ology – science or the study of a subject BIOLOGY Biology – the study of life bio – life or living organism ology – science or the study of a subject

Characteristics of Living Organisms Also known as Properties of Life: Cellular Organization Growth and Development Reproduction Heredity Metabolism Homeostasis Responsiveness

Cellular Organization Every living organism is composed of one or more cells. A cell is the smallest structure capable of carrying out all life functions.

Organisms consisting of only a single cell are called unicellular Organisms consisting of only a single cell are called unicellular. Ex: bacteria or protists like amoebas and paramecium Most of the organisms you are familiar with, such as dogs and trees, are multicellular. Multicellular organisms contain hundreds, thousands, even trillions of cells. Multicellular organisms have their cells organized into tissues, organs, and systems.

Growth & Development All organisms begin their lives as single cells. Over time, these organisms grow and develop.

Reproduction The process by which organisms make more of their own kind. For life to continue, organisms must replace themselves. Is reproduction essential for the survival of an individual organism? Reproduction is not essential for the survival of an individual organism. However, it is essential for the continuation of an organism’s species.

Heredity The passing of traits from parent to offspring. A gene is the basic unit of heredity. All organisms pass on their genes to their off-spring. Genes which are composed of DNA have all the information that are hereditary in nature.

Metabolism The sum of all of the chemical reactions carried out in an organism in order to obtain and use energy. Some organisms obtain energy from the foods they eat (heterotrophs) or, in the case of plants, the foods that they produce (autotrophs).

Why is energy important? Energy is important because it powers all life processes such as the ability to grow, reproduce, maintain balance and other life functions.

Homeostasis The ability to maintain a stable internal environment, despite changes in the external environment. Internal conditions may include the level of water inside the body, sugar levels, body temperature and hormone levels. Adjustments to internal changes help organisms maintain a constant internal environment. You can just think of it as keeping everything in BALANCE!

For example, you have a “thermostat” in your brain that reacts whenever your body temperature varies slightly from 37°C (about 98.6°F). If this internal thermostat detects a slight rise in your body temperature on a hot day, your brain signals your skin to produce sweat. Sweating helps cool your body. What happens when your body detects it is cold?

Responsiveness To respond and adjust to the environment. External environmental factors can act as stimuli and cause a response from living things. Organisms need to respond to these changes in order to stay alive and healthy.

Examples of responsiveness: If you go outside on a bright summer day, the sun may cause you to squint. A specialized leaf of the Venus flytrap senses the light footsteps (pressure) of a fly. The plant responds to this environmental stimulus by rapidly folding the leaf together. As the seasons change, the Arctic fox changes the color of its coat. In spring it has a dark coat to match the dirt and in the winter it turns white to match the snow.

What does it mean to be alive? *Life is characterized by the presence of ALL of these properties at some stage in an organism’s life.

Which piece of evidence below exhibits all of the properties of life?

Self Check Questions: What distinguishes a living organism from a nonliving organisms? What is homeostasis? Give an example of homeostasis? 4. Is it essential for an individual to reproduce? 5. What would happen if all individuals of a species were sterile? 6. How do organisms obtain energy?

7. Why is energy required by living things? 8. What do we call organisms that can make their own food? Cannot make their own food? 9. What does cellular organization mean? When an organisms moves to or away from a stimulus, which property of life is it exhibiting which? 11. Jane has freckles and so do her two daughters. What characteristic of life does this represent?