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Kingdom: Protists Domain Eukarya Domain Bacteria Archaea Eukarya
Common ancestor
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General characteristics
Classification criteria eukaryotes not animal, plant or fungi That’s more of what they’re not & not what they are!
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Protista was defined partly by structural level (mostly unicellular eukaryotes) and partly by exclusion from the definitions of plants, fungi, or animals. However, this created a group ranging from single- celled microscopic members, simple multicellular forms, and complex giants like seaweeds. Fig. 28.1 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
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PROTISTS Asexual Mitosis and cytokinesis
REPRODUCTION Asexual Mitosis and cytokinesis Budding – similar to mitosis except daughter cell is smaller than parent Schizogony – nucleus divides many times and cytoplasm divides to form as many daughter cells as there are nuclei 4
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PROTISTS SEXUALLY Meiosis – special nuclear division to reduce chromosome number to haploid Union of gametes = diploid zygote Syngamy – fertilization between two individuals Autogamy – two gametes fuse within one organism Parthenogenesis – development of organism from gamete without fertilization Conjugation – exchange of nuclear material between two individuals 5
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Protist Diversity The full spectrum of modes of life
from unicellular to multicellular autotrophic to heterotrophic asexual to sexual reproduction pathogenic to beneficial sessile to mobile
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Mobility How Protists move flagellum cilia pseudopod
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Protist Diversity Animal-like Protists heterotrophs, predators Amoeba
Paramecium with food vacuoles stained red Animal-like Protists heterotrophs, predators Amoeba Paramecium Stentor Amoeba ingesting a Paramecium
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Protist Diversity Plant-like Protists autotrophs, photosynthesis
Euglena algae diatoms
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Protist Diversity Parasitic & pathogenic Protists malaria Giardia
trypanosomes Plasmodium African Sleeping Sickness and South American Chagas Disease Giardia Trypanosoma
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Protist Diversity Beneficial & necessary Protists phytoplankton
small algae + diatoms much of the world’s photosynthesis produces ~90% of atmospheric oxygen zooplankton heterotrophic protists + animals key ecological role at base of marine food web Mmmmmm! Sounds like breakfast!
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Brown Algae Brown algae are the largest and most complex algae
All are multicellular, and most are marine Brown algae include many species commonly called “seaweeds” Brown algae have the most complex multicellular anatomy of all algae
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Giant seaweeds called kelps live in deep parts of the ocean
The algal body is plantlike but lacks true roots, stems, and leaves and is called a thallus The rootlike holdfast anchors the stemlike stipe, which in turn supports the leaflike blades
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Fig Blade Stipe Figure Seaweeds: adapted to life at the ocean’s margins Holdfast
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Oomycetes (Water Molds and Their Relatives)
Oomycetes include water molds, white rusts, and downy mildews They were once considered fungi based on morphological studies Most oomycetes are decomposers or parasites They have filaments (hyphae) that facilitate nutrient uptake Their ecological impact can be great, as in Phytophthora infestans causing potato blight
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Kingdom: Fungi Domain Eukarya 2007-2008 Domain Bacteria Archaea
Common ancestor
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General characteristics
Classification criteria eukaryotes heterotrophs feed by absorption mostly multicellular except unicellular yeasts cell wall chitin rigid polysaccharide sexual & asexual reproduction Nutrition and Reproduction
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Fungal Structure Fungal body Cells Cell wall mycelium multiple nuclei
thread-like cells hyphae Cells multiple nuclei Cell wall chitin just like crab shells Chitin
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Fungi can produce spores from different types of life cycles
Fungi propagate themselves by producing vast numbers of spores, either sexually or asexually Fungi can produce spores from different types of life cycles Fig. 31-2 Reproductive structure Spore-producing structures Hyphae Mycelium 20 µm
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Aaaaah, structure–function relationship!
Internal structure chitin cell wall septum Eukaryotic cells long, thread-like cells filamentous incomplete divisions between cells septum Coenocytic fungi lack septa multiple nuclei pore nuclei Aaaaah, structure–function relationship!
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Fungi live IN their food! It’s like you living in Chocolate cake!
Modes of Nutrition Heterotrophic secrete digestive enzymes feed by absorption parasites feeding on living creatures predators paralyzing prey decomposer breakdown dead remains plant cell fungal hypha plant cell membrane plant cell wall Fungi live IN their food! It’s like you living in Chocolate cake!
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Fungal Diversity Zygomycota Ascomycota Chytridiomycota Basidiomycota
Fungi
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Lichens are fungi that have discovered agriculture!
Ecological Roles Decomposers recycle nutrients Symbiotic Relationships lichen fungi + algae cyanobacteria or green algae pioneer species in ecosystems makes soil from bare rock mycorrhizae fungi + plants enables plants to absorb more water Lichens are fungi that have discovered agriculture! Lichens grow in the leftover spots of the natural world that are too harsh or limited for most other organisms. They are pioneers on bare rock, desert sand, cleared soil , dead wood, animal bones, rusty metal, and living bark. Able to shut down metabolically during periods of unfavorable conditions, they can survive extremes of heat, cold, and drought. As adaptations for life in marginal habitats, lichens produce an arsenal of more than 500 unique biochemical compounds that serve to control light exposure, repel herbivores, kill attacking microbes, and discourage competition from plants. Among these are many pigments and antibiotics that have made lichens very useful to people in traditional societies.
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Mycorrhizae Mycorrhizae are mutually beneficial relationships between fungi and plant roots Ectomycorrhizal fungi form sheaths of hyphae over a root and also grow into the extracellular spaces of the root cortex Arbuscular mycorrhizal fungi (endomycorrhizal fungi) extend hyphae through the cell walls of root cells and into tubes formed by invagination of the root cell membrane
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Mycorrhizae Critical role in plant growth
extends water absorption of roots without mycorrhizae with mycorrhizae Endomycorrhiza Ectomycorrhiza
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Lichens A lichen is a symbiotic association between a photosynthetic microorganism and a fungus in which millions of photosynthetic cells are held in a mass of fungal hyphae
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Ascocarp of fungus Soredia Fungal hyphae Algal layer Algal cell
Fig Algal cell Ascocarp of fungus Soredia Fungal hyphae Fungal hyphae Algal layer 20 µm Figure Anatomy of an ascomycete lichen (colorized SEM)
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Crustose (encrusting) lichens A foliose (leaflike) lichen
Fig Crustose (encrusting) lichens A fruticose (shrublike) lichen A foliose (leaflike) lichen Figure Variation in lichen growth forms
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Zygomycete (Bread Mold) Life Cycle
spores (haploid) mating strain hypha sporangium MEIOSIS mating strain (2n) diploid (n) haploid FUSION of + and – gametangia
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