LIFE

SO….What does it mean to be living? Biology…What is it? Biology is the study of life. SO….What does it mean to be living?

Characteristics of Life To be considered living, an organism must….. Be based on a universal genetic code. DNA 2. Grow and develop

Characteristics of Life 3. Be able to Reproduce -Asexually -Sexually 4. Use materials and energy -Metabolism

Characteristics of Life 5. Be able to respond to their environment -stimulus response Humans: Plants:

Characteristics of Life 6. Maintain stable internal environment -Homeostasis

Characteristics of Life 7. Change over time, as a group. -Evolution Made of units called Cells -Unicellular -Multicellular

Cell Theory Cell Theory all living things are made up of cells Matthias Schleiden concluded that all plants are made of cells (1838) Theodore Schwann concluded that all animals are made of cells (1839) Rudolf Virchow concluded that all cells came from pre-existing cells (1855) Cell Theory all living things are made up of cells cells are the basic units of structure and function in an organism new cells are produced from existing cells

Levels of Organization Function Example Organism Single living thing Organ System Different organs function together Organ Different tissues function together Tissues Similar cells function together Cells Smallest unit of life Molecules Smallest unit of a substance with the same properties Atom Smallest unit of matter Human Nervous System Brain Nervous Tissue Nerve Cell Protein Carbon

Viruses…Living or not? Viruses come in many different shapes and they cause many different diseases but, they all have something in common…. Now that we know what makes something living, let’s look at a virus.

Viruses and Living Cells Characteristic Virus Cell Structure Genetic material surrounded by a protein capsid Cell membrane, cytoplasm; genetic material, ribosomes Reproduction Only within a host cell Yes, sexually and asexually Genetic Code DNA or RNA DNA Growth and Development No Yes Obtain and Use Energy Response to Environment Evolve Homeostasis

Verdict? No, Viruses are not considered a living thing because they do not meet all of the living characteristics.