A hydrometer or areometer is a <span> instrument that always </span><span>measures the specific gravity relative density of liquids and the ratio of density of the liquid to the density of liquid to water.
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Answer:
Reflex action is the sudden uncontrolled reaction towards a certain stimuli eg response to hot iron
Reflex arc is the path taken by reflex action to a certain stimuli
Diagram depends to
Receptor(eg skin), receptor nerve(sensory neurone),centre reflex arc(spinal cord most of reflex action) they met relay neurone, motor neurone and ends at reflexor (eg muscle)
→ Darwin believed that the need to adapt, in similar words, the changes occruing in the environment caused evolution.
The main cause of evolution, according to Darwin, was natural selection. Natural selection is a process in which a group of organisms with certain characteristics survive and thrive, in comparison to other organisms with different characteristics. This idea basically means that having some characteristics makes you suited for an environment.
And how would that ↑ explain Evolution?
Well, evolution is the change in species that occurs during time. But for you to change, there must be a cause for that change, which is none other than the need to survive, reproduce, etc.
→ As mentioned before, not all characteristics are enough to surive, and hopefully the image pasted below will help you.
Hope it helped,
BioTeacher101