Chapter 12. Eukaryotes. Characterizing and Classifying. 8/3/2014 MDufilho 1

Transcription

1 Chapter 12 Characterizing and Classifying Eukaryotes 8/3/2014 MDufilho 1

2 General Characteristics of Eukaryotic Organisms Five major groups Protozoa Fungi Algae Water molds Slime molds Include both human pathogens and organisms vital for human life 8/3/2014 MDufilho 2

3 Protozoa Diverse group defined by three characteristics Eukaryotic Unicellular Lack a cell wall Motile by means of cilia, flagella, and/or pseudopodia Except subgroup, apicomplexans 8/3/2014 MDufilho 3

4 Protozoa Distribution of Protozoa Require moist environments Most live in ponds, streams, lakes, and oceans Critical members of plankton Others live in moist soil, beach sand, and decaying organic matter Very few are pathogens 8/3/2014 MDufilho 4

5 Protozoa Morphology of Protozoa Great morphologic diversity Some have two nuclei Macronucleus Contains many copies of the genome Micronucleus Variety in number and kinds of mitochondria Some have contractile vacuoles All produce trophozoites; some produce cysts 8/3/2014 MDufilho 5

6 Protozoa Nutrition of Protozoa Most are chemoheterotrophic Obtain nutrients by phagocytizing bacteria, decaying organic matter, other protozoa, or the tissues of host Few absorb nutrients from surrounding water Dinoflagellates and euglenoids are photoautrophic 8/3/2014 MDufilho 6

7 Protozoa Reproduction in Protozoa Most reproduce asexually only Binary fission or schizogony Few also have sexual reproduction Some become gametocytes that fuse with one another to form diploid zygotes Some utilize a process called conjugation 8/3/2014 MDufilho 7

8 Protozoa Classification of Protozoa Based on 18S rrna and features visible by electron microscopy One scheme classifies into six taxa 8/3/2014 MDufilho Pearson Education Inc.

9 Fungi Chemoheterotrophic Have cell walls typically composed of chitin Do not perform photosynthesis Lack chlorophyll Related to animals 8/3/2014 MDufilho 9

10 Fungi The Significance of Fungi Decompose dead organisms and recycle their nutrients Help plants absorb water and minerals Used for food and in manufacture of foods and beverages Produce antibiotics Serve as important research tools 30% cause diseases of plants, animals, and humans Can spoil fruit, pickles, jams, and jellies 8/3/2014 MDufilho 10

11 Figure Fungal morphology-overview 8/3/2014 MDufilho 11

12 Fungi Nutrition of Fungi Acquire nutrients by absorption Most are saprobes Haustoria allow some to derive nutrients from living plants and animals May use ionizing radiation as energy source Most fungi are aerobic Many yeasts are facultative anaerobes. 8/3/2014 MDufilho 12

13 Fungi Reproduction in Fungi All have some means of asexual reproduction involving mitosis and cytokinesis Most also reproduce sexually Budding and asexual spore formation Yeasts bud in manner similar to prokaryotic budding Pseudohypha Series of buds that remain attached to one another and to parent cell Filamentous fungi produce lightweight spores that disperse over large distances 8/3/2014 MDufilho 13

14 Figure Representative asexual spores of molds-overview 8/3/2014 MDufilho 14

15 Fungi Classification of Fungi Division Zygomycota - Division Ascomycota Division Basidiomycota Deuteromycetes 8/3/2014 MDufilho 15

16 Fungi Division Zygomycota Most are saprobes. Form rough-walled sexual structures called zygosporangia Microsporidia are zygomycetes that are obligate intracellular parasites, some of which are known to cause disease in immunocompromised persons. 8/3/2014 MDufilho 16

17 Fungi Division Ascomycota Form haploid ascospores within sacs called asci. Ascomycetes include most of the fungi that spoil food, as well as plant pathogens - Dutch elm disease Many human pathogens( Aspegillosis in humans and many others). Beneficial in baking and brewing(saccharomyces), research, and pharmaceuticals (penicillium). 8/3/2014 MDufilho 17

18 Fungi Division Basidiomycota Mushrooms and other fruiting bodies of basidiomycetes, produce projections called basidia, the ends of which produce sexual basidiospores. Most basidiomycetes decompose cellulose and lignin in dead plants and return nutrients to the soil. Many produce hallucinatory chemicals or toxins Cryptococcus neoformans human pathogen 8/3/2014 MDufilho 18

19 Fungi Division Deuteromycetes The deuteromycetes, formerly classified in the division Deuteromycota, are an informal grouping of fungi having no known sexual stage. Recently, the analysis of rrna sequences has revealed that most deuteromycetes belong in the division Ascomycota, and thus modern taxonomists have abandoned Deuteromycota as a formal taxon. 8/3/2014 MDufilho 19