Metabolism is
1. a measure of the hydrogen ion concentration in a solution
2. the energy required to start a chemical reaction
3. all of the chemical reactions in an organism required to sustain life
4. a chemical reaction in which the substrates trade constituent parts

3 : All of the chemical reactions in an organism required to sustain life.

Explanation: Metabolism is the process of converting food into energy form ( ATP). Metabolism is set of biochemical reactions which is completed in presence of necessary enzymes and is essential to sustain life.

they each offer a fresh glut of resources to the organisms that can arrive and exploit them. as individuals and new species continue to appear, they actively and passively alter the environment. competition for shared resources increases, local abiotic and biotic conditions shift, and the relative abundances of species change accordingly. the process is called ecological succession, and it is one of the earliest and most well-known concepts in ecology.

the answer is d. chordata