What is the most recent taxonomic group to be added to the hierarchy classification system and, in order, what are the 7 taxonomic groups that follow it?
- 1. Domain
- 2. Kingdom, Phylum, Class, Order, Family, Genus, Species
Why do scientists classify organisms?
- ☉ To identify species
- ☉ To predict characteristics - if a number of species in same group have similar characteristics, it is likely another species from that group will too.
- ☉ To find evolutionary links - similar characteristics within a group are likely to have evolved from a common ancestor
How many Domains are there and what are they?
- 3 Domains
- ☆Archaea: 70s ribosomes, RNA polymerase has 8-10 proteins
- ☆Bacteria: 70s ribosomes, RNA polymerase has 5 proteins
- ☆Eukarya: 80s ribosomes, RNA polymerase contains 12 proteins
What is Binomial Nomenclature?
- -Used worldwide so scientists can communicate effectively
- -First word indicates Genus - generic name (equivalent to surname)
- -Second word indicates species - specific name
What are the 5 kingdoms?
What are the general features of Prokaryotae?
- 'The prokaryotes'
- No nucleus or membrane-bound organelles
- No visible feeding mechanism - nutrients either absorbed or produced internally e.g. by photosynthesis
What are the general features of Protoctista?
- (Mainly) unicellular
- Nucleus and other membrane bound organelles
- Some with chloroplasts
- Some are sessile, others move by cilia, flagella, amoeboid mechanisms
- Some autotrophic, some heterotrophic, some both - parasitic
What are the general features of Fungi?
- Uni or multi cellular
- Nucleus & other membrane-bound organelles
- Cell wall of chitin
- No chloroplasts/chlorophyll
- No locomotion mechanisms
- Body or mycelium made of threads or hyphae (most)
- Saprophytic feeders - nutrients absorbed mainly from decaying material
- Most store food as glycogen
What are the general features of Plantae?
- Nucleus, membrane-bound organelles
- Chloroplasts & chlorophyll
- Cell wall of cellulose
- Most do not move
- Autotrophic feeders by photosynthesis
- Store food as starch
What are the general features of Animalia?
- Nucleus & other membrane-bound organelles
- NO cell wall
- No chloroplasts
- Move with cilia, flagella, contractile proteins
- Heterotrophic feeders - nutrients from ingestion
- Food stored as glycogen
How does the Three Domain System group organisms?
- Differences in sequences of nucleotides in cells rRNA
- Cell membrane lipid structure
- Sensitivity to antibiotics
- Six kingdoms
Which original kingdom from the 5 kingdoms is divided in two, and what are they called?
- Becomes Archaebacteria and Eubacteria
What are the differences between Archaebacteria and Eubacteria?
- Eubacteria contain peptidoglycan in cell walls
- Eubacteria (true bacteria) found in all environments
- Archaebacteria (ancient bacteria) live in extreme environments
What is phylogeny?
The name given to the evolutionary relationships between organisms.
What is phylogenetics?
The study of evolutionary history of groups of organisms.
What are 'sister groups' on a phylogenetic tree?
Two descendants that split from the same node (common ancestor).
Advantages to phylogenetic classification?
- Can be done without reference to Linnaean classification.
- Produces continuous tree and doesn't require organisms to be put in a group which they don't fit
- Gives idea of time scales
What is evolution?
The theory that describes the way in which organisms evolve, or change over a period of time, as a result of natural selection.
Who pioneered the theory of evolution?
Darwin and Wallace
Evidence for evolution?
- Fossils (palaeontology)
- Comparative anatomy (similarities/differences between organisms' anatomy)
- Comparative biochemistry (similarities/differences between organisms' chemical makeup)
Evidence provided by the fossil record:
- Earliest life forms found in oldest rock, matching ecological links to each other
- Gradual evolution from simple organisms to vertebrates over a long period of time
- Similarities in anatomy can be seen between organisms
- Show relationships between extinct and living organisms
Disadvantages of Fossil Record as evidence:
Incomplete - many soft-bodied organisms wouldn't have a chance to fossilise; incorrect conditions; fossils destroyed by earth, or still undiscovered
What is a homologous structure?
- Structures that appear different, and may perform different functions, but have the same underlying structure.
- E.G. Vertebrate limbs can be used for running, jumping, flying, swimming, suggesting a common ancestor
- Provide evidence for divergent evolution
Comparative Biochemistry as evidence:
- Some important molecules are highly conserved throughout evolution
- Cytochrome c (involved in respiration)
- Number of differences plotted against rate the molecule undergoes neutral base pair substitutions
What is interspecific variation and what is intraspecific variation?
- INTER: Variation between different species. E.g a mouse has four legs, a pigeon has two.
- INTRA: Variation within a species
What causes genetic variation?
- Alleles: different versions of the same gene
- Mutations: changes to the DNA sequence and therefore the proteins produced by it
- Meiosis: the production of gametes, independent assortment and crossing overSexual reproduction: offspring inherit an allele from each parent for each gene.
- Random fertilisation
What is continuous and discontinuous variation?
- Continuous: A characteristic that can take any value within a given range. Represented on a line graph/histogram. Controlled by environment and multiple genes.
- Discontinuous: A characteristic that can only result in certain values. Represented on a bar chart. Controlled by single gene.
What are the different types of adaptations?
- Anatomical: physical features
- Behavioural: how an organism acts (innate - instinctive, and learned)
- Physiological: processes that take place inside the organism (e.g. poison production, antibiotic production, water holding, reflexes, temperature regulation)
What is convergent evolution?
- When unrelated species begin to share similar traits. They adapt to fill similar niches.
- E.G. marsupial and placental moles: both burrow through soft soil/sand to find food, have body shape and forelimbs for digging, have velvety fur. Differ in colour.
What is the founder effect?
When a few individuals colonise a new area, the initial genetic variation is relatively small, resulting in offspring that are physically and genetically different from their source population.
The variety of all living organisms present in an area.
What is habitat biodiversity?
- The number of different habitats found within an area.
- Generally the greater the habitat biodiversity, the greater the species biodiversity.
What is species biodiversity made up of?
- Species richness: the number of different species living within an area
- Species evenness: a comparison of the numbers of individuals of a species living in a community.
What is genetic biodiversity?
- The variety of genes that make up a species. Different alleles for a gene leads to genetic biodiversity.
- Greater genetic biodiversity allows a species to adapt better to new environments and resist disease.
What types of non-random sampling are there?
- Opportunistic - uses organisms that are conveniently available
- Stratified - a population is divided into a number of strata (sub-groups) based on a particular characteristic. E.g. male and female. A random sample is then taken proportionally to the group's size.
- Systematic - Different areas within a habitat are identified and sampled separately. E.g. sea - beach
What type of sampling is a line/belt transect used for, and what is the difference between these two?
- SystematicLine: samples taken at specific points on a marked line
- Belt: Two parallel lines marked, and samples taken between the two.
What are the three methods of sampling organisms using frame quadrats?
- Density - when individuals can be seen clearly, count the number per 1x1m quadrat, giving density per square meter.
- Frequency - used when individuals are hard to count (e.g. grass). Use a grid quadrat and count number of squares the organism appears in.
- Percentage cover - used for speed when an organism is abundant or difficult to count, an estimate by eye
For each of the following factors, what units and equipment would you use to measure them? What type of factors are they?
O2 content in water
- Wind speed: anemometer, m/s
- Light intensity: light meter, lx
- Relative humidity: humidity sensor, mg/dm3
- pH: pH probe, pH
- Temperature: thermometer, °C
- O2 content in water: dissolved oxygen probe, mg/dm3All abiotic factors
What is the diversity of organisms usually proportional to with regard to their ecosystem?
The ecosystem's stability. The most stable communities have high species richness and evenness
How is biodiversity calculated?
- Simpson's index of diversity (D)Takes into account species evenness and richness
- ∑ = sum of
- n = total number of organisms of all species
- N = total number of organisms of particular species
What does the result of Simpson's Index of Biodiversity show?
- Results between 0 and 1
- 0 = no diversity
- 1 = infinite diversity
How is genetic biodiversity increased and how can this occur?
- An increase in the possible alleles in a population
- Mutation(s) of the DNA creating a new alleles
- Interbreeding between different populations allowing alleles to be passed between the populations - aka gene flow
How is genetic biodiversity decreased and how can this occur?
- A decrease in the number of possible alleles in a population.
- Selective breeding/Artificial selection - individuals selected to breed based on a characteristic
- Captive breeding programmes eg in zoos, only a small number of individuals are available
- Artificial cloning - eg for farmed plants
- Natural Selection - species evolve to have advantageous characteristics to fit with selection pressures
- Genetic bottlenecks when a few individuals survive an event, hence reducing the gene pool
- Founder effectGenetic drift - alleles may disappear from a population by chance as they are/aren't passed on from parents to offspring
What is polymorphism?
Polymorphic genes have more than one allele
How can you measure genetic biodiversity?
- Calculate the proportion of polymorphic gene loci of an organism.
- Proportion of polymorphic gene loci = number of polymorphic gene loci divided by the total number of loci
What are some reasons for maintaining biodiversity?
- Aesthetic:-maintaining landscapes
- -e.g. going for a walk in local woodland
- Economic:-reducing soil depletion ~ helps keep land fertile and healthy to ensure we are able to get healthy and substantial crops
- -must conserve organisms we need in order to make things. E.g. non-sustainable removal of hardwood will lead to the collapse in the industry
- -conserve organisms that may be useful to us in the future, e.g. chemically or medically
- -high biodiversity protects against stress, e.g allowing a crop species to survive a disease
- -promote tourism to an area
- -plant varieties needed for cross-breeding/GM crops, and wild varieties can lead to better characteristics e.g. disease resistance or higher yield
- Ecological: -all organisms are interdependent on each other, so decreasing the number of one will have effects on the others
- -keystone species need to be protected as they affect many other organisms in an ecosystem
- -maintaining genetic resource
Conservation is the preservation and careful management of the environment and natural resources. "The maintenance of biodiversity"
What two types of conservation are there?
- In situ: within the natural habitat
- Ex situ: out of the natural habitat
Explain and give examples of in situ conservation.
- Takes place in the organisms natural habitat
- Maintains genetic diversity
- Maintains evolutionary adaptations
- Maintains interdependent relationships between species
- Generally cheaper
- Wildlife Reserves: control grazing, human access, poaching, feed animals, reintroduce species, cull/remove invasive species, halt succession
- Marine Reserves
Explain and give examples of ex situ conservation
- Takes place outside of the organism's natural habitat
- Usually in addition to in situ conservation
- Botanic GardensSeed Banks - a store of genetic material, carefully stored to maintain their viability. (Don't work for all plants)
- Captive Breeding Programmes:-produce offspring in a controlled environment. E.g Zoos.
- -may not always allow for individual's release due to disease, behaviour, genetic difference to wild population meaning interbreeding cant occur, lack of habitat
What are some conservation agreements?
- International Union for the Conservation of Nature (IUCN):-assists in securing agreements between nations
- -publishes the Red List - statuses of current threatened animals
- Convention of International Trade in Endangered Species (CITES):-regulates trade of wild plant and animal specimens and their products
- -requires international cooperation at countries' borders
- The Rio Convention:
- -The Convention on Biological Diversity (CBD): requires nations to develop national strategies to maintain biodiversity
- -The United Nations Framework Convention on Climate Change (UNFCCC): agreement between nations to stabilise greenhouse gas concentrations
- -The United Nations Convention to Combat Deforestation (UNCCD): aims to prevent fertile land being converted to desert to reduce effects of drought
- Countryside stewardship scheme:England
- Offered payment to farmers/land owners to enhance and conserve English landscape
- Aimed to make conservation part of normal farming/land management practice.
What different types of pathogen are there?
How are bacteria classified?
- By basic shapeBy cell wall:
- Gram positive bacteria appear purple/blue after gram staining eg MRSA
- Gram negative appear red e.g E.coli
What modes of action do pathogens use?
- Damaging host tissue directly:Viruses take over cell metabolism, inserting genetic material into it's DNA
- Some protoctista take over cell, using its contents as they reproduce
- Fungi digest living cells
- Producing toxins which damage host tissue:Most bacteria ~ poisoning/damaging host cells
- Some fungi
Plant disease: Ring Rot
- Caused by: bacteria gram positive)
- Affects: potatoes, tomatoes. Damages leaves, tubers and fruit.
- Prevention: /
- Cure: None
Plant disease: Tobacco mosaic virus
- Caused by: virus
- Affects: damages leaves, flowers, fruit, stunts growth, reduces yield.
- Prevention: resistant strains available
- Cure: none
Plant disease: Potato blight
- Caused by: protoctist
- Affects: hyphae penetrate host cells, destroys leaves, tubers, fruit
- Prevention: resistant strains, careful management and treatment can reduce risk
- Cure: none
Plant disease: Black sigatoka
- Caused by: fungus
- Affects: banana leaves, reduces yield
- Prevention: fungicide, good husbandry, resistant strains under development
- Cure: no cure
Animal Diseases: Tuberculosis (TB)
- Caused by: bacteria
- Affects: humans, cows, pigs, badgers
- Damages lung tissue and suppresses immune system
- Prevention: improved living standards, vaccines
- Cure: antibiotics
Animal diseases: bacterial meningitis
- Caused by: bacteria
- Affects: meninges of the brain, can cause rapid death. Young children and teenagers
- Red/purple rash that doesn't disappear
- Prevention: vaccines
- Cure: antibiotics
Animal Diseases: HIV/AIDS
- Caused by: virus
- Affects: targets T-helper cells, destroying immune system
- Prevention: avoid mixing of bodily fluids
- Cure: None - drugs can slow progress of disease
Animal diseases: Influenza (flu)
- Caused by: virus
- Affects: affects/kills ciliated epithelial cells leaving airways open to secondary infection.
- Prevention: vaccines
- Cure: no cure
Animal diseases: Malaria
- Caused by: protoctista spread by mosquitoes
- Affects: red blood cells, liver, and brain
- Prevention: insecticides, removing water where mosquitoes breed, nets
- Cure: limited
Animal diseases: Ring worm
- Caused by: fungus
- Affects: cattle, dogs, cats, humans
- Causes crusty, infectious, circular areas of skin
- Prevention: don't mix towels
- Cure: antifungal creams
Animal diseases: Athlete's foot
- Caused by: fungus
- Affects: skin between toes
- Prevention: don't share towels
- Cure: antifungal creams
How can direct transmission occur? (of pathogens)
- Direct contact: kissing, sex, skin-skin contact, microorganisms on hands
- Inoculation: through break in skin, animal bites
- Ingestion: contaminated food/drink, pathogens from hands
How can indirect transmission occur? (of pathogens)
- Fomites: inanimate objects (eg bedding/towels)
- Droplet infection: droplets from talking, sneezing etc. containing pathogens
- Vectors: transmit pathogen from host to host, often animals (eg mosquitoes). Water.
What factors affect transmission of communicable diseases in animals?
- Poor nutrition
- Compromised immune system
- Poor disposal of waste
- Climate change - may introduce new vectors and diseases to an area
- Culture and infrastructure - eg medical practices
- Socioeconomic factors - eg lack of trained health workers
How can pathogens be transmitted between plants?
- Directly - close contact
- Indirectly:Contaminated soil
- Vectors such as wind, water, animals and people and their farming practices
What factors affect transmission of communicable diseases in plants?
- Plant varieties that are susceptible to disease
- Poor mineral nutrition
- Warm, damp conditions
- Climate change
How can you reduce spread of disease between plants?
- Room between plants
- Clear fields thoroughly
- Rotate crops, so pathogen dies without its host
- Control vectors
How do plants recognise an attack?
- Receptors in cells respond to molecules from the pathogens or chemicals produced when the plant cell wall is attacked.
- Triggers release of signalling molecules that switch on genes in nucleus
What physical defenses do plants have?
- Produce high levels of calloseDeposited between cell wall and membrane in surrounding cells, acting as barriers
- Further callose and lignin added after infection making barrier stronger and thicker
- Callose blocks sieve plates, sealing off infected part
- Calose deposited in plasmodesmata
What chemical defenses to plants have?
- Insect repellents - eg pine resin
- Insecticides eg caffeine - toxic to insects and fungi
- Antibacterial compounds eg. phenols - antiseptics
- Antifungal compounds eg. phenols and chitinases (enzymes that break down chitin in fungal cell wall)
- Toxins eg compounds that break down to form cyanide when plant is attacked
How do animals keep pathogens out of their body?
- Mucous Membranes that secrete mucus
- Lysozymes in tears and urine
- Stomach acid
Explain the blood clotting cascade.
- Thromboplastin enzyme that triggers cascade of reactions to form clot
- Serotonin makes smooth muscle contract, reducing blood flow
Explain the inflammatory response
- Results in inflammation
- 1. Mast cells activated in damaged tissue
- 2. release histamines & cytokines3. Histamines cause dilation of blood vessels - heat prevents pathogens reproducing
- 4. Histamines make blood vessels leaky releasing blood plasma
- 5. Cytokines attract white blood cells, disposing of pathogens by phagocytosis
What non-specific responses get rid of pathogens?
- Fever - cytokines stimulate thermostat to be reset so temperature is increased, inhibiting pathogen reproduction, speeding up specific immune response
- Phagocytosis - phagocytes (specialised white blood cells) (neutrophils and macrophages)
What are the steps of phagocytosis?
- 1. Pathogens produce chemicals, attracting phagocytes
- 2.Phagocytes recognise non-self proteins, binds to pathogen
- 3.Engulfs pathogen, encloses it in vacuole called a phagosome4.Phagosome binds with lysosomes to form phagolysosme5.Enzymes digest pathogen
- Macrophages only:
- 6.Pathogen's antigens combine with MHC (major histocompatibility complex) in cytoplasm
- 7.MHC/antigen complex displayed on cell surface membrane making it an antigen presenting cell (APC)
What helpful chemicals are involved in the response and what do they do?
- Cytokines:Released my phagocytes that have engulfed pathogen
- Cell-signalling molecules informing phagocytes of attack & stimulating their movement to the site
- Increase body temperature
- Stimulate specific immune system
- Opsonins:Bind to pathogens and tag them so they are more recognisable to phagocytes
- Phagocytes have receptors that bind to opsonins
Label and explain the structure of an antibody.
- Chains held together by disulfide bridges
- Variable region is specific to the type of antibody
How do antibodies work?
- 1.Antibody binds to antigen on pathogen forming antigen-antibody complex2.Antigen-antibody complex acts as opsonin so pathogen is easily engulfed
- 3.A-A complex often prevents successful invasion of pathogen to host cells
- 4.Antibodies act as agglutinins making pathogens stick together - prevent spread
- 5.Antibodies can act as anti-toxins binding to toxins produced to make them harmless
What types of T cells are there and what do they do?
- T helper cells: (CD4) receptors bind to antigens on APC's
- Produce interleukins ~ stimulate B cells for antibody production, the production of other T cells, and attracts+stimulates macrophages
- T killer cells:Destroy pathogen carrying the antigen.
- Perforin (enzyme) makes holes in its cell membrane making it freely permeable
- T Regulator Cells:
- Stop immune system once pathogen is eradicated
- Ensure body recognises itself
- Prevent autoimmune responseT memory cellsLive long time as part of immunological memory
- In presence of antigen they divide rapidly to make T killer cells
What types of B cells are there and what do they do?
- Plasma Cells:Produce antibodies to particular antigen
- 2000 per second
- B effector cellsDivide to form plasma cell clones
- B memory cellsLive long time as part of immunological memory
- Respond quickly in the presence of the antigen on 2nd encounter
Where do T and B lymphocytes come from?
Explain cell mediated immunity
- Response to cells that have been changed in some way, eg. by virus infection, antigen processing, or mutation, as well as transplanted tissue
- 1. Non-specific immune system ~ macrophages engulf&digest pathogens and form APCs
- 2. Receptors on T helper cells fit antigens on APC activating T helper cell to produce interleukins3. Interleukins cause T cells to divide rapidly to form clones of T helper cells
- 4. Cloned cells may:
- -develop into T memory cells
- -produce interleukins to stimulate phagocytosis
- -produce intereukins to stimulate B cells to divide
- -stimulate development of a clone of T killer cells
Explain Humoral Immunity
- Response to antigens found outside cells, eg. bacteria, fungi, and APCs
- 1. Clonal selection: activated T helper cell binds to B cell APC , and the B cell with correct antibody is selected for cloning
- 2. T helper produces interleukins, activating the B cell
- 3. Clonal expansion: activated B cell divides to produce clones of plasma and B memory cells
- 4. Plasma cells produce antibodies (primary immune response)
- 5. B memory cells cause secondary immune response if antigen is detected again, dividing to produce plasma cells
What is an autoimmune disease, how is it managed, and what examples are there?
- When the body stops recognising self cells and attacks healthy body tissue
- Immunosuppressant drugs given
- Type 1 diabetes
What is natural immunity and how is it achieved?
- Natural active immunity: the body acts to produce antibodies and memory cells when you first meet a pathogen
- Natural passive immunity: some antibodies cross the placenta to the fetus, colostrum milk is rich in antibodies and infant gut allows them into the bloodstream undigested.
- Lasts until infants own immune system kicks in
What is artificial passive immunity?
- Antibodies formed in one individual and injected into another
- Temporary immunity
- Can be life saving
- E.g tetanus and rabies
What is artificial passive immunity and how does it work?
- Immune system of body stimulated to make its own antibodies
- 1. Pathogen made safe eg killed, weakened, isolated antigens, genetically engineered
- 2. Small amount injected into blood
- 3. Primary immune response triggered ~ body produces antibodies and memory cells
- 4. Secondary response kicks in if pathogen is encountered again.
- May last a year to a lifetime
What is an epidemic and a pandemic?
- When a disease spreads through a lot of people on a...
- Epidemic: local/national level
- Pandemic: international level
What is herd immunity?
When a significant number of people are vaccinated for something, those who aren't have some protection since the disease cant spread/have an outbreak
Where does Penicillin come from?
What sources of medicines are there?
- Plants, microorganisms (and animals)
- Therefore it is important to maintain biodiversity so we do not loose these
What is pharmacogenetics and how does it work?
- Personalised medicine
- Work in combination with your genetics and disease (including genome of invading pathogen)
What is synthetic biology?
- Genetically engineering organisms to produce drugs for our use
- Nanotechnology where tiny, non-natural particles deliver drugs to certain sites in the pathogen cells or tumours
How do antibiotics work?
Selective toxicity ~ interfere with metabolism of bacteria without affecting human cells
Give two examples of antibiotic resistant bacteria.
- MRSA (methicillin-resistant Staphlyococcus aureus)
- C. difficile
How can we reduce antibiotic resistant infections?
- Minimise use of antibiotics
- Ensure antibiotic course is taken to completion
- Good hygiene