Lateness will make it difficult to effectively work together - and lead to a lower grade. An in-class exam will be given on the first half of the course material. You will be asked to reflect in a take-home exam on questions raised during the semester. If you have a valid reason for needing an extension, you need to talk with the professor beforehand. Class discussions will often be based on assignments and research exercises and if you haven't done your part, class discussion as a whole will suffer.
Attendance is required for the same reason.
You can't contribute if you're not there. If you have a valid reason for missing class, let the professor know so that your absence can be excused. You are all expected to collaborate and contribute equally to the final product and everyone will receive a common grade. If it becomes obvious, however, that someone is not pulling their weight, it will have consequences for that individual's grade. Everyone is responsible for understanding and following the guidelines for academic honesty.