Answer:(a) fibrous roots
Fibrous [ 100% covered from NCERT]
👉
👉In majority of the dicotyledonous plants, the direct elongation of the radicle
leads to the formation of primary root which grows inside the soil.
It bears lateral roots of several orders that are referred to as secondary,
tertiary, etc. roots. The primary roots and its branches constitute the
tap root system, as seen in the mustard
plant (Figure 5.2a). In monocotyledonous
plants, the primary root is short lived and
is replaced by a large number of roots.
These roots originate from the base of the
stem and constitute the fibrous root
system, as seen in the wheat plant (Figure
5.2b).In some plants, like grass,
Monstera and the banyan tree, roots arise
from parts of the plant other than the
radicle and are called adventitious roots
(Figure 5.2c). The main functions of the
root system are absorption of water and
minerals from the soil, providing a proper
anchorage to the plant parts, storing
reserve food material and synthesis of
plant growth regulators.
👉In coconut which is also a drupe, the mesocarp is fibrous.
👉Occupational Respiratory Disorders: In certain industries, especially
those involving grinding or stone-breaking, so much dust is produced
that the defense mechanism of the body cannot fully cope with the
situation. Long exposure can give rise to inflammation leading to fibrosis
(proliferation of fibrous tissues) and thus causing serious lung damage.
Workers in such industries should wear protective masks.
👉The atrium and the ventricle of the same side are also
separated by a thick fibrous tissue called the atrio-ventricular septum.
👉The blood flows strictly by a fixed route through Blood Vessels—the
arteries and veins. Basically, each artery and vein consists of three layers:
an inner lining of squamous endothelium, the tunica intima, a middle
layer of smooth muscle and elastic fibres, the tunica media, and an
external layer of fibrous connective tissue with collagen fibres, the tunica
externa. The tunica media is comparatively thin in the veins
👉Coronary Artery Disease (CAD): Coronary Artery Disease, often referred
to as atherosclerosis, affects the vessels that supply blood to the heart
muscle. It is caused by deposits of calcium, fat, cholesterol and fibrous
tissues, which makes the lumen of arteries narrower.
👉A detailed study of the myofibril has established that the striated appearance
is due to the distribution pattern of two important proteins – Actin and
Myosin. The light bands contain actin and is called I-band or Isotropic
band, whereas the dark band called ‘A’ or Anisotropic band contains
myosin. Both the proteins are arranged as rod-like structures, parallel to
each other and also to the longitudinal axis of the myofibrils. Actin
filaments are thinner as compared to the myosin filaments, hence are
commonly called thin and thick filaments respectively. In the centre of
each ‘I’ band is an elastic fibre called ‘Z’ line which bisects it. The thin
filaments are firmly attached to the ‘Z’ line. The thick filaments in the
‘A’ band are also held together in the middle of this band by a thin fibrous
membrane called ‘M’ line. The ‘A’ and ‘I’ bands are arranged alternately
throughout the length of the myofibrils. The portion of the myofibril
between two successive ‘Z’ lines is considered as the functional unit of
contraction and is called a sarcomere
👉Pelvic girdle consists of two coxal bones
(Figure 20.10). Each coxal bone is formed by
the fusion of three bones – ilium, ischium and
pubis. At the point of fusion of the above bones
is a cavity called acetabulum to which the thigh
bone articulates. The two halves of the pelvic
girdle meet ventrally to form the pubic
symphysis containing fibrous cartilage.
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👉Joints have been classified into
three major structural forms, namely, fibrous, cartilaginous and synovial.
Fibrous joints do not allow any movement. This type of joint is shown
by the flat skull bones which fuse end-to-end with the help of dense fibrous
connective tissues in the form of sutures, to form the cranium.
Question: 100% NCERT covered from Particular Keyword.Explanations are 100% from NCERT | [Difficult level: Easy] From NCERT NEET 2012
Gymnosperms are also called soft wood
spermatophytes because they lack
(a) cambium (b) phloem fibres
(c) thick-walled tracheids (d) xylem fibres. (2012)
Answer: d
Question: 100% NCERT covered from Particular Keyword.Explanations are 100% from NCERT | [Difficult level: Easy] From NCERT NEET2010
The chief water conducting elements of xylem in
gymnosperms are
(a) vessels (b) fibres
(c) transfusion tissue (d) tracheids. (2010)
Answer: d
Question: 100% NCERT covered from Particular Keyword.Explanations are 100% from NCERT | [Difficult level: Easy] From NCERT NEET 2010
Heartwood differs from sapwood in
(a) presence of rays and fibres
(b) absence of vessels and parenchyma
(c) having dead and non-conducting elements
(d) being susceptible to pests and pathogens.
(2010)
Answer: c
In old trees, the greater part of secondary xylem is dark brown due to deposition of organic compounds like tannins, resins, oils, gums, aromatic substances and essential oils in the central or innermost layers of the stem. These substances make it hard, durable and resistant to the attacks of microorganisms and insects. This region comprises dead elements with highly lignified walls and is called heartwood. The heartwood does not conduct water but it gives mechanical support to the stem. The peripheral region of the secondary xylem, is lighter in colour and is known as the sapwood. It is involved in the conduction of water and minerals from root to leaf.
