Defences

Question 1

Human physical barriers

Answer 1

-mucus is produced by cells that line some surfaces of the body (traps pathogens)
-ciliated cells line the inside of the respiratory system (moves pathogens out of the body / into the throat)
-skin is a thick covering over the body (pathogens are unable to enter the body through the skin)
-tears wash pathogens away
-ear wax traps pathogens
-nasal hairs trap pathogens
-blood clots / scabs cover wounds (prevents the entry of pathogens)

Question 2

Human chemical defences

Answer 2

-skin has glands that secrete lysozymes
-lysozymes are enzymes found in tears, saliva and mucus
-lysozymes kill some bacteria
-hydrochloric acid in the stomach has a low pH (kills many pathogens)

Question 3

Plant physical defences

Answer 3

-Plant leaves have waxy cuticles (impermeable)
-Plant cells have cell walls
-Cell walls are made of cellulose (difficult for pests or pathogens to penetrate)
-Leaf cuticle and cell walls are physical defences
-Some plants have spines or hairs which deter pests

Question 4

Plant chemical defences

Answer 4

-Chemicals can deter pests
-Production of chemicals which are toxic to pests and pathogens
-Chemicals have anti-microbial properties
-Bad taste (deters pests)
-Bad smell (deters pests)