B6

Why do we sample?

Find presence/distribution of organisms in the area
Impossible to count the population
Random and repeated so they’re representative and reliable

How are quadrats used?

Abundance: For large plants where there’s only a few, count how many there are within the whole quadrat

Percentage cover: For small plants where there’s a lot, count how many squares of quadrat are atleast half-filled

How to use random sampling?

Measuring tapes placed along 2 sides of areas and generate random numbers to use as co-ordinates to choose sampling points within the area
Used when you want a representative sample of the whole area
Should always be a large sample to minimise chance of anomalies
Aim to sample atleast 2% of the whole area

Why are transect lines used?

To investigate how population changes across a gradient eg. shade to light

Population size = (no. in 1st sample x no. in 2nd sample) / no. in 2nd sample previously measured

Why are keys used and what is a Dichotomous key?

Keys- method of identification where groups of organisms are divided into smaller and smaller groups, based on shared features

Dichotomous keys- we only split each group into two groups each time.

Why is biodiversity important?

Species are interdependent so removal of one can affect others
Essential for maintaining a balanced ecosystem
We rely on it for raw materials eg. oxygen, food and wood

How is biodiversity lost?

Pollution: Eutrophication (too much growth), kills plants and animals
Deforestation: Loss of habitats, contributes to CO₂ in air so more global warming
Agriculture: Intensive farming, pesticides, herbicides, insecticides
Hunting and fishing: Overfishing, removes food for other species, unchecked growth of some plant species

How is biodiversity increased?

Conservation: Protection of environments prevents habitat loss, increases species survival but requires active management (restricted access, feeding)

Captive breeding: Creates stable, healthy population of species to reintroduce into natural habitat however difficult to maintain genetic diversity

Seed banks: Seeds stored so new plants can be grown in future even past extinction. Millenium Seed Bank preserves over a billion seeds

How is biodiversity maintained?

International agreements: International Union for conservation of Nature publishes “Red List” states conservation status of threatened animals and plants

CITES- Convention on International Trade in Endangered Species. Treaty which regulates trade of wild plants and animals and their products

CBD- Convention of Biological diversity. Requires countries to: develop strategies for sustainable development, reduce greenhouse emissions, combat desertification

Why can it be difficult to maintain biodiversity?

Many countries need to work together but some may not be willing to sign up to agreements
Local residents may object due to reasons such as reduced income
Can be very difficult to monitor eg. tracking fishing quotas

What is ecotourism?

Aims to ensure tourism has minimal negative impact on the local ecosystem by supporting conservation.
Money from tourism reinvested into protecting the ecosystem eg. restricting certain areas

How do environmental changes affect distribution of organisms?

Availability of water- Distribution changes between seasons due to more/less water being available
Atmospheric gases: Some species can’t grow in polluted areas eg. some lichens can’t grow where sulphur dioxide content is high
Temperature: Global warming can cause loss of habitats which forces species to move elsewhere

Outline the greenhouse effect

Solar radiation from sun passes through atmosphere and hits earth
Some energy reflected back towards space, some absorbed by earth and then reemitted towards space.
Much is absorbed by small molecules called greenhouse gases. 
These molecules then reemit the energy and process of absorption and emission can happen again
Trapped energy keeps atmosphere warmer and more stable than it would otherwise be. 

Difference between Global warming and climate change

Global warming refers to overall increase in the earth's temperature
Climate change a consequence of global warming and refers to the effects on the climate, such as large-scale shifts in weather patterns

Define Food security

Food security- ability of human populations to access affordable food of sufficient quality and quantity

Factors affecting food security

Increasing human population: more mouths to feed
Changing diets: More wealth = more varied diet = more meat = more energy intensive to produce
Changing climate: Global warming will cause more draughts and desertification. However, CO₂ increase may mean increased yield of some crops
New pests and pathogens may evolve

How can we increase food production?

Using herbicides, pesticides and insecticides- gets rid of predators and competition so maximum energy and mass conserved

Gene technology- crop varieties that are pest resistant or produce higher yields

Maximise photosynthesis- increases yield

Biological control- release natural predators to kill predators of the plant eg. ladybirds to kill aphids

How can we prevent over-fishing?

International fishing quotas
Limit mesh size of nets
Fish farms:
-Fish bred and raised in large cages
-Protection from predators and makes them easier to catch
-Helps wild populations recover but disease can spread

How can we reduce use of fertilisers and pesticides?

Spread manure- Replace minerals and improve soil texture
Crop rotation- Diff. crops take diff. nutrients from soil, gives soil chance to recover and maximises growth
Biological control- Natural predators to kill predators of plants
Gene technology: Develop pest and disease resistant varities

What are hydroponics and their benefit

Hydroponics- method of growing plants without soil, using a nutrient-rich water solution to deliver essential minerals directly to the roots

Benefits:
Fast-growth
Higher yield
No soil (Less disease and less pesticide use)
Affordable
Water-saving

Outline the process of selective breeding

Decide desired characteristics
Select parents with high levels of this
Breed from these individuals
Select best offspring and breed again
Repeat for many generations

Disadvantages of selective breeding

Reduces number of alleles in gene pool (less variation)
New disease arises, may not be organism with resistant allele- species may become extinct
Increases chance of inheriting genetic disorders
Desired characteristic may not show in offspring due to other dominant characteristic
Can take many generations of breeding (long time + lots of money)

Define Genetic engineering

Altering organism’s genome to produce organism with desired characteristics

Outline process of genetic engineering

Desired gene cut out using restriction enzyme (recognises sequence of DNA)
Plasmid cut open using same restriction enzyme
Creates sticky ends on DNA (short tails of unpaired complementary bases)
Plasmid and DNA mixed together with ligase enzymes
Plasmid vectors containing new DNA inserted into host cells.
Host cells can use inserted gene to produce desired characteristic
Not all host cells modified successfully so select those who successfully received desired gene

How can we check genetic engineering has worked?

Insert antibiotic resistance gene into plasmid at same time as desired gene
Transfer bacteria to agar plate containing antibiotic and then incubate
Only those bacteria with resistance gene grow- will also contain desired gene

Benefits and concerns of Genetically modified crops

+Higher yields so more people fed
+More capable of thriving in regions of poor soil
+Inbuilt resistance to pests, weeds and disease (less herbicide and pesticide use so more environmental)

-Farmers may find genetic technologies expensive
-GM tech. companies engineer crops so harvested grain germs incapable of developing
-Ends food diversity if everyone grows same crop
-Herbicide and pesticide resistance could give rise to super-weeds and pest
-Could cross-pollinate with wild plants, impossible to control

Define biotechnology

Biotechnology- use of biological processes or living organisms to manufacture products

Define health and disease

Health- absence of any type of disease
Disease- condition caused by any part of body not functioning correctly

Properties of communicable diseases

Communicable diseases spread between organisms and caused by pathogens

Different types of pathogens with examples of disease they cause (1 animal vs 1 plant disease)

Fungus- athlete’s foot and powdery mildew
Bacteria- Tuberculosis and crown gall disease
Virus- Influenza and tobacco mosaic virus
Protoza- malaria and coffee phloem necrosis

Causes of non-communicable diseases and example of a disease they cause

Poor diet- scurvy
Obesity- Type II diabetes
Genetic- cystic fibrosis
Body processes not functioning properly- cancer

How can pathogens spread between plants

Soil and water
Wind- spreads fungal spores and infected seeds
Direct contact of sap from infected plant
Vectors- animals that spread disease eg. insects

How can pathogens be spread between animals

Airborne transmission- Infected droplets inhaled
Sexual reproduction
Insect/animal bites
Sharing food/drink

How do pathogens cause disease?

Incubation period, reproduces rapidly
Causes cell damage (mainly virus)
Some produce toxins (bacteria)

How do scientists monitor disease?

Epidemiology- study of how diseases spread
Incidence- eg. number of cases or morbidity
Rate at which new cases occur in a population over time
Can be used to monitor efficacy of treatments or prevention techniques

How can you prevent spread of disease

Wash hands
Drink clean water
Cover nose and mouth when coughing
Protection during sex
Protect yourself from animal/insect bites
Cook food properly

How do farmers prevent spread of disease

Spray plants with fungicide
Vaccinate livestock
Chemical dip for footwear and tyres
Burn diseased plant materials
Treat livestock with drugs
Burn and slaughter livestock

Different ways the body protects itself from pathogens

Eyes: Tears (contain lysozyme which digests bacteria)
Nose: Path of entry, nose hairs + mucus
Skin: Sebum (oil which waterproofs skin so it doesn’t crack), secretes antimicrobial substances to kill pathogens
Stomach: Produces hydrochloric acid which kills pathogens
Respiratory tract: lined with mucus and cilia which traps particles. Cilia waft mucus to back of throat where it can be swallowed.
Wounds: Platelets clot up wounds to prevent blood loss and microorganisms from entering

What are the 2 different types of white blood cells?

Lymphocytes- Produces antibodies or antitoxins, Specific ( each produces only one type of antibody which is specific for only one antigen)

Phagocytes- Engulf and digest microorganisms, Non-specific

Outline the process of immunity

Infection by pathogen
Lymphocytes produces antibodies
Pathogen neutralised
Some lymphocytes become “memory cells”
Reinfection by same pathogen
Memory cells quickly produce antibodies
Pathogen neutralised before it causes illness

Outline the process of vaccination

Small sample of weakened/dead version of pathogen introduced into body
Lymphocytes produce antibodies
Some become memory cells
Infection by same pathogen
Memory cells quickly produce antibodies
Pathogen neutralised before it causes illness

Examples of some chemical defences?

Disinfectants: Effective against all pathogens, suitable for non-living surfaces only
Antiseptics: Effective against all pathogens, Suitable for human tissues
Antivirals: Only effective against viruses. Prevent them from replicating: Block entry to host cell, prevent release of genetic material, prevent insertion of genetic material and host genome
Antibiotics: Effective against bacteria only, Prevents them from growing and reproducing, kills different range of bacteria

How to test antibiotics by measuring the zone of inhibition

Measure diameter of zone then calculate radius (1/2 of diameter)
Calculate area of circle by using π r²

What is aseptic technique?

Approach to working which prevents cross-contamination from unwanted organisms- both apparatus and environment remain sterile

Steps of the aseptic technique and why each step is done

Autoclave apparatus before and after use- Sterilise apparatus, preventing contamination
Clean working area with alcohol before and after working- working area sterilised
Work close to bunsen flame- prevents contamination of open sample due to convection current
Wear gloves if working with pathogens- prevents transfer from sample to skin or vice versa

How are new medicines released to the public?

Discovery: many from plant extracts but some synthesised in lab with computer testing

Pre-clinical testing: Computer modelling on human and bacteria tissue cultures (most fail at this stage by damaging cell or not working)

Animal testing: On one invertebrate and one mammal

Clinical trials: Test small sample of healthy volunteers to see side effects, tested on few hundred volunteer patients to check if it works then tested on several thousand to measure efficacy, dosage, safety and side effects

Approved for use by MHRA (Medicines and Healthcare products regulatory agency)

Prescribed by doctors

Continued monitoring: find unexpected side effects or problems in certain groups

What are double blind trials?

Ppl sometimes feel better taking a drug as they expect to (placebo) so “double-blind trials” are used
Some patients given drug but others given an exact replica with no active ingredient
Nobody knows who’s been given what until after trial is over (only researchers know)

What are monoclonal antibodies?

Antibodies produced by a single clone of cells. All antibodies identical and only target one specific antigen

Outline process of producing monoclonal antibodies

Antigen injected into mouse which is neutralised by antibodies from lymphocytes
Lymphocyte taken from mouse spleen and myeloma (tumour) cells taken from lab
Lymphocyte and tumour cell fused to form Hybdridoma cell (not all successful)
Hybridoma cells clone to get many identical cells
These cells divide really quickly to produce same antibodies

How are monoclonal antibodies used for pregnancy testing?

Two weeks after conception, hCG produced
Home pregnancy sticks impregnated with band of monoclonal antibodies for hCG
hCG in urine binds to antibodies causing a colour-change reaction which causes a line to form (positive pregnancy)

How are monoclonal antibodies used to detect disease?

Monoclonal antibodies act as markers
Confirm presence of specific antigen by binding to it
Allows doctors to diagnose disease at early stage
Early diagnosis of cancer essential for successful treatment

How are monoclonal antibodies used to treat cancers?

Monoclonal antibodies designed to target a specific cell type
Bind to antigens on target cells
Kill them or prevent from operating effectively
Can also carry drugs or radioactive substances directly to cells, increasing efficacy and minimising damage to surrounding healthy tissue (magic bullet)
Used to treat a range of cancers

What are the substances inhaled from smoking and their effects?

Tar- carcinogenic → Lung cancer
Nicotine- Addictive, Increases heart rate and constricts blood vessels (heart disease)
Carbon monoxide- Attaches to haemoglobin instead of oxygen → heart needs to work harder (heart disease)
Particulates- Engulfed by phagocytes → enzyme released which weakens walls of alveoli → less oxygen enters blood → emphysema
Cyanide- Paralyses cilia → mucus flows into lung → bronchitis

Effects of drinking alcohol?

Depressant- slows nervous system
Affects behaviour- relaxed/sad/aggressive
Blurred vision/Slurred speech/loss of balance
Addictive- Dependency
Cirrhosis of liver/heart disease/stomach ulcers/brain damage

Define cardiovascular disease

Cardiovascular disease- Disease of the heart or blood vessels

What is Atherosclerosis?

Build up of fatty deposits inside an artery
Causes it to harden and narrow
Reduces blood flow which increases blood pressure

What is thrombosis?

Blood clot forms in blood vessel
Obstructs blood flow
Coronary artery blocked → heart attack
Artery in brain blocked → stroke

Which lifestyle factors increase risk of cardiovascular disease?

Poor diet: too much saturated fat or salt. Causes cholesterol deposition in artery valves. Salt increases water reabsorption by kidneys
Too little exercise
Smoking- Carbon Monoxide increases BP
High BP

How does exercise affect health

Reduced body mass- reduces risk of CVD and Type 2 Diabetes
Healthier joints- reduces risk of arthritis
More muscle- stronger heart
Lower cholesterol levels

How can CVD be treated through lifestyle changes

Less processed food- reduces salt and saturated fat and sugar intake. Reduces risk of Type 2 diabetes which reduces risk of CVD
Regular exercise- strengthens heart muscle and weight loss which reduces risk of high BP
Less alcohol- less risk of heart disease
Stop smoking- less risk of atherosclerosis and heart attack

How can CVD be treated through drugs?

Statins- reduced blood cholesterol (prevents formation)
Anti-platelets- reduced risk of heart-attacks as platelets less sticky so less clotting
Beta blockers- reduced blood pressure due to blocked effects of adrenaline, slowing heart and improved flow
Nitrates- Dilate blood vessels so more blood flow at lower pressure

Side effect to these drugs

Statins- upset stomach
Anti-platelets- internal bleeding
Beta blockers- Dizziness and tiredness
Nitrates- headaches and dizziness

How can CVD be treated surgically?

Valve replacement- Valves become faulty with age or infection. Backflow causes heart failure
Angioplasty- Widens partially blocked arteries using stent
Bypass- bypasses blocked coronary arteries using blood vessels from elsewhere in body
Transplant: When heart too damaged to repair

What are the conditions for organ transplantation?

Similar age and size- work as effectively and as long as possible but limited availability
Same blood group- prevents rejection but limited availability
Close tissue match- prevents rejection
Lifelong course of anti-rejection drugs- prevents rejection but reduces immune system ability to fight infection

What are embryonic stem cells and how can they be used

Can differentiate into any cell type if taken from embryos up to 5 days old

Used for:
Testing new drugs for safety and efficacy
Reversing damaged caused by diseases- eg. rebuild bones for arthritis
Make replacement heart valves
Could be used in future to develop tissues and whole organs for transplant

What are the disadvantages of using stem cells

Risk of rejection
Ethical implications (some believe life begins at conception)
Increased risk of cancer
Risk of transferring viral infections

Define gene therapy and outline its steps

Gene therapy- Placement of fully functioning allele into cell containing faulty allele for same gene

Cut out normal allele from donor cell using restriction enzymes
Produce many copies of allele
Insert into recipient’s cells via modified virus (virus altered so can’t reproduce)
Cells become transgenic and injected back into patient’s body

What is the human genome project

Locate genes linked to inherited disease
Develop drugs that target disease- genes or proteins they code for
Develop new gene therapy for incurable diseases
Develop personalised medicine by using patient’s genetic make up

What organisms can cause plant disease?

Viruses- Tobacco mosaic virus
Bacteria- Agrobacterium tumefaciens
Fungus- powdery mildew
Insects

What are the signs of plant disease?

Stunted growth
Tumour-like Growths
Discolouration
Spots on leaves
Areas of decay
Presence of pests
Malformed stems or leaves

What physical defences does a plant have?

Cuticle- prevents direct contact of pathogens with epidermal cells. Hydrophobic preventing water collection on leaf so spores can’t germinate

Cell wall- structural barrier to fungi and bacteria. Many cells form secondary wall inside primary for further barrier

What chemical defences does a plant have?

Insect repellent
Insecticides
Antibacterial compounds- phenols disrupt bacterial cell wall
Antifungal compounds
Cyanide- some plants produce chemicals which break down to form cyanide compounds

What mechanical defences does a plant have?

Some have thorns or hairs to prevent consumption
Some use mimicry to trick insects
Leaves that close up rapidly so less surface area for herbivores

How are plant diseases identified

Observation- looking for visual symptoms
Microscopy- many diseases same symptoms so microscopy used to identify pathogen (electron microscope may be needed)
DNA profiling
Identification of antigen- chemical analysis. Diagnostic test kits enable farmers to identify common pathogens