Chapter 27 Eukaryotic Cells Learning Objective Describe how prokaryotes impact human health Describe the basic differences between prokaryotes and eukaryotes Explain the endosymbiont hypothesis for the origin of eukaryotic cells and describe the evidence for this hypothesis Outline the phylogeny of the major groups of eukaryotes I Structure of Eukaryotes A Eukaryotic cells have a structurally more complex organization 1 It has a nucleus in the cell 2 Dynamic cytoskeleton that enables cells to change shape by 3 The nuclear membrane separates transcription and translation in remodeling quickly eukaryotes 4 A network of membranes is able to change shape and package molecules and particles for transport within the cell 5 Vesicles budding of from membranes transport materials into the cell in endocytosis and release materials from the cell in exocytosis B Things prokaryotes and eukaryotes have in common 1 Plasma membrane 2 Chromosomes 3 Ribosomes II Cell Division and Reproduction in Eukaryotes A Cell division in eukaryotes is through the process of mitosis or meiosis B Eukaryotes can have cell walls ex Plants and Fungi but they are biochemically different than prokaryotic cell walls C Many species of eukaryotes reproduce sexually D Some clades are characterized by alternation of haploid and diploid generations III Phagocytosis E Some clades have species that can reproduce either asexually or sexually A Phagocytosis is the engulfment of food by cells B Only eukaryotes can perform phagocytosis IV Mitochondria and Chloroplasts A Energy producing reactions that utilize or produce O2 take place in special organelles 1 Mitochondria aerobic respiration 2 Chloroplast oxygenic photosynthesis B Mitochondria and chloroplasts are believed to have evolved from internal symbiotic bacteria 1 Symbiosis interaction between two different organisms living in close physical association typically in which both benefit V Symbiosis and Origin of Chloroplasts A Genes in chloroplasts DNA are most closely related to cyanobacteria genes B Cyanobacteria and chloroplasts both have layer structures VI Symbiosis and the Origin od Eukaryotes A Hypothesis One Eukaryotic cells evolved from an archaea like prokaryote and only later incorporate the protobacterial cell that became B Hypothesis Two Eukaryotic cells evolved from a symbiosis between an archaeon and a protecobacterium The proteobacterium became a a mitochondrion mitochondrion C The Opisthokont clade includes animals fungi and chanoflagellates D The trypanosomes are eukaryotic pathogens are in the excavate group E The archeoplastids include plants F Allvelolates include malaria VII The Opisthokonts A 75 of known eukaryotic species are in this group B 1 3 million animal species 75 000 fungi species plus protists including choanoflagellates C Choanoflagellates have a single flagellum VIII The Amoeba A No cell walls IX The Archaepltida A AKA plants B Clearly visible pseudopodia C Cells coagulate to produce an amoeba structure B The 2nd most conspicuous and diverse clade of eukaryotes C Land plants have 300 000 described species and dominate eukaryotic biomass on the planet D Green algae are a paraphyletic group separate from plants
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