Biology-Mr.Willets
Lab-Algae/Mold
Algae are members of Kingdom Protista. They are all autotrophic and are unicellular or colonial.
There are 6 phyla of algae based on their color. You will examine two kinds of algae.
Mold is a type of fungus. Fungi have thread like bodies and reproduce using spores.
I. Spirogyra
This is a colonial green algae (Phylum Chlorophyta) that grows as filaments with many cells attached end to end. Make a slide with a filament of Spirogyra and examine under low power. You may switch to high power to examine individual cells.
Each cell has a green ribbon-like chloroplast. On the chloroplasts are dots called pyrenoids. These are made of protein and starch and are used to store food. The nucleus is suspended in the center of the cell by strands of cytoplasm. Most of the cytoplasm is located near the edges of the cell. The middle of the cell is mostly vacuole. Examine individual cells to find one where the nucleus is visible.
The entire filament is covered with a jelly like material (gelatinous sheath). This can protect against being eaten and drying out.
Diagram a filament. Include several cells. In one of the cells, label the following: chloroplast, pyrenoids, nucleus, central vacuole, cytoplasmic strands, cell wall. Use the book to help.
II. Spirogyra in Conjugation
Spirogyra, like many algae have a form of sexual reproduction called conjugation. During this process, two filaments line up. Cells opposite each other grow tubes to connect and the material from one cell (called the male) moves through the tube and joins with the material from the other (called the female). This forms a zygote (also called a zygospore) which usually can survive the winter or drying out. When conditions become favorable, the zygote will divide to form a new filament of cells. Conjugation, besides being a method of reproduction, is also a method of survival during harsh conditions.
Get a prepared slide of Spirogyra in conjugation. Examine under low power to find cells that are in the process. Look for two cells that are connected. Look for cells that are empty. Look for cells that appear to contain zygospores. Look for filaments where the tubes started to grow but did not connect or were separated when the slide was made. (This may be shown on the TV scope)
Make several diagrams showing what happens during the process of conjugation. Use the book.
III. Diatoms
Diatoms are members of Phylum Chrysophyta. They are unicellular algae that have a two part shell. These shells come in a wide variety of shapes, some of which are quite pretty. There is a picture on the front desk showing several dozen different diatom shells. The entire display is about the size of a postage stamp. When the diatoms die, their shells can form a powder we call diatomaceous earth. This is used in swimming pool filters (DE) and some car polishes.
Make a slide from the diatom culture jar. Search around to find a diatom. It should have a geometric shape. Make a diagram of any diatoms you find.
IV. Bread Mold- Rhizopus
Look at a prepared slide of Rhizopus. Note the mass of fibers that make up the main part of the organism. Individual fibers are called hypae. The whole mass of interconnected fibers is called the mycelium. Scattered throughout the mycelium are large round structures. These are where the spores are made. They are called sporangia. Make a diagram of Rhizopus. Label- hypha, mycelium, sporangium
Questions- Name__________________________
1) What kingdom are algae in? ___________________________
2) Spirogyra is in what phylum? _______________________ What are members of this phylum commonly called? _____________________
3) Sexual reproduction in Spirogyra is called ___________________ Besides reproduction, this is also a method of ___________________
4) What is the function of pyrenoids? ______________________________
5) What is different about diatoms compared to most algae? _________________________
6) What phylum are diatoms in? ______________________________
7) What part of a fungus is usually exposed to the open air? __________________ Why?___________
_____________________________________________________
DIAGRAMS
I. Spirogyra
II. Spirogyra in Conjugation (make several diagrams to show the entire process)
III. Diatoms
IV. Rhizopus