ch.28 eukaryotic diversity
TRANSCRIPT
The Origins of Eukaryotic Diversity
Chapter 28
Protists
• 1st eukaryotes
• Protists lived 2 billion years before the evolution of plants, fungi & animals
• Most diverse group of eukaryotes
• Live anywhere there is water
• Protists could include as many as 20 kingdoms
Definition of Protists
• Mostly single-cellular
• Some colonial and multicellular
• Eukaryotic
Protist Nutrition
• Aerobic, use mitochrondria
• Can be– Photoautotrophs (algae)– Heterotrophs (protozoa)– Mixotrophs
Protist Motility
• Cilia or flagella– Most have one at some point in life– 9+2 arrangement of microtubules
Trends toward the evolution of eukaryotes
• Multicellular prokaryotes
• Prokaryotic communities
• Compartmentalization of functions within cell
Serial Endosymbiosis
Secondary Endosymbiosis
A hypothetical history of plastids in the photosynthetic eukaryotes
Traditional hypothesis for how the three domains of life are related
An alternative hypothesis for how the three domains of life are related
The kingdom Protista problem
A tentative phylogeny of eukaryotes
Evolution of Multicellularity
• Eukaryotes– Organization allowed for development of more
complex structures– Opportunities to specialize & adapt
• Multicellularity evolved several times– Multicellular algae (seaweeds)– Ancestors of plants, fungi & animals
Survey of Protistan Diversity
Diplomonadida & Parabasala
• Lack mitochondria
Giardia lamblia Trichomonas vaginalis
Euglenazoa
• Photosynthetic & heterotrophic flagellates
Alveolata:unicellular protists w/ subcellular cavities
• Dinoflagellates
Alveolata:unicellular protists w/ subcellular cavities
• Apicomplexans
Alveolata:unicellular protists w/ subcellular cavities
• Ciliates
Ciliates: Stentor (left), Paramecium (right)
Conjugation and genetic recombination in Paramecium caudatum
Stramenopila:Water molds & Heterokont algae
“hairy” flagella
• Oomycota (water molds)– Resemble fungi (but not closely related)– Cell walls made of cellulose– Diploid life cycle
The life cycle of a water mold
• Heterokont algae– 3-membraned plastids
– Types• Diatoms• Golden algae• Brown algae
Stramenopila:Water molds & Heterokont algae
“hairy” flagella
• Diatoms– Box-like silica walls– Freshwater & marine plankton
Stramenopila:Water molds & Heterokont algae
“hairy” flagella
• Golden algae
• (Chrysophyta)– Yellow and brown
pigments • (carotene and
xanthophyll)
– Can form resistant cysts
Stramenopila:Water molds & Heterokont algae
“hairy” flagella
• Brown algae (Phaeophyta)– Largest & most complex algae– Brown pigments
Stramenopila:Water molds & Heterokont algae
“hairy” flagella
Alternation of Generations
Rhodophyta: Red Algae
• Lack flagella
• Phycoerythrin – red pigment (a phycobilin)
• Can absorb light in deep water
• Most are marine
Chlorophyta: Green Algae• Share common ancestor with plants• Most are freshwater• Unicellular, colonial & multicellular species• Some are seaweeds• Form lichens
Protists that Use Pseudopodia
• Rhizopods (amoebas)– Move and feed w/ psuedopodia
• Actinopods – Axopodia help cell float and feed by phagocytosis
• Foraminferans – Porous, calcareous shells– Cytoplasmic strands extend through pores and
function in swimming, shell formation & feeding
Use of pseudopodia for feeding: Amoeba
Actinopods: Heliozoan (left), radiolarian (right)
Foraminiferan
Mycetozoa: Slime Molds
• Resemble fungi b/c of convergent evolution (not actually related)
• Plasmodial slime molds– Heterotrophic– Grow on rotting plant material– Feeding stage is called a plasmodium
• Multinucleate amoeboid mass
• Cellular slime molds– Feeding stage: haploid amoeboid cells– In absence of food: form a slug-like mass
Plasmodial slime mold
Figure 28.29 The life cycle of a plasmodial slime mold, such as Physarum
The life cycle of a cellular slime mold (Dictyostelium)