B5 - Communicable Diseases (Y10 - Spring 1)

Question 1

🟢 What is Health?

Answer 1

Your health is a state of physical and mental well-being, not just an absence of disease. It is at partly based on individual perceptions. A cold or headache that might make you feel ill enough to stay in bed on a school day might be less likely to be a problem if your on holiday.

Question 2

🟢 What Makes People Ill (Explanation + Factors)

Answer 2

Communicable (infectious) diseases (e.g tubercolosis, flu, and COVID-19) are caused by pathogens such as bacteria and viruses that can be passed from one person to another. Non-communicable diseases camnot be passed on through human-to-human transmission. Both communicable and non-communicable diseases are major cuases of ill health, but other factors can also affect health like:

• Diet: If you do not get enough of the right food and nutriengs, you may suffer from diseases ranging from starvation to anaemia or rickets. Too much fodd, or the wrong type can lead to problems such as obesity, some cancers, or type 2 diabetes.
• Stress: A certain level of stress is inevitable in everyone’s libes amd is probably needed for our bodies to function properly. However, scientists are increasingly linkingtoo much stress to an increased risk of developing a wide range of health problems. These can include heart disease, certain cnacers, and mental health problems.
• Life situations: Where in the World you live, your gender, you financs, your ethnic group, the levels of free heathcare you have, how many children you have, and even the local sewage and rubbish disposal.

All of these factors can have such a big affect on your health and can even lead to communicable diseases like diarrhoeal diseases and malaria, as well as non-communicable diseases like heart disease and cancer. These factors can be especially bad for children, as they don’t have the power to get away from and to change or control the 3 factors mentionned above.

Question 3

🟢 How Can Health Problems Interact (Explanation + Examples)

Answer 3

It is important to remember that in the real world, different diseases and health conditions happen at the same time. They interact and often one problem can make/lead another to become worse. These are a number of examples:

• COVID-19 (if it hits someone hard) for example, can lead to other health conditions such as pneumonia, and possibly to a person’s death
• Viruses living in cells can trigger changes that lead to cancers, for example the human papilloma vrius can cause cervical cancer
• The immune system of your body helps you destroy pathogens and get better. If there are defects in your immune system, it may not work effectively. This may be a result of genetic makeup, poor nutrition, or infections such as HIV/AIDS. This means you will be more likely to suffer from other communicable diseases.
• Immune reactions initially caused by a pathogen, even something like the common cold, can trigger allergies to factors in the environment. These allergies may cause skin rashes, hives, or athsma.
• Physical and mental health are often closely linked. Severe physical ill health can lead to depression and other mental illness.
• Malnutrition is often linked to health problems including deficiency diseases, a weakened immune system, obesity, cardiovascular diseases, type 2 diabetes, and cancer.

Question 4

🟢 What are Communicable Diseases And Their Cause?

Answer 4

Communicable Diseases are found all over the world. Microorganisms that cause disease are called pathogens. Pathogens may be bacteria, viruses, protists, or fungi, and they infect animals and plants, causing a wide range of diseases. It is a disease causing organism.

Communciable diseases are caused either directly by a pathogen or by a toxin made by a pathogen. The pathogen can be passed from one infected individual to another individual who does not have the disease. Some communicable diseases are fairly mild, such as the common cold and tonsillitus. Other are known as killers such as tetanus, influenza, and HIV/AIDS.

Sometimes communicable diseases can be passed between different species of organisms. For example, infected animals such as dogs or bats can pass rabies on to people. Tubercolosis can be passed from badgers to cows and from cows to people.

Question 5

🟢 The Differences Between Bacteria and Viruses

Answer 5

Bacteria and viruses cause the majority of communicable diseases in people. In plants, viruses and fungi are the most common pathogens. Bacteria are single-celled living organisms that are much smaller than animal and plant cells. Bacteria are used to make food such as yogurt and chesse, to treat seage, and to make medicines. Bacteria are important both in the environment, as decomposers, and in your body. Scientists estimate that most people have between 1 and 2kg of bacteria in their guts and they are rapidly discovering that these bacteria have a major effect on our health and wellbeing.

Pathogenic bacteria are the minority - but they are significant because of the major effects they can have on individuals and society. Viruses are even smaller than bacteria. They usually have regular shapes, and viruses cause diseases in every type of living organism.

Another thing is that Bacteria and Viruses may reproduce rapidly inside the body. Bacteria may prodyce posions (toxins) that damage tissues and make us feel ill. Viruses live and reproduce inside cells causing cell damage.

Question 6

🟢 How Pathogens Cause Disease

Answer 6

Once bacteria and viruses are inside your body, they may reproduce rapidly.

• Bacteria divide rapidly by splitting into two (called binary fission). They may may produce toxins (poisons) that affect your body and make you feel ill. Sometimes they directly damage your cells.
• Viruses take over the cells of your body. They live and reproduce inside cells, damaging and destroying them.

Common disease symptoms are a high temperature, headaches, and rashes. These are caused by the way your body responds to the cell damage and toxins produced by the pathogens.

Question 7

🟢 How Do Pathogens Spread? (Explanation + Examples)

Answer 7

The more pathogens that get into your body, the more likely it is that you will develop an infectious disease. There are a number of ways in which pathogens spread from one individual to another.

• By Air (including droplet infection): Many pathogens including bacteria, viruses, and fungal spores (that cause plant disease) are carried and spread from one organism to another in the air. In human diseases, droplet infection is common. When you are ill, you expel tiny droplets full of pathogens from your breathing system when you cough, sneeze, or talk. Other people breathe in the droplets, along with the pathogens inside of them, so they pick up the infection too (e.g flu/influenza, tubercolosis, common cold, and COVID-19)
• Direct Contact: Some diseases are spread by direct contact of an infected organism with a healthy one. This is common in plant diesases, where a tiny piece of an infected plant material left in a field can infect an entire new crop. In people, diseases including sexually transmitted infections, such as syphilis and chlamydia, are spread by direct contact of the skin. Pathogens such as HIV/AIDS or hepatitis enter the body through direct sexual contact, cuts, scratches, and needle punctures that give access to the blood. Animals can act as vectors of both plant and animal diseases by carrying a pathogen between infected and uninfected individuals
• By Water: Fungal spores carried in splashes of water often spread plant diseases. For humans, eating raw, undercooked, or contaminated food, or drinking water containing sewage can spread diseases such as diarrhoeal diseases, cholera, or salmonellosis. The pathogen enters your body through your digestive system.

Question 8

🟢 Diseases caused By Bacteria, and key points to note on them/ how they spread

Answer 8

Diseases:

• Tubercolosis
• Salmonella
• Gonorrhoea

Key Points To Notes:

• Bacteria can survive in very harsh conditions including deep areas of the Earth’s crust and Radioactive waste.
• Bacteria can spread and multiply very quickly
• Bacteria cause disease by secreting or excreting toxins, by producing toxins internally, which are released when the bacteria disintegrate (like in typhoid), or by inducing sensitivity to their antigenic properties (like in tuberculosis).

Question 9

🟢 Diseases caused By Viruses, and key points to not on them/ how they spread

Answer 9

Diseases:

• Cold
• Flu
• COVID-19
• Measles
• HIV
• Tobacco Mosaic Virus

Key Points To Notes:
-Viruses spread by getting into and infecting cells, before spreading and infect more and more cells, until the patient is unwell, or the antibodies ans T-Cells start to stop and kill it.

-Viruses are not alive – they are inanimate complex organic matter. They lack any form of energy, carbon metabolism, and cannot replicate or evolve. Viruses are reproduced and evolve only within cells.

Question 10

🟢 Diseases caused By Fungi, and key points to note on them/ how they spread

Answer 10

Diseases:
-Rose Black Spot

Key Points To Notes:
-Fungi can cause disease in plants and humans, but do play an important role in the ecosystem

-Human interactions with fungi can be harmful in many ways including poisonings, exposure to ‘mycotoxins’ produced by fungi that cause food spoilage, and allergies stimulated by inhalation of airborne spores.

Question 11

🟢 Diseases caused By Protists, and key points to note on them/ how they spread

Answer 11

Diseases:
-Malaria

Key Points To Notes:

• Protists as a group have very little in common. They are eukaryotic microorganisms with fairly simple eukaryote cell structures. Other than this, they are any organism that is not a plant, animal, bacteria, or fungus.
• Most protist diseases in humans are caused by protozoa. Protozoa make humans sick when they become human parasites.

Question 12

🟢 Measles: Symptoms, How it Spreads, What and How Many People does it Affect, and how is It Treated (+What Type of Pathogen is it?)

Answer 12

Pathogen: Viral Disease

Measles is a viral disease showing symptoms of fever and a red skin rash. Measles is a serious illness that can be fatal if complications arise. For this reason most young children are vaccinated against measles. The measles virus is spread by inhalation of droplets from sneezes and coughs.

Question 13

🟢 HIV/AIDS: Symptoms, How it Spreads, What and How Many People does it Affect, and how is It Treated (+What Type of Pathogen is it?)

Answer 13

Pathogen: Viral Disease

HIV initially causes a flu-like illness. Unless successfully controlled with antiretroviral drugs the virus attacks the body’s immune cells. Late stage HIV infection, or AIDS, occurs when the body’s immune system becomes so badly damaged it can no longer deal with other infections or cancers. HIV is spread by sexual contact or exchange of body fluids such as blood which occurs when drug users share needles.

Question 14

🟢 Tobacco Mosaic Virus: Symptoms, How it Spreads, What and How Many Plants does it Affect, and how is It Treated (+What Type of Pathogen is it?)

Answer 14

Pathogen: Viral Disease

Tobacco mosaic virus (TMV) is a widespread plant pathogen affecting many species of plants including tomatoes. It gives a distinctive ‘mosaic’ pattern of discolouration on the leaves which affects the growth of the plant due to lack of photosynthesis.

Question 15

🟢 Salmonella Food Poisoning: Symptoms, How it Spreads, What and How Many People does it Affect, and how is It Treated (+What Type of Pathogen is it?)

Answer 15

Pathogen: Bacterial Disease

Salmonella food poisoning is spread by bacteria ingested in food,
or on food prepared in unhygienic conditions. In the UK, poultry are vaccinated against Salmonella to control the spread. Fever, abdominal cramps, vomiting and diarrhoea are caused by the bacteria and the toxins they secrete.

Question 16

🟢 Gonorrhoea: Symptoms, How it Spreads, What and How Many People does it Affect, and how is It Treated (+What Type of Pathogen is it?)

Answer 16

Pathogen: Bacterial Disease

Gonorrhoea is a sexually transmitted disease (STD) with symptoms of
a thick yellow or green discharge from the vagina or penis and pain on urinating. It is caused by a bacterium and was easily treated with the antibiotic penicillin until many resistant strains appeared. Gonorrhoea
is spread by sexual contact. The spread can be controlled by treatment with antibiotics or the use of a barrier method of contraception such as a condom.

Question 17

🟢 What Bacterial Diseases are in Plants (+ where are they found in the world, and why they can be useful)

Answer 17

They are relatively few bacterial diseases of plants and these diseases are usually found in tropical and sub-tropical regions. Agrobacterium tumefacuens us a bacterium that causes crown galls - a mass of unspecialised cells that often grow at the join between the root and the shoot in infceted plants. It infects many different plant types including fruit trees, vegetables, and garden flowering plants. The bacteria insert plasmids into the plant cells and cause a mass of new undifferentiated genetically modified cells to grow. For this reason, these bacteria have become a key tool for scientists when genetically modifying plant cells. Scientists make use of the way when bacteria naturally infect plants cell and give them new added genes. They manipulate the bacteria so they carry desirable tenes into the cells they infect.

Question 19

🟢 Rose Black Spot: Symptoms, How it Spreads, What and How Many People does it Affect, and how is It Treated (+What Type of Pathogen is it?)

Answer 19

Pathogen: Fungal Disease

Rose black spot is a fungal disease where purple or black spots develop on leaves, which often turn yellow and drop early. It affects the growth of the plant as photosynthesis is reduced. It is spread in the environment by water or wind. Rose black spot can be treated by using fungicides and/or removing and destroying the affected leaves

Question 20

🟢 What are Fungal Diseases

Answer 20

There ae realtively few fungal diseases that affect people. Althelete’ foot is a well-known, relatively minor fungal skin condition. A small number if human fungal disease can be fatal when the attack the lungs or brains of people who are already ill. Damaged heart valves can also develop serious fungal infections. However, these conditions are rare. Antifungal drugs are usually effective agaunst skin fungi like athlete’s foot, but it can be hard to treat deep-seated tissue infections.

In plants, however, fungal diseases are common and can be devastating. Huge areas of crops from cereals to bannanas are lost every year as a result of fungal infections, inclduing stemrusts and various rooting diseases.

Question 22

🟢 What are Diseases caused by Protists (+ Example

Answer 22

Protists (a type if single-celled organism) cause a range of diseases in animals and plants. They are relatively rare pathogens but the diseases they cause are often serious and damaging to those infected. Diseases caused by protists usually involve a vector that transfers the protist to the host. One of the best known and globally serious protist disease is malaria.

Question 23

🟢 Malaria: Symptoms, How it Spreads, What and How Many People does it Affect, and how is It Treated (+What Type of Pathogen is it?)

Answer 23

Pathogen: Protist Disease

Malaria is a disease caused by protist pathogens that are paresites - they live and feed on other living organisms. The life cycle or the protists includes tume in the human body ane time in the body of a female Anopheles mosquioto. The protists reproduce sexually in the mosquito and asexually in the human body. The mosquitoes act as vectors of the disease. The female mosquito needs two meals of human blood before she can lay her eggs, and this is when the protists are passed into the human bloodstream. The protists travel around the human body in the circulatory system. They affect the liver and damage red blood cells. Malaria causes recurring episodes of fever and shaking when the protists burst out of the blood cells, and it can be fatal. It weakens the affected person over time even if it does not kill them. Globally several hundred million cases of malaria occur each year, and around 660,000 people die from the disease.

If malaria is diagnosed quickly, it can be treated using a combination of drugs, but this is not always avaliable in the countries most affected by malaria. The protists have also become resistant to some of the most commonly used medicines. The spread of malaria can be controlled in a number of ways, most of which target the mosquito vector. These include:

• Using insecticide-impregnated insect nets to prevent mosquitoes biting humans and passing in the protists.
• Using insecticides to kill mosquitoes in homes and offices.
• Preventing the vectors from breeding by removing standing water and spraying water with insecticides to kill the larvae.
• Travellers can take antimalariwl deigs that kill parasotes in the blood if they are bitten by an infected mosquito.

Question 24

🟠 What was the Work of Ignax Semmelweis?

Answer 24

Ignaz Semmelweis believed that keeping sanitisation, and keeping clean, as well as washing, was cruicial to stop the spread of fever and disease. At the time, Ignax wanted people to wash their hands in chloride of lime, while everyone else believed that the spread was down to miasma, which was uncontrolable and unpredictable.

Semmelweis was a doctor in the in the mid-1850s. At the time, many women in hospital died from childbed fever a few days after giving burth. However, no one knew what caused it.

Semmelweis noticed that his medical students went straight from dissecting dead body to delivering a baby without washing their hands. The woman delivered by medical students and doctors rather than midwives were much more likely to die. Semmelweis womdered if they were carrying the cuase of disease from the corpses to their patients.

He noticed that another doctor died from symptoms identical to childbed fever after cutting himself while working on a body. The convinced Semmelweis that the fever was caused by some kind of infectious agent. He therefore insisted that his medical students wash their hands before delivering babies. Immidiatly, fewer mothers died from the fever. However, other doctors were resistant to Semmelweis’s ideas.

Question 25

🟠 Other Scientific Discoveries on Prevent the Spread of Pathogens, in addition to The Work Of Ingax Semmelweis

Answer 25

Also, in the mid to late 19th Century

• Louis Pasteur showed that microorganisms caused disease. He developed vaccine against disease such as anthrax and rabies
• Joseph Lister started to use antiseptic chemicals to destroy pathogen before they caused infection in operating theatre.
• As microscopes inmprobed, it became possible to see pathogens more clearly. This helo convince people that they were really there.

Understanding how communicable diseases are spread from one person to another helps us prevent it was happening.

Question 26

🟢 Ways you can Prevent the Spread of Communicable Disease

Answer 26

There are a number of key ways to help prevent the spread of communicable diseases between people, between animals and people, and between plants. Some of these are:

• Hygiene
• Isolating Infected Individuals
• Destroying or Controlling Vectors
• Vaccination

Question 27

🟢 How can Hygiene Prevent the Spread of Disease

Answer 27

Simple hygiene measures are one of the most effective ways of preventing the spread if pathogens. These can include:

• Hand washing, especially after using the toilet, befire cooking, or after contact with an animal or someone who has an infectious illness.
• Using disinfectants on kitchen work surfaces, toilets, ect. to reduce the number of pathogens.
• Keeping raw meat away from food that is eaten uncooked to prevent the spread of pathogens.
• Coughing or sneezing into a handkerchief, tissue, or on your hands and immidiatly washing them.
• Maintainung the hygiene of people and agricultural machinery to help prevent the spread of plant diseases.

Question 28

🟢 How can Isolating Infected Individuals Prevent the Spread of Disease

Answer 28

If someone has an infectious disease, especially a serious disease such as Ebola, or cholera, they need to be kept in isolation. The fewer healthy people whi come into contact with the infected person, the less likely it is that pathogens will be passed on. This is also true of plants infected with diseases but it is only possible wuth smaller plants tnat can be moved and destroyed easily.

Question 29

🟢 How can Destroying or Controlling Vectors Prevent the Spread of Disease

Answer 29

Some communicable diseases are passed on by vectors. For example, mosquitoes carry a range of diseases, such as malaria and dengue fever. Housfiles can carry over 100 human diseases, while rats also act as vectors of disease. Aphids transmit over 150 different plant diseases and different types of beetle carry disease to plangs in the form of bural, bactertial, and fungal pathogens. If the vectors are destroyed, the soread of the disease can be orevented. By cintrolling the number of vectors, the spread of disease can be greatly reduced.

Question 30

🟢 How can Vaccination Prevent the Spread of Disease

Answer 30

During vaccination, doctors introduce a small amount of a harmless form of a specific pathogen into your body. As a result, if you come into contact with the live pathogen, you eill not become ill as your immune system will be prepared. Vaccination is a very successfulnway of protecting large numbers or humans and animals against serious diseases. However, it cannot protect plants agianst disease as they do not have an immune system.

Question 31

🟢 Why is it Important to Prevent Microoganisms Getting into the Body

Answer 31

Each day, you meet millions of disease-causing microorganisms. Every body opening as well as any breaks in the skin give pathogens a way in. The more pathogens that you get into your body, the more likely it is that you will get an infectious disease. Fortunately, your body has many defence mechanisms that work together to keep the pathogens out.

Question 32

🟢 How do Skin Defences Prevent Microoragnisms from Getting into the Body

Answer 32

• Your skin covers your whole body and acts as a barrier. It prevents bacteria. It prevents bacteria and viruses reaching the tissues beneath. If you damage or cut your skin, the barrier is broken but your body restores it. You blled, and the platelets in your blood set up a chain of events to form a clot that dries into a scab. This forms a seal over thecut, stopping pathogens getting in. It also you bleeding to death.
• Your skin produced antimicrobial secretions to destroy pathogenic bacteria.
• Healthy skin is covered with microorganisms that help help keep you healthy amd act as an extra barrier to the entry of pathogen.

Question 33

🟢 How do Defences of the Respiratory and Digestive Systems Prevent Microoragnisms from Getting into the Body

Answer 33

Your respiratiory system is a weak link in your body defences. Every time you breathe in, you draw air full of pathogens into the airways of your lungs. In the same way, you take food and drink, as well as air, into your digestive system through your mouth. Both systems have good defences to help prevent pathogens constantly casuing infections

• Your nose is full of hair and pridced a sticky liauid called mucus. The hairs and mucus trap particles in the air that may contain pathigens or irritate your lungs. If you spend time in an envirnoment with lots of air pollution, the mucus you produce when you blow your nose is blackened, show that the system works.
• The trachea and bronchi also secrete mucus that traps pathogens from the air. The lining if the tubes is covered in cilla (tiny hair-like projections from the cells). The cilla beat to waft the mucus up to the back of the throat where it swallowed.
• The stomach produced hydrochloric acid, and this destroys the microorganisms in the mucus you swallow, as well as the majority if the pathogens you take in through your mouth in your food and drink.

Question 34

🟢 How does The Immune System Prevent Microoragnisms from Getting into the Body

Answer 34

In spite of your body’s defence mechanisms, some pathogens still get inside your body. Once there, they will meet your second line of defence - the white blood cells of your immune system. The immune system will try to destroy any pathogens that enter the body in several ways:

Ingesting Microorganisms (Phagocytosis) - Some white blood cells ingest pathogens, digesting and destroying them so they cannot make you ill.

Producing Antibodies - Some white blood cells produce special chemicals called antibodies. These target particular bacteria or viruses and destroy them. You need a unique antibody for each type of pathogen. When your white blood cells have produced antibodies once against a particular pathogen, they can be made very quickly if that pathogen gets into the body again. This stops you getting the disease twice.

Producing Antitoxins - Some white blood cells producd antitoxins. These counteract the toxins released by pathogens.

The different body system work together to help protect you from disease. For example, some white blood cells contain green coloured enzymes. These white blood cells destroy the cold viruses and any bacteria trapled in the mucus of your nose when you have a cold. The dead white blood cells, along with the dead bacteria and viruses, are removed in the mucus, making it look green.

Question 35

🟢 What are Phagocytes and Lymphocytes?

Answer 35

Phagocytes go to infected tissues and kill pathogens as often and as effective as possible. Lymphocytes are foud all around the body. They produce antibodies and antitoxins to stops the pathogens from being effective, rendering them useless so the Phagocytes can come to kill them.

Question 36

🟢 The Three Stages of Immune Responses

Answer 36

Stage 1 - Includes Skin and Mucus Membranes
(non-specific)

Stage 2 - Includes Macrophages (phagotic white blood cells)
(non-specific)

Stage 3 - Includes B and T cells (lymphocytes - specific type of white blood cells)

Question 37

🟢 What is the Definition of Herd Immunity, and how is it affected by the ‘r’ number and the number of people who are immune?

Answer 37

A herd is a group of animals that stay together for protection. The basic reproduction number is the ‘r’ number, which is the rate of infection (if the ‘r’ number is above 1, then there will be more people getting the infection, but is the ‘r’ number is below 1, then the pathogen will shrink). But if a person does get over the disease, then they will gain immunity. So if a good enough amount of people get immunity, then it will result in a ‘herd immunity’ meaning that the pathogen won’t be able to spread quick or effectivly enough through the population. The greater the ‘r’ number, the higher the amount of people in the herd need to be immune, or vaccinated.

Question 38

🟠 What Plant Pathogens are there, and example how how they are spread through animals/insects

Answer 38

Plants are vunerable to viruses, bacteria, and fungi, but are also attacked by pests that can cause lots of damage too. Insect pests may destroy plants directly, and also act as vectors of disease. One important group of insect plant pest is the aphids. Aphids have sharp mouthparts that penetrate into the phloem vessels of the plant so they can feed on the sugar rich phloem sap. Aphids attack in huge numbers, depriving the plant cells of the products of photsynthesis. This can seriously damage and weaken the plant. Aphids also act as vectors, tranferring viruses, bacteria and fungi from diseased plants into the tissues of healthy plants on their mouthparts.

Aphids can be destroyed using chemical pesticides, or in enclosed spaces such as greenhouses, using biological pest contril. Releasing aphid-eating insects like ladybirds and their larbae can control the pathogen population so it dies not have an impact on the success of the crop.

Other plant lests, including nematode worms and many insect larvae that live in the soil, feed in or on plant roots, damaging them so they cannot absorb water and mineral ions effectively. As a result, the plant fails to griw and thrive.

Question 39

🟠 Mineral Deficiency and how it can affect the plant (with magnesium ions, for example)

Answer 39

Some plant diseases are the result if mineral deficiencies in the soil where the plants are growing. They are non-communicable - they are not passed from one plant to another. For example, plants need a good supply of nitrate ions from the soil to convert the sugars made in photosynthesis into proteins needed from growth amd protein synthesis. If there is littke nitrate deficiency in the soil, protein growth will be limited, the growth of plants will be stunted, and they will not produce a crop properly.

Plants take magnesium ions from the soil to make chlorophyll needed for photosynthesis. If the level of magnesium ions in the soil is low, the plant cannot make enough chlorophyll. The leaves become yellow and growth slows down because the plant cannot photosynthesise fully. The yellowing of the leaves due to lack of magnesium ions is known as chlorosis. If the missing mineral ions are replaced using fertilisers fairly quickly, the damage can be repaired and the plant can recover, but if this does not happen, then it will slowly die.

Question 40

🟠 Why is important that Plant Disease is detected early, and some outcomes if a plant is infected

Answer 40

In plants, as in people, the sooner a disease can be detected, the more likely it is that it can be treated effectively. Fast detection also helps reduce the slread if disease between plants, bevause diseased plants can be treated or removed. Symptoms if disease in plants include:

• Stunted growth (e.g Nitrate deficiency)
• Spots on leaves (e.g Black spot fungus on roses)
• Areas of decay or rotting (e.g black spot on roses, blights on potatoes)
• Malformed stems and leaves (e.g due to aphid or nematode infestation)
• Discolouration (e.g yellowing ir chlorosis in magnesium deficiency, mosaic patterns resulting from tobacco mosaic virus)
• Presence of visible pests (aphids, catipillars)

Identifying plant diseases is not easy. Many diseases give similar symptoms. However, it is very important to identify the cause of problems in plants. Some can be treated using pesticides or antifungal treatments, while mineral deficiencies can also be treated. But the sooner the treatment starts, the more likely it is to be a success. Some diseases cannot be treated - meaning it is inportant to remove the diseased plants as quickly as possible to prevent the spread of the pathogen throughout the garden, field, or woodland.

Question 41

🟠 How do you Identify Disease in different types of Plants

Answer 41

You can identify disease in garden plants, by comparing them to other, as well as images online and a gardening manual or website. When symptoms of disease occur in crop plants or forest trees, experts may visit the field or woodland to observe the symptoms in their natural environment. They may then take samples of diseased materials to a laborotary to identify the pathogen, using techniques that include DNA analysis to find out.

Plant scientists, foresters, farmers, and matket gardeners can use testing kits that cintain monoclonal antibodies to identify the presence of certain plant pathogens, fot example, the fungal pathogen Botrytis.

Question 42

🟠 Nematode Worms: Symptoms, and How it causes damage to the plant

Answer 42

Symptoms:

• There are root symptoms like root knots or galls, root leisons, excessive root branching, injured root tips and stunted root systems.
• The plants growth and strength will be less

How it causes damage to the plant:
These worms feed in or on plant roots, which damages them. This means the roots cannot absorb water and mineral ions effectively. The plant will fail to grow and thrive as a result.

Question 43

🟠 Aphids: Symptoms, and How it causes damage to the plant

Answer 43

Symptoms:

• Aphids can cause decreased growth rates, mottled leaves, yellowing, stunted growth, curled leaves, browning, wilting, low yields
• If symptoms worsen, the end resilt will most likely be in the pant dying.

How it causes damage to the plant:
Aphids deprive the plant cells of the products of photosynthesis, which can seriously damage and weaken the plant. This is done by the aphids’s sharp mouthparts that penetrate into the phloem of the plant and feed on the sugar rich sap.

Question 44

🟠 Potassium Deficiency: Symptoms, and How it causes damage to the plant

Answer 44

Symptoms:

• Symptoms could be a drown scorching and curling of the leaf tips and yellowing of the leaf veins
• Purple spits could also appear underneath the leaf
• Plant growth and root development will be less

How it causes damage to the plant:
A lack of potassium will result in enough energy ti grow, with the roots not being able to form properly. They will also have wek stems and stalks. Also, the edges of older plant leaves will look like they have been burned.

Question 45

🟠 Nitrogen Deficiency: Symptoms, and How it causes damage to the plant

Answer 45

Symptoms:

• Symptoms include poor plant growth, and leaves become pale green or yellow because they are unable to make sufficient chlorophyll.
• Lower leaves (older leaves) show symptoms first, since the plant will move nitrogen from older tissues to more important younger ones.

How it causes damage to the plant:
Without nitrogen, a plant cannot make the proteins amd amino acids (even in it’s DNA). This is why a nitrogen deficiency in the soil leaves plants stunded, because they simply can’t make their own cells.

Question 46

🟠 Physical Plant Barriers that can reduce Pathogen Invasion

Answer 46

Plants have a number of physical barriers that reduce the invasion of pathogens:

• The cellulose cell walls strengthen the plant also help to resist invasion by microorganisms. This is ine reason why the actions of aphidss that pierce the cellulose dell walls are so damaging. It greaches the barrier and gives pathogens a wat into the cells
• The tough waxy cuticle on the surface of the leaves acts as a barrier to the entry if pathogens. It is only at the stomata that pathogens actually have access to the cells within the leaf
• Bark on trees, and a layer of dead cells on the outside if stems, form a protective layer that is hard for pathogens to penertrate. When the dead cells are lost of shed, the pathigens will fall with them
• Leaf fall - deciduous tress lose their oeaves in autumn. Any pathogens that infect the leaves, such as rose black spot, fall off the tree when the leaves are lost

Question 47

🟠 Chemical Plant Barriers that can reduce Pathogen Invasion

Answer 47

Many plants produce antibacterial chemicals that protect them againsg invading pathogens, and these are very effective at preventing bacterial diseases in many plants. Until recently, people have not extracted and used plant chemicals as antibiotics. As current antibiotics become less effective, scientists are increasingly investigating plant antibacterial chemicals to see if they can be adapted fir use as antibiotics against human pathogens. Mint and witch hazel are often used as mild intissptics in cosmetics and over-the-counter medicines. Compounds from plants including pines, crypress, and euphorbias also have promising antibiotic properties.

Question 48

🟠 Plant barriers that can defend against Herbivores

Answer 48

Plants don’t just defend themselves against microorganisms. They also defend themselves against animals that want to eat them. Obviously if a plant is eaten by a large herbivore, it is destroyed and will not flower and reproduce. If smaller herbivores such as aphids, caterpillars, or beetles attack a plant, they can damage the plants and act as vectors of pathogens themselves. Not only that, the damage they do may allow other disease-causing organisms get in. Some of these defences are chemical and others are mechanical.

Question 49

🟠 Examples of Chemical and Mechanical Defences

Answer 49

Chemical Defences:
-Poison is used to deter herbiovires, for example, foxgloves, deadly nightshade, and yew. Animals quickly learn to avoid eating plants that make them unwell

Mechanical Defences:
-Thorns make it unpleasant and painful for large herbivores to eat them, for example, brambles, cacti, and gorse. Thorns are unlikely to deter insects

• Hairey stems and/or leaves deter insects and larger animals from feeding on them or laying their eggs on the leaves or stems, for example, lamb’s ears. Some plants combine hairs with poisons, for example, nettles.
• Dropping or curling leaves when touched are a rare but effective adaptation for leaves. This means insects are dislodged and larger animals could get frightened
• Mimicry is when some plants dropp to mimic unhealthy plants and this tricks animals into not eating them. Some mimic butterfly eggs on their surfaces, so real butterflies do not lay eggs in them to avoid competition with other caterpillars.

Question 50

❌ What Are The Aspectic Techniques (How to Culture Microorganisms Practical)

Answer 50

Aseptic techniques are designed to avoid contamination by unwanted microorganisms which could affect your results i.e. the growth of pathogens.

• Disinfect all work surfaces in the laboratory - alcohol is very effective, but very inflammable!
• The agar gel, all glassware and other equipment must be sterilised before use.
• The Petri dishes and culture medium - agar gel, must be all sterilised before conducting the experiment by heating to a high temperature e.g. >100°C.

This can be done in an autoclave which uses steam at high pressure to kill any microorganisms/pathogens present. The higher temperature should kill any unwanted microorganisms.

Question 51

❌ How is the Metal Inocluating Loop and the Bacterial Cultures Sterilised? (How to Culture Microorganisms Practical)

Answer 51

The metal inoculating loop is sterilised by placing it in a roaring blue bunsen flame until it glows red - no microorganism will survive this heat treatment!

The liquid bacterial cultures should be kept in special culture vials with lids. The lids should only be removed briefly, when transferring the bacteria to the petri dishes, to stop other microorganisms getting in.

You can briefly flame the neck of a glass container of bacteria just after its opened and just before its closed - the hot convecting air moves air out of the container preventing microbes in the air getting in.

Question 52

❌ What should you do to the Petri Dish To Prevent Future Contamination? (How to Culture Microorganisms Practical)

Answer 52

When the Petri dish is ready with the agar gel added and set, a lightly taped lid should be placed on it to stop any microorganisms in air getting in.

The Petri dishes should be stored upside down to prevent drops of condensation falling on the agar jelly.

The prepared agar gel petri dishes must not be incubated in case other bacteria begin to grow.
After use the agar plates should be sterilised in an autoclave to complete the steps to avoid contamination - to complete the aseptic procedure.

Question 53

❌ What is an Autoclave? (How to Culture Microorganisms Practical)

Answer 53

An autoclave is a device that uses steam under pressure to kill harmful bacteria, viruses, fungi, and spores on items that are placed inside the heated pressurised vessel. The items to be sterilised are heated to an appropriate sterilization temperature for a given amount of time.

Question 54

❌ How Do You Grow Microorganisms In The Lab

Answer 54

To culture (grow) microorganisms, you must provide the, with everything they need. This means giving them a liquid ir gel containing nutrients - a culture medium. This contains carbohydrate as an energy source, various minerals, a nitrogen source so they can make proteins, and sometimes other chemicals. Most microorganisms also need warmth and oxygen to grow.

Hot agar gel is poured into a Petri dish. It is then left to cool and set, befire you add the microorganisms. You can also culture microorganisms in a flask of sterile nutrient broth solution.

You need uncontaiminated cultred of microorganisms to investisgte the effects of chemicals such as dinfectants and antibiotics. Contamination can come from your, the air, the soil, or the water around you. It is important to agoid any unneccessary contamination. You must take great care when you are culturing microorganisms. The bacteria you want to grow may be harmless. However, there is always the risk that a mutation (a change in the DNA) will take place and produce a new dangerous pathogen.

Question 55

❌ Method To Prepare An Uncontaminated Culture of Microorganisms

Answer 55

• The Petri dishes on which you will grow your microorganisms mudt be sterilised before use. The nutrient agar must also be sterilised to kill off anh u wanted microorganisms. Glass dishes can be sterilised by heating. A special oven called an autoclave is often used. It sterilises using steam at high pressure. Plastic Petri dishes are often bought ready-sterilised. UV light or gamma radiation is used to kill the bacteria.
• The next step is to inoculate the sterile agar with the microorganisms you want to grow.
• Once you have inoculated your plates, the secured Petri dishes need to be incubated (kept warm) for several days so the microorganisms can grow. Petri dishes should be stored upside down so condensation does not fall from the lid onto the agar surface.

Question 56

❌ Method To Culture Microorganisms Safely In A Lab

Answer 56

1. Sterilise the inoculating loop used to transfer microorganisms to the agar by heating it until it is red hot in the flame of a Bunsen burner and then letting it cool. Do not put the loop doen or blow on it as it cools.
2. Dip the sterilised lp in a suspension of the bacteria you want to grow and use it to make zigzag streaks across the surface of the agar. Replace the lid on the dish as quickly as possible to avoid contamination.
3. Fix the lid of the Petri dish with adhesive tale to orevent microorganisms from the air cintsminating the culture - or microbes from the culture escaping. Do not seal all the way round the edge x as oxygen needs to get into the dish to prevent harmful anaerobic bacteria from growing.
4. The Petri dish should be labelled and stored upside doen to stop condensation falling onto the agar surface.

Question 57

❌ What Temperature/Conditions Should Cultures be Grown In?

Answer 57

In school and college laborstories, the maximum temperature at which cultures are incubated is 25°C. You are surrounded by disease-causinh bacteria all kf the time. If you cultured bacteria at 37°C (human body temperature), there would be a high risk of growing some dangerous pathogens. If you use a lower temperature, you reduce the likelihood of growing pathogens that might be harmful to people. In industrial conditions, bacterial cultures are often grown at higher temperatures to enable the microorganisms to grow more rapidly - for examp,e, insulin-producing genetically modified (GM) bacteria. A hospital lab also incubates human pathogens at 37°C, so that 5hey grow as fast a possible and are identified sooner.

Question 58

🟠 How Do Bacteria Reproduce?

Answer 58

Bacteria reproduce by simple binary fission - they split in two. If bacteria have the right conditions, including enough nutrients and a suitable temperature, they can grow very fast, dividing every 20 minutes.

Question 59

🟠 How Do You Calculate Bacterial Growth

Answer 59

The growth rate of bacteria population is affect by many different factors, including temoerature, avaliable nutreints, oxygen levels, and pH. Chaning any of these factors can affect the growth rate of a population.

You can calculate the number of bacteria in a population after a given time as long as you know the mean division time. This varies greatly, from 15 to 20 minutes, to hours, days, or even years. For example, if you hsve one bacterium with a mean division time of 20 minutes, in 24 hours you would have 4.7x10^21 (2sf) bacteria.

Question 60

🟠 Example Question - How To Calculate The Number Of Bacteria In A Population:

The mean division time for a population of bacteria is 30 minutes. Calculate how many bacteria will result from each individual bacterium after 8 hours.

Answer 60

Step 1: Calculate How Many Times The Bacteria Will Divide In 8 Hours
If the bacteria divide every 30 minutes, they will divide 60/30 or two times every hour.

If the colony grows for 8 hours, each of the initial bacteria will divide 8 x 2 or 16 times, meaning there is 16 divisions in total.

Step 2: Calculating The Number Of Bacteria In The Population
Every time tne bacteri divide, the population doubles, so we can find the number of bacteria using tne following equation:

Bacteria at the end of the growth period = Bacteria at the beginning of the growth period x 2^number of divisions.

So, in this case the:

• Number of bacteria at beginning = 1
• Number of divisions = 16

Number of bacteria at the end of the growth period = 1 x 2^16 = 1 x 65,536 = 65,536 bacteria.

Question 61

❌ How Can You Prevent Bacteria Growth

Answer 61

There are a number of ways to prevent the growth of bscteria. One way is to raise or lower the temperature. Also, chemicals can be used to stop them trowing or to kill them. Disinfectants are chemicals used to kill bacteria in the environment around us. An antiseptic is a disinfectant that is safe ro use on human skin. Antibiotics are chemicsls that can be used inside our bodies, which kill bacteria or prevent them from growing. You can investigate the effectiveness of temperature changes or chemicals at oreventing the growth of bacteria. In each case you need a way of working out how many bacteria have grown.