Referencing is giving credit where credit is due. When you reference, you are recognising the work of others and their contribution to the development of your ideas.
Referencing is required in all university study.
Any time you fail to reference, you are claiming your content is all original work and ideas. This is unethical, and contravenes both university and professional standards.
Referencing is very important in the scientific community. According the Code of Ethics of the Astronomical Society or Australia (ASA), scientists 'have an obligation to their colleagues and the scientific community to include a set of references that communicates the precedents, sources, and context of the reported work.' (2015, para. 8). This code also states 'Plagiarism is the presentation of others' words, ideas or scientific results as if they were one's own. It is unethical behaviour and is never acceptable.' (2018, para. 9).
Most of the science courses will require you to use the USQ Harvard AGPS referencing style. This is not the same as other Harvard styles, though it is very similar.