Evolution Class 12th Biology CBSE Solution

Class 12th Biology CBSE Solution

Exercises
Question 1.

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


Answer:

• Darwinian Selection Theory states that “The organisms with the characteristics that enable them to survive better in natural conditions (the existing environmental conditions) would outbreed others that are less-endowed to survive under those conditions.


• Bacteria have been subjected to antibiotics since the earliest discovery of the first antibiotic i.e. Penicillin. Due to these constant treatments, certain strains of bacteria, due to mutations, developed resistance, or the already present resistance gene, now got selected as they could still survive in the presence of the antibiotics.


• Only the ones that survived the antibiotic treatment could further perpetuate and produce offsprings, resulting in the increase of antibiotic resistance in the bacterial population.


• Hence, the antibiotic resistance was observed in bacteria.



Question 2.

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


Answer:

STUNNING DISCOVERY


Some 110 million years ago, this armoured plant-eater lumbered through what is now western Canada, until a flooded river swept it into open sea. The dinosaur’s undersea burial preserved its armour in exquisite detail. Its skull still bears tile-like plates and a grey patina of fossilized skins.



In life this imposing herbivore—called a nodosaur—stretched 18 feet long and weighed nearly 3,000 pounds. Researchers suspect it initially fossilized whole, but when it was found in 2011, only the front half, from the snout to the hips, was intact enough to recover. The specimen is the best fossil of a nodosaur ever found.



A cluster of pebble-like masses may be remnants of the nodosaur's last meal.


Quote from the article:


The more I look at it, the more mind-boggling it becomes. Fossilized remnants of skin still cover the bumpy armor plates dotting the animal’s skull. Its right forefoot lies by its side, its five digits splayed upward. I can count the scales on its sole. Caleb Brown, a postdoctoral researcher at the museum, grins at my astonishment. “We don’t just have a skeleton,” he tells me later. “We have a dinosaur as it would have been.”



Question 3.

Attempt giving a clear definition of the term species.


Answer:

A Species includes all those organisms with the characteristics similar enough, so that they can interbreed and perpetuate.



Question 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 are as follows:






Question 5.

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


Answer:

i. Various animals such as Chimpanzees, Bottlenose dolphins, Gorillas, Orcas and even elephants have been observed to show variable levels of self-consciousness.


ii. Self-consciousness is the ability to introspect and identify self from the others. It is checked through various techniques and one such is mirror test in which many animals including Dolphins passed.


iii. They exhibit intimacy and chemistry with their partners and communicate with through various body gestures including certain specific sounds and movements.



Question 6.

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


Answer:




Question 7.

Practise drawing various animals and plants.


Answer:


Darwin’s finches



Kangaroo-A marsupial



Thorns in Bougainvillea and tendrils in Cucurbita- examples of homology.



Question 8.

Describe one example of adaptive radiation.


Answer:

i. Adaptive radiation is the evolution of organisms such that a single species diverges into many through changes in the habitat and other habits so as to survive in a particular geographical area without facing competition. The best example of adaptive radiation is Darwin’s Fiches.


ii. During his journey, Darwin observed a variety of birds in the Galapagos Islands. He observed that all these birds had evolved from a common ancestor.


iii. The birds, originally fed on seeds. But due to increase in population and limited resources, started facing competition. As a result, various birds acquired different features depending on the kind of food they procured.


iv. So, earlier to be of a single kind, these birds diverged into having different variety of beaks depending on their food habits- Seeds, insects, nectar, etc. thus enabling them to survive in the same geographical area without facing any competition.


v. Another example of adaptive radiation is Australian marsupials.



Question 9.

Can we call human evolution as adaptive radiation?


Answer:

No, we cannot call human evolution as adaptive radiation.


Adaptive radiation is the diversifying of organisms from a single species due to various factors such as competition for resources, isolation in a different environment, etc.


Human evolution was a gradual process of anatomical, physiological and changes that took place over a long period of time. The humans did not diversify into many species from a common ancestor. They rather enhanced over the period of time, suiting best according to their current environment.



Question 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:

Evolutionary stages of a horse (Equus) occurred in the following way:




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