Biodiversity and Natural Selection

• Plants provide macronutrients (carbohydrates, lipids and proteins).
• They also provide micronutriets (vitamins and minerals).
• They store starch, which is a good energy source.
• Rice, wheat, potato and maize are examples of staple foods.

• Selective breeding is breeding only invididual plants with desired characterists/features.
• Someestimes called artificial selection.
• The selectively bred plants give higher yields, resistant to diseases, resistant to insect pest damage, and can survive harsher conditions. 

• Poorer farmers cannot afford to grow varieties of crop that have highly desired characteristics, as there are only a few varieties that have enough quality to be sold.
• Genetically modified plants are engineered to prevent them from breeding (so that they don't cross breed).
• This means that farmers have to continuously buy new seeds or seedlings.
• This is difficult for poorer farmers. 

• The thickening of plant stems, by sclerinchyma and lignification of xylem, makes thems strong and resistant to tensile and compressive forces.
• This is why wood has such good construction features. 

• Fibres can be removed from plant stems by retting.
• Field retting is when plant stems are cut or pulled up and left in a field to rot; microbial actions breaks down the stalks, and fibres are collected.
• Water retting is the same, except rotting occurs in water by aqeuous bacteria and fungi.
• Water retting produces more uniform, high quality fibres, but is more expensive and produces more waste. 

• Cotton fibres are produced in pure form, not within a matrix of other materials. 
• This means that cotton does not need retting, it can be picked straight from the plant, unlike jute and hemp. 

• Scientists extract the active ingredient of a medicinal plant instead of using the whole plant.
• This removes impurities in the whole plant.
• Ingredient is extracted and purified to make it more effective.
• Also means we can use more accurate dosages.
• Ingredient is synthesised and modified, so that it can produced on an industrial scale. 

• Scientists identify and extract active ingredient.
• Impurities are removed, drug is purified and modified so its effectiveness is optimised.
• New compound is tested in cell/tissue cultures to see if drug has desired effect.
• Drug moves out of research and into development.
• The drug is tested on animals to ensure no risk of breaking down into something toxic.

• Phase 1 trials: drug given to small number of healthy volunteers, to investigate side effects.
• Phase 2 trials: drug is given to patients affected by the disease. Between 100-500 volunteers given drug.
• Phase 3 trials: Over 5000 patients normally used. 
• Phase 2 and 3 trials are double-blind, which means neither the doctor nor the patients know whether drug is real or a placebo. 

• Withering tested digitalis on patients are a pain killer.
• His method was scientific in that he: identified the active ingredient, tested on a large number of patients over many years, made careful observations of methods of preparation aand recording results including side effects.
• His method was unacceptable in that: He experimented on patients without testing for safety and effectiveness in other ways beforehand, and experimenting with dosages that could kill patient.

• Biodiversity is the variety of living organisms in an area.
• Two types: species and genetic.
• Species diversity is the number of different species and the abundance of a species in an area. 
• Genetic diversity is the variation of alleles within a species. 
• Endemism is when a species is unique to one area in the world.
• E.g the giant touroise is endemic to to the Galapogous island.

• Biodiversity is the variety of living organisms in an area.
• Two types: species and genetic.
• Species diversity is the number of different species and the abundance of a species in an area. 
• Genetic diversity is the variation of alleles within a species. 
• Endemism is when a species is unique to one area in the world.
• E.g the giant touroise is endemic to to the Galapogous island.

• Endemic species are very susepitble to extinction, because they are used to having no competition for food in their unique habitat.
• Species richness is the amount of different species in an area (like half of species diversity).
• Species richness can be measured simply by counting the number of different species in an area.
• Species diversity can be measured by counting the number of different species and the number of animals in each species. 

• It would be very time consuming and expensive to count all the species and their relative abundancies, so instead we use a sample area.
• Choose area to sample, to avoid bias the sample to be random. 
• Count the number of species and their relative abundancies, using a quadrat, sweep net, pitfall trap or a net.
• Repeat the process in different areas to improve relaiblity.
• Use results to estimate species richness/diversity.

• Indivuals in the same species may vary because they have different alleles.
• Genetic diversity is the variety of alleles in the gene pool of a species.
• A gene pool is the complete set of alleles in a species. The greater the variety of alleles in a gene pool, the greater the genetic diversity. 
• By looking at the different phenotypes within a population of a species, you can see the diversity of alleles in a species.

• Another way of measuring genetic diversity is through the genotypes of animals in a population.
• Samples of an organisms DNA can be taken and a sequence of bases analyses.
• The order of bases different alleles is slightly different.
• By doing this for many organisms in a species, you can look at the genetic similarities and differences, and count how many different alleles there are in the species for one characteristic in a gene pool. 

• Reduction or extiction of a species or the reduction in genetic diversity of a species causes a reduction in the glab biodiversity. 
• Zoos and seed banks help to conserve endangered species.

• Seed banks store the seeds of endangered plants.
• They help to conserve biodiversity.
• If the plants become extinct in the wild, seeds from the seed bank can be used to replenish the species.
• They also help conserve genetic diversity, because they store a range of seeds from plants with a range of genetic characterists (different alleles). 
• They create cool, dry conditions for storage.
• Live seeds are cleaned and sterolised.
• Test seeds for viability (X-ray)

• Zoo's have captive breeding programs where animals of the same endangered species are bred in controlled environments. This increased their population.
• Organisms from zoo's can be reintroduced into the wild. 
• This reintroduction can save not only an endangered species, but species that rely on the endagnered species.

Zoo's maintain genetic diversity by:

• Collecting sperm of endangered species.
• Storing it in sustainable conditions.
• Captive breeding programs.
• Careful mate selection for breeding.
• Ultimate aim of reintroducing captive bred animals into the wild habitat.
• Recording breeding in a stud book.
• NOTE: some animals find it difficult to live in wild one reintroduces from zoo life. 

• Individuals in a population show variation in their phenotype.
• Predation, diseases and competition create a struggle for survival.
• Indivuals with better adaptations are more likely to survive, reproduce and pass on their advantagous adaptations to their offspring.
• Over time the number of individuals with the advantageous adaptations increases.
• Over generations this leads to evolution, as the advantageous adaptations become common.