The incorrect statement is option 2. In NCERT, the infective part of a virus is its nucleic acid (DNA or RNA), not the protein coat. The protein coat (capsid) encases the nucleic acid but is not itself the genetic material. Hence, viruses are obligate parasites that need a host to reproduce. Viroids lack a protein coat, and prions are infectious proteins with no nucleic acid, consisting only of abnormally folded proteins.
🧠 Did You Know?
NCERT emphasizes that the key infectious nature of viruses lies in their nucleic acid, while prions are misfolded proteins and viroids are naked RNA without a capsid.
💡 NCERT Memory Line:
Viruses have nucleic acid enclosed in a protein coat; infective material is nucleic acid.
Consider following features:
(A) Organ system level of organisation
(B) Bilateral symmetry
(C) True coelomates with segmentation of body
Select the correct option of animal groups which
possess all the above characteristics.
Explanation:
The correct option is 2: Annelida, Arthropoda and Chordata. All three groups show organ system level of organisation and bilateral symmetry. They are true coelomates and exhibit body segmentation (Annelida and Arthropoda are clearly segmented;Chordata shows segmentation in its body plan, such as somites in many groups). Thus they possess all the features listed: organ-system level, bilateral symmetry, and true coelomate with segmentation.
🧠 Did You Know?
While Mollusca are bilaterally symmetrical and coelomate with organ systems, they are not typically described as having true body segmentation like Annelids or Arthropods in the NCERT context.
💡 NCERT Memory Line:
Organ system level, bilateral symmetry, and true coelom with segmentation are characteristic of Annelida and Arthropoda; Chordata also shows segmentation in its body plan.
Which of the statements given below is not true
about formation of Annual Rings in trees?
Explanation:
Annual rings are formed due to seasonal variation in wood, with spring wood (light, spacious vessels) and autumn wood (darker, dense vessels) produced within one year. The cambium’s differential activity creates these light and dark bands. In temperate regions, distinct rings are visible because seasons differ markedly; in tropical regions, rings may be faint or absent due to less pronounced seasonality. Statement 3 says rings are not prominent in temperate region, which is not true. Therefore option 3 is the incorrect statement.
? Did You Know?
In NCERT books, annual rings are used to estimate the age of a tree and study past climatic conditions.
? NCERT Memory Line:
Annual rings result from cambial activity varying with seasons; they are prominent in temperate regions where seasons differ.
The ciliated epithelial cells are required to move
particles or mucus in a specific direction. In humans, these cells are mainly present in:
Explanation:
Ciliated epithelial cells help move mucus or particles in a fixed direction. In humans, these ciliated cells line the bronchioles, helping clear inhaled dust, and the Fallopian tubes, helping move the egg towards the uterus. Thus, option 1 (Bronchioles and Fallopian tubes) is correct according to NCERT concepts about ciliated lining in these organs.
🧠 Did You Know?
In the respiratory tract, cilia beat together to push mucus upward toward the throat, a process called mucociliary clearance.
💡 NCERT Memory Line:
Ciliated epithelium is present in the Fallopian tubes and in the bronchi/bronchioles, aiding movement of cells or mucus in a specific direction.
