A scientist transfers blood plasma from an animal producing hormone X to another animal. A target organ in the second animal responds. No nerve connection exists between the animals.
Which conclusion is supported?
An impulse in plasma can carry the signal.
A shared nerve connection must carry the signal.
A substance in plasma can carry the signal.
A shared endocrine gland must carry the signal.
89 exam-style questions on Edexcel GCSE Biology 7.1 Hormones and coordination, covering 7.1.1 Endocrine glands and hormone transport, 7.1.2 Adrenalin and fight or flight, and 7.1.3 Thyroxine and negative feedback. Each one has a worked solution and a mark scheme showing where the marks go.