Fill in the blank

26. a sense organ is made up of and other cells that gather information.

27. salmon reproduce by fertilization, because a female salmon releases her eggs onto the riverbed before the male covers them with his sperm

receptors, external

Explanation:

1. A sense organ is made up of receptors which are made up of cells or group of cells which can detect external stimuli like touch, light, sound and others.

2. Salmon reproduce by the mode of external fertilization. In this process both eggs and sperms are released in water. It occurs when females and males secreate their gametes in the same area of water. The females secreate eggs before males release sperms. The eggs get covered with sperms. The eggs get fertilized in water.

rain is the best answer

a bird that nests only in a particular tree species.