Kingdom Protista Learning Outcome B1

Characteristics Appeared in the fossil record 1.5 billion years ago Protists have an evolutionary advancement over bacteria, because they have a membrane-bound nucleus. Protists also have ribosomes, mitochondria and lysosomes Protists are classified within the Domain Eukarya and Kingdom Protista Generally microscopic and unicellular Live in fresh/salt water and shady moist terrestrial environments Example – plankton

Characteristics Plankton is one of the most important producers and consumers in the food chain Plant-like protists are heterotrophs, which are organisms that must consume food and Can not make their own food. Phytoplankton are photosynthetic autotrophs

Protist Diversity There are three major groups: Plant-like protists Animal-like protists

Examples of Plant-like Protists Phylum Euglenophyta Example – Euglena

Characteristics of the Phylum Euglenophyta Found mainly in fresh water, especially stagnant water Over 800 species in lakes and pont Obtain food via photosynthesis, but during periods of darkness they become heterotrophic (take in food) Have two distinguishing characteristics: eyespot and flagellum The eyespot has photoreceptors and plays a role in the organisms sensory motor system Eyespot allows movement towards or away from light

Characteristics of Phylum Euglenophyta Flagellum is used to propel organism through aquatic environments in a whip-like fashion. Have large green chloroplasts and central vacuole Food is stored as starch granule just like in land plants Reproduce asexually; following nuclear division the rest of the cell divides lengthwise This is known as longtitudinal fission, this involves a growth in cell circumference while the organelles are duplicated. During unfavourable conditions Euglena may form thick resting cells similar to an endospore

Examples of Plant-like Protists Phylum Chrysophyta Example – diatoms Found in fresh and marine environment Diatoms are the most abundant plant-like protist Make up diatomaceous earth, makes up kitty litter and pool filters Autotrophic Many are flagellated and encased in shells or skeletons Shells are made up of silica

Examples of Plant-like Protists Phylum Pyrrophyta Example – dinoflagellates Autotrophic Contains chlorophyll and other green pigments Major component of oceanic plankton Large blooms of dinoflagellates cause red tide, which can infect shellfish and poison humans. These dinoflagellates release a neurotoxin that is harmful to humans.

Examples of Animal-like Protists All heterotrophic Generally move to find food Feed on bacteria and other microbes Holozoic is a term used to describe a microorganisms that obtains their food by engulfing it Saprozoic organism absorb predigested or soluble nutrients directly through the cell membrane Can be free living or parasitic Live in a diverse range of habitats: salt water, fresh water and Most terrestrial habitats Undergo asexual reproduction by fission May form a resting cell during unfavorable conditions called a cyst Range in size – example blood parasites = 2 um vs. Foraminferans = 5 cm

Examples of Animals-like Protists Phylum Sarcodina Generally free-living May have a motile adult form and develop pseudopods for locomotion They also use these finger-like projections o obtain food This phylum can be divided into 4 groups Amoeba Formainferians Radiolarian Heliozoans.

Amoeba No shell Demonstrate cytoplasmic movement, this movement is caused by repeated extensions and retractions of the pseudopods The cytoplasm has two layers: Ectoplasm Thin semi rigid layer under the plasma membrane Endoplasm The more fluid part that fills the inside of the cell Continuous movement of the endoplasm causes the amoeba to change shape constantly as it moves

Amoeba Linnaes name the amoeba “chaos chaos” Engulfing food particles is known as phagocytosis The food particles are stored within an organelle known as a food vacuole. A contractile vacuole regulates the amount of water within the amoeba, it has the ability to remove excess water. As the vacuole expands the water is discharged through a pore in the plasma membrane Reproduction is asexual through binary fission Once the amoeba splits in two the organelles grow to their full size although they may split again.

Examples of Animal-like Prostists Phylum Ciliphora Example - paramecium Characterized by the presence of hair-like structures called cilia Cilia may cover the entire body Cilia also function in motility but are shorter and more abundant Cilia are synchronized for swimming In sessile organism such as Stenor or Vorticelli the cilia attach the microorganism to a substrate Most advanced protist

Examples of Animal-like Protists Phylum Sporozoa Example – plasmodium No independent locomotion Do not have pseudopods, cilia or flagella Parasitic Have spore-like stage during their lifecycle Sometimes involved two or more hosts Reproduce sexually in one and asexually in the other Insects are frequently responsible for transmitting sporozoa from one host to another Plasmodium causes malaria

Examples of Fungus-Like Protists Phylum Gymnomycota Example – slime molds Live in cool, shady, most places and are often found under fallen leaves or rotting logs. Leave a slimy trail as they move At some stages in their lifecycle slime molds resemble protozoans and become amoeba-like or have flagella, at other times they produce spores similar to fungi