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Definitions • Parasites feed on living hosts • Saprophytes feed on dead matter • Decomposers breakdown dead matter and recycle the nutrients • Pathogens are disease causing organisms (most parasites are also pathogens) • Extra cellular digestion is the process by which bacteria and fungi feed • Binary fission is the process by which bacteria reproduce Viruses Viruses 3 Char. Of Life Virus Movement No Reproduction Yes Sensitivity No Growth No Respiration No Excretion No Nutrition No Viruses • • • • Viruses are simple but effective pathogens Viruses can infect all living things Range from 20 to 20millionth of a millimetre. Can only be seen with an electron microscope. Viral structure • Viruses come in a variety of shapes • Consists of a core of genetic material surrounded by a protein coat=capsid • Some viruses also have a membrane. This membrane can have proteins embedded in it 7 Viral reproduction • Essentially all a virus is is a set of instructions for making new viruses. • MRS GREN is not followed by viruses and the only ‘living’ characteristic that they have is reproduction • They lie on the border between the living and no living worlds Viral reproduction • Essentially all a virus is is a set of instructions for making new viruses. • MRS GREN is not followed by viruses and the only ‘living’ characteristic that they have is reproduction • They lie on the border between the living and no living worlds Viral replication A virus cannot reproduce itself independently, it needs another cells parts to replicate itself. When a virus lands on the surface of a cell it inserts its genes into the host cell. The viral genes take over the cells processes to produce new viruses. These build up in the cell until it eventually bursts releasing the new viruses into the host where they can infect new cells. Smallpox, Mumps, Measles - Virus POXVIRUSES BACK 14 Bacteria Bacteria • Bacteria are unicellular organisms with no nucleus • Sphere, rod, or spiral shaped • Usually 0.01mm in length and only visible under the higher powers of the microscope • Over 3000 known kinds • They are found almost everywhere including in living things • Colonies growing on agar look like shiny spots of various colours Shape Spherical (coccus) Rod shaped (bacillus) Spiral (spirillum) Example Staphylococcus E.coli Vibrio cholerae Bacteria structure Structure functions Cell wall: Maintains cell shape Cell membrane: Controls entry and exit of materials Chromosome: Carries genetic information Cytoplasm: fills cell and provides medium for chemical reactions to occur Flagellum: Assists the bacterium to move Capsule: Provides protection from external environment MRS GREN Movement Respiration Sensitivity Growth Reproduction Excretion Nutrition Movement • Many bacteria move by hair-like threads called flagella. • These are made up of long stands of protein • Non-flagellum bacteria float in water or on the wind. • Or are carried/spread by their hosts Respiration • Not breathing! • The process of releasing energy from food molecules • Bacteria carry out: - Aerobic respiration (requires oxygen) - Anaerobic respiration (without the presence of oxygen) http://www.youtube.com/watch?v=d0UfS1bqscM Sensitivity Bacteria display sensitivity to their environment. They can move along concentration gradients until they reach their optimum environment. i.e. Temperature/ acidity/ Oxygen/ Magnetic Growth In optimum conditions bacteria do grow, but their goal is reproduction so they grow up to a certain point where they have enough resources to reproduce. Reproduction • Reproduce asexually by a process called Binary fission • The bacterium’s chromosome is duplicated and the cell then pinches in half and two identical daughter cells are produced Excretion Bacteria excrete by allowing waste to diffuse out of the cell membrane into the environment i.e. CO2 from aerobic respiration Nutrition • Bacteria ‘feed’ by secreting enzymes which break down their food source into smaller molecules that can be absorbed by the bacteria. • This is called extra-cellular digestion. • Parasites – Live on or in larger organisms and feed off them. If they cause disease they are called pathogens. • Saprophytes – Consume dead matter. These bacteria are scavengers and decomposers. • Autotrophs – Self-feeders. They can make food from non-living materials i.e. chemicals/ sunlight. - Green and purple sulfur bacteria. Factors that inhibit bacteria growth • • • • • Light Temperature Chemicals Acidity Food supply Bacterial Growth Number of bacteria Log or Exponential Optimal conditions Rapid growth Stationary Toxin production causes human sickness Lag Time Copy Death or Decline Competition for food and space means bacteria die Fungi Fungi • A group of immobile organisms that feed on dead or living organisms and exposed food • 70,000 known kinds • 50 fungi among NZ’s most threatened species • Can be unicellular and multi-cellular • Most common cause of plant disease Structure • Hyphae: Fine feeding threads • Sporagium: Spore capsule that produces spores • Spores: reproductive cell, germinates and spreads out hyphae Mass of Hyphae MRS GREN Movement Respiration Sensitivity Growth Reproduction Excretion Nutrition Movement • Immobile • But can spread by producing networks of hyphae. Reproduction • Asexual and sexual production of spores • Spores germinate when they land on tissue and put out hyphae. Yeasts Sensitivity • Show active responses to their surroundings Growth • Grow by spread of hyphae Respiration • Carry out aerobic and anaerobic respiration to create energy from food Excretion • Allow waste to diffuse out of cells and into the surrounding envrionment Nutrition • Secrete enzymes that break down food, the absorb digested food • Extra-cellular digestion in fungi Copy Respiration • Carry out aerobic and anaerobic respiration to create energy from food Micro-organisms are helpful • Food production • • • • Bread Alcohol Cheese Yoghurt • Nutrient recycling • Composting • Medicine production • Antibiotics • Insulin Sewage treatment by microbes Microbes clean our water 1. Reservoir 1. Stores rainwater 2. Metal grids keep out weeds and debris 3. Coagulation 3. Chemicals make particles stick together 4. Stands for 3hr to let large particles sink (digested by microbes) 5. Filtration 5. Gravel and sand removes most particles 6. Kills microbes 2. Screening 4. sedimentation 6. Chlorination