Question

Why are Syngamy and meiosis processes in the life cycles of organisms ?

What function do you think the spores have in physarum?

How do myxamoebae aggregate?

How does a pseudoplasmodium differ from a true plasmodium? What function does the E. Cool have in the culture of dictyostelium?

Answer 1

Syngamy - the fusion of two cells, or of their nuclei during fertilisation, in reproduction.

Meiosis - process of production of two haploid gametes from diploid mother cell.

These processes occur in the life cycle of living organisms to ensure variation which is important for evolution and survival of a healthy population.

Spores are the reproductive stage of Physarum. Spores can remain dormant for years if need be. However, when environmental conditions are favorable for growth, the spores germinateand release either flagellated or amoeboid swarm cells (motile stage); the swarm cells then fuse together to form a new plasmodium(the vegetative stage of Physarum).

During aggregation, starvation initiates the creation of a biochemical machinery that includes glycoproteins and adenylyl cyclase. The glycoproteins allow for cell-cell adhesion, and adenylyl cyclase creates cyclic AMP. Cyclic AMP is secreted by the amoebae to attract neighboring cells to a central location. As they move toward the signal, they bump into each other and stick together by the use of glycoprotein adhesion molecules.

True plasmodium:- where individual cells come together and fuse to form one large multinucleate individual. E.g.. Plasmodium, such as those of Fuligo septica.

Pseudoplasmodium:- the amoebae aggregate but maintain their individuality so that they do not form a true plasmodium. Such aggregations of individual amoebae are called pseudoplasmodia.