Answer:
Early land animals had both lungs AND gills, and their bodies consisted of few hard parts. Meaning they lacked things like an exoskeleton for instance. Animals today have either lungs OR gills and many have protecting hard parts of their bodies.
Explanation:
The kidneys.
The kidneys keep blood isotonic by removing excess salt and water through urine.
Answer: Negative feedback serves to reduce an excessive response and to keep a variable within the normal range. Negative feedback loops control body temperature and the blood glucose level.
D. Universal Law of Gravitation.