Core Practicals: Biology, Questions and Answers PDF

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Core practical – measuring the tensile strength of plant fibres Tensile strength – maximum load the fibre can take before it breaks. 1. Plant material - stinging nettles- should be left to soak in a bucket for a week to make fibre extraction easier (retting). Or, celery can be used and should be left in beaker of coloured water for fibres to be seen easily and pulled out. 2. Once fibres removed, measure lengths of fibres used (must all be the same length) and then connect between two clamp stands 3. Gradually add mass in the middle until the fibre breaks, and record the mass. 4. Repeat the experiment with different samples of the same fibre – to increase reliability. 5. Must make sure other variables are constant – temperature, size of each individual mass used. Safety precautions: wear goggles to protect eyes and make sure the area where weights will fall is clear. Importance of water and inorganic ions to plants Water is needed for photosynthesis, to maintain structural rigidity, transport minerals and regulate temperature. Magnesium ions – Needed for the production of chlorophyll. Deficiency results in yellow areas developing and growth slows down Nitrate ions – Needed for production of DNA, proteins and chlorophyll. Deficiency results in stunted growth, poor seed and fruit production and leaves appear light green/yellow. Calcium ions – Important components of plant cell wall, and required for plant growth. Deficiency results in leaves turning yellow and crinkly, and poor fruit development. Core practical: Investigating plant mineral deficiencies Using Mexican hat plantlets making sure they are the same height. 1. 9 test tubes – 9 different nutrient solutions. 2 used as a control: all nutrients present and lacking all nutrients 2. Cover test tubes with black paper – this prevents algae growing in test tubes which will take up the nutrients. 3. Put the nutrient solutions into the test tubes and label each one. Solutions should be filled to the top so that the roots will be completely submerged. Label each one. 4. Cover test tubes with foil so that solutions don’t evaporate and to keep the plant stable 5. Pierce hole in the top of each one, and gently push the Mexican hat plantlets through the holes so that it is in the solution below. 6. Put in test tube racks and on a windowsill so that leaves are exposed to sunlight and to maximise photosynthesis. 7. Check and observe after one week to see effect of the nutrient deficiencies.

Drug testing and drugs from plants William Withering and his digitalis soup: He was a scientist in the 1700s Discovered that an extract of foxglove plants could be used to treat dropsy (swelling brought about by heart failure. The extract contained the drug Digitalis Withering made a chance observation, gave digitalis to patients and they were cured, but some died due to the poisonous nature of foxgloves. As a result of this, he tested different versions of the remedy with different concentrations of digitalis Found that dried, powdered form was the most effective. Through trial and error he discovered the right amount to give to the patient. Modern drug testing protocols are more rigorous and controlled: Must pass each stage of testing to go onto the next: 1. Computers are used to model the potential effects of a substance 2. Tested on human tissues in a lab 3. Tested on animals – this sees the affects it has on an entire organism. Testes on rats and mice and then rodents and non-rodents to compare to other animals. 4. CLINICAL TRIALS – three phases Phase 1: Drug tested on small group of healthy volunteers – to find out whether its a safe dosage and to see how the body reacts to the drug. Phase 2: Drug tested on a larger group of patients with the disease – to see how well the drug actually works Phase 3: The drug is compared to existing treatments – hundreds or thousands of patients. They are randomly split into two groups, one receives new treatment, and other group receives existing treatment. This aims to see if the new drug is better than existing drugs. During phase 2, the patients are split into 2 groups, and one is assigned a placebo – this allows scientists to see if the drug actually works compared to a placebo. Phase 2 and 3 – double blind study design – the doctors and patients don’t know who has been given the placebo or the drug, or in phase three the existing or new treatments. This reduces bias.

Core practical - investigating antimicrobial properties of plants Equipment: agar plate seeded with bacteria, plant material: e.g. garlic and mint, pestle and mortar, 10cm^3 industrial denatured alcohol, sterile pipette, paper discs, sterile Petri dish, sterile forceps, hazard tape, marker pen

1. Make plant extracts by crushing 3g of plant material with 10cm^3 alcohol and shake occasionally for 10mins (must shake for long time to ensure there is enough active ingredient) 2. Pipette 0.1cm^3 of the separate extracts onto sterile paper discs, and place on the sterile Petri dish and allow it to dry. Two paper discs are controls: With water and with nothing. 3. Label the agar plates with the different plant extracts and split into 4 sections, 1 for each type of extract. 4. Place the discs into each quadrant of the agar plate and close and tape with hazard tape. 5. Leave to incubate and observe zone of inhibitions. Outcome: control discs completely covered with bacteria, and some plant extracts will have larger inhibition zones than others which show they are more effective at lower concentration. Must make sure surfaces, and all equipment used is STERILE, otherwise unwanted microbes will grow on the agar plates.

Adaptation and evolution: Niche – the role of an organism or species within its habitat, its way of life. Includes its interactions with other living and non-living environment. Every species has its own unique niche, and a niche can only be occupied by one species. If two species try to occupy same niche – they will compete and then only one species will be left. Adaptations to niche: Adaptations: features that increase an organisms chance of survival and reproduction 1. Anatomical: structural features of an organisms body/ body characteristics e.g.: whales and seals have blubber which protects them and has many functions. 2. Physiological: processes inside an organisms body that increases its chance of survival e.g.: the mammalian diving reflex – allows diving mammals to stay under water for longer because their heart rate drops and the blood pumps less oxygen. 3. Behavioural: ways an organism acts e.g.: penguins huddle together to stay warm, and birds of paradise have a special dance when they want to mate. Adaptations become more common by evolution: Natural selection: one of the processes by which evolution occurs. It explains why living organisms change over time to have the anatomy, functions and behaviour that they have 1. Individuals within a population show variation in their phenotypes and genotypes. 2. Predation, disease, and competition create a struggle for survival

3. Individuals that are better adapted – have characteristics which are favourable and give them an advantage and are more likely to survive, reproduce and pass on their advantageous adaptations to offspring. 4. Over time, the number of individuals with the advantageous adaptations increases 5. Over generations, this leads to evolution as the favourable adaptations become more common in the population. Biodiversity and Endemism Biodiversity: the variety of organisms in an area. This includes: Species diversity: number of different species and abundance of each species in an area Genetic diversity: Variation of alleles within a species or population of species. Conservation – needed to help maintain biodiversity Endemism – species unique to a single place. Conservation of endemic species is very important as they are the most vulnerable to extinction. Measuring Species diversity: 1. Count number of different species in an area – species richness. The higher the number of different species, the greater the species richness. However, this gives no indication of the abundance of each individual species. 2. Count the number of different species AND the number of individuals in each species. Then use a biodiversity index e.g. Simpson’s Index of Diversity to calculate the species diversity. This way takes into account abundance of each species. Samples can be taken to make estimates on whole habitat based on the sample. 1. Choose a random area within habitat to sample – random reduces bias in results. 2. Sampling techniques: Plants – use a quadrat (a frame placed on ground) Flying insects – sweepnet Ground insects – pitfall trap Aquatic animals – net Then count the number of species in the sample that you’ve got. 3. Repeat, and take as many samples as possible, as it will give a better indication of the whole habitat. 4. Use results to estimate total number of individuals or total number of different species (species richness) 5. When sampling different habitats and comparing, the same sampling technique should be used....