The question asks for the definition of a tissue. To answer this, we need to recall the levels of organization in multicellular organisms, starting from cells.
A) A group of similar cells performing a particular function. This definition accurately describes a tissue. Tissues are collections of specialized cells that work together to carry out specific tasks within an organism.
To answer this question, we need to understand the basic classification of plant tissues and their primary functions. Plant tissues are broadly divided into meristematic and permanent tissues. The key is to identify which of these is responsible for active cell division and growth.
Correct Option: B) Meristematic tissue is responsible for the growth in plants because its cells are actively dividing, leading to an increase in the plant's length and girth.
The question asks about the location of apical meristematic tissue in plants. Apical meristems are responsible for primary growth, which increases the length of the plant. Understanding the function of meristematic tissues helps in identifying their location.
C) At the growing tips of stem and roots. Apical meristems are found at the apex (tip) of stems and roots. These tissues consist of undifferentiated cells that divide continuously, leading to the elongation of the plant body, a process known as primary growth.
UPSC - 2019
The question asks about the Cas9 protein, a term frequently encountered in scientific news. To answer this, one needs to recall its primary function and the scientific field it is associated with.
Correct Option: A) A molecular scissors used in targeted gene editing
Cas9 (CRISPR-associated protein 9) is an enzyme that plays a crucial role in the CRISPR-Cas9 gene-editing system. It functions as a molecular scissor, capable of making precise cuts in DNA at specific locations guided by a small RNA molecule. This allows for targeted modifications to the genome, making it a powerful tool for gene editing.
The question asks about the constituents of phloem, which is a complex permanent tissue in plants responsible for the translocation of food. Understanding the different types of cells that make up phloem is key to answering this question.
Correct Option: B) Sieve tubes, companion cells, phloem fibres, phloem parenchyma
This option correctly lists all four main components of phloem. Sieve tubes (or sieve tube elements) are the main conducting elements. Companion cells are closely associated with sieve tube elements and help in their functioning. Phloem parenchyma cells are involved in storage and lateral conduction. Phloem fibres provide mechanical support.
The question asks to identify the plant tissue responsible for providing both flexibility and support. We need to recall the functions of different permanent plant tissues.
Correct Option: B) Collenchyma provides mechanical support and flexibility to plant parts like young stems and petioles. Its cells have unevenly thickened cell walls, allowing for bending without breaking.