I have to disagree with Joanna. I don’t believe all animals have brains, only those animals with distinct body cavities possess brains. This includes life forms as diverse as earth worms, clams, fish, insects, birds, and of course, human beings. As a general rule, animals with more tissue types have more intricate brains. But for example jelly fish or starrish don’t have brains, instead they have a cluster of nerves that is called ganglia.
I think what Louise meant was that some non vertebrates do not have brains because they do not have an area within their body to hold a brain and they don’t have enough tissues to support a brain.
I was really thinking more about mammals over the other animals so I apologise for forgetting about the invertebrates!
I have had another look online and the link below summaries it quite well and it would seem that not all animals have brains but all vertebrates do (animals with a backbone)
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hannahdixonn commented on :
Thanks for answering, but I’m still a bit confused, some animals have brains and some don’t? x
Jo commented on :
I think what Louise meant was that some non vertebrates do not have brains because they do not have an area within their body to hold a brain and they don’t have enough tissues to support a brain.
I was really thinking more about mammals over the other animals so I apologise for forgetting about the invertebrates!
I have had another look online and the link below summaries it quite well and it would seem that not all animals have brains but all vertebrates do (animals with a backbone)
http://www.pa.msu.edu/sciencet/ask_st/090893.html