Lesson 14: Plant-Like Protists

While the protozoans are some of the most interesting organisms in creation, algae are perhaps the most beautiful.  Algae are protists that produce their own food, usually by photosynthesis.  They live in all natural bodies of water and produce most of the oxygen required for our life on earth.  They also are the most important source of food for many water-dwelling organisms.  People eat algae too, and we also use it to thicken our food and add it to our makeup and medicine.  Check the labels of the food and toiletries in your house.  Do you see carageenan, alginate, or beta carotene listed as one of the ingredients? If so you are eating algae.  Here is a list of foods that might contain algae:

• Brownie mix                                                                       
• Ice cream
•  Toothpaste
• Mayonnaise
• Pet food
• Salad dressing
• Chocolate milk
• Vitamins

…see how many you can find and send me your list!

Algae is very diverse.  Check out these pictures: 

It’s hard to believe that these are all examples of algae.  We could spend months learning about all the different kinds of algae, but lets just concentrate on looking more closely at one particular unicellular variety: Spirogyra, which is in phylum Chlorophyta.

 

Spirogyra gets its name from the long spiral chloroplasts that twist through the cells. Do you remember the function of chloroplasts? They store chlorophyll, which is a green pigment  many autotrophs use in photosynthesis.  They live in colonies of long strings of cells called filaments.  If you look closely you can see the cell wall that separates each individual cell from the next.  Print and color this diagram of a typical Spirogyra:

 

     Color the cell wall pink. 

     Color the long spiral chloroplast green. 

     In the middle you can see the round nucleus.  Color it blue.

If you have a prepared slide of spirogyra, take a look at it now.  Spirogyra is fairly large, so you will need to observe your slide on medium magnification and adjust your fine focus to see all through the organism.  Also check your pond water sample for Spirogrya – it is commonly found in almost all pond water.  Even if you don’t see any Spirogyra, you will likely see other types of algae – look closely at anything green. It’s probably algae!

And now…it’s time for the Protista Pro-TEST-a.