The Nature of science and the Scientific Method Evolutionary Origins
Applying Science - the hypothesis testing approach
• Human lineage separate from apes 5-7 million years ago ○ STIMULUS - climate change ○ LED TO - bipedialism ○ INCOURAGED - brain development ○ LED TO - tool use • Major evolutionary trends 1. Bipedalism 2. Increased brain size 3. Shortened jaw, flatter face 4. Reduced sexual dimorphism 5. Longer infancy • Modern Human Characteristics ○ Tools ○ Language use ○ Culture: the social behaviours and institutions of society ○ Science & technology
• Mensurative experiments: measuring the abundance of the target species living in different habitats REQUIRE ○ Same requirements as below BUT these experiments make comparisons between groups that are already thought to differ in some way • Manipulative Experiments: change the habitat see what happens to the target species REQUIRE: ○ Treatment groups - where a single deliberate change is carried out ○ Control groups - where the change is not carried out - any difference between control and treatment groups should be cause only by the single factor changed ○ Replicates, meaning that there must be more than one treatment froup and one control group to allow statistical testing of differences ○ Randomisation or interspersion of control and treatment groups to ensure that any difference between them is not caused by changes across the landscape or in time.
Human Cultural Developments
3 broad stages … 1. Pre-agricultural - Hunter / gatherers 2. Agricultural - domestication (farming, settling in one place) 3. Urban - very high population densities (Industrial revolution)
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Controlled Variable: held constant throughout the experiment Independent Variable: Variable chosen to be manipulated (habitat) Dependant Variable: the variable measured to determine the effect of changing independent variables (target species) Null Hypothesis: unable to be proven easier to refute ○ Rejection of the null hypothesis provides support for the hypothesis Designs for Hypothesis Testing
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Pre-Agricultural Ecosystems Solar energy input Large scale recycling of matter ~100,000 years ago - humans survived well ~ 50,000 years ago humans began to develop more sophisticated tools / weapons ENVIRONMENTAL IMPACTS? N/A Agricultural Ecosystems Domestication of plants : ~10,000 - 15,000 years ago Sun still major source of energy ENVIRONMENTAL IMPACTS Vegetation cleared for crops population = demands on food production → land degradation and loss of productive capacity
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1. Replication Replicates should not be correlated or similar in any way 2. Controls 'artefacts' of the experiment must be present at all test sites 'yardsticks against which experimental treatments are compared' 3. Placement of treatments & controls Control sites should be far enough apart to prevent animals moving between them BUT close enough to minimise differences in weather or other factors Location of treatment and controls sites should be mixed up (randomized) Control & experimental treatments should be monitored at the same time Interpreting the Results of Hypothesis tests • Is a real difference displayed AND does it allow for rejection of the null hypothesis? • Statistical Evaluation: allows us to evaluate how likely the results are to occur by chance, allowing us to determine whether or not any differences are significant. • Differences between treatment and control groups are determined by statistical tests, which give the probability that any observed difference is caused by chance. To be accepted as significant a difference must have only a 5% probability or less of having occurred by chance. Information Theoretic Approach