In this section, the emphasis switches from proximate (molecular, cellular, physiological and behavioural) types of explanation to ultimate types of explanation. In order to proceed, we need to understand two key concepts: life history and trade-off. Both of these concepts are important tools in organising thoughts about why organisms are so diverse. An organism's life history is the set of key biological events in its life, including b
Author(s): The Open University

After studying this course, you should be able to:

• identify the four main strategies shown by organisms for coping with winter

• appreciate and give examples of the levels and types of explanation used for understanding these strategies

• describe ways in which the strategies can be subjected to experimental manipulation

• provide examples of how plants, birds and mammals can remain active through winter

• give examples of orga
Author(s): The Open University

This free course provided an introduction to studying Science. It took you through a series of exercises designed to develop your approach to study and learning at a distance, and helped to improve your confidence as an independent learner.

Author(s): The Open University

Formulas are important because they describe general relationships, rather than specific numerical ones. For example, the tins of paint formula applies to every wall. To use such a formula you need to substitute specific values for the general terms, as the following examples show.

As mentioned in the animation in Section 1.2 writing mathematics has a lot in common with writing English. When you write mathematics, you should write in the equivalent of sentences, with full stops at the end. As in English, each new statement should follow on logically from the previous one or it should contain an indication that a new idea is being introduced. However, laying out mathematics differs from laying out English: because mathematics is more condensed than written English
Author(s): The Open University

Section 4 introduces some important mathematical theorems.

Click the link below to open Section 4 (7 pages, 237KB).

Section 4

Author(s): The Open University

The use of renewable energy usually involves environmental impacts of some kind, but these are normally lower than those of fossil or nuclear sources.

Approaches (a) and (b) are essentially 'supply-side' measures â€“ applied at the supply end of the long chain that leads from primary energy production to useful energy consumption.

Author(s): The Open University

So far, we have briefly introduced three key approaches to improving the sustainability of human energy use in the future. These are:

• (a) 'cleaning-up' fossil and nuclear technologies;

• (b) switching to renewable energy sources;

• (c) using energy more efficiently.

Author(s): The Open University

But apart from these relatively few enlightened examples, the efficiency with which humanity currently uses its energy sources is generally extremely low. At present, only about one-third of the energy content of the fuel the world uses emerges as 'useful' energy, at the end of the long supply chains we have established to connect our coal and uranium mines, our oil and gas wells, with our energy-related needs for warmth, light, motion, communication, etc.

Author(s): The Open University

Except in the form of food, no one needs or wants energy as such. That is to say, no one wants to eat coal or uranium, drink oil, breathe natural gas or be directly connected to an electricity supply. What people want is energy services â€“ those services which energy uniquely can provide. Principally, these are: heat, for warming rooms, for washing and for processing materials; lighting, both interior and exterior; motive power, for a myriad of uses from pumping fluids to lifti
Author(s): The Open University

Renewable energy sources are generally sustainable in the sense that they cannot 'run out' â€“ although, as noted above, both biomass and geothermal energy need wise management if they are to be used sustainably. For all of the other renewables, almost any realistic rate of exploitation by humans would be unlikely to approach their rate of replenishment by nature, though of course the use of all renewables is subject to various practical constraints.

Renewable energies are also relative
Author(s): The Open University

Most societies have had traditional methods of preserving food: drying, baking, pickling, salting, smoking, the use of sugar, and in cold climates, freezing or chilling, with the use of ice houses in the summer. These techniques were usually carried out at a local level, which meant that most perishable food was consumed near to where it was produced, and any food processing was usually small-scale and localised. Cattle and livestock, for example, were moved 'on the hoof' from their pastures
Author(s): The Open University

Except for third party materials and otherwise stated (see terms and conditions), this content is made available under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 Licence

This free course is adapted from a former Open University course called 'Living in a globalis
Author(s): The Open University

System dynamics diagrams, also sometimes called â€˜stock flowâ€™ diagrams, can be derived from causal diagrams, although in some cases it might be easier to start directly with the system dynamics diagramming technique, especially if you need to explore around one particular objectâ€™s attribute, such as population number.

System dynamics diagrams are drawn using four symbols: boxes representing attributes or â€˜stocksâ€™ of objects (e.g. level of water in a tank); valves representing
Author(s): The Open University

This free course provided an introduction to studying Environment & Development. It took you through a series of exercises designed to develop your approach to study and Author(s): The Open University

After studying this course, you should be able to:

When the temperature of an object increases (say, by Î”T) it expands. According to the linear model of thermal expansion the length increase is described by

What if there is a temperature change, but some constraint prevents the proper thermal size
Author(s): The Open University

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