This document outlines the key characteristics of living things. It discusses how organisms are organized from cells to tissues to organs to systems. The human body contains 10 main systems like the respiratory, skeletal, and circulatory systems. Living things respond to stimuli, adapt to their environments, grow and develop over their lifespan, reproduce offspring, and need resources like space, water, oxygen, and food to survive. Homeostasis and energy usage are also described as essential characteristics of living things.

1. Chapter 1: Nature of Science
Section 2: Living Things

2. Chapter 1 Section 2: Living Things
A. Organism: Any living thing
1. Organisms vary in size. (microscopic to very
large)
2. Behaviors vary from one organism to the next.
3. Needs differ from one organism to the next.

3. B. Living Things Are Organized
1. Organisms must show some level of organization;
here are the levels.
a. Cell: Basic unit of life working together to do a certain
job.
b. Tissue: Cells working together to do a certain job.
i. Example: heart tissue, brain tissue
c. Organs: A group of tissues working together.
i. Example: Heart, Kidney, Brain, Skin
d. System: Group of organs working together.
i. Example: 10 human body systems
e. Organism: Group or organ systems working together.

4. C. Human Body Systems:
1. Respiratory: Helps breathing; Lungs, nose, etc
2. Skeletal: Support; femur, skull, ribs, etc.
3. Integumentary: Protection; Skin, fingernails, hair.
4. Digestive: break down food and get rid of solid
waste; Stomach, Large intestine, mouth
5. Muscular: Controls movement; biceps, triceps, etc.
6. Excretory: Get rid of liquid waste; kidney, bladder.
7. Reproductive: Reproduce; testes, ovaries.
8. Nervous: controls feeling; brain, spinal chord,
nerves.

5. 9. Endocrine: Controls hormones and chemicals;
thyroid, pituitary, ovaries.
10. Cardiovascular (Circulatory): moves blood;
heart, capillaries, arteries.

6. D. Living Things Respond
1. Living things respond to a stimulus.
a. Stimulus: anything that causes some change in the
organism.
b. Response: the reaction to the stimulus
2. Internal and External Stimulus
a. External: Dog running to kitchen when hearing food
bag being opened.
b. Internal: Cells regulate amount of water, temperature,
and energy being used.
3. Homeostasis is the regulation of an organism’s
INSIDE despite outside changes.
a. Example: sweating when you have a fever even if the
room you are in is cold.

7. E. Living Things Adapt
1. Adaptation is a characteristic an organism has
which makes it better able to survive in its
surroundings.
F. Living Things Must Use Energy
1. Energy gives the organism the ability to do work.
a. Most energy comes from the sun; directly or indirectly.
b. Do we get our energy from the Sun?

8. G. Living Things Grow and
Develop
1. Growth: Increase in size and
mass
2. Development: change from an
infant to an adult; changing
into a more complex organism.
3. All living things have a Life Span.
a. The length of time an organism is
expected to live.
b. Life span is made up of: Birth,
Development, and Death.

9. H. Living Things Reproduce
1. Reproduction: The ability to make similar
offspring to the parents.
2. Without reproduction, living things would not
exist to replace those that die.
a. Without reproductions species would become extinct.

10. I. What do living things Need?
1. Living Things need a place to live.
a. Living things are limited in where they live by the
environment.
b. When the environment they live in becomes too
crowded the competition for space costs lives;
organisms then relocate.
c. Example: Desert, Bottom of the ocean, hot/cold.
2. Living Things Need Raw Materials
a. Every organism needs water, oxygen, and food.
b. Most organisms are 50% water.
c. Humans are 70 % water.