The human eye can be compared to a camera as both functions by gathering, focusing and transmitting the light through the lens for creating an image of an object.

Prokaryotic cell lacks a distinct nucleus and membrane bound organelles
eg: bacteria.

Characters of Pteridophytes:
1 Pteridophytes are the first true land plants with xylem and phloem. Hence it is called vascular cryptogams.
2 Pteridophytes exhibit alternation of generation. The diploid sporophytic phase alternates with the haploid gametophytic phase.
3 The main plant body is sporophytes, which is the dominant phase, differentiated into true root, stem and leaves.
4. Sporophytes reproduce by means of spores. Spores are produced in sporangium.

Agar Agar:
1. Agar Agar is extracted from some red algae namely Gelidium, Gracillaria etc
2. which is used to prepare growth medium in laboratories.
Algae in space travel:
1. Chlorella pyrenoidosa is used in space travel to get rid of Co, and decompose human wastes
Single cell protein (SCP):
1. Some of the single cell algae and blue green algae are used to produce protein.
2. Eg: Chlorella, spirulina

Applications of a concave mirror:
i) Used as shaving mirror as they provides magnified image
ii) Used in torches, search lights as they direct the light to a long distance.
Applications of a convex mirror:
i) Used in vehicles as rear view mirror
ii) Used on roads where there are sharp curves and turns

Effects of Acid rain
(i) It irritates eyes and skin of human beings
(ii) It inhibits germination and growth of seedlings
(iii) It changes the fertility of the soil, destroys plants and aquatic life.
(iv) It causes corrosion of many buildings, bridges etc.
Preventive measures
(i) Minimising the usage of fossil fuels such as petrol, diesel etc.
(ii) Using CNG (Compressed Natural Gas)
(iii) Using non-conventional source of energy
(iv) Proper disposal of the industrial wastes.

a) Carbon - Carbondioxide CO₂
b) Sulphur - Sulphur dioxide SO₂
c) Phosphorous - Phosphorous trioxide P₂O₃
Phosphorous pentoxide P₂O₅
d) Magnesium - Magnesium Oxide MgO
e) Iron - Iron oxide Fe₃O₄
f) Sodium - Sodium Oxide Na₂O

Inspiration (Inhalation)
► The process of taking air into the lungs is called inspiration,
► During inspiration, the sternum is pushed up and outward and the diaphragm is pulled down
► This increases the volume of the thoracic cavity the pressure decreases.
► The air outside the body flows into the lungs.
► Here the exchange of gases takes place between the air and blood.
Expiration (Exhalation)
► The process of expelling air from the lungs is called expiration or exhalation.
► Upon exhalation, the lungs recoil to force the air out of the lungs
► The intercostal muscles relax, returning the chest wall to its original position.
► During exhalation, the diaphragm also relaxes, moving higher into the thoracic cavity.
► This increases the pressure within the thoracic cavity relative to the environment.
► Air rushes out of the lungs due to the pressure gradient.
► This movement of air out of the lungs is a passive event.
Exchange of gases in the Alveoli:
► The content of oxygen in the inhaled air in alveoli is more than the blood flowing through the capillaries
► So, the oxygen moves into the blood by simple diffusion.
► Haemoglobin in the blood combines with oxygen to form oxyhaemoglobin.
► The blood carrying oxygen reaches the heart through blood vessels.
► The heart pumps it to all the tissue in the body.
► The tissue releases carbon-dioxide which is carried back to alveoli by the blood.
► Carbon dioxide diffuses from the blood to the air in the alveoli and it sent out of the body when the air is exhaled.

Periscope:-
(i) Periscope is an instrument used for viewing bodies or ships, which are over and around another body or a submarine.
Working:-
(i) It is based on the principle of the law of reflection of light
(ii) It consists of a long outer case and inside this case mirrors or prisms are kept at each end,  inclined at an angle of 45^o.
(iii) Light coming from the distant body falls on the mirror at the top end of the periscope and gets reflected vertically downward.
(iv) This light is reflected again by the second mirror kept at the bottom so as to travel horizontally and reach the eye of the observer.
(v) In some complex periscopes, optic fibre is used instead of mirrors for obtaining a higher resolution.
(vi) The distance between the mirrors also varies depending on the purpose of using the periscope.

False

False

Physical properties of Oxygen
(i) Oxygen is a colourless, odorless and tasteless gas
(ii) It is a poor conductor heat and electricity
(iii) Oxygen dissolves readily in cold water
(iv) It is denser than air
(v) It can made into liquid at high pressure and low temperature
(v) It supports combustion.

Specific heat capacity of a substance is defined as the amount of heat energy required to raise the temperature of 1 kilogram of a substance by 1^oC the symbol C. It's SI unit is Jkg^-1K^-1.

Effects of heat:
When heat energy is supplied to any substance, it brings about many changes.
The three important changes are:
(i) Expansion
(ii) Increase in temperature
(ii) Change in state.

► Air enters in Inspiration
► Air comes out Expiration

► Alveoli are the workhouses of respiratory system.
► The exchange of oxygen and carbondioxide takes place in alveoli.
► It takes up oxygen and gives out carbondioxide.

There are 4 types of tissues.
i) Epithelial tissue
ii) Muscular tissue
iii) Connective tissue
iv) Nervous tissue

Seeds of gymnosperm plants are naked because the ovule is not enclosed by ovary.

The plant body of algae are called thallus. It means the plant body is not differentiated into root, stem and leaf.