9 Biology, Ms. Mayfield
1.4 Evolutionary development of the nervous system
As animals became more complex and
sophisticated over the process of evolution, so did their nervous systems. This is due to several factors, among them the development of sensory organs such as eyes and ears.
Task:
Read through the information on the three organisms displayed and look at the pictures.
Discuss with your neighbours:
a) What are the most important differences in the nervous system between these three animals?
b) Explain why these changes occurred
1) Jellyfish:
- No front or back side, only top and bottom - No sight, hearing, smell or taste
- Touch-sensitive tentacles
3) Insect:
- Front and back as well as top and bottom - Fully fledged senses
Complex eyes, antennae and taste receptors in “head” region Sensory bristles in each segment as
important touch receptors
Taste, touch and light/dark receptors situated in “head”-region
2) Earthworm:
- Front and back as well as top and bottom - No sight or hearing
- Touch, taste, gravitation and rudimentary light/dark recognition