Biology Facts for Competitive exams
1) Cell is the fundamental unit of life.
2) Cell is a Latin word which means ‘little room’.
3) Robert Hooke discovered and coined the term cell, while he observed a thin slice of cork in the year 1665.
4) It is enclosed by plasma membrane composed of lipids and proteins.
5) Cell membrane regulates the transport of materials between interior of the cell and external environment.
6) In plant cells, there is a rigid outer covering called cell wall made up of cellulose.
7) Osmosis is the transfer of water molecule through a selectively permeable membrane.
a) Plasma membrane is a selectively permeable membrane.
b) When plant cell loses water through osmosis, the contents of cell shrinks away from the cell wall.
c) Osmosis is also the passage of water from a region of higher water concentration through a semi-permeable membrane to a region of lower water concentration.
8) In a hypotonic solution, the plant or animal cell swell due to gain of water content whereas in a hypertonic solution the cell shrinks.
9) There will be no change in cell size in an isotonic solution.
10) The nucleus in eukaryotes is separated from cytoplasm by double layered membrane.
11) Endoplasmic reticulum acts both as a passageway for intracellular transport and as a manufacturing surface.
12) Golgi apparatus was first described by Camillo Golgi.
i) It consists of stacks of membrane bound vesicles called cisterns.
ii) These cisterns are utilized in storage, modification, packaging of substances manufactured in the cell.
13) Lysosomes are waste disposal system of the cell.
i) It keeps the cell clean by digesting all the foreign material.
14) Mitochondria is known as powerhouse of the cell.
a) Energy required for metabolic activities is released by mitochondria in the form of ATP molecules.
b) ATP stands for Adenosine Tri- Phosphate.
SIGNS OF LIFE
1) Movement of various kinds is taken as the indication of life.
2) Maintenance of life requires:
iii) Transport of materials within the body and
iv) Exertion of waste products.
3) There are two types of nutrition :
a) Autotrophic nutrition: involves intake of inorganic materials from environment.
i) Utilize sun to synthesize complex material high-energy organic materials.
b) Heterotrophic nutrition: involves intake of complex materials prepared by other organisms.
4) Plants are autotrophs and chlorophyll absorbs sunlight energy from sunlight.
5) Transport of soluble products of photosynthesis is called translocation.
6) Humans and animals are heterotrophs.
7) In humans food eaten get digested in numerous steps along the alimentary canal.
a) Alimentary canal starts from mouth and ends at anus.
b) Preliminary digestion begins at mouth.
c) Partial digestion takes place in the large intestine
d) Digestion is completed in the small intestine.
8) During respiration, complex organic compounds like glucose is broken down to provide energy in the form of ATP.
9) Respiration may be aerobic or anaerobic.
a) Aerobic respiration makes more energy available.
10) The circulatory system in human body takes care of
i) Transport of oxygen, carbon dioxide, food and excretory products.
ii) It consists of heart, blood and blood vessels.
iii) In humans, excretory products are removed by nephrons.
iv) The heart pumps fresh blood to every part of the body.
v) Heart prevents the mixing up of fresh oxygen-rich blood with the carbon dioxide containing blood.
vi) Amphibians and reptiles have 3 chambered heart whereas fishes have two chambered heart.
vii) Humans have 4-chambered heart.
11) Blood pressure is measured by sphygmomanometer.
12) High blood pressure called hypertension is caused by constriction of arterioles.
a) It can lead to rupture of an a artery or internal bleeding.
13) The property of blood clotting is due to accumulation of platelets at the point of injury.
CONTROL AND COORDINATION
1) Control and coordination are the functions of the nervous system and hormones.
2) Response of nervous system is classified into :
i) Reflex action
ii) Voluntary action and
iii) Involuntary action
3) The nervous system uses electrical impulses to transmit messages.
4) Nervous system acquires information from sense organs and reacts through muscles.
5) Hormones produced in one part of an organism move to another part to achieve the desired effect.
6) A feedback mechanism regulates the action of hormones.
7) ‘ Touch me not ‘ plant is an example of chemical coordination inside the plant cell.
REPRODUCTION IN ORGANISMS