Biodiversity, Evolution and Disease Flashcards
10.1
What is taxonomy?
All organisms share a common ancestor, from which they diversified into the forms we have today through variation and evolution. Because of this fact, techniques of classification can be used to make a taxonomy of life on Earth. Smaller groups are placed within larger groups, with no overlap between them. Each group is called a taxon, plural taxa.
10.1
In taxonomy, what is the hierarchy used now?
- (D, K, P, C, O, F, G, S)
The hierarchy now used from the largest tax onto the smallest is: Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.
10.1
In taxonomy, what are trees of life?
- what are they used for
Trees of life used to be solely based on physical similarities between organisms, but now we can use many other lines of evidence such as genetics, biochemistry, and the fossil record to construct phylogenetic trees to illustrate relationships.
10.1
In Classification, what are the 3 domains?
- how is a species named
Based on recent evidence, the new taxon domain comes above Kingdom. There are three domains: Bacteria, Archaea and Eukarya.
Each species is universally identified by a binomial consisting of the name of its genus and species (e.g. Homo sapiens)
10.1
What is Classification?
- when is a species name written in italics
- The genus name must always start with a capital letter, but the species name is always in lower case.
- when identifying a binomial, it is written in italics
10.2
Based on shared characteristics, what can living organisms be classified into?
Living organisms can be classified into groups based on their shared characteristics. Until recently, classification divided life into 5 kingdoms: Prokaryotes are Protoctista, Fungi, Plantae, Animalia.
10.2
What does each domain contain?
Each of the domains contain unique ribosomal RNA (rRNA)
10.2
What is Bacteria (prokaryotes)?
- describe what they are
- give an example
- They differ from Archaea as they have slightly different membranes.
- Hugely diverse and impossible to decide upon the number of species of bacteria as they can share genetic information through horizontal gene transfer.
-For example cyanobacteria
10.2
What is Archaea (prokaryotes)?
- describe what they are
- give an example
- These often inhabit extreme environments because they have adaptations in their cell membranes to withstand high temperature, pH and soil concentrations.
- They are very small in size, similar to bacteria or mitochondria.
10.2
What is Eukarya (eukaryotes)?
- describe what they are
- give an example
- These have membrane-bound organelles and are divided into 4 kingdoms, Protoctista, Fungi, Plantae, Animalia.
10.3
What is the definition of a biological species?
- A biological species is: a group of similar organisms that can breed together to produce fertile offspring.
10.3
What is the phylogenetic species definition?
- For asexual organisms (e.g. bacteria and some plants) we can use the phylogenetic species definition: the smallest group of organisms that are descended from a single common ancestor.
10.3
What is one way in which classification can be ahieved
- Classification can be achieved through comparing observable features.
10.4
What is fossilisation?
- how does it occur
- fossilisation occurs in particular conditions where hard tissues (such as bones and teeth) are replaced with minerals and sedimentary rock.
10.4
What is the fossil record?
- how is it useful
The fossil record is a useful tool to see how organisms evolve over time and when different species started to appear (e.g. Horses and humans). The fossil record is incomplete, so there are some gaps in what we know of past diversity.
10.4
What DNA evidence is used in classification?
- Comparing DNA can help determine how closely related different species are. The fewer genetic similarities, the more distantly related the species are.
10.4
What molecular evidence is used in classification?
- Like DNA, other molecules can be compared for similarities (e.g. RNA and DNA polymerase of vital enzymes that are evolved slowly over time but have been present since the earliest organisms).
10.4
What is the evidence for the theory of evolution by natural selection?
- Contribution of Darwin and Wallace.
Charles Darwin is credited with the theory of evolution by natural selection from his field work on the Galapagos Islands. Alfred Russell Wallace researched a similar conclusion at the same time from his field work in Malaysia. They later worked together, leading Darwin to publish On the Origin of Species.
10.5
What is genetic variation in a population?
In a population, not all organisms survived to be able to reproduce. Individuals die or fail to reproduce due to predation, disease or competition for resources: food, water, space, mates and environmental change.
10.5
What is natural selection?
Organisms with characteristics that allow them to survive will have a selective advantage when there is a new selection pressure, and are more likely to reproduce (high reproductive success).
10.5
What is passed onto the next generation in genetic variation?
Favourable alleles are passed onto the next generation. Those allele frequencies increase in the gene pool over many generations
10.5
What is evolution?
Evolution is the change of allele frequency within a population over time as a result of these processes.
10.5
What are the different types of variation.
- Intraspecific variation.
- Interspecific variation.
10.5
What is Intraspecific variation?
Variation between individuals within the same species.
10.5
What is Interspecific variation?
Variation between individuals in different species.
10.5
What are the two causes of variation?
- Environment.
- Genetics.
10.5
How can the environment cause variation?
The conditions in which an Organism develops can cause variation.
- For example, intensity of light and the supply of water and nutrients will cause variation in the phenotype of plants.
10.5
How can genetics cause variation?
- Mutation; Random spontaneous change in the base sequence of DNA.
- Meiosis; Two main events that can cause variation:
- Independent assortment of homologous chromosomes
- Crossing over that happens between the non-sister chromatids of homologous chromosomes - Random fertilisation of gametes; sperm and egg (or equivalent) meet by chance, contributing to novel combinations of alleles.
10.6
What are the different types of variation?
- continuous variation
- discontinuous variation
10.6
What is continuous variation?
No distinct groups. Quantitative differences in phenotype e.g., mass, height.
10.6
What is discontinuous variation?
Distinct groups, qualitative differences in phenotype, e.g. blood groups, eye colour.
10.6
What is standard deviation?
A measure of how spread out the data is. The greater the standard deviation, the greater the spread of data. In terms of variation, a characteristic that has a high standard deviation has a large amount of variation
- The standard deviation gives an indication of the range of values about the mean
10.6
How do you investigate variation in a species?
Quantitative investigations of variation within a species involved:
- Collecting data from random samples from a single population.
- Calculating a mean value and the standard deviation of that mean.
- Interpreting mean values and their standard deviations.
10.6
What are the 2 ways to reduce sampling bias?
- Samples must be collected to reduce the risk of sampling bias.
- Sampling bias can also be reduced by having a large sample size.
10.6
What is the Spearman’s rank correlation coefficient (rs)?
This tells us the strength and direction of a correlation between 2 variables. Correlation will always fall between +1.0 and -1.0.
- If rs is a negative number. It shows that there is a negative relationship between the two variables.
- If rs is a positive number, it shows that there is a positive relationship between the two variables.
- If rs = 0, there is no relationship between the variables.
The closer rs is to +1.0 or -1.0, the stronger the correlation and therefore the better is to use for predictions.
10.7
What are adaptations?
- what are the 3 categories of adaptations
Adaptations are inherited features that allow an Organism to survive in its niche.
- Adaptations can be anatomical, physiological or behavioural.
10.7
Anatomical (related to body structure).
- In high-predator environments, water fleas tend to have thicker exoskeletons than those in low-predator environments.
- Some bacteria have flagella to help them move independently.
10.7
Physiological (related to bodily function).
- Animal species, such as yaks, that live in high altitudes have more red blood cells that support living in low-oxygen conditions than those at low altitudes.
- Plants produce bitter-tasting chemicals when being eaten and have stomata that close to prevent water loss.
- Yeast Change biochemical pathways in response to environmental sugar levels.
10.7
Behavioural (related to behaviour).
- Fish that shoal decrease their individual chance of being eaten by a predator.
- Some bacteria will move towards food sources.
10.8
What is Convergent evolution?
Organisms from different taxonomic groups can have similar anatomical features. This is because they have adapted through natural selection to occupy similar niches.
10.8
Give an example of convergent evolution.
For example, even though marsupials and placental mammals diverged over 100 million years ago, the marsupial mole and placental mole have evolved to converge and share these anatomical features.
- This phenomenon can be seen in many marsupials and their placental counterparts.
10.8
What is speciation?
- explain how it works
- Under certain conditions, a new species can arise from a population of an existing species.
- If two populations are reproductively separated, their gene pools become different.
- If these differences make it impossible for the two populations to breed and produce fertile offspring, they become two species.
11.1
What is biodiversity?
biodiversity refers to the variety of living organisms with a particular are. It includes plants, animals, fungi, bacteria, and other microorganisms, as well as the genes they contain, and the ecosystems they inhabit.
11.1
Why is it important to study biodiversity?
biodiversity is important in the study of habitats as an indicator of their health
11.1
Why is maintaining biodiversity important?
Maintaining biodiversity is important for the economy, aesthetics, and ecology, and action to preserve it must be taken at local, national, and global levels
11.1
What are the 3 levels at which biodiversity can be studied at?
- Habitat biodiversity (e.g., sand dunes, woodland, meadows, streams)
- Species biodiversity (species richness and species evenness)
- Genetic biodiversity (e.g., different breeds or varieties within a species)
11.1
What is species richness?
- a measure if the number of different species in habitat - the more species in a habitat the richer it is
- estimate using a qualitative study (i.e., observe and record the different species found in the habitat)
11.1
What is species evenness?
- a measure of the number of individuals of each species in a habitat
- requires a quantitative study:
> plants; count individuals of each species or percentage cover
> animals; can be counted directly, or a population estimated using a mark-recapture technique
11.2
What is sampling?
sampling is a method of measuring the biodiversity of a habitat.
11.2
What are the 2 different ways to sample in a field?
- random sampling
- non-random sampling
11.2
What does random sampling involve?
- where samples are measured at random sampling sites in a habitat
- a random number generator could be used to select sites to prevent bias
11.2
What does non-random sampling involve?
- stratified; where samples are taken in proportion to the size of each population, which must be identified beforehand
- systematic; where samples are taken at regular intervals
- opportunistic; samples are selected deliberately
11.3
What are sampling techniques used for?
The techniques used to sample a habitat will depend on the samples being collected and include:
- sweeping nets
- pitfall traps
- pooters
- Tullgren funnel
- kick sampling
11.3
What are sweeping nets used for?
to collect invertebrates in low-growing vegetation
11.3
What are pitfall traps used for?
to collect small invertebrates that are found on the soil surface or leaf litter
11.3
What are pooters used for?
to collect insects found in crevices or in sweep nets
11.3
What are Tullgren funnels used for?
to collect small invertebrates from soil and leaf litter
11.3
What is kick sampling used for?
to dislodge freshwater invertebrates on stream beds which are then collected in a pond net
11.4
What can be used to calculate the biodiversity of a habitat?
Simpson’s Index of Diversity (D) can be used to calculate the biodiversity of a habitat, using both species richness and species evenness.
- It is always between 0 and 1
11.4
In the Simpson’s Index of Diversity, what does the ‘n’ and ‘N’ stand for?
n = number of individuals of each species (or percentage cover for plants)
N = total number of all individuals of all species (or percentage cover)
11.4
What does a Simpson’s index value close to 1 show?
A Simpson’s index value close to 1 shows a diverse habitat, rich in species number and population size. These habitats tend to be resilient to change (e.g. disease, famine, or drought)
11.4
What does a low value of Simpson’s index show?
A low value of Simpson’s index shows a habitat dominated by one or a few species. A small change could be catastrophic for the habitat
11.5
How doe genes exist?
- what is polymorphisms
genetic diversity is an important indicator of population health
- monomorphic genes only have one form.
- But most genes exist in several forms, alleles, which are also known as polymorphisms
11.5
What does an increase in polymorphisms show?
the higher the number if polymorphisms in a population, the greater the genetic diversity
11.5
How can genetic diversity of a population be calculated?
The genetic diversity of a population can be calculated by:
proportion of polymorphic gene loci = number of polymorphic gene loci/ total number of gene loci
11.5
How can low genetic diversity occur?
- why must polymorphisms be tested regularly
Low genetic diversity can occur through inbreeding, so zoos conservation programmes, and pedigree breeders must test regularly for polymorphisms
11.6
What factors affect biodiversity?
Factors that reduce biodiversity include:
- human population growth
- agriculture, including the growing of monocultures
- habitat destruction, such as deforestation for plantations
- climate change
- pollution, including plastic waste
11.7
What are 3 main reasons for maintaining biodiversity?
- Ecological
- Economic
- Aesthetic
11.7
Explain the ecological reasons for maintaining biodiversity.
includes protecting keystone species (independence of organisms) and maintaining genetic resources (e.g. crop wild species)
11.7
Explain the economic reasons for maintaining biodiversity.
includes reducing sol depletion (continuous monoculture) so crop yields remain high
11.7
Explain the aesthetic reasons for maintaining biodiversity.
includes protecting beautiful landscapes, mental health, and emotional wellbeing
11.8
What is conservation?
conservation is the active management of an ecosystem to maintain biodiversity
- to maintain and protect biodiversity, two forms of conservation exist
11.8
What are the 2 methods of maintaining biodiversity?
- In situ conservation
- Ex situ conservation
11.8
What is in situ conservation?
- conservation in the natural habitat
- examples include marine conservation zones, national parks, and wildlife reserves
11.8
What is ex situ conservation?
- conservation in areas other than the natural habitat
- examples include seed banks, botanic gardens, and zoos’ captive breeding programmes
11.8
Why do conservation agreements exist?
The endangering of wildlife and loss of habitats is a global concern. At local, national and international levels, conservation agreements exist to protect species and habitats.
11.8
What are the 3 legislation to protect biodiversity?
- when were the signed
- what do they prevent
Historic and current agreements include.
- The Convention on International Trade in Endangered Species (CITES) of Wild Flora and Fauna - First agreed in 1973 to control the trade in wild species to protect their survival.
- The Rio Convention on Biological Diversity (CBD), signed by 150 world leaders in 1992 to promote sustainable development.
- The International Union of the Conservation of Natural Red List of Threatened Species (also known as the IUCN Red List) was founded in 1964. The extinction risk of species is estimated through evaluating a list of specific criteria, from Green Least Concern to Black, extinct in the wild or extinct.
It is used all over the world to improve the conservation status of endangered species and is considered to be the most comprehensive guide on global biodiversity.
12.1
What is a communicable disease?
- how are they caused
A pathogen is an organism that causes disease
- communicable diseases of animals and plants are caused by pathogens that can be transmitted from one organism to another
12.1
What are the 4 types of pathogen?
- bacterium
- virus
- fungus
- Protoctista
12.2
What are some examples of bacterial diseases?
- tuberculosis (TB; human, bovine)
- bacterial meningitis (human)
- MRSA (human)
- ring rot (potatoes, tomatoes)
12.2
What are some examples of viral diseases?
- HIV/AIDS (human)
- influenza (animals)
- rubella (Human)
- COVID-19 (animals)
- tobacco mosaic virus (plant)
12.2
What are some examples of fungal diseases?
- ringworm (mammals)
- athlete’s foot (human)
- black sigatoka (bananas)
12.2
What are some examples of Protoctista diseases?
- malaria (human)
- potato/tomato late blight
12.3
How are pathogens transmitted?
In order to cause disease, animal and plant pathogens must be transmitted from one organism to another, either directly or indirectly
12.3
What are the different ways for direct transmission of a pathogen to take place?
- person-to-person skin contact (ringworm)
- exchange of bodily fluids (HIV/AIDS)
- across the placenta (rubella)
- animal bites (rabies)
- contaminated food and drink (salmonella)
- sharing infected needles (HIV/AIDS, hepatitis B)
the transmission can be increased by social factors, e.g. poor living conditions, overcrowding, climate
12.3
What are the different ways for indirect transmission of a pathogen to take place?
- a vector (malaria, yellow fever)
- droplet infection (common cold, COVID-19)
- touching contaminated objects
a vector is an organism, like a mosquito, that carries a disease-causing pathogen from one host to another
12.4
What are the 3 types of plant defences?
- Physical defences (e.g. bark)
- Mechanical defences (e.g. thorns)
- Chemical defences (e.g. toxins)
12.4
What are plant defences against pathogens?
- describe each of them
- what is callose
- Plants have bark and a waxy cuticle to prevent entry of pathogens.
- They can also produce chemicals, e.g., Antimicrobial enzymes, saponins, and Phytoalexins, in response to pathogen attacks.
- Plants can also limit the spread of a pathogen by depositing callose.
Callose, a polysaccharide, is deposited to block pores in phloem sieve plates., between phloem sieve tubes to prevent pathogen spreading.
12.5
What are primary non-specific defences?
These prevent pathogens from gaining entry to the body
12.5
What are the 7 primary non-specific defences?
- The skin: A tough, waterproof outer layer made-up of dead keratinocytes
- Mucous membranes: In the gut knows and genital areas lined with mucus.
- Chemical defences: Lysozyme in tears, Hydrochloric acid in the stomach.
- Blood clotting: Dash of protein fibres and blood cells form a scab to prevent pathogen entry through broken skin.
- Inflammation: Pain, swelling, heat and redness; damaged cells make capillaries dilate and attract white blood cells to the affected area.
- Wound repair: cells at the wound edge divide to repair damage to the skin.
- Expulsion reflexes: coughing + sneezing in response to irritation of the airways
12.5
What are fevers?
- how are they a defence
12.5
What is Phagocytosis?
The second line of defence is phagocytosis, the engulfing and destroying of pathogenic cells that have entered the body by phagocytes.
12.5
What are the 2 types of phagocytes?
- neutrophils
- macrophages
12.5
What is a neutrophil?
Has a multi lobed nucleus, Short lived, Found in large numbers during infections.
12.5
What is a macrophage?
Larger than neutrophils, can display pathogen antigens on their surfaces after phagocytosis and become antigen presenting cells (APC).
12.5
What are the stages of phagocytosis?
1) Chemical products from the pathogen attract a phagocyte to move towards the pathogen (chemotaxis). Opsonins (small molecules, e.g. antibodies) bind to the pathogen, marking it for phagocytosis.
2) The phagocyte attaches to the pathogen.
3) The phagocyte surrounds and engulfs the pathogen in a vesicle called a phagosome.
4) Lysosomes move towards, and fuse with, the phagosome.
5) Lysosome enzymes digest the pathogen. Macrophages do not digest the pathogen completely and will display the pathogen’s antigens on its membranes, becoming an APC.
6) Finally, the phagocyte secretes cytokines which act as messenger molecules, attracting more phagocytes to the area.
12.5
How are blood cells counted?
- what can be found
12.5
What are cytokines?
12.5
What is opsonin?
12.6
What is an antibody?
An antibody is a globular protein produced by a plasma cell in response to the presence of a specific complementary antigen.
12.6
What is the structure of an antibody?
It is composed of four polypeptide chains: two heavy chains and two light chains. These chains are arranged in a Y shape and held together by disulfide bridges
12.6
What do the tips of the antibodies Y shape form?
The tips of the antibodies Y shape form the antigen binding sites. Each tip has a variable region formed by unique amino acid sequences that produce specific tertiary structures, 3D shapes. This allows them to bind to different complementary antigens.
12.6
What are the different regions antibodies have?
All antibodies have the identical constant regions. The variable region is the only part of the antibody that changes.
12.6
What is the receptor binding site and what does it enable?
The receptor binding site enables an antibody to attach to the cell surface membrane of a lymphocyte or to other antibodies to form antibody complexes.
12.6
What is the specific immune response?
The specific immune response involves white blood cells called lymphocytes, which are divided into two types: T and B.
12.6
Describe the T lymphocyte cells.
- They are produced in bone marrow, mature in the thymus
- They are involved in cell-mediated immunity.
- Their roles in immunity are to respond to antigens inside cells and to respond to own cells altered by viruses or cancer and transplanted tissue.
- Cloned T lymphocyte cells develop into either T helper cells, T memory cells, T killer cells, and T regulator cells.
12.6
Describe the B lymphocytes cells.
- They are produced in and mature in bone marrow.
- They are involved in humoral immunity, which involves antibodies.
- Their roles in immunity are to respond to antigens outside of cells, respond to pathogens and produce antibodies.
- Cloned B lymphocyte cells develop into plasma cells or B memory cells.
12.6
How do T and B lymphocytes communicate?
T and B lymphocytes communicate via cell signalling through the secretion of chemical messengers called cytokines.
12.6
What are interleukins?
- Interleukins are a group of cytokines released by T and B lymphocytes and macrophages to stimulate division of B and T cells.
- Other cytokines include monokines and Interferon.
12.6
What lymphocyte does Cell-mediated immunity involve?
Cell-mediated immunity involves T lymphocytes
12.6
What does the Cell-mediated immunity process involve?
1) Pathogens are engulfed by a non-specific macrophage which breaks down the pathogen and becomes an antigen presenting cell APC.
2) The APC presents the pathogens partially digested antigens to T helper cells.
3) The antigens bind to complementary receptors on one type of cell of the T helper cell - clonal selection
4) The T helper cell is activated and divides rapidly. This is clonal expansion.
5) The cloned T cells:
- Secrete interleukins to stimulate phagocytes
- Secrete interleukins to stimulate B cells to divide.
- May become T killer cells that kill infected cells by making holes in their cell surface membranes.
- May become T regulator cells that control the immune response by inhibiting cytokine production.
12.6
What does the humoral response involve?
- what is the primary immune response
- what is the secondary immune response
1) Free antigens of the pathogen are taken up by phagocytes.
2) The phagocytes process and present the antigens on their cell surfaces.
3) T helper cells bind to the antigens, stimulate B cells to divide by mitosis and differentiate into short-lived plasma cells and long-lived memory cells.
4) The plasma cells produce complementary antibodies to the antigens. This is the primary immune response, and the infected person will show symptoms until the pathogen is destroyed.
5) When the memory cells come into contact with the antigen again, they divide rapidly to form plasma cells and memory cells. Asthma cells rapidly produce high levels of antibodies, so the pathogen is destroyed before the person feels unwell. This is the secondary immune response.
12.6
What is an autoimmune disease?
- when does it occur
An autoimmune disease occurs when a person’s immune system recognises their own antigens as non-self and mounts an immune response to the body’s own cells.
12.6
What are some examples of autoimmune disesase?
Examples of autoimmune disease include:
- rheumatoid arthritis
- lupus erythematosus
- multiple sclerosis.
12.7
What are the four different types of immunity?
- Natural immunity: The body’s ability to recognise, neutralise or destroy non-self substances.
- Artificial immunity: Gained through deliberate exposure to antigens or antibodies.
- Active immunity: Immunity gained through activation of the immune system creating memory cells.
- Passive immunity: Immunity gained through antibodies which have been made externally.
12.7
What does natural active immunity involve?
- Natural exposure to the antigens on pathogens and immune response and making of memory cells.
- Most diseases develop only once.
- Long-term immunity.
12.7
What does natural passive immunity involve?
- Antibodies transferred from mother to baby via breast milk and placenta.
- Short-term, but essential immunity.
12.7
What does artificial active immunity involve?
- Immune response by exposure to a dead or weakened pathogen and production of memory cells, e.g. TB, Rubella.
- Long-term immunity.
12.7
What does artificial passive immunity involve?
- Antibodies made by another organism e.g. rabies immunoglobulin injections.
- Short-term immunity as the antibodies are broken down over time.
12.7
What are vaccinations?
A vaccination is the introduction of a substance containing appropriate antigens into the body to stimulate artificial active immunity against a pathogen.
12.7
What are routine vaccinations and why are they started at baby stage?
Teen in vaccinations are given to babies starting at 8 weeks of age with the 6-in-1 vaccine diphtheria, whooping cough, hepatitis B, polio, tetanus and haemophilus influenzae Type B.
12.7
What can some pathogens cause worldwide?
- what happened in 1980 with smallpox
Some pathogens cause a pandemic: a large-scale global outbreak. In these circumstances, vaccination programmes will target those people who are most at risk (global immunisation can occur).
- A global vaccination programme against smallpox successfully eradicated the disease from the population in 1980.
12.7
What can some pathogens do?
- how can this happen with bacteria
- Some pathogens randomly mutate and change their antigens. When this happens, a new vaccine needs to be developed against the new strain of pathogen to ensure antibodies are made for the new antigen.
- some people do not finish course of antibiotics and cause bacteria to mutate
12.7
Why are new drugs required?
- New pathogens are constantly emerging, e.g. SARS-CoV-2
- Many existing diseases are not yet treatable, nor curable.
- Bacteria have become resistant to current antibiotic treatments.
12.7
What is personalised medicine?
Personalised medicine involves using a person’s Genotype to choose the best treatment. DNA sequencing and clinical information can provide individual treatment plans using medicines and lifestyle choices.
12.7
What is Synthetic biology?
Synthetic biology involves using genetically modified bacteria or animals, and nanotechnology to produce drugs that might be rare, expensive or difficult to make.
12.7
What has bacterial resistance led to?
- Bacterial resistance to antibiotics has led to the development of infections such as MRSA, which is now common in hospitals.
- Various factors contribute to bacteria becoming resistant to antibiotics
12.7
What are the four factors that include bacteria becoming resistant to antibiotics?
- Using antibiotics to treat trivial, minor or viral.ailments.
- Patients not completing courses of antibiotics.
- Doctors prescribing antibiotics unnecessarily in response to patient demand.
- Use of antibiotics in intensive farming to prevent infections.
Bacteria that have developed multi antibiotic resistance are very difficult to treat.
