Biology chapter 10

• What is a disease?

  an unhealthy condition, illness, or disorder
• what is a pathogen?

  A microorganism that causes disease
• communicable disease


  a disease caused by pathogens that can be spread
• non-communicable disease


  a disease not caused by pathogens that cannot be spread
• Name the microorganisms that are pathogens

  bacteria, fungi, viruses, Protoctista
• Features of bacteria


  - prokaryotic organisms

  - some can be non parthenogenic

  - pathogenic bacteria can remain in body and not infect host cells
• name the bacteria animal infections

  tuberculosis, bacterial meningitis
• tuberculosis


  - bacteria infects lungs ands causes chronic cough and bloody mucus

  - associated with poor hygiene
• Bacterial Meningitis


  - crosses the meninges barrier ( the membrane surrounding the brain and spinal chord) and infects it

  - causes inflammation and symptoms like headache and fever
• plant bacterial infection


  ring rot
• ring rot


  - disease in potato plant

  - infects vascular tissue and prevents transport of water cause the plant to wilt and die

  - infection spread to potato tubers and vascular tissue arranged in ring produces a black ring of rot
• features of viruses


  - non living infectious agents

  - do not have cellular structure

  - infect host cell by inserting own nucleic acid into DNA of cell

  - infected cell produce more viruses

  - viruses affect all types of organisms
• animal viral infections


  influenza, HIV
• influenza


  - infects ciliated epithelial cells of respiratory system causing flu

  - infects lining of airways causing high temperature and body ache and fatigue
• HIV


  - caused by human immunodeficiency virus

  - enveloped retrovirus ( RNA used to make DNA)

  - able to splice genes into hist chromosomes

  - attacks and destroys T helper cells and compromise host immune system leading to aids
• plant viral infections


  tobacco mosaic virus (TMV)
• TMV


  - first ever discovered virus

  - infects plant leaves causing yellow leaves that produce mosaic pattern

  - result in stunted growth and reduced yield
• Features of Protoctista


  - eukaryotic single celled organisms

  - small % act as a pathogen

  - require vector to transfer disease
• name the Protoctista diseases

  malaria - animal infection

  potato blight - plant infection
• malaria


  - host is bitten by infected mosquito and the parasite is introduced

  - plasmodia travel in the blood to the liver to multiply and enter the red blood cells

  - symptoms include headache chills and fever
• potato blight


  - some fungal characteristics

  - transmitted via spores

  -causes potato tubers to rot and turn into foul smelling mush
• features of fungi


  - eukaryotes than can be uni or multicellular

  - composed of filaments called hyphae

  - many are saprophytes ( feed of dead decaying matter)

  - affect plants more than animals as they infect leaves and prevent photosynthesis

  - produce millions of spores to rapidly infect other organisms
• animal fungal diseases


  ringworm, athletes foot
• ringworm


  - A highly contagious, fungal infection of the skin or scalp

  - spores break through skin causing rash
• athlete's foot


  - fungal infection on skin on feet

  - symptoms: itching and redness
• plant fungal diseases


  black sigatoka
• black sigatoka


  - causes leaf spot disease in banana plants

  - reduces the ability to photosynthesise
• how pathogens affect organisms

  - damage tissue and produce toxins

  - combine with immune system response to cause symptoms of infection
• damage to tissues


  Viruses: take over cellular metabolism

  - viral genetic material is inserted into genes of host cell

  - host cell then makes mire virus and burst out cell destroying it

  Protoctista: take over cell, digest insides and use the medium to reproduce then burst out

  Fungi: digest and destroy living cells
• Producing toxins


  - pathogenic bacteria produces toxins which are poison

  - toxins damage cells by breaking down membrane and inactivating cells
• how do pathogens cause disease

  - damaging cells

  -producing toxins

  exotoxins secreted by normal pathogen

  endotoxins released when pathogen is damaged
• disease transmission


  - transfer of pathogens from an infected host to an uninfected host

  - pathogens transfer host to host to survive
• 2 types of disease transmission

  direct - from one host to another

  - indirect - a second organism (vector) that is unaffected by the pathogen and transfers it to host
• Direct transmission


  - physical contact - TMV leafs touch and spreads virus

  - close proximity - influenza spreads in water droplets breathed in

  - spores - small reproductive structures released into environments and dispersed by wind/water
• transmission of HIV


  - spread through intimate human contact

  - exchanged by body fluid in: sex, blood donation, sharing needles, breastfeeding
• Transmission of TB


  - infected people cough and sneeze causing bacteria to enter air as droplets

  - uninfected inhale droplets

  - spread quickly in overcrowded conditions

  - from cattle - spread by contaminated milk
• Indirect transmirrsion


  - involves vectors

  - vector - organism that transfers pathogen from infected individual to uninfected individual while not being harmed

  - reproduce in large numbers - increase likelihood of pathogen transmission
• Transmission of malaria


  - mosquito feed on human blood to obtain proteins to develop eggs

  - they bite an infected person to take up pathogens and pass to next humans blood

  - also transmitted in blood transfusion with unsterilised needles
• factors that affect disease transmission

  - presence of the pathogens

  - presence of susceptible individuals
• endemic disease


  disease constantly present in a population