What is the reason that one petal of mediterranean orchid flower resembles in size, colour and markings of the female bee?Explain.

A colloidal solution is a type of mixture which consists of particles whose size varies between 1 and 1000 nanometres. In colloidal solution the particles are distributed evenly. During this process the particles do not settle down. This is one of the best know thing about colloidal solutions. Properties of colloids and their variation are a well-known area ever since the primitive age. The best example to prove their familiarity with us is that we know from very early times that coagulation of milk results in the formation of curd. Physical properties of colloids 1. The nature of the colloidal solution is heterogeneous i.e. unlike. These solutions dwell with two different phases : • Dispersed medium Dispersed phase. 2. Despite the fact that colloidal dispersions are unlike in description (nature), yet the dispersed fragments are not detectable by the human eye. This is due to the microscopic size of the particles in the solution. 3. The colour of the colloidal dispersion is determined by particles in the solution based on their size. The wavelengths of light that is absorbed will be longer ifthe size of the particle is large. 4. As a result of its size, the colloidal fragments can easily be passed through a traditional filter paper. However, these particles can be filtered by using membranes such as animal, cellophane, and ultrafilters. What are colloidal solution particle.

A colloidal solution is a type of mixture which consists of particles whose size varies between 1 and 1000 nanometres. In colloidal solution the particles are distributed evenly. During this process the particles do not settle down. This is one of the best know thing about colloidal solutions. Properties of colloids and their variation are a well-known area ever since the primitive age. The best example to prove their familiarity with us is that we know from very early times that coagulation of milk results in the formation of curd. Physical properties of colloids 1. The nature of the colloidal solution is heterogeneous i.e. unlike. These solutions dwell with two different phases : • Dispersed medium Dispersed phase. 2. Despite the fact that colloidal dispersions are unlike in description (nature), yet the dispersed fragments are not detectabJe by the human eye. This is due to the microscopic size of the particles in the solution. 3. The colour of the colloidal dispersion is determined by particles in the solution based on their size. The wavelengths of light that is absorbed will be longer ifthe size of the particle is large. 4. As a result of its size, the colloidal fragments can easily be passed through a traditional filter paper. However, these particles can be filtered by using membranes such as animal, cellophane, and ultrafilters. What type of phases of colloidal solutions ?

Long Answer Questions Five mark Each QUESTIONS FROM CBSE BOARD EXAMINATIONS : A flower of tomato plant following the process of sexual reproduction produces 240 viable seeds. Answer the following questions giving reasons: (a) What is the minimum number of pollen grains that must have been involved in the pollination of its pistil? (b) What would have been the minimum number of ovules present in the ovary? (c) How many megaspore mother cells were involved? (d) What is the minimum number of microspore mother cells involved in the above case? (e) How many male gametes were involved in this case?

• Take three iron nails and clean them by rubbing with sand paper. • Take two test tubes marked as (A) and (B). In each test | tube, take about 10 ml copper sulphate solution. • Tie two iron nails with a thread and immerse them 'carefully in the copper sulphate solution in test tube B for about 20 minutes [Fig. (a)]. Keep one iron nail aside for comparison. • After 20 minutes, take out the iron nails from the copper sulphate solution. • Compare the intensity of the blue colour of copper sulphate solutions in test tubes (A) and (B) (Fig. (b)]. Also, compare the colour of the iron nails dipped in the copper sulphate solution with the one kept aside [Fig. - (b)]. On the basis of activity , give the answers of th following questions : What is the colour of copper sulphat solution in test tube A ?

Long Answer Questions Five mark QUESTIONS FROM CBSE BOARD EXAMINATIONS : (a) Asa senior biology student, you have been asked to demonstrate to the students of secondary level in your school, the procedure(s) that shall ensure cross pollination in a hermaphrodite flower. List the different steps that you would suggest and provide reasons for each one of them.