Biology Entrance Exam

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What is Synapse? Example of Neurotransmitters

What is Synapse

Synapse is the junction between two neurons or a neuron and a muscle cell or a neuron and a glandular cell. When electric impulses from the axon reach the synaptic knob, certain chemical substances are secreted from there to the synaptic cleft. These chemical substances are called neurotransmitters. They stimulate the adjacent dendrite or cell and new electric impulses are generated. Synapse helps to regulate the speed and direction of impulses.


 Example of neurotransmitters : Acetylcholine and Dopamine

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Structure and Function of Neuron

Neuron or nerve cell is the basic structural unit of the nervous system. Like all other cells, the neuron has a cell membrane, cytoplasm and nucleus.


Axon

 • Longest filament from the cell body. 

• Carries impulses from the cell body to outside.

Axonite 

• Branches of axon.

 • Carries impulses to the synaptic knob.

Dendrite 

• Branches of Dendron

. • Part that receives impulses from adjacent neuron.

Dendron 

• Short filament from the cell body. 

• Carries impulses from dendrites to the cell body.

Synaptic knob

 • Tip of axonite

. • Secretes neurotransmitter.

Schwann cell

 • Encircles the axon.

Axons of most of the neurons are repeatedly encircled by myelin, a membrane containing lipid. This is called myelin sheath.

 Nerve is a group of axons. Myelin sheath in the nerves is formed of Schwann cells. Myelin sheath in the brain and the spinal cord is formed of specialized cells called oligodendrocytes. The myelin sheath has a shiny white colour. The part of the brain and the spinal cord where myelinated nerve cells are present in abundance is called white matter and the part where non-myelinated nerves cells are present is called grey matter. 

The major functions of the myelin sheath are to provide nutrients and oxygen to the axon, accelerate impulses, act as an electric insulator and protect the axon from external shocks. 


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MCQ on Ecology and Environment

MCQ on Ecology and Environment
1. Increase in concentration of the toxicant at successive trophic level is known as
A. Biotransfomation
B. Biomagnification
C. Biogeochemical cycling 
D. Biodeterioration
Ans: B.Biomagnification
2.Which one of the following combination is wrong?
A.Rio convention – Air pollution
B. Kyoto Protocol – Climate Change
C.Montreal Protocol- Ozone Depletion
D. Ramsar convention-Wetland conservation
Ans: A.Rio convention – Air pollution
3. Example of secondary air pollutant is/ are
A. Smog
B. PAN
C. O3
D.All of these
Ans: D.All of these
4. Ionosphere is between  

A. Stratospere and mesosphere
B. Mesospere and thermosphere
C. Trophosphere and stratospere
D. Trospere and thermospere
Ans: B.Mesospere and thermosphere
5. Photochemical smog always contains
 A. O3
B. CO
C. PAN
D. All of these
Ans: A. O3
6. The polluting strength of sewage is usually characterized by
A. Eutrophication
B.Nitrogen content
C.Ozone content
D. BOD
Ans:D. BOD
7. The term ecosystem was coined by
 A. E. haeckel
B. E. Warming
C.E P Odum
D. AG Tansley
                                                                                                    Ans: D. AG Tansley
8.How many hotspot of biodiversity in the world have been identified till date by Norman Myers?
 A. 17
B. 34
C. 25
D. 43
                                                                                                                                                 Ans: B. 34 
9. What is the National aquatic animal of India?
A. Blue whale
B. Sea horse
C. Gangetic Shark
D. River Dolphin
                                                                                                       Ans: D. River Dolphin  
10. Depletion of which gas in the atmosphere can lead to an increased incidence of skin cancers?
 A. Ammonia
B. Ozone
C.Methane
D. Nitrous oxide
                                                                                                                  Ans: B. Ozone  
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Difference between Bacteria and Viruses (Bacteria vs Virus)


Bacteria vs Viruses
Bacteria
Viruses
Most bacteria are either saprophytes or parasites. Certain bacteria, e.g., Rickettsia and Chlamydias are obligate intracellular parasites
Viruses are obligate intracellular parasites
Plasma membrane present
Plasma membrane absent
Binary fission occurs
Binary fission absent
Most bacteria cannot pass through bacteriological filters. A few, e.g., rickettsias and chlamydias are filterable
They can pass through bacteriological filters
Possess both DNA and RNA
Either DNA or RNA, but never both
ATP generating metabolism is present
Absent
Ribosomes present
Ribosome absent
They are sensitive to antibiotics
Insensitive to the available antibiotics

Learn more: 15 Difference between Bacteria and Virus
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Types of Anaemia and its cause


Types of Anaemia and its cause
Types of Anaemia and its cause
1. Microcytic anemia: Deficiency of iron
2. Megaloblastic anemia: Deficiency of folic acid and Vit B12
3. Pernicious anaemia: Deficiency of B12
4. Haemorrhagic anaemia: Excessive bleeding
5. Hemolytic anaemia: Haemolysis (Rupture of RBCs)
6. Aplastic anemia: Destruction of bone marrow
7. Nutritional anaemia: Inadequate food
8. Sickle cell anaemia: Gene mutation
9. Thalassemia: Gene mutation
10. Septicemia: Blood poisoning
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