4.3 Gamete production in men

A sexually mature man is producing sperm all the time at a rate of around 300–600 per gram of testis per second. This provides the 500 million or so which are released at each ejaculation. But the formation of an individual sperm takes about nine weeks (64 days). Sperm are produced in the testes, and production is most efficient at a temperature several degrees lower than the normal body temperature of 371°C. For this reason the testes (plural of testis) are suspended outside the body cavi
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8 Summary

  1. The rate at which water infiltrates into the ground depends on the permeability of the rocks and the state of the ground surface. Below the ground surface there is an unsaturated zone which has air in the pore spaces, and a saturated zone which has all the pores filled with water. The water table is the boundary between the unsaturated zone and the saturated zone, and is the level at which water stands in wells. Water below the water table is called groundwa
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6 Permeability

It is important to distinguish clearly between porosity and permeability. Porosity is a measure of how much water can be stored in a rock, whereas permeability is a measure of the properties of a rock which determine how easily water and other fluids can flow through it (see Section 4). Permeability depends on the exte
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2.5 What is water made of?

The size of a water droplet may seem very small but in terms of the scale of scientific measurement it is relatively large. You already know that water is made up of molecules so now consider a water droplet more closely to see what water molecules are made up of. If you could magnify a water droplet until it no longer has a smooth surface, you would see something similar to that shown in Author(s): The Open University

1 Overview

As you walk down the street one day, you hear a voice from somewhere behind you that seems to be discussing this unit. It says:

‘My dad's tutor's no joker, and he told me the TMA's going to hit home with a bang.’

You turn to find the face behind the voice, which is a gravelly Glaswegian baritone, but the man has gone, leaving you to ponder what he has said. Let us call his sentence exam
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11.2 Frequency discrimination

Some findings indicate that, for moderate loudness levels, humans can detect a frequency change of about 1 to 3 Hz for frequencies up to about 1000 Hz. Figure 37 shows a plot of the smallest frequency difference for which two tones can be discriminated for a number of reference tones. You can see from the figure that up to about 1000 Hz, the D
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1.4.4 O is for Objectivity

One of the characteristics of ‘good’ information is that it should be balanced and present both sides of an argument or issue. This way the reader is left to weigh up the evidence and make a decision. In reality, we recognise that no information is truly objective.

This means that the onus is on you, the reader, to develop a critical awareness of the positions represented in what you read, and to take account of this when you interpret the information. In some cases, authors may be
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13 Post-compulsory science education

In a speech to the Institute of Economic Affairs in 2001, the then UK Secretary of State for Education said:

Young people choosing vocational study will be able to see a ladder of progression that gives structure, purpose and expectation to their lives, in the same way that a future pathway is clear to those who leave school to gain academic A-levels and enter university. Over-16s in full-time education will be abl
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Europe and the law
This unit will give you a basic understanding of EU law and the interaction between EU and domestic law. It will provide a brief explanation of the European Convention on Human Rights and other European legislation, as well as the background to such institutions as the European Council, the European Commission, the European Parliament and the European Court of Justice. First publish
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1.2 The growth of the legal system

The legal system plays a significant and growing role in society as our lives become governed by an increasing number of laws. As our society has become more sophisticated, a greater number of laws have been required. This in turn has resulted in our legal system becoming increasingly more complex. Changes in technology, the way in which we live and the types of relationships we have are all reflected by the law. Society expects the law to reflect its ideas, values and culture, so the law has
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7.1 Reserved and devolved matters

As stated earlier, the UK Parliament can still legislate on reserved matters and also on devolved matters, with the agreement of the Scottish Parliament. This section looks at the law making process at Westminster. It is a very different process, which involves both the Houses of the Westminster Parliament.

An Act of the UK Parliament also starts off as a Bill, which, if approved by a majority in the House of Commons and the House of Lords, will become an Act of the Westminster Parliame
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6.7 Royal Assent

Section 32 of the Scotland Act provides that a Bill, once passed, must be submitted for Royal Assent. This is done after a period of four weeks. During that time, the Bill is subject to legal challenge by the Advocate General for Scotland, the Lord Advocate or the Attorney General, and may also be subject to an order made by the Secretary of State. The Presiding Officer may, however, submit the Bill for Royal Assent after less than four weeks if notified by all three Law Officers and the Secr
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Studying mammals: The opportunists
Many mammals are food specialists, with complex adaptations that gear them toward a particular food source. So how do the omnivores survive and prosper without these fancy evolutionary features? This unit examines the physiology, diet and strategies of some of these opportunistic feeders. It is the sixth unit in the ‘Studying mammals’ series. Fir
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Studying mammals: The insect hunters
From pygmy shrews to armadillos, a wide range of mammals survive on a diet made up largely of insects. Many of these have fascinating adaptations suited to catching or rooting out their prey. In this unit you will learn about these adaptations, along with survival strategies for when food is scarce. This is the second unit in the ‘Studying mammals’ series.Author(s): Creator not set

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Studying mammals: Food for thought
Who were our ancestors? How are apes and humans related? And where does the extinct Homo erectus fit into the puzzle? In this unit we will examine culture, tool use and social structure in both apes and humans to gain an understanding of where we come from and why we behave as we do. This is the tenth unit in the ‘Studying mammals’ series. First publ
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Studying mammals: Return to the water
Some of the most unusual and versatile of all the mammals are the groups that live, feed and reproduce underwater. In this unit we will see how these formerly land-based mammals adapted to a return to the water, discussing such challenges as breathing, movement and communication. This is the seventh unit in the ‘Studying mammals’ series. First pu
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Evolution through natural selection
In this unit, we describe the theory of evolution by natural selection as proposed by Charles Darwin in his book, first published in 1859, On The Origin of Species by Means of Natural Selection, or The Preservation of Favoured Races in the Struggle for Life. We will look at natural selection as Darwin did, taking inheritance for granted, but ignoring the mechanisms underlying it.Author(s): Creator not set

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Animals at the extremes: The desert environment
Animal life has adapted to survive in the most unlikely and inhospitable habitats. This unit looks at the surprisingly diverse desert climates throughout the world and mammals, birds, lizards and amphibians that survive there. It splits these animals into three groups according to their strategy for survival: evaders, evaporators and endurers, then discusses how these strategies work on a biochemical and physiological level.Author(s): Creator not set

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Water for life
Atoms, elements and molecules are the building blocks of everything that makes up our world, including ourselves. In this unit you will learn the basic chemistry of how these components work together, starting with a chemical compound we are all very familiar with – water. First published on Thu, 21 Jul 2011 as Author(s): Creator not set

Studying mammals: Meat eaters
The powerful and majestic carnivores are the focus of many television documentaries. In this unit we will delve into the lives of these fearsome hunters and explore their physical adaptations and social behaviour. This is the fifth unit in the ‘Studying mammals’ series. First published on Thu, 21 Jul 2011 as Author(s): Creator not set