1. Traits of Living Things, Levels of Organization, and Cell Theory Chapters 1 & 7

2. Traits of Living Things 1. Living things are made up of units called cells. A cell is a collection of living matter enclosed by a barrier that separates the cell from its surroundings. Unicellular organisms have only one cell and include bacteria as well as some types of fungi and protists. Multicellular organisms have many cells and include plants, animals, and most fungi. 2. Living things reproduce. In sexual reproduction, two cells from different parents unite to produce the first cell of the new organism. In asexual reproduction, the new organism has a single parent. For example, a unicellular organism may simply divide in half.

3. Traits of Living Things 3. Living things are based on a universal genetic code. Living things pass on their genes from one generation to the next through DNA and/or RNA. 4. Living things grow and develop. Some living things increase in size, but others may have a complete change during their lifetime.

4. Traits of Living Things 5. Living things respond to their environments. Living things must adapt to changes in their environments so that they will survive. A stimulus is a signal to which an organism responds. 6. Living things obtain and use materials and energy. Some living things can make their own food, but others cannot. Either way, living things must be able to gather and use energy to stay alive.

5. Traits of Living Things 7. Living things maintain a stable internal environment. Living things must maintain a balanced temperature, amount of water, etc even though their environments change. This stability is called homeostasis. 8. Taken as a group, living things change over time. GROUPS of living things change over time. Individual living things do not change over time. This process is called evolution.

6. Levels of Organization Smallest LARGEST Molecules: nonliving Organelles: “little organs” in certain types of cells Cells: living, microscopic Tissues: living, made up of cells Organs: living, made up of tissues Organ systems: living, several organs working together for a task Organism: an entire living thing, may or may not have tissues, organs, and organ systems; might be a single- celled organism

7. Examples of Levels of Organization Molecules: carbon dioxide, oxygen, DNA, lipid Organelles: nucleus, mitochondria, cell membrane Cells: onion cell, skin cell Tissues: blood, fat, epithelial Organs: heart, kidney, lung Organ systems: digestive system, respiratory system Organism: cow, bacterium, human

8. Cell Theory A cell is the smallest unit of living things. The cell theory states that… – All living things are composed of cells. – Cells are the basic units of structure and function in living things. – New cells are produced from existing cells.