Which of the following is incorrect about Cynobacteria?
AI-generated explanation. Check against your textbook.
Explanation:
The incorrect statement is option 2. Cyanobacteria are photoautotrophs and carry out photosynthesis. Many cyanobacteria form specialized cells called heterocysts for nitrogen fixation, so they do have heterocysts in several species. They often form blooms in polluted or nutrient-rich water bodies, and they contain chlorophyll a, along with other pigments, which is similar to green plants.
🧠 Did You Know?
Cyanobacteria are sometimes called blue-green algae, but they are bacteria, not true algae. They play a key role in nitrogen cycling due to heterocysts in some species.
💡 NCERT Memory Line:
Cyanobacteria are photosynthetic and may fix nitrogen in heterocysts; they form blooms in polluted waters and possess chlorophyll a similar to green plants.
The size of Pleuropneumonia - like Organism (PPLO) is:
AI-generated explanation. Check against your textbook.
Explanation:
PPLO stands for Pleuropneumonia-Like Organism, which is the organism Mycoplasma pneumoniae. According to NCERT biology, PPLOs are very small, about 0.1 μm in size, much smaller than many bacteria. Thus the correct size is 0.1 μm (option 4).
🧠 Did You Know?
PPLOs lack a cell wall and have a flexible membrane, which helps them survive as small organisms in various environments.
💡 NCERT Memory Line:
PPLO organisms are extremely small, around 0.1 μm, illustrating how some pathogens can be much smaller than typical bacteria.
Which of the following statements about inclusion
bodies is incorrect ?
AI-generated explanation. Check against your textbook.
Explanation:
Inclusion bodies are reserve materials (like glycogen, lipids, pigments) that lie free in the cytoplasm and are not bounded by a membrane. They do not participate in the ingestion of food particles. Therefore, statement 2 is incorrect.
🧠 Did You Know?
NCERT describes inclusion bodies as reserve deposits in the cytoplasm, formed when resources are stored for later use.
💡 NCERT Memory Line:
Inclusion bodies: reserve materials in the cytoplasm, often not membrane-bound.
Which of the following options does correctly represent the characteristic features of phylum Annelida?
AI-generated explanation. Check against your textbook.
Explanation:
The correct statement is option 2. Annelida are triploblastic animals with bilateral symmetry and a segmented (metamerically arranged) body. They are coelomates, having a true coelom lined by peritoneum. This segmentation is a key feature emphasized in NCERT biology for phylum Annelida. Options 1, 3, and 4 describe incorrect features: 1 says unsegmented, which contradicts the segmented body; 3 mentions an acoelomate and flattened body, not true for annelids; 4 describes diploblastic and radial symmetry, which applies to cnidarians, not annelids. Understanding these contrasts helps reinforce the NCERT characterization of annelids as triploblastic, bilaterally symmetrical, and segmented.
🧠 Did You Know?
Segmentation in annelids allows specialization of body segments for movement and function, a feature highlighted in NCERT discussions of Annelida.
💡 NCERT Memory Line:
“Annelids have a segmented (metamerically arranged) body and are triploblastic with bilateral symmetry.”
Match the following group of organisms with their
respective distinctive characteristics and select the correct option :
Organisms
Characteristics
(A)Platyhelminthes
(I)Cylindrical body with no segmentation
(B)Echinoderms
(II)Warm blooded
animals with direct development
(C)Hemichordates
(III)Bilateral symmetry with incomplete
digestive system
(D)Aves
(IV)Radial symmetry with indirect
development
Choose the correct answer from the options given below:
AI-generated explanation. Check against your textbook.
Explanation:
Matchings as per NCERT:
- Platyhelminthes (A) have bilateral symmetry and are unsegmented with an incomplete digestive system (only one opening). => (III)
- Echinoderms (B) show radial symmetry as adults and have indirect development (larval stage). => (IV)
- Hemichordates (C) are worm-like, unsegmented (cylindrical body, no segmentation) organisms. => (I)
- Aves (D) are warm-blooded and show direct development (hatching resembles the adult). => (II)
Thus the correct pairing is A-III, B-IV, C-I, D-II. The other options mismatch these standard NCERT characteristics.
🧠 Did You Know?
Hemichordates and Echinoderms are considered deuterostomes, like chordates, in embryology.
Bilaterally symmetrical and acoelomate animals
are exemplified by:
AI-generated explanation. Check against your textbook.
Explanation:
The correct option is 2) Platyhelminthes. In NCERT, flatworms are described as bilaterally symmetrical and acoelomates (they lack a true body cavity). This distinguishes them from other groups: Ctenophora are diploblastic with biradial/bilateral tendencies; Aschelminthes (Nemathelminthes) are pseudocoelomates; Annelida are bilateral and eucoelomates.
🧠 Did You Know?
Platyhelminthes are the simplest animals to show bilateral symmetry and to lack a true coelom.
💡 NCERT Memory Line:
Flatworms (Platyhelminthes) are the simplest bilaterally symmetric, acoelomate animals in NCERT.
Which of the following statements are true for
the phylum-Chordata?
(A) In Urochordata notochord extends from head to tail and it is present throughout their life.
(B) In Vertebrata notochord is present during the embryonic period only.
(C) Central nervous system is dorsal and hollow.
(D) Chordata is divided into 3 subphyla : Hemichordata, Tunicata and Cephalochordata.
AI-generated explanation. Check against your textbook.
Explanation:
Correct answer: (B) and (C). In Urochordata (tunicates), the notochord is present only in the larval stage and is not extended throughout life, so statement (A) is false. In Vertebrata, the notochord is present during embryonic development but is typically replaced by the vertebral column, so statement (B) is true. The central nervous system in Chordata is dorsal and hollow (a dorsal nerve cord), so statement (C) is true. Chordata is divided into three subphyla: Cephalochordata, Urochordata (Tunicata), and Vertebrata; Hemichordata is a separate phylum, not a subphylum, so statement (D) is false. Therefore, (B) and (C) are true.
🧠 Did You Know?
The dorsal hollow nerve cord is a key hallmark of Chordata, visible in embryos and some larval stages across subphyla.
💡 NCERT Memory Line:
Notochord is a defining chordate feature; in Vertebrata it is typically replaced by the vertebral column during development.