Properties that we share with all other living things… Defining Life Properties that we share with all other living things…

Biology is the scientific study of life Biologists are moving closer to understanding: How a single cell develops into an organism How plants convert sunlight to chemical energy How the human mind works How living things interact in communities How life’s diversity evolved from the first microbes

How would YOU define life? A human definition… Growing Thinking Moving Life is ACTIVE! (well, usually…)

Can you tell what’s living? LIVING = biotic NONLIVING = abiotic

You get the idea… All living things share certain properties… In order to be considered living, ALL FIVE properties must be present. What are they???

Property #1: CELLULAR ORGANIZATION ALL living things are composed of one or more cells (can have 1 to trillions of cells). All cells grow and reproduce

Property #2: METABOLISM Living things need energy! To grow To move To process information Metabolism= sum of chemical reactions carried out by an organism

Property #3: HOMEOSTASIS Living things maintain stable internal conditions. Examples: body temperature and blood sugar. What is the temperature that the human body maintains? A. 95.4 B. 98.6 C. 99.5

Information Normal affects condition disturbed STIMULUS: RECEPTOR Information affects Normal condition disturbed Thermometer STIMULUS: Room temperature rises CONTROL CENTER (Thermostat) HOMEOSTASIS Normal room temperature RESPONSE: Room temperature drops 20o 30o 40o Normal condition restored EFFECTOR Sends commands to Air conditioner turns on Figure 1-3 1 of 6 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Property #4: REPRODUCTION No living thing is immortal (lives forever) so… It must be able to reproduce from one generation to the next – or there would be no life left!

Property #5: HEREDITY DNA is inside cells coding to direct growth and development of all living things Parents pass on characteristics to their offspring through their genes.

Which property of life is most important?? A. cellular organization B. homeostasis C. heredity D. reproduction E. metabolism Be prepared to argue WHY!!!

Why can’t we just choose one characteristic to define life? Do any non-living things possess any of the characteristics of life?

Life’s basic characteristic is a high degree of order Each level of biological organization has emergent properties

Biologists explore life from the microscopic to the global scale The study of life extends from molecules and cells to the entire living planet Biological organization is based on a hierarchy of structural levels

A Hierarchy of Biological Organization Biosphere: all environments on Earth Ecosystem: all living and nonliving things in a particular area Community: all organisms in an ecosystem Population: all individuals of a species in a particular area Organism: an individual living thing

A Hierarchy of Biological Organization (continued) 6. Organ systems: groups of organs functioning together Organs: specialized body parts made up of tissues Tissue: a group of similar cells Cell: life’s fundamental unit of structure and function Organelle: a structural component of a cell Molecule: a chemical structure consisting of atoms

Organs and organ systems Organisms The biosphere Organelles 1 µm Cell Ecosystems Cells Atoms Molecules 10 µm Communities Tissues 50 µm Populations Organs and organ systems Organisms