General Instructions:
- Copy the given assignment of practical in fair practical copy of biology.
- Make the use of black pen for heading and sub-headings and blue pen for writing other content.
- Work should be presentable.
- Make well labelled and proper diagram as provided in this assignment.
Spot No.6
Aim: To study T.S of blastula through permanent slides.
Materials required: Permanent slide of T.S of blastula, Compound Microscope.
Theory: After fertilization zygote is formed which results in the formation of blastula through the process of cleavage where a cell divides and makes copy of its DNA and passes it to next generation.
The process of cell division continues attaining two-celled, four-celled, eight-celled stage and the division continues further also. After about seven cell divisions, the embryo has become a blastula consisting of at least 128 cells. The blastula has an empty space called as blastocoel which is its main feature. During the development of blastula following two different types of cell are present.
- Trophoblast: The outer layer of cell that eventually develops in placenta
- Inner mass: The inner layer of cell which contains embryonic stem cell and will give rise to every single cell of body.
Procedure:
- Clean the slide and microscope’s eye and objective lens and stage with the help of cleaning paper.
- Place slide in the stage of microscope. Observe it under low power of microscope followed by high power.
Observations:
- Blastula appears as a spherical mass of about 64 cells.
- It is composed of two parts namely trophoblast and inner cell mass.
- It is found having fluid filed cavity called as blastocoel.
- The inner cell mass forms embryo.
- The side of blastocyst to which the inner cell mass is attached is called as embryonic or animal pole, while the opposite side is called as abembryonic or vegetative pole.
Precautions
- Always handle microscope carefully.
- Observe slide under low power followed by high power.