1) Ecology is the scientific study of the distribution and abundance of organisms, the interaction among organisms, and the interactions between organisms and their abiotic environment. Ecologists try to understand the inner workings of natural ecosystems and the species they contain.
2) Ecosystems have no particular size. An ecosystem can be as large as a desert or a lake or as small as a tree or a puddle. If you have a terrarium, that is an artificial ecosystem. The water, water temperature, plants, animals, air, light and soil all work together.
3) The biotic factors of an ecosystem include all the populations in a habitat, such as all the species of plants, animals, and fungi, as well as all the micro-organisms. Also recall that the nonliving factors are called abiotic factors. Abiotic factors include temperature, water, soil, and air.
4) For aquatic ecosystems, these factors include light levels, water flow rate, temperature, dissolved oxygen, acidity (pH), salinity and depth.
Compare mitochondria to the digestive system. The cytoskeleton is similar to the skeletal and muscular system. They both provide structure and allows for movement within the cell. The cell membrane is similar to the integumentary system. They both separate and protects the internal structures from the external environment and it regulates water loss.
If DNA is found at a crime scene it can help locate people that were at the crime scene. If the criminal has committed crimes before their DNA will already be in the police system. If not they can take samples from suspects and pinpoint who committed the crime.
