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Lecture19_Protists - Gametophyte = A haploid multicellular...

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Protists I. What are the protists? Analyzing the tree of life Protists = all eukaryotes except plants, animals, fungi • where is the common ancestor of all protists? • where did the nuclear envelope originate? • where did the (2-membraned) chloroplast originate? • where did multicellularity originate? II. Themes in the evolution of protists A. Food 1. Absorptive lifestyles 2. Photosynthesis note huge diversity in pigments and in wavelengths used; distinct pigments in distinct lineages 3. Ingestive feeding (“eating”; predation) B. Sex 1. Meiosis and fusion of haploid gametes to form a diploid zygote (offspring) 2. Variation in life cycles = the sequence of events in the life of an individual Alternation of generations = presence of multicellular diploid and haploid individuals Sporophyte = A multicellular, diploid individual that produces haploid spores by meiosis; these spores germinate and divide by mitosis to form a haploid gametophyte
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Unformatted text preview: Gametophyte = A haploid, multicellular individual that produces gametes by mitosis; these gametes fuse to form a diploid cell (a zygote) that develops into a sporophyte Spore = a single cell produced by mitosis or meiosis that is capable of developing into an adult organism (without fusing with another cell) III. Origins of mitochondria and chloroplasts A. Function of these two organelles Mitochondria produce ATP Chloroplast function is a little like a B. Endosymbiotic theory of origin Is the endosymbiosis hypothesis correct? Data Prediction Observation Size of organelles Number of membranes Genes present? Organelle replication Organelle chromosome structure Organelle genes most similar to …? Contemporary examples? • Which type of evidence is most convincing, and why? Secondary endosymbiosis = acquisition of a chloroplast from a eukaryote that already has a chloroplast...
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Lecture19_Protists - Gametophyte = A haploid multicellular...

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