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Kingdom Protista. General Characteristics. Most are single-celled All are eukaryotic All are heterotrophic Microscopic Come in all shapes, sizes and colours Some have cell walls, some are motile
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General Characteristics • Most are single-celled • All are eukaryotic • All are heterotrophic • Microscopic • Come in all shapes, sizes and colours • Some have cell walls, some are motile • Classified together because they do not fit into other kingdoms, rather than because they are similar or closely related to one another • Most diverse group of eukaryotes, but not as diverse as the bacteria or archaea
Protists • 3 main groups of protists, characterized by how they get their nutrients. • Animal-like Protists • Plant-like protists • Fungus-like protists
Animal-like protists:The Protozoa • Means first animals • Scavengers or predators • Some parasites. • Vary in shape and size. • Most live as single cells but others form colonies • Phyla are divided based on motility and method of reproduction.
Protozoa • Protozoa can move and are classified into four phyla based on their methods of locomotion: • Flagellates: have one or more flagella which whip from side to side to move them about, have a hard protective covering over their outer membrane, some are parasites, some are symbiotic and some are free-living. Most symbiotes live in digestive systems and help break down cellulose. Trypanosomia causes African sleeping Sickness, as it is parasitic.
Protozoa Sarcodines: these are the amoebae, move and engulf their prey by producing pseudopodia, which are extensions of their cytoplasm. Ciliates: move by cilia beating in a coordinated rhythm, they also help move food into the paramecium’s gullet, which leads to a food vacuole. A paramecium is a ciliate. Sporozoans: these are parasites, they have spores at some point in their lifecycle, they contain a number of complex organelles at one end of their bodies to help them invade their victim. Plasmodium vivax causes one type of malaria in humans.
Plant Like Protists“Algae” • Simple, aquatic, plant-like organisms that contain chlorophyll • Lack the leaves, roots, stems and water-conducting materials of plants • Range in size (single cells to giant seaweeds 60 m in length) • They have been on the earth for about 2 billion years and scientists are still discovering new species
Algae Algae are classified into six different phyla based on the type of chloroplasts and pigments they contain. The chloroplasts in different types of algae have different types of chlorophylls and other pigments. This suggests that chloroplast-containing cells evolved three times. Three phyla are unicellular and three are multi-cellular Other differences include the chemistry of their cell walls, the number and position of flagella (if any) and the form that food reserves take in their cells.
Algae • Green Algae (Chlorophytes): The most plant-like of the algae as they have the same type of chlorophyll and the same colour as most land plants. And like plants, their cell walls contain cellulose and store food reserves in the form of starch. Found in freshwater, damp terrestrial places and even live in the fur of sloths!
Algae Brown Algae (Phaeophytes): nearly all multicellular, which are commonly called seaweeds. They have cell walls made of cellulose and alginic acid (similar to pectin, which is used to thicken jams and jellies). They have adaptations to live in rough environments such as holdfasts that anchor the algae to the rocky seashore. Their fronds are tough enough to withstand the pounding of the waves. They are what let Colombus know he was close to land! Found in cold water.
Algae Red Algae (Rhodophytes): multicellular seaweed found in warmer seawater. More delicate and smaller than brown algae. Why are they red? Because they contain pigments that absorb green, violet and blue light and since these wavelengths penetrate the furthest in water, they are able to live at deeper depths.
Single celled Algae • Diatoms (Chrysophyta): most abundant unicellular algae in the oceans. They are one of the biggest components of plankton. As photosynthetic organisms they are also a major source of atmospheric oxygen. They have rigid cell walls that contain silica, a common ingredient in sand and glass. The remains of diatoms stick around for a long time and they are used in filters, sound proofers, insulation and as a gentle abrasive in metal polishes and toothpastes.
Single Celled Algae Dinoflagellates (Pyrophytes): unicellular, photosynthetic and mostly marine. They have protective coats made of stiff cellulose plates. They all have two distinct flagellae. One lies in a long groove on the covering plate with only its far end free. The second is flat and ribbon like and lies in a groove that encircles the dinoflagellate. They are extremely numerous and form an important base for marine food chains. Form red tides which cause toxins to built up in shellfish that eat them.
Single Celled Algae Euglenoids (Euglenophytes): unicellular freshwater organisms with two flagellae, one usually much longer than the other. They contain chloroplasts but if there is no sunlight then they lose their chloroplasts and ingest and eat food.
Fungus-Like ProtistsSlime and Water Moulds • Have the characteristics of fungi, protozoa and plants. They glide from place to place and ingest food like protozoa. They have cellulose in their cell walls like plants. They also absorb nutrients from their environment like fungi.
Slime and Water Moulds • Water Moulds (Oomycotes): includes water moulds, white rusts and downy mildews. They are filamentous organisms that resemble fungi. Most live as saprotrophs on dead organic materials, but some are parasitic on plants, insects and fish. They extend fungus like threads into their host where they release digestive enzymes and absorb the nutrients. The cause of the Irish Potato Famine.
Slime and Water Moulds Plasmodial Slime Moulds (Myxomycotes): visible to the naked eye as tiny slug like organisms that creep over damp, decaying plant material in forests and fields. This blob, called a plasmodium, contains many nuclei. Feed in a similar manner to amoebae. Spores form in improper living conditions.
Slime and Water Moulds Cellular Slime Moulds (Acrasiomycotes): exist as individual amoeboid like cells with one nucleus each. Feed by ingesting tiny bacteria or yeast cells. When food becomes scarce, the cells release a chemical that causes them to gather together to form a pseudoplasmodium. This is a jelly-like mass, which produces a sporangia that releases spores.
