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What is a Protist? How are Protists related to other eukaryotes?

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Presentation on theme: "What is a Protist? How are Protists related to other eukaryotes?"— Presentation transcript:

1 What is a Protist? How are Protists related to other eukaryotes?

2 Does everyone agree how to classify protists? No, at present, biologists do not agree how to classify protists The amount of diversity among the protists, is much greater than within or between the other three eukaryotic kingdoms

3 The Protist Dilemma Protists are grouped together solely because they are not fungi, plants or animals Furthermore, many protists are more closely related to members of other eukaryotic kingdoms than they are to other protists.

4 Current Protist classification It has been proposed that the protista kingdom be divided into six groups or clades Today, while we still use the term Protist, this is not a single kingdom, but a collection of organisms in six clades

5 What is a Protist? A protist is a eukaryote (has a nucleus) A protist is any eukaryote that is not a plant, animal or fungus

6 Evolution of Protista Endosymbiont Hypothesis

7 Are all protists unicellular? No, although most are unicellular, some protists are colonial, and some like the giant kelp are multicellular. UnicellularColonial Multicellular

8 How do Protists Move? Some move with flagella Long whip-like projections One to two per cell Examples – Trypanosoma – Euglena Trypanosoma

9 Euglena  Two flagella  No cell wall  Chloroplasts

10 How do Protists move?  Some move with cilia  Cilia can be used for feeding and movement  Cilia are short and used like oars on a boat  Example  Paramecium

11 Anal pore Gullet Oral groove Trichocysts Lysosomes Food vacuoles Contractile vacuole Micronucleus Macronucleus Cilia Go to Section: Ciliates - Paramecium

12 Some do not move  Those that do not move produce spores and live as parasites  Plasmodium causes malaria  Cryptosporidium spreads through contaminated drinking water and caused intestinal disease

13 Excavates: feeding groove, flagella Diplomonads – Giardia is an intestinal parasite that causes cramping and diarrhea Discicristates – Euglena is free living and can use its chloroplast for photosynthesis or can live as a heterotroph – Trypansoma causes African sleeping sickness; carried by tsetse flies

14 Gullet Chloroplast Nucleus EyespotFlagella Euglena Carbohydrate storage bodies Pellicle Contractile vacuole Go to Section:

15 Chromalveolates: very diverse group; most are photosynthetic Phaeophytes = multicellular brown algae Chrysophytes = unicellular golden algae Diatoms = unicellular algae with intricate silicon dioxide (silica) shells Ciliates = paramecium are not photosynthetic Dinoflagellates = half are photosynthetic, half are heterotrophs; some are luminescent Apicomplexans = parasitic Plasmodium

16 Brown algae Phaeophytes Photosynthetic Chlorophylls a and c Brown accessory pigment fucoxanthin Multicellular Giant kelp, Fucus

17 Photosynthetic protists Chrysophytes  “Golden plants”  Gold-colored chloroplasts  Cell walls contain pectin instead of cellulose  Store food as oil rather than starch  Can form thread like colonies

18 Photosynthetic protists Diatoms  Glass like cell walls  Cell walls contain silicon (Si)  Cell walls like petri dish

19 Photosynthetic protists Dinoflagellates  Luminescent  “Fire plants”  Half photosynthetic  Half heterotrophs  Two flagella

20 Apicomplexan Plasmodium Mosquito borne parasites like the species that causes malaria

21 Cercozoa, Foraminiferan, Radiolarian Have pseudopods Many produce protective shells Heliozoan Foraminiferans

22 Rhodophytes Red Algae Chlorophyll a Red accessory pigment – phycobilin Absorbs blue light Grows very deep Multicellular Nori

23 Ecology of photosynthetic protists Base of the food chain Half of the photosynthesis on earth is carried out by phytoplankton

24 Ecology of photosynthetic protists Algal blooms  Caused by too much pollution or nutrients  Deplete water of oxygen  Kill fish and invertebrates  Dinoflagellates cause “red tides”  Red tides produce toxins which can be taken in by shellfish. Eating these shellfish can cause illness, paralysis and death

25 Green algae Phylum Chlorophyta Same chlorophyll and cell wall composition as green plants Chlorophyll a and b Store food as starch Found in fresh and salt water and on land Unicellular, colonial and multicellular Now classified with plants

26 Unicellular green algae Chlamydomonas  Lives in ponds, ditches and wet soil  Egg shaped  Two flagella  Large, cup-shaped chloroplast

27 Colonial green algae Spirogyra  Filamentous  Forms threadlike colonies  Spiral chloroplasts Volvox  Hollow spheres  500 – 50,000 identical cells  Some cell specialization

28 Human uses of algae Oxygen Food (nori; thickening agent (carrageenan) in ice cream, egg nog, chocolate, salad dressing) Industry (plastics, waxes, paints, lubricants) Science labs (agar)

29 Alternation of generation – alternating between diploid and haploid organisms Diploid – having two copies of each chromosome Haploid – having one copy of each chromosome Gametophyte – haploid gamete producing organism Sporophyte – diploid spore producing organism

30 Heterotrophic protists Amoebozoa = Amoebas use pseudopods for movement and feeding Ciliates = Paramecia use cilia to move food to gullet; food vacuoles and lysosomes digest the food; waste is released through the anal pore Slime Molds and Water Molds absorb food through their cell walls from dead or decaying matter; decomposers

31 Food vacuole Nucleus Contractile vacuole Pseudopods Section 20-2 An Amoeba Go to Section:

32 Slime molds

33

34 Water molds Cells are multinucleate Cell walls of cellulose White fuzz on dead fish in water Plant parasites on land Cause potato blight responsible for potato famine

35 Reproduction in water molds Can produce sexually and asexually Motile (swimming) spores Antheridium produces sperm Oogonium produces eggs

36 Mutualistic relationships Zooxanthellae – live inside coral and provide food through photosynthesis Trychonympha – live in the gut of termites and digest cellulose


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