2. Connecting Link: Organisms that exhibit characteristics of both ancestral and more advanced groups, suggesting evolutionary transitions. They are crucial for understanding the branching patterns of evolutionary lineages.
3. Vestigial Organ: Organs or structures that have lost their original function over time due to evolutionary changes. They often remain as reduced or non-functional remnants of their ancestral forms.
4. Atavism: The reappearance of a trait that was lost in the evolutionary history of a species, often due to mutations or the re-expression of suppressed genes.

List II:

1. Elongated canine teeth: These teeth are characteristic of carnivorous animals and are used for tearing flesh. They are not directly related to any of the terms in List I.
2. Vermiform appendix: A small, finger-like projection from the cecum in the human digestive system. It is considered a vestigial organ, as it is believed to have lost its digestive function in humans.
3. Echidna: A spiny anteater found in Australia and New Guinea. It is a fascinating example of a monotreme, a group of mammals that lay eggs. While it has unique adaptations, it is not considered a living fossil or a connecting link.
4. Latimeria: A type of lobe-finned fish commonly known as the coelacanth. It is considered a living fossil due to its remarkable resemblance to ancient fish species that lived millions of years ago.

Now, let's match the terms:

• (A) Living Fossil - (IV) Latimeria: Latimeria is a prime example of a living fossil, representing a lineage that has persisted for millions of years with minimal changes.
• (B) Connecting Link - (III) Echidna: While Echidna is not a direct connecting link between different groups, its unique characteristics, being a mammal that lays eggs, demonstrate the evolutionary transition from reptilian ancestors to mammals.
• (C) Vestigial Organ - (II) Vermiform appendix: The vermiform appendix is a well-known example of a vestigial organ in humans.
• (D) Atavism - (I) Elongated canine teeth: While not directly related to the term "Atavism," elongated canine teeth are characteristic of carnivores and might reappear in species that have lost this trait due to a shift in their diet, demonstrating the potential for atavism.

Therefore, the correct matching is: A-IV, B-III, C-II, D-I. This corresponds to Option A.

The correct order of periods in the Paleozoic era from oldest to most recent is:

Option B: Silurian, Devonian, Carboniferous, Permian

Here's a breakdown of the Paleozoic periods and their approximate time spans:

• Cambrian Period (541-485.4 million years ago): The Cambrian Period marks the beginning of the Paleozoic Era. Life diversified rapidly during this time, with the emergence of many new animal phyla.
• Ordovician Period (485.4-443.8 million years ago): This period saw the continued diversification of marine life, including the evolution of the first vertebrates.
• Silurian Period (443.8-419.2 million years ago): The Silurian Period was marked by the colonization of land by plants and animals. The first land plants evolved during this time, along with the first arthropods to live on land.
• Devonian Period (419.2-358.9 million years ago): This period is often referred to as the "Age of Fishes" due to the abundance of fish species that evolved during this time. The first tetrapods (four-legged vertebrates) also emerged in the Devonian.
• Carboniferous Period (358.9-298.9 million years ago): The Carboniferous Period was a time of extensive swamp forests, which gave rise to the vast coal deposits that are mined today. Amphibians and insects diversified during this time.
• Permian Period (298.9-251.9 million years ago): The Permian Period ended with the largest mass extinction event in Earth's history, which wiped out over 90% of marine species and 70% of terrestrial species. The Permian extinction paved the way for the rise of dinosaurs in the Mesozoic Era.

The flippers of penguins and dolphins are examples of convergent evolution. Convergent evolution occurs when different species independently evolve similar traits or structures because they adapt to similar environments or ecological niches, despite being of different lineages. This phenomenon leads to analogous structures, which perform similar functions but are not derived from a common ancestral trait.

Penguins are birds, and dolphins are mammals. Their ancestors did not possess flippers, but both these species have evolved this similar structure, which helps in swimming efficiently in aquatic environments. The development of flippers in both cases is an adaptation to enhance their abilities in similar environments (aquatic life), even though they come from different evolutionary paths.

Therefore, the correct answer is:

Option C: Convergent evolution

To correctly arrange the stages of human evolution from past to most recent, we must place these species in chronological order based on when they first appeared according to scientific evidence.

1. Homo habilis - Often considered one of the earliest members of the genus Homo, appearing around 2.1 to 2.8 million years ago.


2. Homo erectus - Appeared around 1.9 million years ago and is known for its longer survival until about 140,000 years ago in some regions.


3. Homo neanderthalensis (Neanderthals) - Emerged around 400,000 years ago and disappeared around 40,000 years ago.


4. Homo sapiens - Our own species, which emerged around 300,000 years ago and is the only surviving species of the genus Homo.

Based on this information, the correct sequence from past to most recent would be:

• A. Homo habilis


• D. Homo erectus


• C. Homo neanderthalensis


• B. Homo sapiens

Thus, the correct sequence is represented by:

Option D: A-D-C-B.

The question requires matching events in historical geological eras to the prevalent life forms of those periods. To do this accurately, knowledge of what characterized each era in terms of biodiversity is essential. Here's a breakdown:

• Mesozoic Era (A): This era, often called the "Age of Reptiles," is renowned for its diverse reptilian species, including the dinosaurs, and also saw the emergence of birds from theropod dinosaurs. Hence, Mesozoic Era matches with "Birds & Reptiles (III)".


• Proterozoic Era (B): The Proterozoic Era is part of the Precambrian period, characterized by the rise of simple, mostly unicellular life, including the first complex eukaryotic cells and multicellular forms like the Ediacara biota. Therefore, it should match with "Lower invertebrates (I)".


• Cenozoic Era (C): Known as the "Age of Mammals," this period saw mammals diversifying after the extinction of the dinosaurs at the K-T boundary (the transition from Mesozoic to Cenozoic). Therefore, Cenozoic Era matches with "Mammals (IV)".


• Paleozoic Era (D): During the Paleozoic Era, marine life flourished, and vertebrates began to emerge, including fishes and the first tetrapods (amphibians). Thus, Paleozoic Era corresponds to "Fish & Amphibia (II)".

Therefore, the correct matching based on the information given would be:

Option D: A-III, B-I, C-IV, D-II. This option accurately aligns each era with the dominant life forms characterized within those eras.

Option A : Homo erectus - Homo erectus was an early human species that existed around 1.9 million to 110,000 years ago. They were the first of the hominins to leave Africa and spread across parts of Europe and Asia. They had a larger brain size compared to earlier human ancestors (with an average capacity of about 900 - 1100 cc), used more complex tools, and were likely able to control fire.

Option B : Neanderthal man - Neanderthals are an extinct species of hominids that lived between about 400,000 and 40,000 years ago in Europe and southwestern to central Asia. They had a brain capacity equal to or slightly larger than that of modern humans, with an average of about 1200 - 1750 cc. They made and used a diverse set of sophisticated tools, controlled fire, lived in shelters, made and wore clothing, were skilled hunters of large animals and also ate plant foods, and occasionally made symbolic or ornamental objects. There is evidence that Neanderthals deliberately buried their dead and occasionally even marked their graves with offerings.

Option C : Homo habilis - Homo habilis is an early human species that lived between approximately 2.1 and 1.5 million years ago. It is considered one of the earliest members of the Homo genus and had a larger brain than earlier hominins, averaging around 650 - 800 cc. They also manufactured primitive tools, giving them their name 'handy man'.

Option D : Australopithecus - Australopithecus is a genus of hominins that lived between about 4 and 2 million years ago. They had a smaller brain size (average around 400 - 500 cc) and were more similar to apes in terms of their physical characteristics. Some species of Australopithecus are considered direct ancestors of the Homo genus. Fossil evidence suggests they walked upright, but it's unclear how much they used tools.

Option (A) is the correct answer because numbat, spotted cuscus and flying phalanger are Australian marsupials exhibiting adaptive radiation.

Option (B) is incorrect because mole and flying squirrel are placental mammals.

Option (C) is incorrect because lemur and wolf are placental mammals.

Option (D) is incorrect because bobcat is a placental mammal.

Option (a) is the correct answer because some scientists believe that life came from outside. Early Greek thinkers thought units of life called spores were transferred to different planets including earth. This transfer of spores was termed Panspermia.

Option (b) is not the correct answer because theory of spontaneous generation gave the idea for creation of life from dead and decaying matter.

Option (c) is not the correct answer because creation of life from chemicals was the basis for chemical evolution.

Option (d) is not the correct answer as formation of sperm in testes is known as spermatogenesis.

Correct answer is option no. (a) because

Hugo de Vries, based on his work on evening primrose brought forth the idea of mutations. He believed that mutation caused speciation and hence called it saltation (Single step large mutation).

Option (a) is incorrect because mutations are sudden (random) and directionless.

Option (b) is incorrect because mutation theory was proposed by Hugo de Vries.

Option (c) is incorrect because Darwinian variations are small and directional changes, but they are not related to mutation theory of evolution.

Option (b) is correct because in directional natural selection more individuals acquire value other than the mean character value.

Option (c) is incorrect because in disruptive change, more individuals acquire peripheral character value at both ends of the distribution curve.

Option (d) is incorrect because there is no random change in natural selection.

Option (a) is incorrect because natural selection leads to stabilisation when more individuals acquire mean character value.

Option (d) is the correct answer because flippers of penguins and dolphins are analogous organs as they help in swimming but do not have the same structure.

Option (c), (a) and (b) are true statements and hence cannot be the correct answer.

Homologous organs have the same structure but have different functions according to the needs of the organisms. Hence, homology indicates common ancestry.

Analogous structures have developed for the same function but do not show a similarity in structure. Hence, they are a result of convergent evolution.

Sweet potato is a root modification for food storage whereas potato is an underground stem modification for storage. Hence they are analogous.

Embryological support for evolution was disapproved by Karl Ernst von Baer.

To elaborate, Karl Ernst von Baer, a pioneering embryologist, analyzed the development stages of embryos and pointed out that embryos of different species do not resemble each other as closely as was previously thought, especially in their early stages. His observations indicated that while there may be superficial similarities in the embryonic stages of different species, these similarities do not necessarily support a common ancestry. This contradicted earlier notions that embryological development could provide strong evidence for evolution.

Therefore, the correct answer is:

Option C: Karl Ernst von Baer

Homologous structures have the same embryonic origin and basic structure, but they do not perform same function, e.g. flipper of whale and wings of bat.

Analogous organs are the structures which are different in their basic structure and developmental origin, e.g. wings of butterfly and wings of bird.

Industrial melanism is an adaptation where the moths living in the industrial areas developed melanin pigments to match their body to the black soot (smoke) covered surroundings. The peppered moths exist into two strains– light (white) coloured and melanic (black). Before industrialisation, all moths were white and were unnotied from predatory birds due to whitish lichens on the bark of trees. After industrialisation, the barks get covered by smoke so the white moths were more evidently visible and thus, picked up by birds. But black moths escaped unnoticed so they managed to survive resulting in more population of black moths and less population of white moths.

Change in population density gives an idea of what is happening to the population, whether it is increasing or declining. This population density depends on natality, mortality, immigration and emigration. In an isolated small tribal population, if boys marry their own tribal girls then there will be decline in population because at some stage marriage will stop due to isolation and on the other hand marriages within same tribe will lead to homozygosity of disease and ultimately death, thus leading to decline in population.