What is Biology? What is Life?

All this creates a Question: What is Life?

Characteristics of Life All life has seven characteristics in common: –Living things are made of cells. –Living things maintain their internal environment. –Living things pass on their traits. –Living things perform chemical activities. This is known as metabolism. –Living things grow and develop. –Living things respond to a stimulus. –Living things reproduce.

Cells –All living things are made of one or more cells. –A cell is the smallest unit capable of all life processes

Homeostasis –All living organisms must maintain a stable internal environment in order to function properly. –The maintenance of a stable internal environment in spite of changes in the external environment is called homeostasis.

Heredity & Evolution –When an organism reproduces, it passes on its own traits to its offspring in a process called heredity. –Inherited characteristics change over generations. This process is called evolution

Metabolism –Living organisms carry out different chemical reactions in order to obtain energy. –The sum of all the chemical reactions carried out in an organism is called metabolism. –Almost all of the energy used by living things originally comes from the sun.

Growth and Development –All living organisms grow. –As organisms grow, many change. This process is called development. –Development differs from evolution because development refers to change in a single individual during that individual’s life.

Response to Stimuli –In addition to maintaining a stable internal environment, living organisms respond to their external environment. –Can you think of a way that you have responded to your environment today?

Reproduction Most living things can reproduce. Reproduction is the process by which organisms make more of their own kind from one generation to the next.

The Cell Theory 1.All living things are composed of cells. 2.Cells are the basic units of structure and function in living things. 3.New cells are produced from existing cells.

Cells Timeline Robert Hooke (1665): studied cork; saw tiny, regular shaped “boxes”; called them cells. Matthais Schleiden (1838) All plants are made of cells Theodor Schwann (1839) All animals are made of cells Rudolf Virchow (1855) Concluded all cells come from other cells Go to Section:

 What is a VIRUS??  Is it ALIVE????

Viruses are 1/1000 to 1/10,000 the size of our cells. Slide # 4

What is a Virus? 1. are not made up of cells 2. Cannot live independently 3. can not reproduce on their own 4. Does not require food/does not grow, develop or move Slide # 5 Classified as non-living:

Viruses are Nonliving  Viruses are parasites of cells. Do not have all eight characteristics of living things so they are classified as nonliving. Do not have all eight characteristics of living things so they are classified as nonliving. Characteristics of Living ThingsCharacteristics of Living Things 1.) Made up of cells 2.) Must reproduce 3.) Must be based on a universal genetic code 4.) Must grow and develop 5.) Must obtain and use materials and energy 6.) Must respond to their environment 7.) Must maintain a stable environment 8.) Must change over time

Bacteriophage virus Tobacco Mosaic Virus Cold virusFlu virus Viruses consist of: 1.Nucleic acid: DNA or RNA (inner core) 2.Protein Coat, called a Capsid Capsid Slide # 7