STD 11 - 2. Biology classification — NEET STD 11 Science — Question

It is an enzyme.

Natural system of classification differs from artifical system in

Animals are

In the five kingdom system of classification, which single kingdom out of the following can include blue-green algae, nitrogen fixing bacteria and methanogenic archaebacteria

Which one of the following is an example of cleistogamy?

Choose the correct one for dicotyledonous stem from given statements.
(i) Epidermis is the outermost protective layer of the stem, covered with a thin layer of cuticle, it may bear trichomes and a few stomata.
(ii) The cells of the endodermis are rich in starch grains and the layer is also referred to as the starch sheath.
(iii) Pericycle is present on the inner side of the endodermis and above the phloem in the form of semi-lunar patches of parenchyma.
(iv) In between the vascular bundles there are a few layers of radially placed parenchymatous cells, which constitute medullary rays.
(v) A large number of vascular bundles are arranged in a ring.
(vi) Vascular bundles are conjoint and closed.

Select the correct statement

Which one of the following statements are correct ?
(i) In flowering plants, tracheids and vessels are the main water transporting element.
(ii) The first formed primary xylem elements are called protoxylem.
(iii) In roots, the proto xylem lies towards periphery and meta xylem lies toward the centre. Such arrangement of primary xylem is called endarch.
(iv) Phloem in angiosperms is composed of sieve tube elements, companion cells, phloem parenchyma and phloem fibers.
(v) The functions of sieve tubes are controlled by the nucleus of companion cells.
(vi) The companion cells are specialized sclerenchymatous cells, which are closely associated with sieve tube elements.
(vii) The sieve tube elements and companion cells are connected by pit fields present between their common transverse walls.
(viii) The companion cells help in maintaining the pressure gradient in the sieve tubes.
(ix) Phloem parenchyma is absent in most of the diocotyledons.
(x) Phloem fibres are made up of sclerenchymatous cells.
(xi) The first formed primary phloem consists of narrow sieve tubes and is referred to as protophloem.
(xii) The outside of the epidermis is often covered with a waxy thin layer called cuticle which prevents the loss of water. Cuticle is absent in roots.
(xiii) Each stoma is composed of two bean-shaped cells known as guard cells. In grasses, those cells are dumb-bell shaped.
Choose the correct option given below :-

Member of auxin, which is widely used to kill the dicotyledonous weed is

Which of the following statements are true for prophase ?
(i) Initiation of condensation of chromosomal material.
(ii) The centriole begins to move towards opposite poles of the cell.
(iii) Chromosomes are seen and composed of two chromatids attached together at the centromere.
(iv) Initiation of the assembly of mitotic spindle, the microtubules.
(v) Cells at the end of prophase, do not show golgi complexes, endoplasmic reticulum. Nucleolus and the nuclear envelope.
(vi) Spindle fibres attach to kinetochores of chromosomes.