1. Prokaryotes
Section 20.2

2. What is a prokaryote?
Smallest and most abundant microorganism on Earth
Unicellular and lack a nucleus
DNA found in cytoplasm
Until recently were all grouped in the same Kingdom
Nowadays – two distinct domains – Bacteria and Archaea
What is the difference?

3. Typical Prokaryote structure
Does the cell belong to domain Bacteria or Domain Archaea?

4. How do prokaryotes vary in their structure and function?
Size – 1 to 5 micrometers
Shape
Rod shaped called bacilli
Spherical called cocci
Spiral called Spirilla
Movement
Some do not move
Others move using a flagella
Some glide over slime

5. How do prokaryotes get their energy?
Prokaryotes need chemical energy
Stored in fuel molecules such as sugars
Energy released during respiration, fermentation or both
Energy can be captured in different ways as well

6. Prokaryote energy release

7. Prokaryote growth, reproduction and recombination
Binary fission – produces direct copy.
Asexual reproduction
Endospore – occurs when growth conditions become unfavorable
Thick internal wall surrounds DNA and some cytoplasm
Remain dormant for months or years
Allows some prokaryotes to survive harsh conditions
Adaptation comes from Mutation or Conjugation
Mutation – random change
Genetic material transferred between two prokaryotes
Plasmids transfer material across hollow bridge
Increases genetic diversity

8. Why are prokaryotes so important?
Prokaryotes maintain every aspect of ecological balance in the living world
Three key roles in nature
Decomposers – recycle material from dead organisms. Also key in sewage treatment
Producers – Numerous food chains are dependent on bacteria that act as a primary producer, especially in the oceans
Nitrogen Fixers – Very few organisms (only prokaryotes) can utilize N2 gas, turning it into useful forms

9. What do humans use prokaryotes for?
Used to produce food – yoghurt
Digest petroleum
Remove human made waste products and poisons from waters
Uses are still being discovered

10. Key point questions What domains of life contain prokaryotes?
What are the characteristics of prokaryotes of each of these two domains?
How do prokaryotes vary in their structure and function?
What roles do Prokaryotes play in the living world?

11. Key points summary
Prokaryotes fall into either Bacteria domain or Archaea domain
Bacteria – peptidoglycan cell wall
Archaea – can survive harsh environments , DNA sequence similar to Eukaryotes
Size, shape, movement, nutrition, metabolism, growth and reproduction can vary between prokaryotes
Prokaryotes are very useful in the natural worlds
Decomposers
Producers
Nitrogen Fixers
Human uses