1. Characteristics of Living Things
Chapter 1
Characteristics of Living Things
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2. Living things are made up of units called cells.
The cell is the basic unit of life.
a. Unicellular: single celled
b. Multicellular: many cells
Human muscle cells
Stentor: single celled organism
Plant cells

3. Living Things Reproduce
1. Living things produce offspring resemble themselves
a. Dogs have puppies
b. Cats produce kittens
2. Purpose of reproduction: to ensure the species does not die out!
Bacteria reproduce every 20 minutes

4. Living things have a universal genetic code
1. All living things store their genetic material as DNA
2. There are 4 different nucleotides that make up DNA: adenine, guanine, cytosine, and thymine.
3. No matter which organism’s DNA you’re looking at, it’s still made up of the same 4 nucleotides.
50% of our DNA is the same as the DNA in a banana.

5. Living things grow and develop.
Living things are not born as “adults”
Even bacteria go through a period of growth & development
EX: Metamorphosis in flies, butterflies & frogs
Development of grass seedlings
Metamorphosis in butterflies

6. Living things Exchange Energy with Their Environment
1. Plants obtain their energy through photosynthesis
Animals obtain energy from consuming other organisms.
Fungi obtain energy by absorbing nutrients from the environment.

7. Living Things Respond to their Environment
1. Stimulus: anything that causes an organism to react or change its behavior.
2. Response: a change in an organism’s behavior due to a stimulus
Examples:
a. plants grow towards light
b. bears hibernate in winter
b. Pillbugs roll into a ball when touched

8. Living things maintain a stable internal environment
1. Homeostasis: process of maintaining constant internal conditions
a. Maintain a constant water balance, constant body temperature, and constant pH
b. Ectotherms: maintain temp by moving into / out of environment
c. Endotherms: have internal control of body temp
When plants lose too much water they wilt!
(Not a stable internal environment)
Dogs pant to lower their body temperature!

9. Taken as a group, living things change over time
1. Evolution: a change in a species over time
2. Populations evolve, not individuals
3. Adaptation: any structural or physiological thing that helps a species survive in its environment.
a. EX: thorns on a rose; stripes on tiger
Birds are closely related to reptiles as seen in this comparison of early development of turtles and birds.