01110001100000111101110Foundations of biology

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1.1

• Well-designed experiments are based on a sound knowledge of what is already understood or ‘known’ and careful observation.

• A hypothesis is a possible explanation for a set of observations that can be used to make predictions, which can then be tested experimentally.

• Controlled experiments allow us to examine one factor at a time; they are the major means of testing hypotheses

• Science can prove that a particular hypothesis is wrong, but it cannot prove it to be true in all circumstances.

• Science cannot be used to evaluate hypotheses that are not testable, nor can it make value or moral judgments.

summary

1 Name the key components of scientifi c method.2 Scientists make observations from which an hypothesis is stated

and this is then experimentally tested. a Defi ne a hypothesis. b How do theories and principles differ from a hypothesis?

3 a What do ‘objective’ and ‘subjective’ mean? b Why must experiments be carried out objectively? c Can scientists really be objective?4 a Explain what is meant by the term ‘controlled experiment’. b Why is it important to ensure that scientifi c experiments are

‘controlled’?

key questions

1.2

Important principles in biologyBiology is a science, and our current understanding of life is based on the results of careful observations and experiments. In biology, some ideas or theories are supported by overwhelming amounts of evidence from such a wide variety of sources that it seems very unlikely they will be found to be untrue in the future. They are accepted as biological principles. Other theories are less strongly supported. Many are being modifi ed or overturned even as you read this book.

Some biological principles and processes are relevant to the ways that almost all living organisms function. For example, living organisms are composed of cells, organisms have common characteristics and requirements, evolution explains the diversity of organisms, and organisms are adapted to their environments.

Organisms are ‘living’ thingsHow do we distinguish what is living from what is non-living? We all have a general idea of the difference between a living organism and a non-living object, such as a possum and a rock. The common wombat (Figure 1.6a) is able to move, eat and respond to a sound in the bush; the young on its back is evidence that the possum is able to reproduce. A tree cannot move about, but we can observe it grow new leaves and reproduce at a certain time of the year by fl owering and producing seeds, which can germinate and develop into new plants. We can observe that a tree obtains materials and energy from its surroundings, since without sunlight, soil nutrients and water a tree will cease to grow. We can also see when an organism is no longer living; it is ‘dead’. In a tree the signs of death may be yellowing and loss of leaves,

biofi leSome popular theories that have been recently modifi ed or overturned include:• that sugar causes tooth decay (bacteria are

the real cause)• that stress causes ulcers (again bacteria are

implicated)• that fi bre in the diet reduces the incidence

of colon cancer (a huge study showed no correlation)

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Chapter 1 POMPEII: interpreting the past

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Examples of non-literary sources• skeletons (bones, teeth, skulls of people)• artefacts (anything made or used by people),

which may include:– smaller things such as tools, pots, jewellery

or artworks such as mosaics, sculpture, paintings

– larger things such as houses, temples or tombs

Examples of literary sources• letters, either personal or offi cial• graffi ti • plays, poems or stories• inscriptions on coins, tombstones or buildings

Source 1

Many years after the eruption of Vesuvius, the covered bodies decayed, leaving a hollow with just the skeleton inside the layer of pumice and ash. Modern archaeologists poured plaster into the hollows and were able to recreate a replica of the bodies.

activities1 a What caused day to turn into night, and

what effects do you think this may have had on the people?

b List the ways in which the people of Pompeii responded to their fear of the eruption.

c Why do you think Terentius never got up?

H Evaluating historical sources2 a Referring to the information above on

literary and non-literary sources, create a table of three columns. In the left-hand column, write down the items listed below. In the middle column, identify whether it is a literary or non-literary source. If you feel an item can be more than one type of source, explain why you think so.• ancient inscription on a tomb saying

how much someone was admired• the walls of a circular stadium that could

seat around 20 000• graffi ti on the stadium wall naming and

describing gladiators as heroes• swords, shields and helmets found

inside the stadium• the skeleton of a dog in the street• coins showing the head of Vespasian,

who became emperor of Rome in AD 69

• remains of a bread oven in a public building opening into the street

• mosaic fl oors and fountains in a private building

• vases with scenes of people playing games

H Using historical evidence to support a point of view b All these sources were found by

archaeologists at Pompeii. Working in pairs, suggest what historians could interpret from them about life in Pompeii. Write your answers in the right-hand column of your table.

3 Look at the painting on the opposite page.

a What type of source is this and which part of the story does it relate to? What information can you get from it?

b Suggest what Claudia would have felt as she looked at the painting.

H Evaluating historical sources4 Look at Source 1.

a What type of source is this and what part of the story does this relate to?

b In pairs, list the information archaeologists can gather about a person from a plaster cast of their body.

InD

T

What are sources? WB • X, Y, Z

TRK • 1.1, 1.2 CD • MG

InD

Mathematical Methods Units 1 & 2

14

14 Each of the following ‘designs’ has been created by use of a single linear rule involving parameters. Parameter lists are used to create each effect. Attempt to reproduce the effect shown and state the function rule and parameter lists used. (In each case, axes have been turned off; window dimensions are [−10, 10] by [−10, 10] using ZStandard on the TI-83/84 calculator.)

a b c

CD1.xTransform

ation creations

Domestic cats live to about 14 years on average. An often-used rule of thumb to compare the age of cats with humans is: 1 cat year is about 7 human years.

a If x is the age in years of a cat and y is the corresponding human age in years, express y in terms of x using this rule of thumb.

b Graph the straight line corresponding to the rule in part a for 0 ≤ x ≤ 15.

In practice, the real comparison is more complicated, and there are different linear rules for different ages.

c A cat that is 1 year old has a corresponding human age of 16 years.

i Plot the point (1, 16) on the same axes as in part b and join it to (0, 0) with a straight line.

ii Write the rule for y in terms of x for 0 ≤ x ≤ 1.

d A cat that is 2 years old is estimated to have a corresponding human age of 22 years.

i Plot the point (2, 22) on the same axes as in part b and join it to (1, 16) with a straight line.

ii Find the gradient m of the straight line joining (1, 16) and (2, 22).

iii Find the rule connecting y and x in the form y = mx + c for 1 < x ≤ 2.

iv An 18-month-old cat corresponds to what age in human years?

e Every year that a cat lives beyond the age of 2 counts as about 4 human years.

i How old in human years is a cat that survives to its average life expectancy of 14?

ii Add a third line segment to the previous graph to show a cat’s life for all values of x.

iii Find the rule connecting y and x in the form y = mx + c for x > 2.

iv A centenarian is someone who is 100 years old. What is the equivalent age for a cat?

f i For what cat ages does the rule of thumb underestimate its human equivalent?

ii For what cat ages does the rule of thumb overestimate its human equivalent?

short analysis task 1—a cat’s life

2790_MEA_BK_ch01_2p.fm Page 14 Tuesday, April 12, 2005 11:45 AM

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