1. Chapter 1: Single-celled Organisms and Viruses
Characteristics of Living Things

2. Microorganisms Most living things are too small to be seen.
Even the tiniest organisms are made of cells.
Very small organisms are called microorganisms. These are mostly unicellular (made of one cell).

3. Kingdoms Remember that all living organisms are divided into kingdoms.
Most microscopic kingdoms: archaea, bacteria, and protists.

4. Characteristics of Microorganisms
Review: all living organisms have four characteristics in common.
Organization  all single celled organisms contain everything they need to function in their one cell
Growth  unicellular organisms do not grow as large as multicellular organisms.
Reproduction  binary fission.
Response to Stimuli (Environment)  light, temperature, and touch.

5. Needs of Microorganisms
Review: all living organisms need three things.
Energy  some transform sunlight, others depend on other organisms for energy.
Materials  water, carbon dioxide, oxygen.
Living space

6. Viruses A virus has genetic material in a protein shell.
They share many of their characteristics with living organisms, but they are not living.
They are not as complex as cells.
Once viruses form they do not grow, and they only “reproduce” by taking over a cell.

7. Chapter 1: Single-celled Organisms and Viruses
Bacteria and Archaea

8. What are bacteria?
Bacteria are the simplest kind of life known on Earth.
they are composes of just one cell without a nucleus (what do we call cells without a nucleus?)
Genetic material is contained in loops within the cell.
Reproduce by binary fission.

9. Bacterial Cells
Bacterial cells are about 1/10 to 1/20 the size of a normal cell.
Most have a covering called a cell wall – surrounds and protects the cell membrane.
Contain many large molecules and structures not found in viruses.

10. Classifying Bacterial Cells
Classified by their external shapes.
Spiral bacteria: occurs in single strands.
Rod bacteria: occurs singly or in chains.
Round bacteria: occurs singly, in pairs, in chains, or in clusters.

11. Archaea
Similar to bacteria but share more in common with more complex organisms.
Archaea: single-celled organisms that can survive in a range of environments.
They are grouped based upon where they live.

12. Methanogens Named for methane, the gas they produce.
die if exposed to oxygen.
Live in dense mud, swamps, marshes.
Guts of animals (cows and termites).

13. Halophiles Live in very salty lakes and ponds.
Some die if water is not salty enough.
They can survive drying, and will begin dividing if water returns to the pond.
Halophiles – halite (salt)

14. Thermophiles Thrive in extreme heat or cold.
Hot springs, hot vents in the sea, or meters deep in ice.

15. Chapter 1: Single-celled Organisms and Viruses
Bacteria and Archaea

16. Bacteria Some contain chlorophyll – what does this allow them to do?
They produce their own food, so they are an important food source for ocean animals and release oxygen gas.
They are called producers.
Example: Cyanobacteria

17. Bacteria
Other bacteria break down dead plants and animals to help recycle matter.
They are called decomposers.

18. Bacteria
Some bacteria live either inside or on the surface of other organisms.
Sometimes, this relationship causes no effect. Other times, there is a benefit to both organisms.
When there is a negative relationship between the two, the bacteria is called a parasite to the host.
Example: Staphylococcus infects humans.

19. Helpful Bacteria Bacteria that breaks down organic matter are helpful.
Cities use these bacteria in sewage treatment plants. They help purify the water before it is released to bodies of water.
Some bacteria changes nitrogen gas to nitrogen compounds (fixation), which allows plants to use nitrogen to make proteins.

20. Helpful Archaea Animals that eat plants depend on archaea.
Methanogens help break down cellulose in cell walls which makes it easier for animals to digest.

21. Harmful Bacteria
Many types of bacteria can harm humans: tuberculosis, cholera, and infant diarrhea.
They can invade parts of the body and multiply in cells/tissues.
They can poison the body with chemicals they release.
They can poison the body with chemicals that are in the bacteria itself.
We try to prevent these infections by getting vaccinations.

22. Chapter 1: Single-celled Organisms and Viruses

23. Characteristics of Viruses
When scientists first discovered bacteria, they were able to filter it out of liquids by using a sieve.
When this process did not always work, they came to the conclusion that there was something smaller than bacteria.
These are now called viruses.

24. Characteristics of Viruses
Contain genetic material contained inside a protein coat called a capsid.
The capsid can be a simple tube or have several layers.
They use living cells to get their DNA copied, so they are able to reproduce.
They do not grow or respond to their environment.

25. Harmful Viruses
A virus uses a cell’s material, energy, and processes to thrive.
Can cause serious diseases such as polio, smallpox, diphtheria, or AIDS.
Influenza (the flu) is a more common virus.

26. Harmful Viruses Viruses can also affect plants.
They can have stunted growth or die because of viruses.
If they infect crops, it can destroy farmland, which impacts the farmers, community, and economy.

27. Chapter 1: Single-celled Organisms and Viruses
Reproduction of Viruses

28. How do viruses multiply?
Viruses must use materials from living cells to make copies of their DNA.
The cells that become infected by viruses are called host cells.
One every common virus is called a bacteriophage because it infects bacteria.

29. Bacteriophage Multiplication
Step 1: attachment.
The virus attaches to the surface of the host cell.

30. Bacteriophage Multiplication
Step 2: Injection.
The virus injects its DNA into the host cell.

31. Bacteriophage Multiplication
Step 3: Production.
The host cell goes through its normal functions to produce copies of the viral DNA.

32. Bacteriophage Multiplication
Step 4: Assembly.
New viruses assemble from the copied DNA.

33. Bacteriophage Multiplication
Step 5: Release.
The host cell bursts, and hundreds of new viruses can be released.

34. Chapter 1: Single-celled Organisms and Viruses
Protists