4.1.1

• disease

  a condition that impairs the normal functioning of an organism
• communicable disease

  a disease that can spread between organisms
• pathogen

  a microorganism which can cause a disease
• host


  the organism a pathogen infects with a disease
• bacteria

  prokaryotic cells containing bacterial chromosomes and plasmids. Contain no membrane organelles

  Their cell wall is made of peptidoglycan
• bacteria's effect on a host

  releases toxins damaging host cells causing symptoms of the disease

  Enter host cells preventing normal function
• bacteria in mammals

  tuberculosis
• bacteria in plants

  potato / tomato ring rot
• virus

  smaller than a bacterial cell

  Contain RNA or DNA, proteins and lipids

  Non living due to lack of cellular structures
• viruses effect on host

  enter host cells

  Use host cell to create copies of virus

  Prevent host cell from functioning normally leading to its death
• example of viruses in humans

  HIV and AIDS
• Example of viruses in mammals

  Influenza
• Example of viruses in plants

  Tobacco mosaic virus
• Fungi

  Can be unicellular or multicellular

  Saprotrophic

  Reproduce via release of spores
• saprotrophic

  Obtain nutrients by releasing enzymes into decaying material and absorbing the products
• Fungi's effect on host

  Process of digestion reduces cell function and destroys host cells
• example of fungi in humans

  athletes foot
• example of fungi in mammals

  ring worm
• example of fungi in plants

  banana black sigatoka
• Protista

  Eukaryotic

  Single celled

  Usually live in a vector
• the effect of Protista on a host

  act as pathogenic parasite destroying host cells
• example of Protista in mammals

  malaria
• example of Protista in plants

  Potato / Tomato late blight
• direct transmission

  When a disease is transmitted directly from one organism to another through direct contact of skin or bodily fluids
• indirect transmission

  When a disease is transmitted from one organism to another via an intermediate or vector. Usually via water , air , food or another organism ( including spores )
• Factors affecting disease transmission

  overcrowding

  climate

  healthcare

  education

  culture and religion

  infrastructure

  travel
• How does overcrowding affect disease transmission?

  Direct exchange of fluids and contact increases direct transmission . The ability of the pathogen to remain in the air for a long period of time increases indirect transmission
• How does climate affect disease transmission?

  Allows different vectors to thrive and move to new places
• How does healthcare affect disease transmission?

  How often and quickly diagnosis and treatment occurs

  The ability to create and distribute a vaccine

  Ability to understand and prevent transmission
• How does education affect disease transmission?

  The knowledge on how a disease spreads and how to prevent spread

  The knowledge on the risk of contracting the disease
• How does culture and religion affect disease transmission?

  Use or rejection of certain medicines

  Contact levels with victims or deceased for burial or healing ceremonies
• how does infrastructure affect diseases transmission?

  Poor waste disposal can lead to contamination and indirect transmission
• How does travel affect disease transmission?

  Spread of disease due to symptomless carriers or infected objects

  ( food , plants )
• A plants physical defences against pathogens

  waxy cuticle

  Cell walls

  Callose deposition

  Necrosis and abscissions
• How does a waxy cuticle protect against pathogens?

  It provides a physical barrier

  It stops water collection on the leaf reducing indirect transmission from water
• How does a cell wall protect against pathogens?

  Provides a physical barrier to the cell
• how does Callose deposition protect against pathogens?

  During times of stress the polysaccharide callose is produced and deposited between cell walls and cell membranes and within plasmodesmata making it harder for pathogens to enter cells and spread to other cells.
• How does necrosis and abscission protect against pathogens?

  The plant allows the infected cells to die and seals them off from the rest of the plant eventually dropping or removing them
• a plants chemical defences against pathogens

  production of antimicrobial chemicals - kill or inhibit pathogens

  Production of toxic chemicals - reduce insect or animal vectors
• what do non specific defences against pathogens in mammals do?

  Defences that work in the same way against all pathogen. they are rapid and prevent pathogens from gaining access to the body