(i) It consists of xylem and phloem tissues.
(ii) They are present in the form of bundles called vascular bundles.
(iii) Xylem conducts water and minerals to different parts of the plant.
(iv) Phloem conducts food materials to different parts of the plant.
There are three different types of vascular bundles namely:
(i) Radial
(ii) Conjoint
(iii) Concentric
(i) Radial Bundles:
(i) Xylem and phloem are present in different radii alternating with each other. Eg: roots.
(ii) Conjoint bundles: Xylem and phloem lie on the same radius. There are two types of conjoint bundles
a) Collateral:
(i) Xylem lies towards the centre and phloem lies towards the periphery.
(ii) When cambium is present in collateral bundles, it is called open. Eg: dicot stem and collateral bundle without cambium is called closed. Eg: monocot stem.
b) Bicollateral:
In this type of bundle, the phloem is present on both outer and inner side of xylem. Eg: cucurbita.
(iii) Concentric bundles: Vascular bundle in which xylem completely surrounds the phloem or vice versa is called concentric vascular bundle. It is of two types:
Types:
a) Amphivasal:
Xylem surrounds phloem. Eg: Dracaena
b) Amphicribral:
Phloem surrounds xylem. Eg: Ferns Endarch: Protoxylem lies towards the centre and metaxylem lies towards the periphery. Eg: stem. Exarch: Protoxylem lies towards the periphery and metaxylem lies towards the centre. Eg: roots.

(i) The horizontal rows are called periods. There are seven periods in the periodic table.
(ii) First period (Atomic number 1 and 2): This is the shortest period. It contains only two elements (Hydrogen and Helium).
(iii) Second period (Atomic number 3 to 10): This is a short period. It contains eight elements (Lithium to Neon).
(iv) Third period (Atomic number 11 to 18): This is also a short period. It contains eight elements (Sodium to Argon).
(v) Fourth period (Atomic number 19 to 36): This is a long period. It contains eighteen elements (Potassium to Krypton). This includes 8 representative elements and 10 transition eIements.
(vi) Fifth period (Atomic number 37 to 54): This is also a long period. It contains 18 elements (Rubidium to Xenon). This includes 8 representative elements and 10 transition elements.
(vii) Sixth period (Atomic number 55 to 86): This is the longest period. It contains 32 elements (Cesium to Radon). This includes 8 representative elements, 10 transition elements and 14 inner transition elements (Lanthanides).
(viii) Seventh period (Atomic number 87 to 118): Like the sixth period, this period also accommodates 32 elements. Recently 4 elements have been included by IUPAC.

(i) The rhythmic closure and opening of the valves cause the sound of heart.
(ii) The first sound LUBB is of longer duration and is produced by the closure of the tricuspid and bicuspid valves after the beginning of the ventricular systole.
(iii) The second sound DUPP is of a shorter duration and is produced by the closure of semilunar valves at the end of ventricular systole.

Given:
\(\mathrm{f}=10 \mathrm{~cm}, \mathrm{u}=-20 \mathrm{~cm}, \mathrm{v}=?  \)
\(\frac{1}{f}=\frac{1}{v}-\frac{1}{u}  \Rightarrow \frac{1}{v} =\frac{1}{f}+\frac{1}{u} \)
\(\frac{1}{v} =\frac{1}{10}+\frac{1}{-20}=\frac{1}{10}-\frac{1}{20}  \)
\(\frac{1}{v} =\frac{2-1}{20}=\frac{1}{20}  \)
\(\mathbf{v} =20 \mathrm{~cm}  \)
Image distance = 20 cm
Nature of image:
Nature of the image is real, enlarged and inverted image.

\(\text {Given } m_{1} : m_{2}=3: 4  \)          
\(a_{2} =12 \mathrm{~m} \mathrm{~s}^{-2}  \)
\(a_{1} =?\)
Using Newton's second law,
\(\mathrm{F} =\mathrm{m \times a}  \)
\(\mathrm{F} =\mathrm{m}_{1} \times a_{1}=3 a_{1}  \)
\(\mathrm{~F} =\mathrm{m}_{2} \times a_{2}=4 \times 12=48 \mathrm{~N}  \)
\(3 a_{1} =48  \)
\(a_{1} =48 / 3=16 \mathrm{~m} \mathrm{~s}^{-2}  \)
\(a_{1} =16 \mathrm{~ms}^{-2}\)
The acceleration produced on the other body is \(16 \mathrm{~m} \mathrm{~s}^{-2}\).

(i) Banyan tree is a dicot. In Dicots cambium is present in the vascular bundle and secondary growth is seen throughout the life of the plant. Hence the stem becomes thicker due to additional formation of xylem and phloem every year.
(ii) Coconut is a monocot. Secondary growth is absent in monocots. Hence the stem does not increase in thickness every year.

Molecular mass of water (H₂O) = H₂O = H x 2 + O x 1
= 1 x 2 + 16 x 1
= 2 + 16
=18
No of moles = \(\frac{Given \ Mass}{Molecular \ Mass}\)
Number of moles = \(\frac{0.18}{8}= \frac{0.18 \times 100}{18 \times 100}=0.01\)
No of moles = \(\frac{Number\ of \ molecules}{Avogadro's \ number}\)
Number of molecules = No of moles x Avogadro's number
= 0.01 x 6.023 x 10²³
= 0.06023 x 10²³
Number of molecules in 0.18 g of water = 6.023 x 10²¹
Alternative method
Gram molecular mass of water = H₂O
= 1 x 2 + 16 x 1 = 2 + 16
= 18 g
Number of molecules \(=\frac{\text { Avogadro's number } \times \text { given mass }}{\text { Gram molecular mass }}\)
Number of molecules \(=\frac{6.023 \times 10^{23} \times 0.18}{18}\) 
= \(6.023 \times 10^{23} \times 0.01\)
Number of molecules of 0.18 g of water = 6.023 x 10²¹ molecules.

Definition:
The inherent property of a body to resist any change in its state of rest or the state of uniform motion, unless it is influenced upon by an external unbalanced force, is known as inertia.
Types of Inertia:
(i) Inertia of rest
(ii) Inertia of motion
(iii) Inertia of direction
(i) Inertia of rest: The resistance of a body to change its state of rest is called inertia of rest.
Example: When you vigorously shake the branches of a tree, some of the leaves and fruits are detached and they fall down (Inertia of rest).
(ii) Inertia of motion: The resistance of a body to change its state of motion is called inertia of motion.
Example: An athlete runs some distance before jumping. Because, this will help him jump longer and higher (Inertia of motion).
(iii) Inertia of direction: The resistance of a body to change its direction of motion is called inertia of direction.
Example: When we make a sharp turn while driving a car we tend to lean sideways 'inertia of direction'.

Neuroglia: Neuroglia are also called as glial cells. They are the non-exciting, supporting cell of the nervous system. They do not initiate or conduct nerve impulse.

It is defined as half the distance between nuclei of adjacent metal atoms.

Imbibition is a type of diffusion in which a solid plant material absorbs water and gets swelled up.
E.g: Absorption of water by dry seeds and dry grapes.

The Indian cattle leech.

(i) Nerve cells or neurons
(ii) Axon and Dendrites
(iii) Synapse
(iv) The chemical is Acetylcholine