ALGAE

ALGAE


PHOTOSYNTHETIC PROTISTS

CHARACTERISTICS

• Eukaryotic cell

• group of photosynthetic organisms

• Recognized by their larger members, such as seaweeds and kelps.

• play an essential role in the aquatic food web and produce most of the earth's oxygen

• Beautifully colored and diverse in appearance

• Often described by their common names such as green algae, brown algae, golden brown algae, and red algae in reference to their predominant colour.



SIZE

• Vary in length from a few micrometers to 100 meters.



FORM

• occur in unicellular, colonial, and filamentous forms

• Larger forms can possess tissues and simple organs.

• as a group contain all of the eukaryotic organelles

• The most noticeable of these are the chloroplast, which contain, in addition to the green pigments chlorophyll a number of other pigments that create the yellow, red, and brown coloration of some group.

• The chloroplast can be of such unique character that they are used in identification.

• Most algal cells are enclosed by a complex cell wall, which accounts for the distinctive appearance of unicellular members such as diatoms, and dinoflagellates.

• The outermost structure in a group called the euglenids

is a thick, flexible membrane called a Pellicle.
pronunciation

 Algae (al'-jee) sing. Alga;L seaweeds

Alga \ˈal-gə\

LOCOMOTION
• Motility by flagella or gliding is common among the algae

• Many members contain tiny light-sensitive areas (eye spots) that coordinate with the flagella to guide the cell toward the light it requires for photosynthesis.
HABITAT RANGE

• Widespread inhabitants of fresh and marine waters.

• One of the main components of the large floating community of microscopic organisms called plankton.

DIVISIONS

A more technical system divides the microscopic algae into divisions or kingdoms based on the types of chlorophyll and other pigments, the type of cell covering, the nature of their stored foods, and genetic factors.
1. Euglenophyta or euglenids

2. Pyrrophyta or dinoflagellates

3. Chrysophyta or diatoms

4. Phaeophyta or brown algae

5. Rhodophyta or reed seaweeds

6. Chlorophyta or green algae
REPRODUCTION

• Reproduce through fragmentation. Binary fission, and mitosis

• Some produce motile spores.

Their sexual reproductive cycles can be highly complex, with stages similar to those of fungi.

IMPORTANCE:
• The primary medical threat from algae is due to a type of food poisoning caused by toxins of certain marine dinoflagellates.
• The capacity of algae to photosynthesis is extremely important to the earth. They form the basis of aquatic food webs and play an essential role in the earth's oxygen and carbon dioxide balance.
• Fossilized marine diatoms yield an abrasive powder called diatomaceous earth that is used in polishes, bricks, and filters, and certain seaweeds are a source of agar and algin used in microbiology, dentistry, food, and cosmetics industries.
• Algae come in mostly red and green. Most freshwater algae are green. This is the stuff that makes water turn green when it is becoming stagnant.
• Green algae are aquatic producers. They catch the sunlight that penetrates the water while they absorb nutrients from the water and produce sugar and oxygen

• Most fish eat algae as at least part of their diet. Other single cell and simple organisms depend on algae for protection and food.
Significance to humans


Beneficial algae

1. Base of the aquatic food chain- especially the diatoms and dinoflagellates

2. Seaweeds are not only food, but shelter for aquatic organisms- especially important are the kelps, which form underwater forests; Sargasso Sea community

3. Some red algae are reef builders in tropical seas; as important or more important than coral animals

Harmful algae- excess growth causes:

4. Clogging of waterways, streams, and filters- when water is polluted with nutrients such as fertilizer or sewage

a. A bad taste to water when present in large numbers

b. Toxicity to animals (paralytic shellfish poisoning, red tides- both caused by dinoflagellates)

c.

Commercial uses of algae

5. Algin- thickening agent in ice cream, marshmallows- from brown algae; carrageenan- in foods, puddings, laxatives, toothpaste- from red algae

6. Iodine- from brown algae

7. Agar- from red algae

8. Food- especially reds and browns-

9. Diatomaceous earth- used for filtering, insulating, and soundproofing