2.4.9
Plants also need water for;
1. Photosynthesis (~5%)
2. Cooling via transpiration (~90%)
3. Transport of substances (e.g. sucrose, mineral ions)
4. Maintain turgor
5. Solvent for chemical reactions
6. Gamete distribution
2.4.10
Dig up your Plant Mineral Deficiencies Core Practical notes
in the Practical Handbook
2.4.11
Dig up your Mint / Garlic Core Practical notes in the
Practical Handbook
2.4.12
William Withering experimented with foxglove extract as a cure for dropsy (oedema caused by congestive heart failure). He gave the drug in increasing amounts until the patient became ill, then he
Mineral Function in plant
Nitrate Used to make amino acids, which the plant uses to form proteins
Calcium Used to make pectin for cell walls Magnesium Central ion in the chlorophyll molecule.
worked out a dose based on that. He also killed someone. His studies, though important are NOT ethical and do not follow the basis of modern clinical trials
Clinical Trial Process:
Stage Purpose of stage Pre-clinical
testing
1. Proposed drug is tested in a lab with cultured cells to see the general effects of the drug
2. Proposed drug is given to animals to see the effects on a whole animal. Any side effects away from target cells are noted.
Clinical Trials – Phase 1
1. A small group of healthy volunteers are given different doses of the drug. They are told what the drug does 2. The distribution, absorbance rate, metabolism &
excretion profile of the drug are assessed.
3. The effects of the different doses are assessed to try and determine the optimum dose
4. An independent organisation (UK Medicines Control Agency) assesses whether it is appropriate to move to Phase 2
Clinical Trials – Phase 2
1. A small group of people with the disease are given the drug.
2. Studies are very similar to Phase 1 3. The optimum dose is worked out Clinical Trials –
Phase 3
1. A large group of people with the disease are given optimum doses of the drug
2. The patients are either given the drug or a placebo in a double-blind test
3. The results are analysed
4. If the drug has had a significant positive effect in the treatment of the disease it is put forward to licensing authority
2.4.13
Biodiversity: The number of species, the number of individuals within those species and the number and variety of alleles those individuals.
Endemic: Where a species is found only within a particular niche in a particular ecosystem.
Species richness: is a measure of biodiversity where the number and variety of species in an area is recorded. Can be measured in different ways;
• Indicator species i.e. the presence of specific species (usually those least tolerant to pollution / climate change etc) are used to indicate the “health” of the ecosystem.
• Population of keystone species i.e. the population of crucial species (usually those providing prey for the rest) are used to measure the “health” of the ecosystem
• Quantitative sampling – a direct way of sampling the biodiversity using quadrats
• Capture / recapture – a direct way of working out populations of species.
Genetic diversity: the number of different alleles within the gene pool. The greater the diversity, the more likely the species is to survive environmental change or disease.
2.4.14
A niche is the specific part of the ecosystem in which a species lives and any adaptations the species has that make it successful there. Adaptations can be;
Behavioural e.g. Iguana on the Galapagos islands dive for seaweed - they are the only lizards to venture into the sea.
Physiological e.g. some Ethiopians have evolved a different shaped haemoglobin molecule that resembles foetal Hb. It loads O2 much
more efficiently at altitude (see end of Topic 1)
2.4.15
Darwin made two observations and a conclusion; O1: More offspring are born than can survive O2: There is variation within a species
Conclusion: There is a “struggle for survival” only the “fittest can survive and reproduce.” This is Natural Selection
In order for NS to lead to evolution a few extra conditions are required;
1. Isolation (see table below) so no flow of alleles 2. Small population & inbreeding
3. Mutation (generates new “fitter” alleles) 4. Mutations accumulate within population
5. Eventually the isolated population cannot reproduce with the originals. At this point a new species has formed (speciation)
Anatomical e.g. the Fiddler crab has two very different claws. One is huge and is used for “fiddling” i.e. signalling for a mate. The smaller claw is, rather disappointingly, used for feeding.
Allopatric speciation occurs when species are far from each other Sympatric speciation occurs when species are close to each other
2.4.16
The taxonomic classification system follows a hierarchy of groups (the 5 Kingdoms at the top, individual species at the bottom) in which all species are categorised according to their anatomy.
However, this is not necessarily the best approach as species with similar anatomies (e.g. dolphin and shark) are not necessarily closely related. A better system is based on molecular phylogeny i.e. comparing the molecules species are comprised of. The best molecule to examine is DNA.
A recent proposal along this line (the three domain theory) argues that all organisms evolved into three broad groups;
Bacteria – prokaryotes, fundamentally different structures
Archaea – those species that exhibit characteristics of both (i.e. “early eukaryotes” and their descendents)
Eukaryotes – eukaryotes, fundamentally different structures
Ecological isolation The species occupy different parts of the habitat
Temporal isolation The species exist in the same area, but reproduce at different times
Behavioural isolation The species exist in the same area, but do not respond to each other’s courtship behaviour Physical incompatibility Species coexist, but there are physical
reasons which stop them from copulating
Hybrid inviability In some species, hybrids are produces but they do not survive long enough to breed
Hybrid sterility Hybrids survive to reproductive age, but cannot reproduce
2.4.17
Seed banks and Zoos help because they allow us to preserve biodiversity, reintroduce species, set up captive breeding programmes, educate people about ecology and generate money from tourism.
However, be aware that some species (those that have a lot of leaned behaviours e.g. tigers) do not tend to fare well on reintroduction programmes.