Difference between Tropic Movements and Nastic Movements – Comparison Table

Tropic vs Nastic Movments

Tropic Movements vs Nastic Movements
Similarities and Differences between Tropic Movements and Nastic Movements in Plants

Tropic movements and Nastic movements are the two types of induced or paratonic movements of curvature in plants.

Tropic movements: The paratonic (induced) movement of growth is called tropic movements. Here the stimuli are external and unidirectional. Example: phototropic movements (movement towards the light) geotropic movements (movement towards gravity), chemotropic movements (movement towards chemicals) etc.

What is Phototropism

Nastic movements: The paratonic movements of variations are called nastic movements. Here the stimuli are external and diffused (not unidirectional). Example: nyctinastic movements (movements in response to darkness), Seismonastic movements or Thigmonastic movements (movements in response to touch) etc.

What is Nastic Movment

The present post discusses the Similarities and Differences between Tropic Movements and Nastic Movements in Plants with a Comparison Table.

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Biostatistics Study Materials

Statistical Data /Variables – Types and Classification (Biostatistics Short Notes)

What is Data or Variable

Statistical Data / Variables – Introduction
(Classification of Statistical Data / Variable – Numeric vs Categorical)

What is ‘data’ or ‘variable’?

Ø  Data is a set of values of qualitative or quantitative variables.

Ø  In biostatistics (also in statistics) data are the individual observations.

Ø  The scientific investigations involve observations on variables.

Ø  The observations made on these variables are obtained in the form of ‘data’.

Ø  Variable is a quantity or characteristic which can ‘vary from one individual to another’.

Ø  Example: Consider the characteristic ‘weight’ of individuals and let it be denoted by the letter ‘N’. The value of ‘N’ varies from one individual to another and thus, ‘N’ is a variable.

Ø  Data and variable are not exact but used frequently as synonyms.

Ø  The variables can also be called as ‘data items’.

Ø  Majority of the statistical analysis are done on variables.

Type of Variables in Statistics

Statistical variables can be classified based on two criterion (I) Nature of Variables and (II) Source of variables

I. Classification of variable based on Nature of Variables

Ø  Based on the nature of variables, statistical variables can be classified to TWO major categories such as (1) Numerical and (2) Categorical.

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Phase Contrast Microscopy – Optical Components, Working Principle and Applications (Short Notes with PPT)

Applications of phase contrast microscope

Phase Contrast Microscopy
(Optical Components, Working Principle and Applications of Phase Contrast Microscope)

Working Principle of an Ordinary Microscope:

contrast in light microscopyIn an ordinary microscope, the object is viewed due to differences in colour intensities of the specimen. To create the colour intensities, the specimen is first stained with suitable dyes which will impart specific colour. In an ordinary microscope, the contrast is obtained when the light rays pass through a stained specimen because different stains absorb different amounts of light. These differential absorption properties of stained specimen modify the intensity or amplitude of the light waves transmitted by different regions of the cells and this ultimately creates contrast in the image. Thus, staining is essential to create contrast in an ordinary microscope. Moreover, the unstained specimen cannot be observed through an ordinary microscope.

Download the PPT (Phase Contrast Microscopy)

Why Phase Contrast Microscope?

The Phase Contrast Microscope is used to visualize unstained living cells. Most of the stains or staining procedures will kill the cells.  Phase contrast microscopy enables the visualization of living cells and life events.

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biological chemistry

Titration Curve of a Weak Acid and its pKa (Biochemistry Notes)

Acetic Acid titration Curve

Titration Curve of a Weak Acid and its pKa
(Titration, Titration Curve, Titration Curve of Acetic Acid and its Significance)

What is Titration?

Titration is a method to determine the concentration of a dissolved substance (analyte or titrand) in a known volume by reacting it with another substance of known concentration and volume (titrant). The volume of the reactants plays a crucial role in the titration and thus the titration is better called as ‘volumetric analysis’.

There are different types of titrations in which the Acid-Base Titration is the most common one. The acid-base titration is used to determine the amount (concentration) of an acid in a given solution. In an acid-base titration, a known volume of acid (of unknown concentration) is titrated against a solution of strong base (usually NaOH) of known concentration in the presence of an indicator. After the titration, the concentration of the acid in the sample is calculated using the concept N1V1 = N2V2.


N1 – Normality of the unknown acid

N2 – Normality of the known base

V1 – Volume of unknown acid

V2 – Volume of the known base

What is Titration Curve?

The titration curve is a graphical representation of a titration in which the volume of titrant is plotted on X-axis (as the independent variable) and the pH of the solution is plotted on the Y-axis (as the dependent variable).

In simple terms, the titration curve is the plot of pH of the analyte (titrand) versus the volume of the titrant added as the titration progresses.

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biological chemistry

Proton Hopping in Water (Grotthuss Mechanism)

What is Proton Hopping

Proton Hopping in Water
(The Grotthuss Mechanism)

Proton Hopping is the process of diffusion of protons (H⁺ ions) through the network of hydrogen-bonded water molecules in the liquid water. Proton hopping is also called as Grotthuss mechanism, named after the discoverer Theodor Grotthuss. The net result of proton hopping is the fast movement of H⁺ ions in water than any other dissolved cations such as Na⁺ or K⁺. Let’s see how proton hopping occurs in water.

Water has a slight tendency of ionization. The H2O molecules can ionize into H⁺ and OH¯ ions as in the equation (1).

ions in water

The ionization reaction of water can be described by its equilibrium constant. The equilibrium constant (Keq) of the ionization of water at 25°C is calculated as 1.8 X 10¯16 M. The equilibrium constant and the concentration of H⁺ and OH¯ ions formed as a result of the ionization of H2O molecules are responsible for the pH of water.

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