Question

Read the following statements and select the correct ones.

Statement (i): Giant ferns, the pteridophytes, were present during the Mesozoic era but fell to form coal deposits slowly.
Statement (ii): The multicellular organisms divided to form single-celled organisms.
Statement (iii): First organisms that invaded land were plants.

• A. Statements (i) and (ii) are correct, but statement (iii) is incorrect
• B. Statements (i) and (ii) are incorrect, but statement (iii) is correct
• C. Statements (i) and (iii) are correct, but statement (ii) is incorrect
• D. All statements are correct

Answer 1

The correct option is C Statements (i) and (iii) are correct, but statement (ii) is incorrect

The first cellular life forms appeared on Earth around 2000 million years ago.

The first formed cells were prokaryotic. Eukaryotic cells evolved later, when the primitive cells engulfed bacterial cells and they started living together. It is a classic example of “endosymbiosis”. This is supported by the endosymbiotic theory which states that some of the organelles (mitochondria and chloroplast) that are seen in the eukaryotic cells today were once prokaryotic microbes.

Slowly single-celled organisms developed into multicellular life forms.

It is believed that plants were the first organisms to invade land. Oldest land plants with conducting tissues (xylem and phloem) originated and colonised the land during the Silurian period of the Paleozoic era.

The image given below is the sketch of the evolution of plant forms through geological periods.


During the Mesozoic era, giant ferns (pteridophytes) fell to form the coal deposits. The coal deposits probably would have formed by the following method. The dead plants fell into the swamp waters and new plants grew in their place. Eventually, this formed a thick layer of dead plants rotting in the swamp. With the evolution of different plant species, several layers of dead plants were formed. After millions of years, many layers were formed, one over the other. With the weight of top layers, water and dirt in the lower layers got packed down. Tremendous heat and pressure produced chemical and physical changes in the layers of plants of ferns, reeds and mosses which forced out the oxygen and left only rich carbon deposits. As time progressed, the deposited plant material became coal. Hence, giant ferns, the pteridophytes, were present during the Mesozoic era but fell to form the coal deposits slowly.

Hence, statements (i) and (iii) are correct, but statement (ii) is incorrect