Chapter 12 eukaryotes

Chapter 12 eukaryotes - Chapter 12: Characterizing and...

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Chapter 12: Characterizing and Classifying Eukaryotes Classification of the Eukarya (figure 12.1) 1. Cell structure in Eukarya is different from that seen in Bacteria or Archaea. 2. Use of the terms algae, fungi and protozoa are not accurate classification terms when you consider the rRNA sequences of these organisms. Protozoa 1. Protozoa are microscopic, unicellular organisms that lack chlorophyll, are motile during at least one stage in their development and reproduce most often by binary fission. Classification of Protozoa 1. In classification schemes based on rRNA, protozoa are not a single group of organisms. 2. Protozoa have traditionally been put into groups based on their mode of locomotion. 3. Sarcomastigophora include the Mastigophora, the flagellated protozoa and Sarcodina which move by means of pseudopodia. 4. Ciliaphora move by means of cilia. 5. Apicomplexa, also referred to as the sporozoa, include Plasmodium sp., the cause of malaria. 6. Microsporidia , an intracellular protozoa, causes disease in immunocompromised individuals. Protozoan habitats 1. Most protozoa are free-living and found in marine and fresh water as well as terrestrial environments. 2. They are important decomposers in many ecosystems and are an important part of the food chain. Structure of protozoa 1. Protozoa lack a cell wall but most maintain a definite shape using the underlying ectoplasm. 2. Life cycles are often complex and include more than one habitat. 3. Protozoa feed by either phagocytosis or pinocytosis. Protozoan Reproduction (figure 12.10)
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Reproduction is often by binary fission; some reproduce by multiple fissions or schizogony . Protozoa and Human Disease (table 12.2) 1. Protozoa cause some serious diseases such as malaria, sleeping sickness, toxoplasmosis and vaginitis. Chapter 12: Characterizing and Classifying Eukaryotes General Characteristics of Eukaryotic Organisms Eukaryotic microbes include a fascinating and diverse assemblage, including species that are vital for human life and numerous human pathogens: Among the 20 most frequent microbial causes of death worldwide, six are eukaryotic . Our discussion of the general characteristics of eukaryotes begins with a survey of the events in eukaryotic reproduction. Reproduction in Eukaryotes Eukaryotes have a variety of methods of asexual reproduction, including binary fission, budding, fragmentation, spore formation, and schizogony, but many reproduce sexually . Algae, fungi, and some protozoa reproduce both sexually and asexually. Every form of eukaryotic reproduction involves two types of division: nuclear division cytoplasmic division. Nuclear Division Most of the DNA in eukaryotes is packaged with histone proteins as chromosomes in the form of chromatin fibers located within nuclei. Typically, a eukaryotic nucleus has either one or two complete copies of the chromosomal portion of a cell’s genome. A nucleus with a single copy of each chromosome is called a
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Chapter 12 eukaryotes - Chapter 12: Characterizing and...

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