Chapter 7

1. Chapter 7 Protists

2. What is a Protist • Diatoms are only one of the vast varieties of protists • Protists are eukaryotes that cannot be classified as animals, plants, or fungi • Most protists are unicellular, but some are multicellular • Some are heterotrophs, autotrophs, or both • Some cannot move, while others zoom around • Scientists divide protists into three categories: • Animal-like protists • Plant-like protists • Fungus-like protists

3. Animal-Like Protists • Like animals, animal-like protists are heterotrophs, and most are able to move from place to place to obtain food • But unlike animals, animal-like protists, or protozoans, are unicellular • Protozoans can be classified into four groups, based on the way they move and live

4. Animal-Like Protists • Protozoans with Pseudopods • Amoeba’s belong to the group protozoans called sarcodines • Sarcodines move and feed by forming pseudopods temporary bulges of the cell • Ex: amoeba’s use pseudopods to move away from bright light • Sarcodines also use pseudopods to trap food by extending a pseudopod on each side of the food particle • Protozoans that live in fresh water, such as amoebas, have a problem; small particles like those of water, pass easily through the cell membrane into the cytoplasm • If excess water were to build up inside the cell, the amoeba would burst • Fortunately, amoebas have a contractile vacuole a structure that collects the extra water and then expels it from the cell

5. Animal-Like Protists • Protozoans with Cilia • Ciliates have structures called cilia, which are hair-like projections from cells that move with a wave-like motion • Ciliates use their cilia to move and obtain food • The cells of ciliates, like paramecium, are complex • They have 2 contractile vacuoles that expel water from the cell • More than one nucleus • One to control the everyday tasks of the cell • One to function in reproduction which is asexually by binary fission but can produce by conjugation

6. Animal-Like Protists • Protozoans with Flagella use long, whip-like flagella to move • Some of these protozoans live inside the bodies of other organisms • Symbiosis is a close relationship in which at least one of the species benefits • Mutualism is when both partners benefit from living together

7. Animal-Like Protists • Protozoans that are Parasites • They are all parasites that feed on the cells and body fluids of their hosts • Many of these parasites have more than one host • Malaria

8. Plant-like Protists • Plantlike protists, which are commonly called algae, are extremely diverse • Like plants, algae are autotrophic • Algae play a significant role in many environments • Ex: algae that live near the surface of ponds, lakes, and oceans are an important food source for other organisms in the water • In addition, much of the oxygen in Earth’s atmosphere is made by these algae • Algae vary greatly in size, some are unicellular or multicellular, some live in colonies, some become specialized to perform certain functions such as reproduction, different colors such as green, yellow, red, brown, orange, or even black

9. Plantlike Protists • Diatoms • Unicellular with beautiful glasslike cell walls • Some float, other attach to objects • Diatoms are a food source for heterotrophs • They can move by oozing chemicals out of slits in their cell walls, then they glide in the slime • When they die their cell walls collect on the bottoms of oceans & lake • Over time they form layers of a coarse substance called diatomaceous which makes a good polishing agent used in household scouring products • Used as an insecticide

10. Plantlike Protists • Dinoflagellates • Unicellular algae surrounded by stiff plates that look like a suit of armor • Different colors • Have 2 flagella that help them move • Glow in the dark

11. Plantlike Protists • Eugleniods • Green, unicellular algae that are found in fresh water • Have one animal like characteristic – can be heterotrophs under certain conditions but when sunlight is available, most are autotrophs • Whip-like flagellum to help them move

12. Plantlike Protists • Red Algae • Multicellular seaweeds • Grow more than 260 m below the ocean • People uses • Ice cream • Hair conditioner • Can be eating fresh, dried, or toasted

13. Plantlike Protists • Green Algae • Very diverse • Unicellular • Some form colonies which make them multicellular • Live in fresh or salt water, on land • Contain the same type of chlorophyll as most plants on land

14. Plantlike Protists • Brown Algae • Commonly called seaweed • Other colors include: green, yellow, or orange • Fig 22 • Found along the Atlantic coast • Giant kelp • Some people eat brown algae • Used in pudding

15. Fungus-like Protists • Spore is a tiny cell that is able to grow into a new organism • Like fungi, fungus-like protists are heterotrophs, have cell walls, and use spores to reproduce • Able to move • Three types: • Slime molds • Water molds • Downy mildews

16. Fungus-like Protists • Slime Molds • Brilliantly colored • Live on forest floors • Ooze along the surfaces of decaying materials, feeding on bacteria • Some are so small you need a microscope to see them • Fig 23

17. Fungus-like Protists • Water Molds & Downy Mildews • Live in water • Grow as tiny threads that look like fuzz • Fig 24 • Attack many food crops such as potatoes, corn, and grapes