Protists
Characteristics of Protists
• Protista - most widely diverse kingdom
• All protists are eukaryotes
• Many are microscopic, however, some
algae can grow many feet long
• Plant-like protists are known as algae
• Diatoms
• Account for > 20% of atmospheric oxygen
• Shell remains deposit as diatomaceous earth
• Well preserved in the form of microfossils
• Microfossils allow researchers to
study the environment at the time the
diatoms lived
Type of protist
Protozoa
Algae
• Protozoa – an animal-like variety of protist that is
unicellular, heterotrophic, and mobile
• Pseudopodia – the foot-like
extensions that help protozoa
move and ingest food
• Fungus-like protists
• Act as decomposers
• Group traditionally includes:
• Water molds
• Slime molds
• Some ecologists have removed slime
molds from the kingdom Protista
Size
Nutrient acquisition
Zooflagelletes
Ciliates
Sarcodines
Unicellular
Unicellular
Unicellular
Heterotrophic ingestion
Heterotrophic ingestion
Heterotrophic ingestion
Dinoflagellates
Unicellular
Autotrophic photosynthesis
Diatoms
Unicellular
Autotrophic photosynthesis
Green algae
Red algae
Brown algae
Fungus-like
Unicellular or
multicellular
Mostly multicellular
Mostly multicellular
Multicellular
Unique Features,
Environment
Flagella
Cilia
Pseudopodia
Two flagella, cellulose-based cell walls,
Fresh and salt water
Two overlapping silica shells,
Aquatic environments
Autotrophic photosynthesis
Most moist environments
Autotrophic photosynthesis
Autotrophic photosynthesis
Heterotrophic absorption
Warm, tropical waters
Cold water
Reproductive spores
Biology 15.4 – Protists
Protists
Ecological Impact of Protists
• Protists play a significant role in the ecology of marine
• Some parasitic protists can cause serious diseases,
ecosystems
including protozoans
• Salt and fresh water algae
• Plasmodium cause malaria in humans
• Contribute large amounts of oxygen through
• Mosquitoes transmit the disease to humans
photosynthesis
• 500 million people are infected
• Primary producers
• 1 million die each year
• Remove carbon dioxide from
• Trypanosoma causes African sleeping sickness
environment as key role in carbon cycle
• Tsetse fly carries
• Major source of food for primary
Trypanosoma
consumers in food chains
• Transmission to
• Fungus-like protists
humans through
the bloodstream
• Decomposers
• Return nutrients to soil
• Excess nitrates and phosphates from human activity can enter water sources
• Rapidly reproducing algae can result in algal blooms
• Red tide – a specific type of algal bloom that occurs when dinoflagellates reach large
numbers, resulting in a red or brown color tide
• Dinoflagellates release a neurotoxin
• When neurotoxin reaches a high concentration, it is absorbed by shellfish
• Humans that eat infected shellfish can become ill from the toxin
• Red and brown algae are used in food products as thickening and emulsifying agents
• Algae used in other products
• Ex) Ice cream, pudding, salad dressing, cheese, and candy
• Medicines
• Diatoms used as filters, polishes, reflective paint, and toothpaste
• Cosmetics
• Algae used to make algal fuel, an alternative to fossil fuels
• Rubber
• Protozoa found in water treatment facilities
• Latex
• Good indicator of water quality
• Fertilizer
Biology 15.4 – Protists