Blastula under microscope

Small-spotted catshark. [a] Cartilaginous fish: their skeleton is made from cartilage rather than bone. There are other cartilaginous fish, such as sturgeon, that are not classified as chondrichthyans but as chondrostei within the predominantly ‘bony’ fish. See here for a See here for a See here for a This page outlines the embryonic development of the major group of cartilaginous fish known as chondrichthyans, the main subgroup of which is the elasmobranches which comprises sharks and rays. The following description is based primarily on the small-spotted catshark ( Scyliorhinus canicula, also known as the lesser-spotted dogfish) which is thought to be fairly typical of elasmobranch embryonic development. Cartilaginous fish: their skeleton is made from cartilage rather than bone. There are other cartilaginous fish, such as sturgeon, that are not classified as chondrichthyans but as chondrostei within the predominantly ‘bony’ fish. See here for a See here for a See here for a Egg and fertilisation Catshark egg, sometimes known as a ‘Mermaid’s Purse’. Note the very long tendrils which can be up to 1m. [b] Elasmobranch eggs are generally quite large and contained within a collagen-based case. The female pronucleus is inside a germinal disc which is orange and located on the outer surface of the yolk, the bulk of which is typically pale yellow-green, except for immediately around the germinal disc where it is white. Figure 1. Schematic of catshark egg. The egg is fertilised w...

After completing the lab, the student will be able to: • Observe the stages of mitosis in whitefish blastula cells; • Identify and describe the stages of mitosis in whitefish blastula cell. Activity 1: Pre-Assessment • List three reasons why organisms need to produce new cells. • What cellular structures must be replicated to ensure that new cells are functional after cell division? • Why are karyokinesis and cytokinesis distinct steps in cell division? • Discuss the answers to the questions with a partner (think, pair, share) and then the class. Activity 1: Observe the Stages of Mitosis in the Blastula of a Whitefish A fundamental property of somatic (nonreproductive or body) cells of multicellular organisms is mitosis which basically provides new cells for growth and regeneration or replacement of dying and dead cells of the living body. A simple example in humans is our continuous shedding of skin cells and their replacement by new skin cells. Mitosis is also vital for development. Many single-celled organisms depend on mitosis as their sole or primary way of asexual reproduction. This asexual reproduction is distinct from multicellular organisms which undergo meiosis to produce reproductive cells (sperms or eggs). Cell division involves the chromosomes and genes of the dividing cells which are duplicated and passed on to the new cells or daughter cells and is the reason why for example, all these new skin cells are genetically identical. Mitosis is a controlled process...