Irritability means that an organism can sense and respond to its environment. For example, most higher animals sense tissue injury as pain and will attempt to withdraw from the source. Some plants show irritability as movement; examples would be the closing of traps on a Venus fly trap or the leaf movements of a sensitive plant.
Metabolism is the occurrence of basic life processes. Examples are respiration, digestion of food, and photosynthesis.
Organization is the way living things are put together. An animal or plant has organ systems; each organ system is made up of organs, the organs are made up of specific tissues, and the tissues are made of cells.
Reproduction is the process of making more of your own species. In plants, reproduction would be the process of forming seeds. In animals it would involve laying eggs, which can be fertilized before they are laid (as in birds) or after they are laid (as in fish and amphibians). In mammals eggs are fertilized internally and then kept in the mother's body until the baby can survive in the outside world.
Evolution is the change of a population due to random mutations in DNA. Individuals do not evolve, but populations do. An example would be how some species of bacteria have become resistant to antibiotics. Originally just one or a few bacteria would have had the resistance, but if the population is exposed to antibiotics, the individuals do are not resistant will die, and the resistant ones will survive and reproduce. Over time the population will be made up entirely of resistant individuals.