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How is heart rate controlled?

The heart muscle is myogenic , meaning that it is able to initiate its own contraction. The wall of the right atria has a region of specialised fibres known as the sinoatrial node (SAN). This node acts as th...
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Answered by Beth M. • Biology tutor
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What is a pathogen and what role do they have in causing disease?

A pathogen is a harmful organism that causes infectious diseases. There are many types of pathogens: bacteria, fungi, viruses, protoctists, worms and insects. They allow diseases to be transmitted from perso...
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Answered by Molly T. • Biology tutor
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What happens when two atoms of potassium react with one atom of sulphur?

Bonding between this compound will be ionic as potassium is a metal and sulphur is a non-metal.Therefore electrons are transferred from potassium to sulphur as metals must lose electrons to gain a full outer...
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Answered by Amrit S. • Chemistry tutor
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Why do many young people leave Spain and come to Germany? (Corresponding text below)

CORRESPONDING TEXT IN PAPER: Jedes Jahr verlassen immer mehr junge Spanier ihre Heimat. Viele von ihnen kommen nach Deutschland, weil mehr als die Hälfte der jungen Spanier zwischen 15 und 24 keine Arbeit in...
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Answered by Katie B. • German tutor
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Describe how the ancestors of modern lemurs may have evolved into the species shown in Figure 14. (June 2018, 5 marks)

The ancestors of modern Lemurs arrived in Madagascar and spread across the island. At some point after this, the once contiguous population became fragmented into three separate populations. Each of these po...
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Answered by Joseph B. • Biology tutor
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