An ecosystem is a geographic area where plants, animals, and other organisms, as well as weather and landscape, work together to form a bubble of life. Ecosystems contain biotic or living, parts, as well as abiotic factors, or nonliving parts. ... Ecosystems can be very large or very small.

• Reflection is the change in direction of a wavefront at an interface between two different media so that the wavefront returns into the medium from which it originated. Common examples include the reflection of light, sound and water waves. Wikipedia

• A mitochondrion is a double membrane-bound organelle found in most eukaryotic organisms. Mitochondria generate most of the cell's supply of adenosine triphosphate, used as a source of chemical energy. Mitochondria were first discovered by Kolliker in the voluntary muscles of insects.

• Molecule, a group of two or more atoms that form the smallest identifiable unit into which a pure substance can be divided and still retain the composition and chemical properties of that substance.

• A vacuole is a membrane-bound organelle which is present in plant and fungal cells and some protist, animal, and bacterial cells.

Answer:

• An ecosystem is a geographic area where plants, animals, and other organisms, as well as weather and landscape, work together to form a bubble of life.
• Reflection is the change in direction of a wavefront at an interface between two different media so that the wavefront returns into the medium from which it originated. Common examples include the reflection of light, sound and water waves.
• A mitochondrion is a double membrane-bound organelle found in most eukaryotic organisms. Mitochondria generate most of the cell's supply of adenosine triphosphate, used as a source of chemical energy. Mitochondria were first discovered by Kolliker in the voluntary muscles of insects.
• Molecule, a group of two or more atoms that form the smallest identifiable unit into which a pure substance can be divided and still retain the composition and chemical properties of that substance.
• A vacuole is a membrane-bound organelle which is present in plant and fungal cells and some protist, animal, and bacterial cells.