1.) everything that can be observed or explained scientifically. - natural phenomenon
2.) a well-supported explanation of all the evidence related to a natural phenomenon. - Theory
3.) the procedure of scientific inquiry used to investigate natural phenomena. -scientific method
The last one...the species is unable to reproduce in any habitat beyond a population of 300 individuals
Answer:
The correct answer is- Immune system
Explanation:
There are physical, chemical and immunological barriers present in our body which helps us to protect from the foreign antigen. They all assist each other and helps in pathogen removal from our body.
The physical barrier includes skin, gastrointestinal tract, respiratory tract, etc which do not allow the microbe to enter the body. Chemical barriers include tear, saliva, acid in the stomach which kills microbes on the body surface.
Immune cells like macrophages, B cells kills microbes when it gets in the body. Lymphatic system also contain immune cells and helps in microbe removal.
So the immune system is assisted by physical barrier, chemical barrier, and lymphatic system.
Organ is an organism that is a collection of tissues and it perform a specific functions.It is found in the higher biological systems like plants, animals, and human beings. While the organelle is a part of a cell that specialized units and capable of performing a specific function for the cell. It is a very small subunits inside a cell.
