Chapter 6 : Evolution

Class 12 Biology Chapter 6 : Evolution Exercise Questions and Answers :

1. Explain antibiotic resistance observed in bacteria in light of Darwinian selection theory.

Answer : Antibiotic resistance in bacteria can be explained within the framework of Darwinian selection theory. Bacteria, like all living organisms, exhibit natural variation within their populations due to genetic diversity. When antibiotics are introduced, they act as a selective pressure, favoring the survival of bacteria with pre-existing resistance traits. These resistant bacteria have a reproductive advantage in antibiotic-rich environments, passing on their resistance genes to offspring. Over time, this process leads to the evolution and proliferation of antibiotic-resistant bacterial strains, demonstrating the principles of natural selection and adaptation to changing environmental conditions, even over long periods of Earth's history.

2. Find out from newspapers and popular science articles any new fossil discoveries or controversies about evolution.

Answer : In 2022, a significant fossil discovery was made in southeastern China, shedding new light on the evolution of bird-like dinosaurs. The discovery of a small, bird-like dinosaur trapped in a swamp, now known as Fujianvenator prodigiosus, challenged some conventional ideas about bird evolution.

Key points from the discovery and expert comments are as follows :

Fujianvenator prodigiosus : The fossilized remains of Fujianvenator prodigiosus were uncovered around 150 million years ago in a swamp in southeastern China. The discovery was published in a recent Nature paper.

Unusual Traits : This ancient animal displayed unusual characteristics, such as long legs and a potential inability to fly. These traits challenge conventional narratives about bird evolution.

Evolution of Bird-Like Dinosaurs : While experts often recognize Archaeopteryx as the first bird, the discovery of Fujianvenator suggests that bird-like dinosaurs had already diversified into various forms by the time Archaeopteryx emerged.

Complex Evolution : According to Hailu You, a paleontologist at the Chinese Academy of Sciences, the bird-like dinosaurs during the Jurassic period may have occupied different ecological niches, making early bird evolution a complex process.

Fossil Similarities : Despite the absence of a head and a complete tail, Fujianvenator's body and limbs share characteristics with other bird-like dinosaurs. These include finger lengths, pelvic features, and vertebral details. However, it lacks several adaptations necessary for flying but did have shortened shoulder blades and specialized fingers for gripping.

Hyper-Elongated Hind Legs : One of the most notable features of Fujianvenator is its hyper-elongated hind legs, with its tibia being twice as long as the thigh bone, suggesting it might have been an adept runner.

Rare Fossil Find : The discovery of Fujianvenator was considered fortunate, as it was found in a site near Nanping, where no previous dinosaur fossils had been uncovered. Late-Jurassic bird-like dinosaurs are rare in the fossil record due to their fragile, hollow bones.

Comment from Bhart-Anjan Bhullar : Bhart-Anjan Bhullar, a paleontologist at Yale University, highlighted the significance of the discovery, stating that even at their earliest stages, the closest fossil relatives of birds were diversifying in interesting ways. He emphasized that there are many more discoveries to be made, and we have only scratched the surface of the anatomical and lifestyle diversity of these animals.

This discovery adds to our understanding of the early stages of bird evolution and the diversity of bird-like dinosaurs during the Jurassic period. It underscores the idea that there is still much to learn about the evolution of these fascinating creatures.

3. Attempt giving a clear definition of the term species.

Answer :  A  clear definition of the term species is :

 "A species is a group of living organisms that can interbreed to produce fertile offspring under natural conditions and are reproductively isolated from other such groups."

This definition encompasses the biological species concept, which focuses on the ability of organisms to interbreed and produce viable, fertile offspring. Reproductive isolation is a key criterion because it implies that members of one species typically do not interbreed with members of other species in nature, preventing the genetic mixing of distinct lineages.

4. Try to trace the various components of human evolution (hint: brain size and function, skeletal structure, dietary preference, etc.)

Answer :  The various components of human evolution, including brain size and function, skeletal structure, dietary preference, and more:

Component of Human Evolution	Description and Significance
Brain Size and Function	* Early hominins had smaller brains; modern humans have larger brains relative to body size.  * Associated with advanced cognitive abilities, including tool-making, language, and social complexity.
Skeletal Structure	* Development of bipedalism (walking on two legs) and changes in pelvic, leg, and foot structure. * Evolution of opposable thumbs for precision grip and tool use.
Dietary Preference	* Early hominins primarily consumed plant materials and scavenged meat. * Transition to hunting and cooking for a diversified diet.
Social Organization	* Early humans lived in small, nomadic groups.  * Development of complex social structures and communication with language.
Cultural Evolution	* Transmission of knowledge, tools, art, and traditions across generations. * Cultural achievements, such as tool use and art, shaping societies.
Biological  Adaptations	* Adaptations to diverse environments, including changes in skin color, body shape, and metabolism.  * Ability to thrive in various climates.
Genetic Evolution	* Genetic mutations and natural selection shaping the human genome. * Examples include lactase persistence in certain populations.
Tool Use and Technology	* Development of tools for hunting, gathering, and other tasks.  * Advancements in technology over time.
Social Cooperation	* Coordination in hunting and cooperative living in larger groups. * Emergence of complex social structures.
Language and Communication	* Development of language for sharing knowledge and coordinating activities.  * Facilitation of cultural transmission.
Art and Ritual	* Expression of creativity through art and the establishment of rituals.  * Reflects cultural and symbolic development.

These components highlight the multifaceted nature of human evolution, with changes occurring in physical, cognitive, cultural, and social dimensions over millions of years .

5. Find out through internet and popular science articles whether animals other than man has self-consciousness.

Answer :  Some studies suggest that certain animals may exhibit self-awareness to varying degrees.

Some examples are :

Great Apes: Great apes, such as chimpanzees, bonobos, and orangutans, have been subjects of research into self-awareness. The mirror test, where an animal is exposed to a mirror and their reactions are observed, has been used to assess self-recognition.

Some studies have indicated that certain great apes, particularly chimpanzees and orangutans, may exhibit self-awareness by showing signs of self-recognition in mirrors.

Dolphins and Elephants: Dolphins and elephants have also been tested using mirror self-recognition tests. Some research suggests that certain individuals of these species may pass the test, indicating a level of self-awareness.

Magpies: A study published in 2008 suggested that magpies might have some form of self-awareness. Researchers found that magpies were able to recognize themselves in mirrors and use the mirror to explore their bodies.

European Jays: In 2020, a study on Eurasian jays indicated that they could pass a modified mirror self-recognition test, which involved using a colored sticker on their chests that was visible only in the mirror.

The interpretation of these results is a subject of debate in the scientific community. Some argue that these behaviors may not necessarily indicate self-consciousness as humans experience it but rather a form of self-awareness or recognition.

The study of animal self-awareness is complex, and researchers use various behavioral and cognitive tests to assess it. While there is evidence to suggest that some animals may possess a level of self-awareness, the depth and nature of this awareness may vary among species.

It's an evolving field of research, and new findings continue to contribute to our understanding of the cognitive capacities of non-human animals .

6. List 10 modern-day animals and using the internet resources link it to a corresponding ancient fossil. Name both.

Answer : Given, 10 modern-day animals along with their corresponding ancient fossil counterparts are :

(i) Modern Animal: African Elephant

Ancient Fossil: Deinotherium

Deinotherium is an extinct genus of prehistoric elephant that lived during the Miocene and Pliocene epochs.

(ii) Modern Animal: Gray Wolf

Ancient Fossil: Dire Wolf (Canis dirus)

The dire wolf was a larger, now-extinct species closely related to the modern gray wolf and lived during the Pleistocene epoch.

(iii) Modern Animal: Great White Shark

Ancient Fossil: Megalodon (Carcharocles megalodon)

Megalodon was an enormous prehistoric shark, known for being one of the largest predators to have ever existed.

(iv) Modern Animal: American Alligator

Ancient Fossil: Deinosuchus

Deinosuchus was a gigantic crocodilian that lived during the Late Cretaceous period and coexisted with dinosaurs.

(v) Modern Animal: Bald Eagle

Ancient Fossil: Teratornis

Teratornis was a giant, now-extinct bird of prey that lived during the Pleistocene epoch.

(vi) Modern Animal: Humpback Whale

Ancient Fossil: Basilosaurus

Basilosaurus was an ancient whale that lived during the Eocene epoch and had a serpentine body shape.

(vii) Modern Animal: Komodo Dragon

Ancient Fossil: Megalania

Megalania was a massive, extinct monitor lizard that lived in Australia during the Pleistocene.

(viii) Modern Animal: Ostrich

Ancient Fossil: Diatryma

Diatryma was a large, flightless bird that existed during the Eocene and Oligocene epochs.

(ix) Modern Animal: Crocodile

Ancient Fossil: Sarcosuchus

Sarcosuchus was a prehistoric crocodilian that lived during the Cretaceous period and was one of the largest crocodile-like reptiles.

(x) Modern Animal: Western Lowland Gorilla

Ancient Fossil: Gigantopithecus

Gigantopithecus was a massive, extinct ape that lived in Asia during the Pleistocene.

7. Practise drawing various animals and plants.

Answer :  Photo

 

 

 

8. Describe one example of adaptive radiation.

Answer : An example of adaptive radiation is the diversification of Darwin's finches in the Galápagos Islands. A single ancestral finch species arrived on the islands, and over time, they adapted to various ecological niches with different food sources. This led to the evolution of multiple finch species with distinct beak shapes and feeding habits. Some developed beaks for cracking seeds, while others had beaks suited for catching insects or feeding on vegetation. This diversification allowed the finches to occupy different niches and thrive in their island habitats, demonstrating adaptive radiation.

9. Can we call human evolution as adaptive radiation ?

Answer : Human evolution is not typically referred to as adaptive radiation. Instead, adaptive radiation is a term commonly used to describe the rapid diversification of a single ancestral species into multiple species, each adapted to different ecological niches within a specific geographical area. While human evolution involves adaptations to various environments and ecological niches over time, it does not fit the specific criteria of adaptive radiation.

Human evolution is better characterized as a complex process driven by a combination of genetic, environmental, and cultural factors. It includes changes in anatomy, behavior, and technology over millions of years but does not represent the rapid and parallel diversification seen in classic examples of adaptive radiation.

10. Using various resources such as your school Library or the internet and discussions with your teacher, trace the evolutionary stages of any one animal, say horse.

Answer : The evolutionary stages of the horse, Equus, span over millions of years. It began with Eohippus (Hyracotherium), a small, multi-toed forest-dweller 55 to 45 million years ago. Through the Oligocene and Miocene epochs, horses like Mesohippus and Merychippus emerged, with adaptations for grazing and a reduction in the number of toes. By the Pliocene, Pliohippus showed a more robust build and further adaptations for grass consumption. Finally, in the Pleistocene, Equus, the modern horse, evolved with single-toed hooves, perfectly suited for running and grazing on grasslands. This evolutionary journey reflects the influence of changing environments on mammalian herbivore adaptation.