Presentation1 cleavage DB.pptx

cleavage ppt by rohail muhammadzai zolologist

1. CLEAVAGE TYPES PATTERN HOLOLBLASTIC VS MEROBLASTIC PURPOSE CHARACTERISTICS

2. Definition of Cleavage Cleavage is defined as the division of cells that takes place during early embryology . After fertilization, the development of a multicellular organism proceeds by a process called cleavage, a series of mitotic divisions whereby the enormous volume of egg cytoplasm is divided into numerous smaller, nucleated cells.

3. The different cells derived from cleavage are called blastomeres and form a compact mass called the morula . Cleavage ends with the formation of the blastula . About… Cleavage

4. Process of Cleavage

5. Types of eggs according to distribution of yolk and types of cleavage in different Organisms

6. Types of cleavage Holoblastic ( complete). I solecithal,alecithal,mesolecithal ) Meroblastic ( incomplete/partial ) T elolecithal,centrolecithal )

7. Subypes and Pattern of Cleavage

8. Pattern of cleavages in different chordates

9. Holoblastic vs Meroblastic Cleavage Holoblastic cleavage is defined as a type of cleavage that takes place in the embryonic cells that contain a moderate or sparse of yolk in the ovum. Meroblastic cleavage is defined as a type of cleavage that takes place in a fertilized egg cell with a large amount of yolk and undergoes partial cleavage.  Mitosis No mitosis occurs in holoblastic cleavage. Mitosis takes place in meroblastic cleavage. Amount of Yolk in the Egg Smaller amount of yolk is present in eggs that show holoblastic cleavage. Larger amount of yolk is present in eggs that show meroblastic cleavage.  Type of Cleavage Holoblastic cleavage results in a complete cleavage. Meroblastic cleavage results in a partial cleavage. Subtypes Bilateral holoblastic, radial holoblastic, rotational holoblastic and spiral holoblastic are types of holoblastic cleavage. Discoidal cleavage and superficial cleavage are types of meroblastic cleavage. Synonyms Holoblastic cleavage – Total cleavage and complete cleavage are synonyms of holoblastic cleavage. Incomplete cleavage or partial cleavages are synonyms for meroblastic cleavage. Examples Most of the deuterostomes and protostomes such as amphibians, mammals, echinoderms, annelids, flatworms, nematodes, etc show holoblastic cleavage. Monotremes , avians , reptiles show meroblastic cleavage.

10. What are the Similarities Between Holoblastic and Meroblastic Cleavage? Both Holoblastic and Meroblastic Cleavage are two types of cleavages. Both take place during the embryonic stage. Both are triggered by cyclin-dependent kinase complex. Both cleavages end with the formation of the blastula.

11. Purpose of cleavage Cells divide to grow To work properly, that body needs well-defined axes (such as head and tail).