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Lecture 3

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Biological Sciences

Bio Lecture 3: 1/29/14 Overview: Living Small a. Even low-power microscope can reveal a great variety of organisms in a drop of pond water 1. Protist is the informal name of the group of mostly unicellular eukaryotes 2. Protists constitute a polyphyletic group and protista is no longer valid as a kingdom Concept 28.1: Most portist eukaryotes are singlr-celled organisms a. Eukaryotic cells hace organelles and are more complex than prokaryotic cells 1. Single-celled portista are complex, and are carried out by subcellular organelles in each individual cell (nucleus, ER, golgi, lysosomes and contractile vacuoles) b. Most protists are unicellular but there are some colonial and multcellular species Structural and Functional Diversity in Protista a. Protista exhibit more structural and functional diversity than any other group of eukaryotes 1. They are most nutritionally diverse of all eukaryotes - Photoautrophs - Heterotrophs - Mixotrophs 2. Some protists reproduce asexually while others reproduce sexually The 4 supergroups of eukaryotes a. LOOK AT FIGURE 28.2 1. Excavates 2. SAR 3. Achaeplastids 4. Unkionts Endosymbiosis in Eukaryotic Evolution a. There Is now considerable evidence that much of the protest diversity has its origins in endosymbiosis b. Endosymbiosis is the process in which a uncellular organism engulfs another cell, which becomes an endosymbiont and then an organelle in the host cell 1. Mitochondria evolved by endosymbiotic of an aerobic prokaryote 2. Plastids evolved by endosymbiosis of a photosynthetic cyanobacterium c. FIGURE 28.3 1. Plastids evolved from a cyanobacteium engulfed by ancestral heterotroph (primary endosymbiosis) which diversified into algae; these were then engulfed by other eukaryotes (secondary endosymbiosis) Concept 28.2: Excavates include protists with modifed mitochondria and protists which unique flagella, several members are parasites a. The clade Excavata is characterized by an “excavated” suspension feeding goove and flagella 1. This controversial group includes the: diplomonads, parabasalids and euglenozoans Diplomonads and Parabasalids a. These two groups lack plastids, have odified mitochondria, and most live in anerobic environments 1. Diplomonads - Have modified mitochondria, called mitosomes - Derive energy from anerobic biochemical pathways - Have two equal sized nuclei and multiple flagella - Are often parasites 2. Parabasilids - Have reduced mitochondria called hydrogenosomes that generate energy anerobically and release hydrogen gas - Have undulating membranes and flagella - Include Trichomonas vaginalis, the pathogen that causes yeast infections in human females Euglezoans a. Euglenozoa are diverse clade that includes predatory heterotrophs, pytosynthetic autotrophs and arasites 1. The main feature distinguishing them as a clade is a priral or mrystalline od of unknown function inside the flagella 2. Clade includes the kinetoplastids and sugleionds Kinetoplastids a. Have single mitochondrion with an organized mass of DNA called a kinetoplast 1. Include free-living consumers of prokaryotes in freshwater, marine, and moist terrestrial ecosystems 2. This group includes genus Trypanosome, members use sleeping sickness in humans - Transmitted by African tsetse fly 3. Another pathogenic trypanosome in latin America causes Chagas’ disease transmitted by bloodsuckers (kissing bugs) can lead to CHF Trypansosomes evade immune-system responsibilities by switching surface proteins a. A cell produces millions of copies of a single protein b. As soon as infection occurs, new generations of the parasite reproduces vey quickly millions of copies of a different protein c. These frequent changes prevent the hose from recognizing the protein an developing immunity Euglenids a. Have one or two flagella that meerge from a pocket at one end of the cell 1. Some species can be both autotophic (sunlight available) and heterotrphic (sunlight not available) 2. Others are able to prey by phagocytosis Concept 28. 3: The SAR clase is a highly diverse group of protists with similar DNA a. The SAR clade includes the stramenopiles, aveolates and phizarians: monyphhyletic and highly controversial 1. Stramenopiles and aveolates are thought to have originated over 1 billion yeas ago when a common ancestor engulfed a single-celled photosynthetic red alga Stramenopiles a. The clade tramenolila includes important phototrophs as well as several clades of heterotrophs 1. Mostly have hair flagellum paired with a smooth flagellum 2. Include diatoms, golden algae and brown algae Diatoms a. Are unicellular algae with unique two-part glass like wall of hydrated silica b. Reproduce asexually, sometimes sexually c. Major component” phytoplankton and highly diverse d. Fossilized diatom walls compose much of the sediments known as diatomaceous earth e. After diatom population blooms, many dead individuals fall to the ocean floor un- decomposed the C remaining in their bodies - This removes carbon dioxide from the atmosphere and pumps it to the ocean floor Golden Algae a. Named for color which re
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