Protists

Key Facts on Protists Eukaryotic Hetereotrophic or autotrophic Reproduce sexually or asexually Live in aquatic or other moist environments

Importance of Protists Protists play key roles in aquatic ecosystems. Protists that perform photosynthesis along with some other prokaryotes, are the major producers in the world’s oceans Non-photosynthetic protists are consumers that dominate the lowest levels of most aquatic food pyramids

Importance of Protists con’t Many protists are parasites – they live in, or on, other organisms Most parasites do not harm their host organism, but some cause serious disease (ex: malaria, sleeping sickness, ameobic dysentry, beaver fever)

Beaver Fever

Importance of Protists Human Uses of Protists sushi (nori is a multicellular protist Porphyra) Agar and carrageeenan (both are food additives)

Origin Protists were the first eukaryotes – their cells have a nucleus and organelles bound by membranes. These internal membranes likely developed from the folded cell membrane of an ancestral prokaryotic cell. This folding would have increased the cell surface area, allowing the cell to better exchange materials with its environment. This ability is a necessary feature of large cells.

Origins

Origins – Chloroplasts & Mitochondria Present-day mitochondria and chloroplasts each have two membranes Their inner membranes are similar to those of their ancestral prokaryote, while their outer membranes match the cell membranes of the eukaryotes

Origins – Chloroplasts & Mitochondria Present-day mitochondria and chloroplasts have their own internal chromosomes (DNA) These chromosomes are very similar to prokaryote chromosomes and contain genetic information used by the organelles Mitochondria and chloroplasts reproduce independently within eukaryotic cells by binary fission, just as prokaryotes do

Origins – Chloroplasts & Mitochondria Because of all of those features, we believe that mitochondria and chloroplasts are thought to have originated by endosymbiosis. ENDOSYMBIOSIS: a relationship in which a single-celled organism lives within the cells of another organism

Origins – Chloroplasts & Mitochondria....conclusion: Mitochondria and chloroplasts were once prokaryotic organisms. These cells were engulfed by early anaerobic eukaryotic cells and incorporated into them. We believe that mitochondria were once aerobic prokaryotes that benefitted from a rich food supply, while the eukaryotes benefited from the excess energy released by the areobic prokaryote

Origins

Typical Protists There are no typical protists! Many protists are parasites that can may or may not harm their host. Malaria is a disease that is caused by a harmful protist called Plasmodium that is transmitted using a mosquito as a vector. Protists can be unicellular or multicellular. They vary in their cell features, ways of moving, ways of getting nutrients and methods of reproducing.

If it is eukaryotic and it’s not a plant, animal or fungi, it’s a protist!

Ecosystems and Protists Protists play key roles in ecosystems as producers or consumers. For example, the large green, red, and brown algae called seaweeds have gas-filled bladders that help them float toward the light . This allows them to produce energy through photosynthesis. Photosynthetic protists are the primary producers in aquatic food webs. The large kelps, belonging to the brown algae group, can grow up to a half metre a day and reach a length of 80 m!

Climate Change and Protists Climate change is affecting many protists, including algae. In aquatic ecosystems the temperatures of oceans and lakes are rising. The water is also becoming more acidic, which may interfere with some protists’ ability to produce their outer protective shells. Without their protective shells, they may not survive. - The loss of these protists may severely damage food webs that rely on the photosynthetic products they create.

Life Cycles Protists reproduce sexually and asexually Single Cell Protists Asexually – Binary Fission Sexually – Conjugation Multi-cellular Protists Sexually – Sex Cells (ie male sperm and female egg)

Complex Life Cycles – Example Malaria

Malaria http://www.youtube.com/watch?v=A2-XTlHBf_4

Comprehension Homework: 2. Some protists are closely related to animals, plants or fungi than they are to each other. What does this suggest about the classification criteria used for members in this kingdom.

Homework Homework: (Research) African sleeping sickness is a serious parasitic disease caused by the protist, Trypanosoma brucei. Use the Internet to find out more about this disease. Where in the world is it most prevalent? How is it spread? What are the symptoms? Can the disease be effectively treated? Go to the WHO website (or other sites) to learn more about malaria. How is it spread? How prevalent is it in the world? How can it be prevented? How is malaria connected to sickle-cell anemia? http://www.youtube.com/watch?v=-zsdYOgTbOk

Videos Overview of Protists http://www.youtube.com/watch?v=-zsdYOgTbOk