OCR biology alevel module 4

What is bacteria?

• cells are smaller than eukaryotic cells, but in the right conditions they can reproduce rapidly some can reproduce every 20 minutes

• once in host body they can multiply rapdily = presence can cause disease by damaging cells or by releasing waste products and/or toxins

• in plants, bacteria often live in the vascular tissue and cause blackening and death of these tissues

state 3 examples of bacteria (pathogens)

Tuberculosis (TB)

Bacterial meningitis

Ring rot (potatoes, tomatoes)

describe tuberculosis

• affects many parts of the body, killing cells and tissues: lungs most often affected

• inhaling tiny droplets from the coughs or sneezes of an infected person

• bacteria: Mycobacterium tuberculosis & M.bovis

• treatment: antibiotics, BCG-vaccination

describe bacterial meningitis

• infection of the meninges - membranes that surround the brain and spinal cord: membranes become swollen and may cause damage to the brain of nerves

• sneezing/coughing: usually caught from people who carry these bacteria in their nose or throat but are not ill themselves

• bacteria: neisseria meningitias or streptococcus pneumonia

• treatment: antibiotics given directly into a vein or fluids given directly into a vein

describe ring rot

• ring of decay in the vascular tissue of a potatoe tuber or tomatoe, accompanied by leaf wilting

• vascular infection of daughter tubers derived from infected seeds

• bacterium: clavibacter michiganensis subsp. sepedonicus

• prevention: regularily cleaning and disinfecting all equipment used during potatoe production

what is a virus?

• are significantly smaller than bacteria and infect host cell and hijack their machinery

• invade cells and take over the genetic machinery and other organelles of the cell = causes the cell to manufacture more copies of the virus, host cell eventually bursts, releasing many viruses which will infect healthy cells

state 3 examples of viruses

HIV/AIDs (humans)

Influenza (animals)

Tobacco Mosaic Virus (plants)

what is HIV/AIDS?

• attacks the cells in the immune system and compromises the immune response

• sharing needles, transfusion of infected blood

• Virus: human immunodeficiency virus

• Treatment: antivetroviral drugs - stops virus from replicating

what is influenza?

• attacks respiratory system and causes muscle pains and headaches

• coughing or sneezing

• Virus: family Orthomyxoviridae - 'flu' viruses

• Treatment: fluids + rest and antiviral medication

what is tobacco mosaic virus?

• causes mottling and discolouration of leaves

• when an infected plant rubs against a leaf of a healthy plant = contaminated

• Virus: tobacco mosaic virus

• Preention: avoid handling plants, remove diseased plants, clean equipment

what is a protoctista?

• unicellular eukaryotes

• vectors: organism that carries a pathogen from the host to another

• causes harm by entering the host cell and feeding on the contents as they grow

state 2 examples of protoctista

malaria

blight (potatoe/tomatoe)

what is malaria

• parasite in the blood that causes headache and fever and may progress to coma and death

• bit of an infective female mosquito - transfusion of blood from infected persons

• protoctisan: Plasmodium falciparum, P. vivax, P. ovale, P. malariae

• treatment/prevention: anti-malarial medicine, putting covers on the bed, screens on window and doors

what is blight?

• affects both leaves and potatoe tubers

• wind: carries spores of the disease from plant to plant

• water: can wash the spores into the soil, where it infects tubers

• protoctistan: phytophthora infestans

• treatment: cut all growth above soil level and burn it ASAP, treat with fungicide before blight appears

what is a fungi?

saprophyte - fungi that lives on dead or decaying organic matter

parasitic - organism that lives on or in a host organism & gets its food from its host

what does fungi have a similar structure to?

Have similar structure to plants and their bodies consist of hyphae which form a network and spread throughout a host/soil

where do fungi live in animals + what does it cause?

Fungus lives in the skin of an animal & its hyphae form a mycelium, grow under thhe skin surface

• fungus can send out hyphae, which grow to the surface of the skin to release spores = cause redness + irritation

where do fungi live in plants and how does it gain nutrients?

In plants, fungus live in vascular tissue, where it gains nutrients

• Hyphae release extracellular enzymes, to digest surrounding tissue, which causes decay = leaves curl & shrivel

state 3 examples of fungi

Black sigatoka (bananas)

Ringworm (cattle)

Athlete's foot (human)

what is black sigatoka?

causes leaf sports on banana plants, reducing yeild

• can spread through contaminated fruit shipments

• fungus: mycosphaerelia fijiensis

• treatment: application of fungicide, remove or burn infected leaves

what is ringworm?

• growth of fungus in skin with spore cases errupting through skin to cause a rash

• direct contact: spores can be spread from animal to animal

• Fungus: trichophyron verrucosum

• Treatment: Antifungal cream, vaccine

what is athletes foot?

• growth under skin of feet - particularly between toes

• contact with fungi in damp areas, contact by touching the affected area

• fungus: trichophyton rubrum

• treatment: antifungal cream, spraying on powder, keep foot clean, dry and cool

define direct transmission

passing a pathogen from host to new host, with no intermediary

define indirect transmission

passing a pathogen from host to new host, via a vector

state 4 means of transmission

direct physical contact

faecal

droplet infection

transmission by spores

describe direct physical contact transmission

Direct physical contact: touching infected person or touching contaminated surfaces that have pathogens

• e.g. HIV, bacterial meningitis, ringworm, athlete's foot

• hygiene: washing hands regularly

• cleaning + disinfecting cuts and abrasions

• sterilising surgical instruments

describe faecal transmission

Faecal: oral transmission, eating food/ drinking water contaminated by pathogen

• e.g. cholera, food poisoning

• thorough washing of all fresh food

• careful preparation + cooking of all food

describe droplet infection transmission

Droplet infection: pathogen is carried in tiny water droplets in air

• e.g. tuberculosis, influenza

• cover mouoth when coughing or sneezing

• use tissue + ensure tissue is disposed of

describe transmission by spores

Transmission by spores: can be carried in air or reside on surfaces or in soil

• e.g. anthrax, tetanus

• use of mask

• washing skin after contact with soil

what are the social factors affecting transmission

• overcrowding: many people living or sleeping together in one house

• poor ventilation

• poor health: more likely to contract other diseases

• poor diet

• homelessness

• living/working with people who have migrated from areas where a disease is more common