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Flashcards in B5 Communicable diseases Deck (225)
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1

What is your health?

a state of physical and mental well-being, not just an absence of disease

2

What are examples of communicable diseases

tuberculosis, flu, diarrhoeal diseases and malaria

3

What are communicable diseases caused by?

pathogens such as bacteria and viruses that can be passed from one person to another

4

What can non-communicable diseases not do?

cannot be transmitted from one person to another

5

Give examples of non-communicable diseases

Heart disease and arthritis, cancer

6

What three other factors affect ill health

Diet, stress and life situations

7

What do life situations include

the part of the world where you live
your gender
your financial status
you ethnic group
the level of free health care provided where you live
how many children you have
local sewage and rubbish disposal

8

Give an example in which viruses living in cells can trigger changes that lead to cancers

the human papilloma virus can cause cervical cancer

9

What may be the cause of a defect in the immune system that helps the body to destroy pathogens?

genetic makeup, poor nutrition or infections such as HIV/AIDS; more likely to suffer other communicable diseases

10

Immune reactions initially caused by a pathogen, even something like the common cold, can trigger allergies to factors in the environment. What can these allergies called?

skin rashes, hives, or asthma

11

What can severe physical ill health lead to

depression and other mental illness

12

What health conditions is malnutrition often linked to

deficiency diseases, a weakened immune system, obesity, cardiovascular diseases, type 2 diabetes, and cancer

13

What are the microorganisms that cause disease called?

pathogens, infecting animals and plants

14

What can pathogens be?

bacteria, viruses, protists, or fungi

15

How are communicable diseases caused?

either directly by a pathogen or by a toxin made by a pathogen

16

What are pathogens able to do?

can be passed from one infected individual to another individual who does not have the disease

17

What are known as fairly mild communicable diseases

common cold and tonsillitis

18

What are known as killer diseases

tetanus, influenza, and HIV/AIDS

19

Sometimes communicable diseases can be passed between different species of organisms. What is an example.

-infected animals such as dogs or bats can pass rabies onto people
-tuberculosis can be passed from badgers to cows, and from cows to people

20

What causes the majority of communicable diseases in people?

bacteria and viruses

21

In pplants, what are the most common pathogens

viruses and fungi

22

What are bacteria

single-celled living organisms that are much smaller than animal and plant cells

23

What is bacteria used for?

to make food such as yogurt and cheese, to treat SEWAGE, and to make medicines

24

Bacteria are important where?

in the environment, as a decomposer, and in the body

25

How much bacteria do scientists estimate that most people have in their guts?

between 1 and 2 kg of bacteria; having a major effect on our health and well-being

26

Pathogenic bacteria are the minority

but they are significant because of the major effects they can have on individuals and society

27

What sort of shape does viruses have?

regular shapes and are even smaller than bacteria

28

What causes diseases in every type of living organism?

viruses

29

What happens once bacteria and viruses are inside your body?

they may reproduce rapidly

30

How may bacteria divide rapidly?

splitting in two (binary fission); may produce toxins (poisons) that affect your body and make you feel ill; sometimes they directly damage your cells

31

What do viruses do?

take over the cells of your body

32

What do viruses do once they have taken over the cells of your body?

they live and reproduce inside the cells, damaging and destroying them

33

What are some common disease symptoms?

high temperature, headaches. and rashes

34

Why do symptoms happen

by the way your body responds to the cell damage and toxins produced by the pathogens

35

The more pathogens that get into your body, the more likely..

you will develop an infectious disease

36

Give three ways in which pathogens spread from one individual to another

by air (including droplet infection)
direct contact
by water

37

What causes infectious diseases?

microorganisms known as pathogens

38

How do pathogens make you ill?

as a result of reaction to toxins produced,
or damage caused to cells

39

By air- droplet infection

droplets full of pathogens expelled in
coughing, sneezing, or talking, droplets breathed in by others,

40

direct skin contact

pathogens spread from skin of one person to skin of another

41

direct contact of body fluids

pathogens pass directly from inside
one person’s body into another

42

by contaminated water

taking in pathogen through digestive
system

43

by under-cooked or contaminated food-

taking in pathogen through digestive system

44

By air in plants

fungal spores carried in air from one plant to another

45

by direct contact-

- pathogens on traces of plant material come into contact with new plants in the soil and infect them

46

by contaminated water

fungal spores carried in splashes of
water from one plant to another

47

Describe and explain the main differences between bacteria and viruses and how they cause diease

Bacteria are single-celled organisms much smaller than plant and
animal cells.
Viruses are even smaller than bacteria.
Bacteria divide rapidly by splitting in two (binary fission).
Viruses take over body cells and reproduce inside them.
Bacteria may produce toxins or directly damage body cells.
Viruses damage and destroy cells.

48

To culture (grow) microogranisms, you must..

provide them with everything they need

49

what is a culture medium

giving bacteria a liquid or gel containing nutrients

50

What do culture mediums contain?

carbohydrate as an energy source, various minerals, a nitrogen source so they can make proteins, and sometimes other chemicals

51

What do most micro-organisms also need to grow?

warmth and oxygen

52

How does one culture bacteria

Hot agar gel is poured into a Petri dish.
It is then left to cool and set before the micro-organisms are added

53

Where can you also culture micro-organisms?

in a flask of sterile nutrient broth solution

54

What sort of cultures of microorganisms do you need to investigate the effects of chemicals such as disinfectants and antibiotics

uncontaminated

55

Where can contamination come from?

your skin, the air, the soil, or the water around you

56

Why is it important to avoid any unnecessary contamination?

The bacteria growing may be harmless, however always the risk that a mutation (change in the DNA) will take place and produce a new and dangerous pathogen

57

Why do scientists culture microorganisms in the labratory

To find out what nutrients they need to grow
and to investigate which chemicals are best at killing them.

58

Explain why agar gel is important in setting up bacterial cultures

Agar gel is a culture medium
giving microorganisms everything they need to grow

59

Suggest why bacteria are grown at 25 degrees Celsius or below in the school lab when this is not their optimum temperature for growth

reduces risk of growing dangerous pathogens

60

Explain why bacteria are often cultured at much higher temperatures in industrial plants and hospital laboratories

Higher temperatures enable microorganisms to grow much more rapidly so that they can be identified sooner (e.g., in hospital labs) or to produce products more quickly in industry (e.g., insulin-producing
GM bacteria).

61

Explain why petri dishes are not opened before incubation once they have been inoculated and sealed.

To prevent contamination of culture by microorganisms from the environment and to prevent release of potentially harmful microorganisms that might
grow.

62

Suggest what might limit the growth of bacteria in a culture on a Petri dish because these ideal conditions do not last forever

Petri dish- limited supplies (nothing new added), bacteria use up available food and oxygen (limiting growth).
Petri dish has no mechanism for removal of waste products (build-up of carbon dioxide and other toxins can poison bacteria and stop growth)

63

What are you surrounded by all the time?

disease causing bacteria

64

What happens if bacteria have the right conditions, including enough nutrients and a suitable temperature?

They can grow very fast, dividing every 20 minutes

65

What factors may affect growth rate of a bacteria population

temperature, available nutrients, oxyygen levels, and pH

66

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 15-20 minutes to hours, days or even years

67

What is the formula for calculating bacteria at the end of the growth period?

bacteria at the beginning of the growth period x 2ⁿᵘᵐᵇᵉʳ ᵒᶠ ᵈᶦᵛᶦˢᶦᵒⁿˢ

68

What are the ways to prevent the growth of bacteria?

-raise/ lower the temperature
-chemicals to stop them growing or kill them

69

What is a disinfectant?

chemicals used to kill bacteria in the environment around us

70

What is an antiseptic?

a disinfectant that is safe to use on human skin

71

What are antibiotics?

chemicals that can be used inside our bodies, which kill bacteria or prevent them from growing

72

In the mid-1850s, who was Semmelweis?

a doctor at ime where many women in hospital died from childbed fever a few days after giving birth; nobody knew why

73

What was something important that Semmelweis noticed?

his medical students went straight from dissecting a dead body to delivering a baby without washing their hands

74

What did Semmelweis wonder?

If they were carrying the cause of disease from the corpses to their patients

75

What did Semmelweis also notice from another doctor?

another doctor died from symptoms identical to childbed fever after cutting himself while working on a body. This convinced him that the fever was caused by some kind of infectious agent

76

As a result of Semmelweis' discovery, what did he insisted to his medical students?

wash their hands before delivering babies; fewer mothers died from the fever. However, other doctors were very resistant to Semmelweis's ideas

77

In the mid-to late-19th century, who are two other people who made scientific discoveries in terms of medicine

Louis Pasteur and Joseph Lister

78

What did Louis Pasteur do?

showed that microorganisms cause disease; developed vaccines against diseases such as anthrax and rabies

79

What did Joseph Lister do?

started to use antiseptic chemicals to destroy pathogens before they caused infection in operating theatres

80

As microscopes improved...

it became possible to see pathogens more clearly. This helped convince people that they were really there

81

What is another way to help us prevent from disease happening?

understanding how communicable diseases are spread from one person to another

82

What are the four ways to prevent the spread of communicable diseases?

Hygiene
Isolating infected individuals
Destroying or controlling vectors
Vaccination

83

What are some simple hygiene measures?

Hand washing; using disinfectants on kitchen work surfaces, toilets, etc, to reduce the number of pathogens; keeping raw meat away from food that is eaten uncooked; coughing or sneezing into a tissue; maintaining the hygiene of people and agricultural machinery to help prevent the spread of plant diseases

84

Explain 'isolating infected individuals'

The fewer healthy people who come into contact with the infected person, the less likely it is that the pathogens will be passed on

85

Why may isolating infected individuals may be difficult for plants

only those plants that are small and can be moved and destroyed easily can this be possible

86

Give a 3 examples of a vectors?

-mosquitoes carry a range of diseases, such as malaria and dengue fever
-Houseflies can carry over 100 human diseases
-rats

87

What happens when vectors are destroyed?

The spread of disease can be prevented

88

What happens when the numbers of vectors are controlled?

the spread of disease can be greatly reduced

89

What happens during vaccination?

doctors introduce a small amount of harmless form of a specific pathogen into your body

90

How do vaccinations work

If you come into contact with the live pathogen, you will not become ill as your immune system will be prepared

91

Vaccination is a successful way of...

protecting large numbers of humans and animals against serious diseases

92

Why can't vaccinations be used in plants?

they don't have an immune system

93

Suggest why other doctors were so resistant to Semmelweis's ideas?

1.Pathogens are very small, so before development of microscopes- people had no way of seeing bacteria or viruses.
2. Inability to see microorganisms made it very difficult to understand how
diseases spread.
3. Evidence (e.g., improved hygiene reducing the deaths from childbed
fever) was seen as challenging normal practice.
4. Difficult to convince people whose ideas are entrenched.
5. Need people prepared to take a chance (e.g., Pasteur, Lister).
6. Takes time for evidence of effectiveness of new idea to build up

94

What can viruses do?

can infect and damage all types of cells

95

Why is it important for viruses to stop them spreading?

Scientists have not developed medicines to cure viral diseases

96

What are symptoms a result of?

the way the body reacts to the viruses damagining and destroying cells as they reporduce

97

What are the main symptoms of measles?

fever and red skin rash

98

How is measles spread?

the inhalation of droplets from coughs and sneezes and is very infectious

99

Measles is a serious disease; what can it cause?

blindness and brain damage; may be fatal if complications arise

100

There is no treatment for measles, so what needs to be done to stop the spread of the virus?

isolating infected individuals

101

How many people died of measles in 2013?

145 700 globally died of measles

102

Why is measles now rare in the UK?

a result of improved living conditions and a vaccination programme for young children

103

What disease can eventually lead to aids?

HIV

104

In 2013, how many people have died of a HIV related disease?

1.5 million people

105

Why do many people not realise they are infected with HIV

the virus only causes a mild, flu-like illness to begin with

106

What does HIV do?

attack the immune cells and after the initial mild illness it remains hidden inside the immune system, sometimes for YEARS, until the immune system is so badly damaged that it can no longer deal with infections or certain cancers

107

How is HIV spread?

direct SEXUAL CONTACTS and the exchange of BODY FLUIDS such as blood, which occurs when drug users share needles or when unscreened blood is used for transfusions

108

What can be used to prevent the development of AIDS for many years and give HIV positive people an almost normal life expectancy

The regular use of antiretroviral drugs

109

Why may it be unfortunate for the majority of people infected with HIV who live in areas such as sub-Saharan Africa

It is hard to get antiretroviral drugs

110

To have the best chance of long-term survival for those with HIV..

antiretroviral drugs must be started as soon as possible after infection

111

Tobacco mosaic virus was the first...

first virus ever to be isolated

112

What is TMV?

a widespread plant pathogen that affects around 150 species of plants including tomatoes and tobacco plants

113

What does TMV cause?

a distinctive 'mosaic' pattern of discoloration on the leaves as the virus destroys the cells

114

How does TMV affect plant growth?

affected areas does not photosynthesise; seriously reducing the yield of crop

115

How is TMV spread?

contact between diseased plant material and healthy plans; insects can act as vectors

116

How long can TMV (virus) remain infectious in the soil for?

for about 50 years

117

There is no treatment for TMV, so what do farmers do?

farmers now grow TMV- resistant strains of many crop plants

118

What can also help the spread of TMV?

good field hygiene and good pest control

119

What is salmonella?

bacteria that live in the gut of many different animals

120

What can antibiotics do?

kill bacteria or stop them growing and cure bacterial

121

Where can salmonella be found

in raw meat, poultry, eggs and egg products

122

What happens if salmonella gets into our bodies?

They disrupt the balance of the natural gut bacteria and can cause food poisoning

123

One common cause for infection of salmonella?

eating undercooked food, when the bacteria have not been killed by heating

124

What is another cause for salmonella?

eating food prepared in unhygienic conditions where food is contaminated with salmonella bacteria from raw meat

125

When do the symptoms develop for salmonella?

within 8-72 hours of eating infected food

126

What are symptoms of salmonella?

fever, abominable cramps, vomiting and diarrhoea are caused by the bacteria and the toxins they secrete

127

Why may salmonella be very fatal to very young children and the elderly

dehydration

128

In the UK, poultry are vaccinated vaccinated against salmonella to control the spread of diease

Campylobacter, another bacterium found in chickens, still causes around 280 000 cases of food poisoning each year

129

To prevent food poisoning...

-keep raw chicken away from food that is eaten uncooked
-avoid washing raw chicken (sprays bacteria)
-wash hands and surfaces well after handling raw chicken
-cook chicken thoroughly

130

What is a gonorrhoea?

a sexually transmitted disease

131

How is gonorrhoea spread?

unprotected sexual contact

132

What are the early symptoms of gonorrhoea?

thick yellow or green discharge or pain in urination

133

What happens to babies born from infected mothers? (gonorrhoea)

severe eye infections and even become blind

134

What may untreated gonorrhoea lead to?

long-term pelvic pain, infertility, and ectopic pregnancies

135

Babies born to infected mothers may have..

severe eye infections and even become blind

136

What can gonorrhoea be treated with and why?

antibiotics as it is bacterial

137

Why did gonorrhoea become increasingly difficult to treat?

it used to be cured easily using penicillin but now many antibiotic resistant strains of gonorrhoea have evolved

138

How can gonorrhoea be prevented?

barrier method of contraception such as a condom and by reducing the number of sexual partners

139

Where are the relatively few bacterial diseases of plants located?

in tropical and sub-tropical regions

140

What is Agrobacterium tumefacians?

a bacterium that causes crown galls

141

What are crown galls?

a mass of unspecialised cells that often grow at the join between the root in infected plants

142

What do crown galls infect?

many different plant types including fruit trees, vegetables, and garden flowering plants

143

What do crown galls do?

the bacteria insert plasmids into the plant cells and cause a mass of new undifferentiated genetically modified cells to grow

144

How may crown galls be beneficial to scientists?

became a key tool for scientists when genetically modifying plant cells. Scientists make use of the way the bacteria naturally infect plant cells and give them new added genes. They manipulate the bacteria so they carry desirable genes into the cells they infect

145

Name one way that antibiotics work to cure bacteria infections

kill bacteria or prevent growth of bacteria

146

Describe how people become infected with food poisoning caused by salmonella

Most common causes are eating either under cooked food contaminated
with Salmonella
or food prepared in unhygienic conditions that becomes contaminated
by Salmonella bacteria.

147

Doctors in the UK rarely treat salmonella food poisoning with antibiotics, why?

doesn’t last long (only a few days)
• unpleasant but not serious for most people
• antibiotics would be lost from system through sickness and
diarrhoea
• risks development of antibiotic resistance

148

Suggest three ways of preventing the spread of gonorrhoea

•being celibate
• having a single sexual partner,
• limiting number of sexual partners,
• always using barrier method
• of contraception (e.g., condom).

149

Until recently gonorrhoea was relatively easy to treat, why?

bacterial infection,
so could be treated with antibiotics

150

Describe the implications of increased antibiotic resistance in the bacteria causing gonorrhoea for the 106 million people who are infected with the disease each year

At this point, lots of people will have the disease

151

A small number of human fungal diseases can be fatal when..

they attack the lungs or brains of people who are already ill?

152

What can also develop serious fungal infections?

damaged heart valves

153

What are usually effective against skin fungi like athlete's foot but it hard to treat against deep-seated tissue infections?

anti-fungal drugs

154

What is most common in plants (and most devastating) but not in animals.

fungal diseases

155

what are some examples of fungal infections?

stem rusts and various rotting diseases

156

What is Rose Black Spot?

a fungal disease of rose leaves

157

What does rose black spot do?

causes purple or black spots to develop on the leaves and it is a nuisance in gardens and for commercial flower growers

158

What happens to the leaves that are affected by rose black spot?

The leaves often turn yellow and drop early.

159

How does rose black spot weaken the plant?

no green pigment, reduces area of leaves available for photosynthesis

160

Rose black spot results in the plant not...

flowering well

161

How are the spores of the fungus spread?

-spread in the environment carried by wind
-spread over the plant after it rains in drips of water that splash from one leaf or plant to another
-spores stay dormant over winter on dead leaves and on the stems of rose plants

162

How may gardeners or horticulturists try to prevent the spreading of rose black spot?

-removing and burning affected leaves and steps
-chemical fungicides (help treat disease, stops it spreading)
-bred types of roses resistant to black spot (but the disease still cannot be prevented or cured)

163

What are protists?

a type of single-celled organisms that cause a range of diseases in animals and plants

164

Protists are relatively ___ pathogens but the _____ they cause are often serious and ____ to those infected

1. rare
2.diseases
3.damaging

165

Diseases caused by protists usually involve a what?

a vector that transfers the protist to the host

166

What is one of the best known and globally serious protists disease called?

malaria

167

What is malaria caused by?

protist pathogens that are parasites

168

What are parasites?

protist pathogens that live and feed on other living organisms

169

What does the life cycle of a protist involve?

time in the human body and time in the body of a female Anopheles mosquito

170

How do protists reproduce?

sexually- in the mosquito
asexually- human body

171

What do mosquitoes act as to disease?

vectors

172

Before a female mosquito can lay her eggs...

she needs two meals of human blood

173

What happens when the protists are passed into the human bloodstream?

the protists travel around the human body in the circulatory system; affecting the LIVER and DAMAGE red blood cells

174

What are the fatal symptoms of of malaria?

recurrent episodes of fever and shaking when the protists burst out of blood cells; weakening the affected person

175

If malaria is diagnosed quickly, it can be treated...

using a combination of drugs, but this is not always available in the countries most affected by malaria

176

What are the ways the spread of malaria can be controlled in a number of ways, most of which target the mosquito vector

-insecticide-impregnated insect nets
-Insecticides
-preventing the vectors from breeding (remove standing water/ spraying water w/ insecticides to kill the larvae)
-antimalarial drugs that kill the parasites in the blood

177

What gives pathogens a way in in the body?

Every body opening as well as any breaks in the skin

178

The more pathogens that get into your body, the most likely it is to...

get an infectious disease

179

What does your skin do?

-covers your body and acts as a barrier.
-prevents bacteria + viruses reaching the tissues beneath

180

What happens if you damage or cut your skin?

the barrier is broken but your body restores it
-you bleed, and the platelets in your blood set up a chain of events to form a lot that dries into a scab

181

Your skin produces what to destroy pathogenic bacteria

antimicrobial secretions

182

What is healthy skin also covered with and why

microorganisms that help keep you healthy and act as an extra barrier to the entry of pathogens

183

Your respiratory system is a ___ link in your body defences

weak

184

Every time you breathe in, you...

draw air full of pathogens into the airways of the lungs (same way w/ food and drink)

185

What features does the nose have to help prevent pathogens constantly causing infections

-full of hairs and produces a sticky liquid
-hairs + mucus: trap particles in the air that may contain pathogens/ irritate lungs

186

What happens if you spend a long time in an envirnment with lots of pollution

The mucus you produce is blackened

187

What does the trachea and bronchi do in response to pathogens.

secrete mucus that traps pathogens from the air

188

What are the lining of the tubes covered in? (trachea and bronchi)

cilia : tiny hair-like projections from the cells
-waft the mucus up to the back of the throat where it is swallowed

189

What does the stomach do to help prevent pathogensconstantly causing infections

produces acid
-destroys the microorganisms in the mucus you swallow (as well as the majority of pathogens you taken in through your mouth in your food and drink)

190

In spite of your body's defence mechanism, some pathogens will get inside your body.

Once there, they will meet your second line of defence- the white blood cells of your immune sustem

191

What are the three ways WBC's get rid of pathogens

1. ingesting microorganisms
2. producing antibodies
3. producing antitoxins

192

What do antibodies do?

target particular bacteria or viruses and destroy them

193

how are antibodies helpful?

When your WBC's have produced antibodies once against a particular pathogen, they can be made very quickly if that pathogen gets into the body again.

194

Some white blood cells produce antitoxins

These counteract (cancel out) the toxins released by pathogens

195

Why is mucus green?

some WBCs contain green-colored enzymes.
-they destroy the cold viruses and any bacteria trapped in the mucus when you have a cold. The dead wbcs along with the dead bacteria and viruses, are removed in the mucus, making it look green

196

The global loss of food crops to plant pathogens is what percentage

15-40% a year

197

Other than viruses, bacteria, and fungi, plants are also vulnerable to?

attacks by pests that cause a lot of damage

198

Insect pests can..

destroy plants directly and act as vectors of disease

199

What do aphids have?

sharp mouthparts to penetrate into the phloem vessels of the plant so they can feed on the sugar-rich phloem sap

200

How do aphids attack?

in huge numbers, depriving the plant cells if the products of photosynthesis; seriously damaging and weakening the plant

201

Aphids can be destroyed by?

using chemical pesticides or using biological pest control (in enclosed spaces such as greenhouse gases)

202

What is an example of biological pest control?

releasing aphid-eating insects such as ladybirds and their larvae can control the pathogen population so it does not have an impact on the success of the crop

203

Why do plants fail to grow and thrive due to pests?

Other plant pests, including tiny 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

204

Some plant diseases are the result of mineral deficiencies in the soil where the plants are growing.

They are non-communicable- they are not passed from one plant to another

205

Why may plants need a good supply of nitrate ions from the soil?

to convert the sugars made in photosynthesis into proteins needed for growth in protein synthesis

206

What happens in there is a 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

207

Why do plants take magnesium ions from the soil?

to make the chlorophyll needed for photosynthesis

208

What does it mean 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

209

What is the yellowing of the leaves due to lack of magnesium ions known as?

chlorosis

210

What do the symptoms of disease in plants include?

1. stunted growth (e.g. nitrate deficiency)
2. spots on leaves (black spot fungus in roses)
3. areas of decay or rotting (blights on potatoes)
4. growths (crown galls)
5.malformed stems and leaves (aphids)
6. discoloration (chlorosis)
7.presence of visible pests

211

fast detection helps...

reduce the spread of disease between plants, because diseased plants can be treated or removed

212

What are the four physical barriers that reduce the invasion of pathogens in plants?

1. the cellulose cell walls that strengthen plant cells
2. tough waxy cuticle on the surface
3. bark on trees. and a layer of dead cells on the outside of stems
4. leaf fall

213

Elaborate on 'the cellulose cell walls that strengthen plant cells'

resist invasions by microorganisms
(it is why aphids that pierce cellulose walls are so damaging)

214

elaborate on 'tough waxy cuticle on the surface'

barrier to entry of pathogens
-it is only at the stomata that pathogens actually have access to the cells within the leaf

215

elaborate on 'bark on trees. and a layer of dead cells on the outside of stems'

protective layer hard for pathogens to penetrate
(when the dead cells are lost or shed, the pathogens fall off with them)

216

Elaborate on 'leaf fall'

deciduous trees lose their leaves in autumn. Any pathogens that infect the leaves, such as rose black spot, fall off the tree when the leaves are lost

217

What are chemical barriers for plants

many plants produce antibacterial chemicals that protect them against invading pathogens

218

What are mint and witch hazel used for?

as mild antiseptics in cosmetics and over-the-counter medicines

219

Compounds such as what from plants also have promising antibiotic properties?

pines, cypress, and euphorbias

220

Plants don't just defend themselves against microorganisms

they also defend themselves against the large and small animals that want to eat them

221

What are several defenses against herbivores

-poisons
-thorns
-hairy stems and/or leaves
-drooping or curling when touched
-mimicry

222

What is mimicry

some plants droop to mimic unhealthy plants and this tricks animals into not eating them
-some mimic butterfly eggs on their surfaces

223

hairy stems and/or leaves

deter insects and larger animals from feeding on them or laying their eggs on the leaves or stems

224

drooping or curling when touched

rare but effective- leaves collapse suddenly, dislodging insects and frightening larger animals

225

why are scientists increasingly investigating plant antibacterial chemicals?

to see if they can be adapted for use as antibiotics against human properties