Science Class 5EP: PROTISTS AND ALGAE

PROTISTS

Protozoans and algae

By: Rodrigo Menéndez Laita

I. INDEX

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:

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:

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).

Science Class 5EP