An unknown specimen slowly increases in size by incorporating minerals on its structure. when it gets too big, it splits into smaller components, which will follow the same mechanisms of increasing in size. a certain group of these specimen is able consume molluscs (shellfish). in the presence of pressure, the specimen shrinks in size. just like some marine animals, these specimen can detect and respond to the earth’s magnetic field. is this specimen alive?

No.

Explanation:

In order to consider an entity alive, according to biology it needs to meet certain criteria.

Reproduction: "When it gets too big, it splits into smaller components, which will follow the same mechanisms of increasing in size ". This could be considered as reproduction because is creating a copy of the original specimens.

Metabolism:  "A certain group of these specimen is able consume molluscs (shellfish). "Living things undergo chemical and physical processes to obtain energy and keep a internal stable environment.

Adaptation: In the presence of pressure, the specimen shrinks in size. Living things can change according to the environment to increase its survival rate.

Respond to stimuli: specimen can detect and respond to the Earth’s magnetic field. This could be an example of responding to stimuli because the specimen can " feel" the Earth's magnetic field.

The specimen does comply with most of the characteristics of life. The only thing really important thing missing is having cells. All living things have cells. The specimen would need further investigation but it does comply with most of the important characteristics.

the answer is cell division : )