Characteristics of Life

Biology Biology is the study of life.

A biologist seeks to understand the living world.

“Bio” = life “ology” = study of

Living things…

1) are made up of one or more cells

unicellular = one cell multicellular = many cellsamoeba

2) reproduce (sexual or asexual)

sexual – two different cells from two different parents unite to produce a new individual

asexual – new organism has a single parent

paramecium dividing amoeba

dividing

3) are based on a universal genetic code (DNA)

4) grow (through an increase in the # of cells) and develop (through repeated cell division and differentiation

5) obtain and use materials and energy (exchange chemicals with the environment)

metabolism – the combination of chemical reactions through which an organism builds-up or breaks down materials, as it carries out life processes

6) respond to their environment (..often a complex set of behaviors)

examples:

A plant roots grow down due to gravity---- leaves and stem grow upward in response to light

Example 2: Reflex response

patellar

foot arch

Example 3: Paramecium moves away from chemicals

Example 4: Pupil changes in response to light & blinking response to dryness or irritants.

7) maintain a stable internal environment

(homeostasis – stable internal environment of a living organism)

Examples 1 & 2: respiratory & pulse rate increases and decreases with activity

Example #3 : Perspiration helps cool the body when heated (blood vessels dilate and heat is transferred to the sweat, then to the air.

Example 4: Shivering to keep warm – muscles to give off heat during activity.

8) taken as a group, change over time

(process of evolution —changes may not be significant for many generations)

• Living things adapt to their environment

• Living things need water.

• Living things are highly-organized at a molecular and a cellular level

Describing what makes something alive is

not always easy. Some nonliving thingsshare one or more traits with living

things.

For example, a car uses fuel for energy and is highly organized. A car, however, does not share all of life’s characteristics.

Scientists studyingother worlds for the presence of life, look for things related to these characteristics, such as the presence of water.

All living things on planet earth,

from simple bacteria to humans,

share the characteristics of life.