1. Table of Contents What Is Life? Classifying Organisms
Domains and Kingdoms
The Origin of Life

2. What is an Organism?
-An organism is a complete and whole living thing.
*All organisms share six important characteristics.

3. 1. Made of Cells *A cell is the basic unit of structure
and function in a living organism.
*Unicellular organisms are made of
a single cell—like a bacteria cell.
*Multicellular organisms
are made of many cells--
like an elephant.

4. 2. Contain similar chemicals
-Cells of living things are made mostly of five basic chemicals.
*Water—most abundant
*Carbohydrates —for energy
*Proteins and Lipids—building materials
*Nucleic acids—genetic material

5. 3. Use Energy -All organisms use energy to
carry out their daily activities.
*We need energy to move,
think, digest food, repair cell
damage, etc.

6. 4. Respond to Surroundings
-All organisms react to changes in their environment.
*Stimulus—something that
causes an organism to react.
(a sight, sound, smell, touch
or taste).
Here the stimulus is the sight of the fly.
*Response—how an organism
reacts or behaves to the change.
The response is catching the fly.

7. 5. Grow and Develop -All living things grow and develop.
*Growth—living things increase in size.
*Development—the process of change that
occurs as an organism grows, producing a
more complex organism.

8. 6. Reproduce
-All living things produce offspring similar to themselves.

9. Where does Life Come From
-Four hundred years ago, people believed that living things could come from nonliving material.
This idea was called Spontaneous Generation.
-Two scientists, Francesco Redi and Louis Pasteur worked to prove that this theory was incorrect.

10. Redi’s and Pasteur’s Experiments
- What Is Life?
Redi’s and Pasteur’s Experiments
Click the Active Art button to open a browser window and access Active Art about Redi’s and Pasteur’s experiments.

11. Life Comes From Life - What Is Life?
In 1668, Francesco Redi designed one of the first controlled experiments. In his experiment, Redi showed that flies do not spontaneously arise from decaying meat.

12. Life Comes From Life - What Is Life?
Nearly 200 years later, in 1864, Louis Pasteur’s carefully controlled experiment demonstrated that bacteria arise only from existing bacteria.

13. Biogenesis replaces Spontaneous Generation
-In 1870, Thomas Huxley developed the theory of Biogenesis to replace Spontaneous Generation.
*It states: living things arise from living things through
reproduction.
Bio = life
Genesis = beginning

14. The Needs of Living Things
-All living things have the same basic needs:
Water
Food
Living Space
Makes-up 70% of most living things
Autotrophs—make their own food
Organisms need a place to live
Stable Internal Conditions
(homeostasis)
Organisms must
be able to keep
conditions inside
their bodies constant
Heterotrophs—can not make food

15. The Characteristics of Living Things
- What Is Life?
The Characteristics of Living Things
Click the Video button to watch a movie about the characteristics of living things.

16. Using Prior Knowledge - What Is Life?
Look at the section headings and visuals to see what this section is about. Then write what you already know about living things in a graphic organizer like the one below. As you read, write what you learn.
What You Know
Living things grow.
Living things are made of cells.
What You Learned
Unicellular organisms are composed of only one cell.
The cells of living things are composed of chemicals.
The cells of organisms use energy to do things they must do.

17. End of Section: What Is Life?

18. Classifying Organisms
-Classification is the process of grouping things based on their similarities.
-Taxonomy is the science of classifying living things.

19. Aristotle and Classification
- Classifying Organisms
Aristotle and Classification
Many hundreds of years before Linnaeus, a Greek scholar named Aristotle developed a classification system for animals. Aristotle first divided animals into those he considered to have blood and those he did not. This graph shows Aristotle’s classification system for “animals with blood.”

20. Aristotle and Classification
- Classifying Organisms
Aristotle and Classification
Reading Graphs:
Into how many groups were these animals classified? 3

21. Aristotle and Classification
- Classifying Organisms
Aristotle and Classification
Interpreting Data:
Which group made up the largest percentage of animals?
Animals that fly

22. Aristotle and Classification
- Classifying Organisms
Aristotle and Classification
Calculating:
What percentage of these animals either fly or swim?
78%

23. Aristotle and Classification
- Classifying Organisms
Aristotle and Classification
Inferring:
In Aristotle’s classification, where would a cow be classified? A whale?
Cow- animals that walk, run, or crawl; whale- animals that swim.

24. Aristotle and Classification
- Classifying Organisms
Aristotle and Classification
Predicting:
Would Aristotle’s classification system be used today? Explain.
Possible answer: This system includes only three categories, so it may not be very useful today. It also does not match that of modern scientists, who use characteristics other than movement to classify animals. For example, frogs
and lions belong to
very different groups.

25. The Naming System of Linnaeus
-In the 1750s Swedish scientist, Carolus Linnaeus developed the system of naming living things called binomial nomenclature.
*Each organism is given a unique, two-part name made up of its genus and its species.
*Example: Felis domesticus
(house cat)

26. Levels of Classification
-Today, organisms are grouped together based on shared characteristics into various levels. The largest level is called the Domain.
-A domain is then divided into: kingdom, phylum, class, order, family, genus and species levels.
*Use this to help you remember the correct order :
“Didn’t King Phill Come Over From Great Spain?”
“Don’t Kids Prefer Candy Over Fresh Green Salad?”

27. Levels of Classification
- Classifying Organisms
Levels of Classification
As you move down the levels of classification, the number of organisms decreases. The organisms at lower levels share more characteristics with each other.

28. Group Name Species Human Chimp Cat Lion Fly Kingdom Phylum Class Order
Animalia
Phylum
Chordata
Arthropoda
Class
Mammalia
Insecta
Order
Primates
Carnivora
Diptera
Family
Hominidae
Pongidae
Felidae
Muscidae
Genus
Homo
Pan
Felis
Panthera
Musca
sapiens
troglodytes
domestica
leo
Scientific name
Homo sapiens

29. - Classifying Organisms
Taxonomic Keys
Taxonomic keys are useful tools for determining the identity of organisms.

30. What is it????

31. Evolution and Classification
- Classifying Organisms
Evolution and Classification
Species with similar evolutionary histories are classified more closely together. These Galapagos finches may have arisen from a single species and changed gradually over time to become three separate species. Notice the differences in their appearance, especially their beaks.
eats
eats
eats

32. Asking Questions - Classifying Organisms
Before you read, preview the red headings. In a graphic organizer like the one below, ask a what, why, or how question for each heading. As you read, write the answers to your questions.
Question
Answer
Why do scientists classify?
Scientists classify because they want to organize living things into groups so they are easier to study.
What system did Linnaeus use to name organisms?
He used a system called binomial nomenclature.
What are the levels of classification?
Domain, kingdom, phylum, class, order, family, genus, species

33. More on Classifying Living Things
- Classifying Organisms
More on Classifying Living Things
Click the PHSchool.com button for an activity about classifying living things.

34. End of Section: Classifying Organisms

35. Three Domains of Life - Domains and Kingdoms
In the three-domain system of classifications, all known organisms belong to one of three domains–Bacteria, Archaea, or Eukarya.

36. Domains and Kingdoms
-Organisms are placed into domains and kingdoms based on their cell type, the number of cells in their bodies, and their ability to make food.
*Note: Cell type is either: eukaryotic—with a nucleus or
prokaryotic—without a nucleus
Bacteria—prokaryotic, single cells. Some can make food and some can not.
Archaea—prokaryotic, single cells. Some can make food and some can not. The difference is they do NOT need oxygen to live.
Eukarya—eukaryotic cells. Divided into four kingdoms: Protists, Fungi, Plants and Animals.

37. Comparing and Contrasting
- Domains and Kingdoms
Comparing and Contrasting
As you read, compare and contrast the characteristics of organisms in domains Bacteria, Archaea, and Eukarya by completing a table like the one below.
Characteristics of Organisms
Domain or Kingdom
Cell Type and Number
Able to Make Food?
Bacteria
Prokaryotes; unicellular
Some are able to make food
Archaea
Prokaryotes; unicellular
Some are able to make food
Eukarya:
Protists
Eukaryotes; unicellular or multicellular
Some are able to make food
Fungi
Eukaryotes; unicellular or multicellular No
Plants
Eukaryotes; multicellular
Yes
Animals
Eukaryotes; multicellular No

38. Click the SciLinks button for links on kingdoms.
- Domains and Kingdoms
Links on Kingdoms
Click the SciLinks button for links on kingdoms.

39. End of Section: Domains and Kingdoms

40. The Origin of Life
-If living things come only from other living things then….
-where did the first living thing come from?
-Scientists have a theory…

41. The Atmosphere of Early Earth
- The Origin of Life
The Atmosphere of Early Earth
On ancient Earth, water vapor, carbon dioxide, and methane were probably the most abundant gases in the atmosphere. There were frequent volcanic eruptions, earthquakes, and violent storms. There was no oxygen in the atmosphere. Most of the living things present today could not have survived these conditions.

42. Life on Early Earth
-A Russian scientist, Alexander Oparin, suggested that over millions of years, chemical elements and compounds joined together under these very different conditions to form proteins—the building blocks of cells.
-Eventually, these could copy themselves and use other chemicals for food.
-They evolved into the first living cells about billiion years ago.

43. Evidence for this Theory
-Fossils resembling today’s archaebacteria have been discovered dating back to 3.5 billion years ago.
-American scientists, Stanley Miller and Harold Urey’s electric spark experiment in 1953, showed that substances present in living things (like proteins) could come from nonliving material.
-This experiment did not PROVE that this happened—only that it is a possibility.

44. Identifying Supporting Evidence
- The Origin of Life
Identifying Supporting Evidence
As you read, identify the evidence that supports scientists’ hypothesis of how life arose on Earth. Write the evidence in a graphic organizer like the one below.
Evidence
Fossil evidence of achaea-like organisms
Hypothesis
Origin of life
Fossils dated to be between 3.4 and 3.5 billion years old.

45. Links on the Origin of Life
Click the SciLinks button for links on the origin of life.

46. Modeling Conditions on Early Earth
- The Origin of Life
Modeling Conditions on Early Earth
Click the Video button to watch a movie about modeling conditions on early Earth.

47. End of Section: The Origin of Life

48. Graphic Organizer Living Things Food Homeostasis Water Living space
need
Food
Homeostasis
Water
Living space
made by
to provide
Autotrophs
Shelter
Food & water
eaten by
Heterotrophs

49. End of Section: Graphic Organizer