Biology unit 5

Pathogen

Disease-causing microoganism

Toxin

Harmful chemical produced by microorganism

Protist

Example of a microoganism

Positive effects of using bacteria

Assist in digesting food

Some bacteria produce vaccines, antibiotics and/or drugs

Act as decomposers

Pathogens can enter the body by:

Water (eg drinking contaminated water)

Air (eg breathing in droplets)

Direct contact (eg touching an infected person)

Droplet infection

An infection spread from one person to another by droplets of water released from the upper respiratory tract by sneezing/coughing. Can be prevented by wearing masks.

Bacteria

Single celled organisms

Have a circular strand of DNA rather than a nucleus

Do not contain mitochondria

May have a flagellum

Living cells

Viruses

NOT cells

Smaller than bacteria

Consist of genetic material and a protein coat

How do bacteria cause disease

Reproduce rapidly by splitting in 2 (binary fission) and produce toxins which can damage cells

How do viruses cause disease

Live and reproduce rapidly inside host cells, continuing until the cell bursts. Cell damage is what causes people to feel unwell

Health

A state of physical and mental wellbeing

2 examples of how health problems interact

Viruses can trigger changes in cells leading to cancer

Defects in the immune system mean someone is more likely to suffer from infectious diseases

Reactions initially caused by a pathogen can trigger allergies such as asthma and skin rashes

Poor physical health can lead to mental illnesses such as depression

Malnutrition can link to other conditions such as obesity, cancer, type 2 diabetes and a weakened immune system

4 types of pathogens

Bacteria

Fungus

Viruses

Protists

Louis Pasteur

Developed the germ theory of disasae, showing that it was caused by living microoganisms

Joseph Lister

Introduced the use of carbolic acid to sterilise instruments and to clean wounds in surgeries

Ignaz Semmelweis

Proved that hand-washing could dramatically reduce the number of deaths during childbirth

Florence Nightengale

Introduced handwashing and other hygienic practices into hospitals

How to prevent the spread of infection

Hygiene- cleans away/kills pathogens

Isolating infected individuals- reduces the spread by limiting contact

Destroying/controlling vectors- reduces spread of pathogens

Vaccination- Strengthens immune systems defences against the disease

Symptoms of measles

Cold-like symptoms

Sore, red and swollen eyes

Red skin rash

Fever

Aches and pains

Loss of appetite

Tiredness

How is measles spread

Droplet infection and direct contact

Symptoms of HIV

Fever

Fatigue

Swollen lymph nodes

Diarrhoea

Weight loss

Other flu-like symptoms

How is HIV spread

Direct sexual contact and sharing blood (eg sharing needles)

TMV symptoms

Mottled leaves

Stunted growth

Reduced yields in affected crops

How is TMV spread

Mechanically- from infected plants to scratched/damaged leaves of normal plants

Salmonella symptoms

Fever

Cramps

Vomiting

Diarrhoea

How is salmonella spread

By bacteria ingested in food or on food prepared in unhygienic conditions

How is the spread of salmonella managed

Poultry are vaccinated against it

Gonorrhoea symptoms

Thick yellow/green discharge

Pain on urinating

How is gonorrhoea spread

Direct sexual contact

How is the spread of gonorrhoea controlled

Treated with antibiotics (although some strains are resistant)

Barrier method of contraception (eg condoms)

Physical defences of plants against disease

Waxy cuticle

Cell walls made from cellulose

Layers of dead cells around stems (eg bark on trees)

Chemical defences of plants against disease

Some plants produce antibacterial chemicals- eg mint and witch hazel