Biology as a Science Chapter 2

Characteristics of Living Things Generally accepted characteristics of life – All living things: Are made up of one or more cells Reproduce Grow and develop Obtain and use energy Respond to their environment

Characteristics: Cells Unicellular – organisms consisting of only a single cell. Multicellular – organisms which contain more than one cell (hundreds, millions, trillions, etc.)

Characteristics: Reproduction Two basic kinds of reproduction: Sexual – requires two cells from different individuals to unite to produce the first cell of a new organism. Asexual – single organism is able to reproduce without the aid of another organism.

Characteristics: Growth and Development Growth – to increase in size by natural means. Development – cycle of changes that brings an organism into maturity.

Characteristics: Obtain and Use Energy Anabolism – any process in a living thing that involves putting together (synthesizing) complex substances from simpler substances. Catabolism – the final breakdown of a complex substance into a simpler substance. Metabolism – total sum of all chem. Rxns in the body.

Characteristics: Respond to Their Environment Homeostasis – the process by which an organism responds to stimuli in ways that keep conditions in their internal environment suitable for life.