default_background
✕

Find the best tutors and institutes for Class 12 Tuition

Find Best Class 12 Tuition

Please select a Category.

Please select a Locality.

No matching category found.

No matching Locality found.

Q1:
Explain antibiotic resistance observed in bacteria in light of Darwinian selection theory.

Solution :

Given Variables & Theoretical Foundation

In the context of Darwinian selection, the development of antibiotic resistance in bacterial populations is not an induced change in individuals, but a shift in the genetic composition of the population over successive generations due to differential survival [Darwinian Theory of Natural Selection].

  • Variation: Naturally occurring genetic variations exist within a bacterial population (arising from mutations or horizontal gene transfer).
  • Selection Pressure: The introduction of an antibiotic serves as an environmental filter.
  • Differential Reproduction: Only bacteria possessing resistance genes survive to reproduce, passing those traits to progeny.

Step 1: The Pre-Selection State (Stochastic Variation)

In any large population of bacteria, stochastic genetic mutations occur. Occasionally, a mutation confers a biochemical advantage, such as the synthesis of an enzyme (e.g., $\beta$-lactamase) capable of degrading a specific antibiotic, or an alteration in the cell wall protein structure that prevents antibiotic binding [Mutation Theory]. At this stage, the resistant strain exists in a negligible frequency.

Step 2: The Introduction of Selective Pressure

When an antibiotic is administered, it acts as a selective agent. Bacteria lacking the resistance gene are susceptible and undergo lysis or inhibition of metabolic pathways.
Mathematically, if $N_s$ is the number of susceptible bacteria and $N_r$ is the number of resistant bacteria, the fitness function $W$ for susceptible bacteria drops to $W_s \approx 0$ upon exposure to the antibiotic, while $W_r \approx 1$ for the resistant strain.

Step 3: Visual Representation of Selection

A: Population with rare mutation R B: Post-Antibiotic Selection R

Step 4: Inheritance and Population Shift

The few resistant bacteria survive the selection event. Because bacteria possess high reproductive rates ($R_0 \gg 1$), the resistant survivors undergo rapid binary fission. Through vertical gene transfer (reproduction) and horizontal gene transfer (conjugation, transformation, transduction), the resistance gene spreads throughout the remaining population [Principles of Bacterial Genetics].

Mechanism Impact on Evolution
Natural Selection Eliminates unfit phenotypes (susceptible bacteria).
Reproductive Success Resistant bacteria pass alleles to next generation.
Directional Selection The population mean phenotype shifts toward resistance.

Analytical Summary

Darwinian selection dictates that the environment does not create the mutation; rather, the environment selects for the pre-existing advantageous variation. Antibiotic resistance is a classic example of Directional Selection, where the allele frequency of the resistant gene increases over time within the bacterial gene pool, rendering the antibiotic ineffective against the evolved population.

Final Solution: Antibiotic resistance is an evolutionary phenomenon driven by natural selection, wherein environmental pressure (antibiotics) eliminates susceptible individuals, allowing survivors with pre-existing resistance mutations to propagate their genotype, ultimately leading to a resistant bacterial population.


More Questions from Class 12 Biology Evolution EXERCISES


CBSE Solutions for Class 12 Biology Evolution


Chapters in CBSE - Class 12 Biology


Top Tutors who teach Evolution

Sai V. Class 12 Tuition trainer in Madappanahalli
(150)
Top Tutor
locationImg Itagalpura Main Rd, Madappanahalli
experience 16 yrs of Exp students 9 students
greenClock 4353 hrs of classes completed
rsIcon 600 per hour
MSc, BEd , (Phd), Member of Royal Society UK
Online Classes Online Classes

Class 12 in the CBSE/ICSE system in India is a crucial year for students, as it is the final year of their secondary education. Learning Methodology in physics. Understand the Basics First: Start with a solid foundation by grasping the fundamental concepts and principles of physics. Ensure you have a good grasp of mathematics, as it is an essential tool in physics. Begin by understanding the fundamental concepts of physics, such as motion, forces, energy, and matter. A strong foundation is essential. Chunk Information: Break down the material into smaller, manageable chunks. Focus on one concept at a time, master it, and then move on to the next. Active Learning: Engage actively with the material. Instead of just reading or listening, try to solve problems, ask questions, and make connections between concepts. Practice Problem-Solving: Physics involves a lot of problem-solving. Work through a variety of physics problems regularly to reinforce your understanding. Seek out practice problems and solutions in textbooks or online resources. Start with straightforward physics problems and gradually work your way up to more complex ones. Practice problem-solving regularly. Visualize Concepts: Physics concepts can often be abstract. Use visual aids, diagrams, and animations to help you understand and remember complex ideas. Relate physics concepts to everyday experiences or familiar analogies. For example, compare the flow of electricity in a circuit to the flow of water in pipes Create concept maps or mind maps to connect related physics concepts. This can help you see the relationships between different ideas. I am teaching Physics with the concept of a child-centered education system. Currently, I am working in a CBSE school having 12years of experience. I have 9 years of online teaching experience with technical skills. I can teach Physics with the basic concepts following the standards of the CBSE Curriculum with practical applications, and numerical solving methods. I can ensure that I will give complete value to the student for their academics. Please have a look at my profile for more information

Skills: Physics
Also teaches: Class 11 Tuition, Class 8 Tuition and more

(157)
Top Tutor
locationImg Sector 54 Suncity, Gurgaon
experience 8 yrs of Exp
greenClock 1185 hrs of classes completed
rsIcon 800 per hour
Spoken English Teacher with 16 years of experience
Online Classes Online Classes
regularClasses Tutor's home

I have a varied experience of over 16 years and have enjoyed all roles as a writer, editor, banker, business analyst, teacher and marketer. I love a challenge, and during the course of my career, I took up English Language classes for working professionals. My classes are learner-centric and interactive, packed with activities, games and exercises that draw learners out of their shells and infuse them with confidence. Students are encouraged to think, raise questions, absorb new vocabulary and finally adopt the language as their own. My ability to connect and engage with students from all sections make my classes friendly, approachable and non-intimidating. My varied work experience across sectors further adds to my understanding of job and situation requirements.

Skills: English
Also teaches: Class 11 Tuition, Interview Skills and more

Lubna F. Class 12 Tuition trainer in Karari
(11)
Top Tutor
locationImg Zafarpur Mahawan, Karari
experience 10 yrs of Exp students 6 students
greenClock 287 hrs of classes completed
rsIcon 400 per hour
Certified in Finance (from IIM) with over 20 years of experience of teaching in CBSE school
Online Classes Online Classes
regularClasses Tutor's home

I am an experienced, qualified teacher and tutor with over 20 years of experience in teaching accountancy, business studies and English literature in CBSE school. Passionate about communication in English, over the years I have helped thousands of students overcome their stage fright and nervousness in expressing themselves in public. So far, I have worked with Dr. Rizvi Springfield School (Prayagraj) and Global Classroom, Lucknow (branch of CMS) and currently freelancing with Planet Spark as an Expert in Public Speaking & Creating Writing. I specialize in teaching Accountancy and Business Studies to classes 11 and 12, along with Spoken English. With a strong academic background, including a B. Com., M. Com., and an M.Ed., as well as completing a Management Development Program, I bring a wealth of knowledge and expertise to my teaching. With over 22 years of administrative experience and 10 years of teaching, I have had the privilege of holding key roles such as PGT English, Commerce teacher, Headmistress, and Principal. These experiences have helped me develop a profound understanding of education, enabling me to cater to the unique needs of my students effectively. Teaching has been the most enjoyable and fulfilling part of my professional journey. Over the years, I have built strong connections with my students, fostering an environment of trust and growth. My passion for education has been recognized through several accolades, including a prestigious Principal Award in Delhi. I conduct online classes where I follow a structured lesson plan to ensure my sessions are engaging and interactive. I use PPTs and videos to make concepts clear and relatable, catering to the diverse learning styles of my students. I also provide comprehensive notes and content to support my students' learning and revision. These resources are meticulously prepared to align with the curriculum and focus on enhancing students’ understanding and performance. My approach to teaching is rooted in creating a supportive and motivating environment. I am committed to helping my students achieve their academic and personal goals while instilling confidence and a love for learning in them. Teaching is not just my profession; it is my passion and purpose.

Tanvi D s

Ms.Lubna is the best tutor for accountancy grade 12 cbse. She is extremely kind and top tier teaching skills.

Skills: Accountancy , Business Studies
Also teaches: BCom Tuition, Spoken English and more

(1)
Top Tutor
locationImg Kunnathurmedu, Palakkad
experience 2 yrs of Exp students 1 student
greenClock 20 hrs of classes completed
rsIcon 400 per hour
Entrepreneur by job, teacher by passion
Online Classes Online Classes
homeTutions Student's Home
regularClasses Tutor's home

Hello, my name is Sreedevi. I live in a beautiful village in Kerala. Those who are looking to learn to talk in Malayalam, I can help you. I do not hold a degree in the language. But I am a native speaker and my grandfather was a renowned poet of his times and we love the language to the core as a family. I can teach to speak in simple and fun methods that's not textbook oriented referring to everything in daily life from food to movies to asking directions :)

Also teaches: Malayalam Speaking, Handwriting and more

(79)
superTutorSuper Tutor
locationImg Raj Nagar Extention, Ghaziabad
experience 20 yrs of Exp students 32 students
greenClock 374 hrs of classes completed
rsIcon 800 per hour
Senior Chemistry & Biology Educator | Double MSc | CBSE–ISC–NEET–JEE–IB–IGCSE–A Level | 20+ Years
Online Classes Online Classes

• Responsible Chemistry Teacher with excellent communication skills demonstrated by 20 years of teaching experience. • Motivated enthusiastic educator fosters a cohesive student learning atmosphere. • Proven results in delivering excellent curriculum management and achievement to students of varying backgrounds while motivating educational success

Pahal

I liked your classes a lot. You have made complex A - level chemistry concepts easy to understand, and your support really helped me to improve throughout the year. Thank you for being patient, encouraging and motivating.

Skills: Chemistry , Biology

Other Subjects in CBSE - Class 12

Worksheet Icon

Download free CBSE - Class 12 Biology Evolution EXERCISES worksheets

Download Now

Find Best Class 12 Tuition ?

Find Now »