Biology MCQs
Topic Notes: Biology
MCQs and preparation resources for competitive exams, covering important concepts, past papers, and detailed explanations.
Plato
- Biography: Ancient Greek philosopher (427–347 BCE), student of Socrates and teacher of Aristotle, founder of the Academy in Athens.
- Important Ideas:
- Theory of Forms
- Philosopher-King
- Ideal State
21
What type of microscope utilizes visible light passing through a specimen to create an image?
Answer:
light microscope
A light microscope, also known as an optical microscope, uses visible light and a system of lenses to magnify images of small samples. It is the most common tool in biological laboratories for observing cells and tissues. Unlike electron microscopes, which use beams of electrons, light microscopes allow for the observation of living specimens in their natural state.
22
What was the typical magnification range provided by the earliest compound microscopes?
Answer:
3X to 9X
Early compound microscopes, developed in the late 16th and early 17th centuries, utilized two lens systems to magnify specimens. Due to the limitations of lens grinding technology at the time, these instruments provided relatively low magnification, typically ranging from 3X to 9X, which was sufficient for observing basic cellular structures.
23
In the context of electron microscopy, where are the specimen and the objective lens typically positioned?
Answer:
vacuum chamber
Electron microscopes require a high vacuum environment to function because electrons are easily scattered by air molecules. Therefore, the specimen and the lens system must be housed within a vacuum chamber to ensure a clear image.
24
What is the typical resolving power of a standard electron microscope?
Answer:
0.2 nm
The resolving power of an electron microscope is significantly superior to that of a light microscope because electrons have a much shorter wavelength than visible light. A typical transmission electron microscope can achieve a resolution of approximately 0.2 nanometers, allowing scientists to visualize ultrastructural details of cells and molecules that are otherwise invisible.
25
Which of the following biological features cannot be resolved using a standard light microscope?
Answer:
internal structure
Light microscopes are limited by the wavelength of visible light, which restricts their resolution. While they can visualize larger organelles like the nucleus or cell walls (chitin), they lack the resolving power to clearly distinguish the fine internal ultrastructure of organelles, which requires electron microscopy.
26
What term describes the minimum distance between two points at which the human eye can distinguish them as separate entities?
Answer:
resolution of human eye
Resolution, or resolving power, is the ability of an optical system to distinguish two closely spaced objects as separate. For the human eye, this limit is determined by the density of photoreceptors on the retina and the optics of the lens.
27
How does the maximum magnifying power of a standard electron microscope compare to the resolving power of the unaided human eye?
Answer:
250,000 times
The electron microscope utilizes a beam of electrons rather than light, allowing for significantly higher resolution and magnification. While the human eye has a limited resolving power, modern electron microscopes can achieve magnifications of up to 250,000 times or more, enabling the visualization of ultrastructural details within cells that are invisible under light microscopy.
28
Which scientist is credited with the invention of the first compound microscope?
Answer:
Zacharias Janssen
Zacharias Janssen, a Dutch spectacle-maker, is widely credited with the invention of the first compound microscope in the late 16th century, which laid the foundation for the development of modern microscopy and cell biology.
29
What is the standard maximum magnification power typically achieved by a conventional light microscope?
Answer:
1500 X
A standard compound light microscope typically achieves a maximum useful magnification of approximately 1000x to 1500x. This limit is imposed by the wavelength of visible light, which restricts the resolution of the image regardless of how much the magnification is increased.
30
What is the typical resolution limit of a standard electron microscope?
Answer:
0.2nm
The resolution of a microscope is the shortest distance between two points that can still be distinguished as separate entities. Due to the extremely short wavelength of electrons compared to visible light, electron microscopes can achieve a resolution of approximately 0.2 nanometers, allowing for the visualization of ultrastructural details within cells.