PROTISTS
Protozoans and
algae
By: Rodrigo Menéndez Laita
I. INDEX
- MAIN
CHARACTERISTICS
- CLASSIFICATION
- PROTOZOANS
- ALGAE
- FUN FACTS
- RECOMMENDED
VIDEOS
- GLOSSARY
II. MAIN CHARACTERISTICS
Protista is one of the five kingdoms in which living organisms are
classified.
 |
| The five kingdoms of living things |
- Protists are a
very diverse group of organisms.
- Most of
them are microscopic unicellular eukaryotic organisms.
- A few are
large multicellular eukaryotic organisms, like brown algae, kelps and
slime molds, but they never form specialized tissues.
- Most of them
live in wet places such as oceans, lakes, ponds or moist soils.
III. CLASSIFICATION
There are different classifications for this kingdom. One of them
differenciates three groups:
- Animal-like
protists: the protozoans.
- Plant-like
protists: the algae.
- Fungus-like
protists: the slime molds.
IV. PROTOZOANS
 |
| Protozoan types |
- Protozoan are
animal-like protists.
- They are unicellular organisms that can move independently and feed by heterotrophy.
- Nutrition:
they are heterothropic. They swallow-up and digest their food.
- Motion: they move
around in search of food, using:
- Flagella,
which look like Indiana Jones´ whip. Ie: Trypanosoma.
- Cillia, which
are like tiny hairs. Ie: Paramaecium.
- Pseudopodia,
which look like little false feet. Ie: Amoeba.
- Reproduction:
some reproduce sexually using gametes, while others reproduce asexually by
division.
V. ALGAE
 |
| Unicellular microscopic algae |
 |
| Multicellular algae: Kelps |
- They are
plant-like protists. But they are not plants because they do not have
stems or leaves, their roots are different from plant roots and they do
not produce flowers or seeds.
- Most of them
are microscopic unicellular organisms, like phytoplankton. But some are
larger multicellular organisms, like kelp, which can reach 60 meters
in length.
- Nutrition:
algae are autotrophic organisms because they can produce their own
nutrients. Like plants, they have clorophyll and they perform the
photosyntesis.
- Motion:
unicellular algae move using flagella or pseudopodia; multicellular
don´t usually move.
- Reproduction: some reproduce sexually (combining male and female gametes), asexually (forming spores) or through fragmentation or simple division.
 |
| Photosynthesis process |
VI. FUN FACTS
- Some
protozoans can be pathogenic parasites for humans and other animals,
causing severe diseases like malaria, sleeping sickness or amoebiasis.
- Algae are the most important photosynthesizing organisms of Earth. They produce more oxygen than all plants combined (around 87% of all the oxygen on Earth).
- Algae are important to humans in the form of food and medicine.
- Algae are also used for the production of biofuel, fertilizers and livestock feed.
- The phytoplankton is composed of microscopic algae and is key part of oceans and seas, as it is the basis of the feeding of a great variety of marine animals.
- In some areas of the Indian ocean the sea surface lights up at night. It is so bright that one can read a newspaper. This light is caused by tiny sea algae, the Dino-flagellata (a phenomenon called bioluminiscence).
 |
| Dinoflagellate algae bioluminescence in Jervis Bay (Australia) |
VII. RECOMMENDED VIDEOS
I recommend you to watch these interesting videos about protista kingdom and algae.
VIII. GLOSSARY
- Eukaryotes: single-celled
or multi-celled organisms that do contain a nucleus and
membrane-bound organelles.
- Protists: the group of eukaryotic organisms that can not be classified as animal, plants, fungi or bacteria.
- Heterotrophs: organisms that cannot produce their own food, relying on the intake of nutrition from other sources of organic carbon, mainly plants and animal matter.
- Autotrophs: organisms that can produce their own food using energy derived from the sun (photosynthesis) or from chemical reactions (chemosynthesis).
- Photosyntesis: is the
process used by plants and algae in which energy is taken from sunlight
and then is used to convert carbon dioxide and water into food (sugar).
