Concept explainers
To analyze :
The organism that is motile and has diploid nuclei but no separate cells.
Introduction :
Slime molds are
Answer to Problem 34A
The correct term is plasmodium.
Explanation of Solution
The somatic phase of acellular slime molds is a diploid multinucleate plasmodium. Plasmodium is formed because cell wall formation is not followed by the division of the nucleus. All the nuclei in the plasmodium divide simultaneously.
The multinucleate protoplasm of the sporangium undergoes meiotic division to form uninucleate spores. The sporangia burst and release the spores. The spore falls on the suitable substratum and releases either biflagellate spindle-shaped swarm cell or non-flagellated myxamoeba. Myxamoebae fuse in pairs while swarm cells fuse in pairs at the posterior non-flagellate ends respectively, to form a diploid zygote.
The zygote grows in size. The diploid nucleus of the zygote divides without the formation of cell walls. It changes into a multinucleate amoeboid structure known as plasmodium. The plasmodium, on maturity, bears sporangium, and the whole cycle repeats.
In the life cycle of acellular slime molds, the zygote forms plasmodium. It is a motile and multinucleate organism with no separate cells. It is because the nuclear division is not followed by wall formation or cytokinesis.
Chapter 19 Solutions
Biology Illinois Edition (Glencoe Science)
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