Review for Cell Test
Characteristics of Organisms
(Life Processes)
1. Movement
.
2. Reproduction
3. Growth
4. Excretion (waste removal)
5. Respiration (exchange of gases)
6. Response to stimuli
7. Adaptation to environment
Living things or organisms must exhibit all of the life processes
Living things in an environment are called biotic factors.
Non-living things in an environment are called abiotic factors.
Levels of Organization
1. cell – Cells that work together to perform a specific function are called tissues.
2. tissue - Tissues that work together perform a specific function are called organs.
3. organ – Organs that work together are called an organ system.
4. organ system – Organ systems that work together compose an organism.
5. organism – a complete living thing that carries out ALL of the life processes.
There are two types of cells:
1. Prokaryotes – Single-cell (unicellular) organisms that do not have a nucleus in their cell. An example of a procarotic organism is
bacterium. Bacteria are very simple organisms.
2. Eukaryotes – Eukaryotic cells have nuclei. They may be either unicellular or multicellular. Examples of unicellular eukaryotic
organisms include euglena, paramecia, and amoeba. Multi-cellular eucaryiotic organisms include fungi, plants, and animals.
The Impact of the Microscope
Robert Hooke first witnessed cork cells in the mid 17 th century. Although what he saw was dead cell walls, h is discovery opened the door
for future discoveries. It wasn’t until 9 years later that he saw a live cell (spirogyra). Because of the movement of the spirogyra, he called
it an “animalcule” or little animal. Later, Schleidan, Schwann, and Virchow purposed the Cell Theory, one of the most important theories
in the history of science.
Cell Theory
1. All living things are composed of cells.
2. The cell is the basic unit of life.
3. All new cells come from pre-existing cells.
Later, after further research and discovery, more was added to the cell theory:
4. Energy flows within a cell.
5. Genetic information (DNA) is passed down to offspring.
6. All cells are composed of the same basic chemical compounds.
The cell is the smallest living unit and carries out all of the life processes or characteristics of organisms.
Within the cell are several organelles.
1. Nucleus – the nucleus is the control center of the cell; it controls all of the cells activities.
2. Cell membrane – The cell membrane is porous and controls what can enter and leave the cell.
3. Cytoplasm – The cytoplasm is a gel-like substance that fills the cell and creates the working area for the organelles.
4. Ribosomes – Ribosomes are scattered throughout the cell and are responsible for making needed proteins.
5. Mitochondria – The mitochondria are the “power plant” of the cell because it produces energy.
6. Endoplasmic reticulum – The ER is a network of pathways extending from the nucleus to the cell membrane transporting what the
nucleus instructs it to.
7. Lysosomes – Lysosomes are the “digestive bodies” that break down wastes and other materials.
8. Vacuoles – Vacuoles are storage areas that store different compounds. The vacuoles in plants are much larger because they need to be
able to store more water to push against the cell walls to give the plant support.
9. Cell Wall – The cell wall is found only in plants and is located just outside the cell membrane. It is composed of rigid cellulose and
gives the plant support and also protects plant cells.