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LIVING THINGS
Cells
Unit 2, Part 1
H. Carter
Organism
•Any living thing
Characteristics of Life
1. Have cellular organization
▫ All living things are made of cells
 basic unit of structure and function in
an organism
 Unicellular: made of one cell
 Multicellular: made of many cells
2. Contain similar chemicals
▫ Cells are made up of chemicals
 Water: most abundant
 Carbohydrates: energy
 Proteins & Lipids: building materials of
cells
 Nucleic Acids: genetic material
3. Use Energy
▫Cells use energy to do what
they need to do, to work
4. Respond to their surroundings
▫ Stimulus: a change in an organism’s
surroundings that caused the organism
to react (ex. Changes in temperature,
light, sound)
▫ Response: an action or change in
behavior due to a stimulus (ex. Squinting
eyes when light turned on)
5. Grow and Develop
▫ Growth: process of becoming
larger
▫ Development: process of change
that occurs during an organism’s
life to produce a more complex
organism
6. Reproduce
▫ To produce more of one’s kind
Life Comes from Life
• Living things come from other living
things through reproduction
• Spontaneous Generation: idea that
living things can come from nonliving things
• Francesco Redi (1600s)
▫ disproved that flies came from decaying
meat
• Louis Pasteur (1800s)
▫ Showed that bacteria come from
bacteria
Needs of Living Things
• Water- all reactions occur in the presence
of water
**most abundant chemical in cells
• Food- source of energy
▫ Autotrophs- make their own food
▫ Heterotrophs- cannot make their own food;
feed on others
*The sun is the source of energy for all
organisms
•Living Space
•Stable Internal Conditions
▫ Homeostasis- maintenance of stable
internal conditions (ex. Body
temperature, feeling thirsty after
exercise)
Development of the Cell Theory
• Invention of microscope made it possible
for people to discover and learn about cells
• Robert Hooke (1663)
▫ Looked at a piece of cork
▫ Saw empty spaces that looked like rooms
▫ Called them “cells” (small rooms)
• Anton van Leeuwenhoek (1663)
• Matthias Schleiden (1838)
▫ All plants are made of cells
• Theodor Schwann (1839)
▫ All animals are made of cells
▫ All living things are made of cells
• Rudolf Verchow (1855)
▫ New cells are formed only from cells that
already exist
▫ “All cells come from cells”
The Cell Theory
• Widely accepted explanation of the
relationship b/n cells and living
things
▫ All living things are made of cells
▫ Cells are the basic unit of structure and
function in organisms
▫ All cells come from other cells
Cell Structure
• Organelles- tiny structures w/in cells that
perform certain jobs
▫ Cell wall- surrounds cells of plants and other
organisms; protects and supports
▫ Cell membrane- controls what comes into and
leaves the cell
▫ Nucleus- control center, “brain” of cell
 Nuclear envelope- protects the nucleus
 Chromatin- strands in nucleus that contain genetic
material, instructions for the cell
 Nucleolus- structure in nucleus that makes
ribosomes
▫ Mitochondria- powerhouse of cell; converts
energy in food to energy the cell can use
▫ Endoplasmic Reticulum (ER)- passageways that
carry proteins and other materials around the cell
(“highway” of the cell)
 Rough- have ribosomes attached to it
 Smooth- no ribosomes attached
▫ Ribosomes- produce proteins (“factories”)
▫ Golgi Bodies- receive proteins and other materials
from ER, package them, and send out to other
parts of the cell (“mailroom”)
▫ Chloroplasts- contain chlorophyll (green) which
traps energy from the sun and uses it to make
food- autotrophs (ex. plants)
▫ Vacuoles- storage area of the cell (“storage tank”)
 most plants have one large vacuole
 Some animal cells have them; others don’t
▫ Lysosomes- small, round structures containing
chemicals that breakdown certain materials in cell
 Ex. Large food particles into smaller; old cell parts
Specialized Cells
*Multicelled Organisms*
• Tissues- group of similar cells that work
together to perform specific functions
• Organ- group of tissues that work together
• Organ System- group of organs that work
together to perform a major function
Cells
Tissues
Organs
Systems
Organism