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Lecture 12

BIO SCI 94 Lecture 12: Protists Part 1Premium

Biological Sciences
Course Code
Brad Hughes

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Third domain on tree of life-Eukarya
Eukaryotes- size of single celled organism to sequoia trees and blue whales
Eukaryotes diverse, but share important features:
Most large, lots of organelles, cytoskeleton
Nuclear envelope
Multicellularity common
Asexual and sexual reproduction
Protists- organisms include eukaryotes except land plants, fungi, animals
Not a monophyletic group
Only represent some of the descendants of single common ancestor
Not defined by synapomorphies
Impacts on Human Health and Welfare
Types of protists cause disease in human or crops
Worst crop failure-Irish potato famine of 1845 caused by Phytophthora
Malaria-One of worst chronic public health problems
Caused by five species of parasitic protist Plasmodium
Protist comes from mosquitoes
Cell types of Plasmodium’s life cycle specialized for infecting specific host
Plasmodium lives in mosquitoes and humans→ causes malaria
Harmful Algal Bloom
Unicellular species’ population grows quickly + high density in aquatic
environment→ bloom occurs
Cause of bloom- dinoflagellates, photosynthetic, toxic producing protist
Blooms harmful to humans because toxins builds up in clams and shellfish
Shellfish not harmed
People eat shellfish→ several types of poisoning
Ecological Importance of Protist
Protists abundant, represent 10% of named eukaryotic species
Protists Play a Key Role in Aquatic Food Chains
Primary producers- Uses photosynthesis to produce chemical energy
Half of total carbon dioxide on Earth-represented by marine protists which
produce organic molecules
Planktons-diatoms and other small organisms which drift in oceans or lakes
Phytoplankton- photosynthetic plankton
Food chain- describes nutritional relationships among organisms:
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