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LO chapter 16.doc

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York University
BIOL 1500
Tanya Da Sylva

Learning Objectives •Distinguish between Bacteria, Archaea and Protists. Note unique features of each.  Prokaryotic cell walls maintain cell shape, provide physical protection, and prevent the cell from bursting in a hypotonic environment – In a hypertonic environment, most prokaryotes lose water and shrink away from their wall  Bacterial cell walls can be distinguished with a gram stain – Gram-positive bacteria have simple walls with a thick layer of peptidoglycan – Gram-negative bacteria have complex walls with less peptidoglycan and an outer membrane of lipids bonded to carbohydrates Explain how populations of prokaryotes can adapt rapidly to changes in their environment; explain how this has contributed to the success of prokaryotes.  Some prokaryotes stick to the substrate or each other with hair-like appendages called pili  Sex pili join prokaryotes during conjugation  The flagella of Bacteria and Archaea allow them to move in response to chemical and physical signals in their environment  The prokaryotic flagellum is a naked protein without microtubules  The flagellum rotates like a propeller  Some prokaryotes can withstand harsh conditions by forming endospores within an outer cell  The endospore has a thick protective coat  It can dehydrate and is tolerant of extreme heat or cold  When conditions improve, the endospore absorbs water and resumes growth, sometimes after centuries •Describe the nutritional diversity of prokaryotes.  Some prokaryotic cells have specialized membranes that perform metabolic functions – Aerobic prokaryotes carry out cellular respiration on infoldings of the plasma membrane – Cyanobacteria carry out photosynthesis on infolded thylakoid membranes – Prokaryotic DNA forms a circular chromosome – Smaller rings of DNA called plasmids carry genes that may provide resistance to antibiotics or metabolize rare nutrients, among other metabolic activities – In some prokaryotes, metabolic cooperation occurs in surface-coating colonies called biofilms – Biofilms form when cells in a colony secrete signaling molecules that recruit nearby cells – Channels in the biofilm allow nutrients and wastes to move inside and outside the biofilm – Biofilms cause ear and urinary tract infections and the dental plaque that produces tooth decay •Compare the characteristics of the three domains of life; explain why biologists consider Archaea to be more closely related to Eukarya than to Bacteria. - Archaea o thrive in extreme environments—and in other habitats o are among the most abundant cells on Earth o They are a major life-form in the oceans - Protists are eukaryotes o •Describe the diverse types of Archaea living in extreme and moderate environments. - Extreme halophiles • Salt lovers ..mmhhmmhhh good :p • Found in great lakes, dead seas, and seawater evaporating ponds that produce salt - Extreme Thermophiles: • Heat lovers… its getting hot in here • Found in deep ocean vents, wh
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