Slime molds and sex

Outline

Eukaryotes

• nuclear envelope
• cytoskeleton
• membrane-bound organelles

Dictiosteliomycota

Cells -- myxamoebas with no cell walls or flagella, have centrioles and normal mitosis

Ecology -- heterotrophs, in dead logs, moist soil -- eat bacteria etc

Reproduction

asexual reproduction

mitotic cell division

(form microcysts if too dry)

dispersal as spores -- form pseudoplasmodium and sporangium and spores

sexual reproduction

• sexual reproduction -- new individuals with different genes

  switching between diploid and haploid

  two myxamoebas merge (fertilization) and form macrocyst, which undergoes meiosis and later germinates -- haplontic life cycle

Myxomycota

Cells

myxamoebas, swarm cells, or a multinucleate plasmodium

no cell walls, have centrioles and normal mitosis

Ecology

dead logs, moist soil -- eat bacteria etc

Life cycle

diploid plasmodium, can form sclerotium

sporangium produces haploid spores

spores become myxamoebas or swarm cells, which can reproduce asexually or become microcysts

haploid cells fuse and form zygote, which becomes plasmodium

 Life cycles -- three basic kinds, which differ in when mitosis occurs

Haplontic

mitosis in haploid phase

Diplontic

mitosis in diploid phase

Diplohaplontic

mitosis in both phases

can have isomorphic or heteromorphic phases

if heteromorphic, either phase can be dominant

 

Vocabulary

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