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1.3.1 Inheritance of colour in maize

We can trace the inheritance of characters in animals and plants by following the phenotype from generation to generation, in breeding experiments. We will describe work with maize (Zea mays), alternatively called corn (sweetcorn, or corn on the cob), which occurs throughout the world as an extremely important commercial crop plant, and which is used extensively in genetic research. We can also study the inheritance of characters at the level of the genotype. In this section we will ju
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1.2 Like begets like

It is possible to follow a character, such as eye colour or hair colour in humans, that is handed down from generation to generation. Such characters are said to be inherited characters (or heritable characters) and are determined by genes. A gene can be considered as a unit of inheritance, which determines a particular character and which is passed on from parent to offspring.

Genes maintain the differences between species, such as oak and human, but they also contribute
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Learning outcomes

After studying this unit you should know:

  • the number of chromosomes is characteristic of each species and can vary enormously between species

  • genetics is based on the concept of the gene as the unit of inheritance

  • that sexual reproduction always includes two distinctive processes: the production of gametes, which involves meiosis, and fertilisation. The two processes are accompanied by changes in the chromosome number, from diploid to haploid and fr
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3.7 Insulin

Insulin is a hormone produced by the pancreas. It has many actions, but is particularly important in keeping the blood glucose level normal.

Question: How does
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3.6 Fat

You may have heard people make comments about their metabolism, for example ‘I am fat because I have a slow metabolism’. Your metabolism refers to all the things that are going on in your body to keep you alive. Different people have different metabolic rates. Some people have low metabolic rates and some have high metabolic rates. Metabolic rate may play a part in someone's weight but it is not usually the whole cause of being fat or thin. Glucose metabolism refers to the way in w
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8 Managing the BSE/vCJD episode up to May 1990

BSE was formally recognised as a new disease in November 1986. However, this information was kept under ‘embargo’ at first while an initial epidemiological study – involving the collection of data from 200 herds – was started. The Ministry of Agriculture, Fisheries and Food (MAFF) was officially informed about BSE by the Chief Veterinary Officer (CVO) in June 1987. By December 1987, those responsible for analysing the data from the initial epidemiological study had concluded that the
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1.7.1 Unit summary

1. A coordinate system provides a systematic means of specifying the position of a particle. A system in one dimension involves choosing an origin and a positive direction in which values of the position coordinate increase. Values of the position coordinate are positive or negative numbers multiplied by an appropriate unit of length, usually the SI unit of length, the metre (m).

2. The movement of a particle along a line can be described graphically by plotting values of the particle's
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1.6.3 The acceleration due to gravity

In the absence of air resistance, an object falling freely under the influence of the Earth's gravity, close to the surface of the Earth, experiences an acceleration of about 9.81 m s−2 in the downward direction. The precise value of the magnitude is indicated by the symbol g and varies slightly from place to place due to variations in surface altitude, the effect of the Earth's rotation and variations in the internal composition of the Earth. Some typical values f
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1.5.6 Velocity and acceleration as derivatives

Recalling that the instantaneous velocity of a particle at time t is given by the gradient of its position–time graph at that time, we can now use the terminology of functions and derivatives to say that the velocity of the particle is given by the derivative of its position function. In terms of symbols:

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1.5.5 Derived functions and derivative notation

Given the function x(t) that describes some particular motion, you could plot the corresponding position–time graph, measure its gradient at a variety of times to find the instantaneous velocity at those times and then plot the velocity–time graph. If you had some time left, you might go on to measure the gradient of the velocity–time graph at various times, and then plot the acceleration–time graph for the motion. This would effectively complete the description of the m
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1.5.4 Functions and the function notation

In Figure 25, the position x of the car depends on the time t. The graph associates a particular value of x with each value of t over the plotted range. In other circumstances we might know an equation that associates a value of x with each value of t, as in the case of the equation x = At + B that we discussed in Section 3. You can invent countless other ways in which x depends on t: for instance x = 
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1.5.3 A note on functions and derivatives

This subsection introduces two crucially important mathematical ideas, functions and derivatives, both of which are used throughout physics.


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5 Who were the ancestors of Homo sapiens?

Large brain size is a defining feature of Homo sapiens, which means that evolution of increased brain size in Homo is crucial evidence. Indeed, an increase in both the size and the complexity of the brain is a defining feature of primate evolution as a whole. It's possible to estimate brain sizes from fossil skulls or parts of skulls, e.g. by filling what there is of the skull with sand and then measuring the volume of the sand. Use of computer technology fills in ‘gaps’ in
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5 Miss Piggy

As the earliest mammals – the insectivores – were specialists, it follows that the omnivore lifestyle must have arisen at some later stage in a group or groups of non-omnivores. In fact, both seed eating and leaf eating arose before omnivory. Twenty million years ago, Dinohyus was undoubtedly a ‘specialist’ omnivore.

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Fur

Fur is important in thermoregulation, but a conspicuous coat may proclaim sexual dominance or warn off competitors. It's similarly important for predators to remain unseen for as long as possible. The most familiar type of camouflage is the colour of the hunter merging into the background environment colour – think about stoat in winter (ermine), polar bears against the ice of the Arctic and lions against the baked soil and dried grass of Africa. But equally important is the patterned fur o
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6 Grazers and browsers

A good deal of the discussion so far has been related to animals that eat leaves in the form of grass and other herbaceous plants, the grazers, but this is not the only type of plant food. Also available as food are the leaves of trees and bushes. These form the diet of the browsers.


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5.3 Hindgut fermenters

The odd-toed ungulates (comprising the order Perissodactyla), the horses, tapirs and rhinoceroses, are hindgut fermenters, as are elephants. Update Table 2 with this information. These animals have a relatively simple, small undivided stomach, but this time an even larger caecum and colon where the microbes are housed and whe
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3 Herbivore teeth

Tables are a useful way of recording key information. The headings for Tables 1 and 2 have been prepared for you, and you can copy and complete the tables in your notebook. If you need to find any of this information again later, then it is very useful to have it summarised in a table.

I
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3 Appendix: Some highlights of physics

c. 624 BC Birth of Thales of Miletus: traditionally ‘the first physicist’.
384 BC Birth of Aristotle: author of Physics.
1543 Nicolaus Copernicus' De Revolutionibus Orbium Celestium.
1600 William Gilbert's De Magnete describing the behaviour of
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