The Origins of Eukaryotic Diversity

Transcription

1 The Origins of Eukaryotic Diversity

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3 Introduction to the protists Kingdom Protista split into as many as 20 kingdoms In the five kingdom system, anything that wasn t a prokaryote, plant, animal, or fungus was grouped as a protist.

4 Protists are the most diverse of all eukaryotes.

5 General Description of Protists -Very few general characteristics can be cited without many exceptions. -Most protists are unicellular, but some are colonial or even multicellular. -Various modes of nutrition, mobility, etc. -Protists are sort of a dumping ground for anything that doesn t belong.

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7 Nutrition Protists may be autotrophic, heterotrophic, or mixotrophic organisms. Mixotrophic organisms combine photosynthesis and food ingestion. Photosynthetic: algae (plant-like) Ingestive: protozoa (animal-like) Absorptive: fungus-like Motility Most protists are motile, with either flagella or cilia. Some move by gliding or by extensions. Note: Eukaryotic and prokaryotic flagella are not homologous structures.

8 Life Cycle -A few protists are entirely asexual. -Most reproduce sexually by meiosis and then go on to reproduce asexually. -Whether haploid or diploid dominates varies. -Cysts form at some point during the life cycle of many protists. Cysts are resistant cells that are capable of surviving harsh conditions. -There can be alternation of generations in many taxa. Habitat -Most protists are aquatic (but some in soil). -Plankton are organisms that drift or swim near the surface of the water. Phytoplankton are responsible for half of the world s photosynthesis and O 2 production.

9 Origin and early diversification of eukaryotes Endomembranes contributed to larger, more complex cells Endomembranes evolved from in-foldings of prokaryotic membranes. Endomembranes allowed for compartmentalization of cellular functions. This contributed to the evolution of increasing complexity and development of new functions.

10 Euglenozoa Characterized by one or two flagella and paramylon which is a glucose polymer. Example: Euglena. Most members of this group are photosynthetic (autotrophs). However, Kinetoplastids (e.g., Trypanosoma) cause sleeping sickness.

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12 Dinoflagellate (phytoplankton) blooms cause red tide and produce toxins. Example: - Pfisteria acts as a carnivore: kills fish, feeds on flesh. -Others form the basis of many food chains in the oceans and function as photosynthetic plankton. -Others are bioluminescent and produce light when disturbed to attract fish that eat predators that eat the Dinoflagellates.

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14 Red Tide: A bloom of dinoflagellates

15 Apicomplexa are animal parasites with complex life cycles involving more than one host. - e.g., Plasmodium causes malaria.

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17 -Ciliophora use cilia for movement. - e.g., Stentor and paramecium. -These ciliates have one macronucleus and several micronuclei.

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21 Water mold: Oogonium

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24 Diatom

25 An example of diatom diversity.

26 More diatoms.

27 A golden algal species.

28 Brown algae

29 Algal life cycles: Alternation of generations Both meiotic/sexual and mitotic/asexual stages have multicellular forms. These forms can be very different (heteromorphic) or similar (isomorphic) in appearance. E.g., plants vs. Clamydomonas

30 Rhodophyta (red algae) -No flagella -Red non-chlorophyll pigments similar to those in cyanobacteria.

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32 Chlorophyta (green algae) Characterized by green chloroplasts, similar to those found in plants. Exist as unicellular (Chlamydomonas), colonial (Volvox), or multi-cellular (Caulerpa) organisms. These are the forerunners of early plants. Multi-cellular chlorophyta (Chara-like species) evolved to become the higher plants.

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37 Chara- very closely related to first land plants

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42 Some protists use pseudopodia for movement and feeding. Pseudopodia are cellular extensions that may bulge from almost anywhere on the cell. Typically heterotrophs. Best known examples are amoebas, Rhizopoda Foraminifera.

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