1. Bellwork: What is a protist
Bellwork: What is a protist? What problems have they caused with classification?

2. Protist classification: The saga continues
Section 21.1

3. When did the first Eukaryotes appear on Earth? What were they like?
More than a billion years ago
Still exist today
Group together by name protists – meaning first
Classified as members of the kingdom protista
Protists are Eukaryotes that are not part of the plant, animal or fungi kingdoms
There are a wide variety of characteristics
Most are unicellular, but some aren’t
Kelp for example (Brown algae) is considered a protist as it resembles more unicellular organisms than it does any of the other kingdoms

4. The dilemma
Protists are more diverse than any other Eukaryotic kingdom
Many ‘protists’ are also more closely related to other Eurkaryotic kingdoms than they are to other protists
So Protists should not form their own kingdom……
BUT, no one can agree on a solution
Attempts to classify on the basis of plant like, animal like and fungus like failed…

5. So, what to do….. Protists can be divided into six major clades
You can actually fit plant, animal and fungi kingdoms into these clades
Animals and fungi kingdoms appear to actually have a shared common protist ancestor
Is this surprising?

6. So, how should you use the term protist?
Although biologists generally prefer the classification cladogram with six major groups of protists, the term protists is still widely used
Just remember – technically it’s not a kingdom!

7. How are protists related to other Eukaryotes?
Modern day protists will have evolved greatly since the evolution of the first protists
To understand the connection between protists and other Eukaryotes you must look at the fossil record
Microscopic eukaryotic cells have been found in rocks up to 1.5 billion years old!
Evidence that Eukaryotes evolved from prokaryotes, and are more closely related to Archaea than Bacteria
Actual split between Archaea and Eukarya may be 2.5 billion years ago
Protists have diversified, most have remained unicellular, but two groups produced plants, animals and fungi.

8. Key questions What is a protist?
What is the dilemma associated with protists?
How is a protist related to other Eukaryotes?

9. Protist structure and function
Section 21.2

10. How do Protists move?
Early protists evolved virtually every possible form of cellular movement before they gave rise to multicellular Eukaryotes
They can move by:
Changing cell shape
Through specialized organelles
Others are moved by the wind, water or other organisms

11. Ameoboid movement
Many unicellular protists move by changing their shapes – using cytoplasmic projections known as pseudopods
Common in amoebas
Powered by cytoskeletal protein called actin (which is also found in a animal muscle cells)

12. Cilia and Flagella Both structures supported by microtubules
Cilia are numerous and move like oars on a boat
Flagella are relatively long and short, some have propellor like motion, but most produce a wavelike motion from base to tip

13. Passive movement Many protists are non motile
Rely on air or water currents or other organisms to transport them
Protists form reproductive cells called spores
Can enter cells of other organisms and live as parasites
Plasmodium – protist carried by mosquitoes and can cause malaria
Cryptosporidium – carried by water and can cause sever intestinal diseases

14. How do protists reproduce?
There are many different ways!
Not surprising considering how diverse protists are
Asexual and sexual reproduction is common..

15. Cell division Ameobas reproduce by mitosis
Most protists have phases in their life cycle during which they produce new cells by mitosis
Allows rapid expansion under ideal conditions

16. Conjugation
Paramecia and most ciliates reproduce asexually using mitosis
When under stress, paramecia can remake themselves via conjugation
Paramecia have two nuclei
Macro nucleus (lending library)
Micro nucleus (back up reserve library)
Not reproduction ( No new individuals formed), but is a sexual process

17. Sexual reproduction
Many protists have complex life cycles during which they alternate between a diploid and haploid phase
Known as alternation of generations
Example - water mold
Reproduce asexually by producing spores in a sporangium
Also reproduce sexually by producing male and female structures
Haploid and fuse during fertilization
Zygote begins new life

18. Key points How do protists move in their environments?
How do protists reproduce?