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Describe the main evolutionary trend in digestion across the phyla: Platyhelminthes, Chordata and Annelida

In platyhelminthes digestion is both intracellular and extracellular whereas in annelida and chordata digestion is completely extracellular.
JH
Answered by Jade H. • Biology tutor
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What is the difference between xylem and phloem?

Plants have both xylem and phloem. The xylem is a tube which runs from the very ends of the roots to all other parts of the plant. Xylem transport water and minerals around the plant . Xylem are tough- they ...
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Answered by Britannie E. • Biology tutor
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Describe how a nerve impulse travels from neurone A to neurone B.

As an action potential arrives at A (the presynaptic terminal), pre-formed vesicles containing a chemical neurotransmitter fuse with the presynaptic membrane, releasing the chemical neurotransmitter into the...
ME
Answered by Medani E. • Biology tutor
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Describe the process of glycolysis

Glycolysis is the first of four steps in cellular respiration, and involves the breakdown of one glucose molecule into two molecules of pyruvate. A 6C glucose molecule is first phosphorylated, using the phos...
GC
Answered by Georgia C. • Biology tutor
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Describe 3 adaptations the ileum has that allow it to maximise the absorption of nutrients from its lumen into surrounding blood vessels.

The ileum is lined with simple cuboidal epithelium. This means there is a short diffusion pathway from the lumen of the gut to the surrounding blood vessels. The lining epithelia also has villi and the epith...
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Answered by Aliza K. • Biology tutor
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