Slide 1
The red algae belong to Kingdom Rhodophyta.
These organisms are multicellular photosynthetic seaweeds with no flagellated cells. The most distinct distinguishing characteristic is the presence of special photosynthetic pigments known as phycobilins.
These phycobilins are a red pigment and give the red algae their red color.
The phycobilins are specialized to absorb blue wavelengths of light and blue light penetrates deeper into water. This allows the red algae to grow at deeper depths than other photosynthetic organisms.
Many of the coralline algae, which secrete calcium carbonate and play a major role in building coral reefs are members of the Rhodophyta.
Slide 2
The red algae are a large group with an estimated 10,000 different
species. Some of them are large and plant-like while others are small
and grow on the surface of other organisms.
Slide 3
Red algaes are used extensively in food production and industry.
Agar is a gelatinous substance that is derived from algae. It is used to make gel tablets for pills, as a cosmetic base, as culture medium for microbiology labs to grow bacteria and other microscopic organisms, and for making jellies and desert.
Red algae are eaten regularly in many parts of the world - including the nori sheets that wrap around sushi.
If you are a food label reader you have probably seen the ingredient carageenan listed on an ice cream or yogurt container. Carageenan is stabilizer that is made from red algae and helps keep ice cream and yogurt creamy. It is also used in cosmetics and paints.
Slide 4
Our last group of protists are the green algae or chlorophyta.
This group will get special attention because it is the group of organisms that gave rise to the true plants of Kingdom Plantae.
The green algae have chloroplasts and they use both chlorophyll a and chlorophyll b. Chlorophyll occurs in several basic forms - including chlorophyll a - which is used by all photosynthetic organisms and chlorophyll b which is used only by the plants and green algae.
It is the presence of chlorophyll b in the green algae and plants that indicates their close evolutionary relatedness.
Other features they share with plants is that they store their carbohydrates as starch and, if a cell wall is present, it is made of cellulose.
They also exhibit alternation of generation which is seen in all plants.
The green algae can be either unicellular or multicellular and there is a great diversity in their forms.
Slide 5
This image shows some of the diversity of size and form in this
kingdom. The top images are microscope images and the bottom images are
of larger green algae.
Slide 6
The green algae Acetabularia is a single-celled organism, but it
is gigantic in size and complex in form so it is an excellent model organism
for studying cell biology.
An individual cell is usually about 5 centimeters tall with a cup about 1 cm across - there are not many cells that can be seen with the naked eye!
Because of its appearance - it is sometimes called Mermaid's chalice.
Slide 6
Some green algae are terrestrial and can survive in quite dry
environments by living symbiotically with a fungus. These symbiotic
relationships are called lichens.
Lichens are composite organisms consisting of a symbiotic association of a fungus with a photosynthetic partner either a green alga or a cyanobacterium. They often live on rocks or the bark of trees.
Lichens are often the first organisms to settle in places lacking soil, constituting the sole vegetation in some extreme environments such as those found at high mountain elevations and at high latitudes. Some survive in the tough conditions of deserts, and others on frozen soil of the Arctic regions.
The European Space Agency has even discovered that lichens can survive unprotected in space!