Exploring the Diverse World of Protists
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Learn about the fascinating characteristics, reproduction methods, and diversity of protozoans, algae, foraminifera, diatoms, and flagellates within Kingdom Protista. Understand their unique roles and structures in the ecosystem.
Exploring the Diverse World of Protists
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Presentation Transcript
Kingdom Protista • This kingdom is also called the protozoan group. • proto = first • zoan= animals
Characteristics of Protozoans • Unicellular • Mostly microscopic • All symmetries represented (oval, spherical, etc…) • No organs or tissues, but some specialized organelles; nucleus may be single or multiple • Free-living, commensalism, mutualism, parasitism all present
Binary Fission • Binary means “two” • Fission means “splitting” • So Protists that reproduce this way are literally splitting in two.
Characteristics of Protozoans • Locomotion by pseudopodia, flagella, cilia, and direct cell movements. • Simple endo- or exo- skeleton, but most are naked. • Nutrition of all kinds: autotrophic, heterotrophic, saprozoic (using nutrients dissolved in the surrounding medium • Aquatic (marine or freshwater) or terrestrial (in moist soil or leaf litter) • Reproduction asexually by budding, fission, or cysts, and sexually by conjugation or syngamy (union of male and female gametes to form a zygote.)
The First Eukaryotes • Protists are thought to be the first eukaryotes. • They evolved about 1.5 billion years ago. • Thought to have formed through the process of Endosymbiosis.
Two important features of eukaryotes that formed first in protists: • Sexual reproduction • Multicellularity
What’s the unifying theme of protists? • They are all eukaryotic organisms that can’t be classified as plants, animals, or fungi. (all of the “leftover eukaryotes”) • They do not form embryos during early development.
Alternation of Generations: • As with some plants, some protists go through an alternation of generations. • This means that there is a diploid form (has two copies of each chromosome) and another form that is haploid (has only one copy of each chromosome).
Alternation of Generations: • The diploid, spore producing phase is called the sporophyte. • The haploid, gamete producing phase is called the gametophyte.
Sporophyte • The adult sporophyte produces reproductive cells called sporangia, which produces haploid spores by meiosis. • These spores grow into multicellular haploid gametophytes.
Gametophyte • The mature gametophytes produce haploid gametes that fuse and complete the life cycle by dividing through mitosis to form a new diploid sporophyte.
Conjugation • This is the temporary union of two protists to exchange nuclear material. Conjugation in paramecium
Ameobas Ameboid Movement: • Members of the phylum Rhizopoda move by using flexible cytoplasmic extensions called pseudopodia. • pseudo = false • podia = feet
Foraminifera • Typically live in sand or attach themselves to other organisms or on rocks. • Characterized by their porous shells, called tests. These shells are made of calcium carbonate. • Long, thin projections of cytoplasm extend through the pores of the tests, in order to catch prey and aid in swimming.
Algae • These protists are strict photoautotrophs. • Multicellular and unicellular forms • Major portion of marine plankton
Algae • Green – (Phylum Chlorophyta) Contain the same pigments found in the chloroplasts of plants. • Red – (Phylum Rhodophyta) Mostly multicellular. Have pigment that absorbs light waves that penetrate deep water. • Brown – (Phylum Phaeophyta) Mostly marine. Kelp is an example of this phylum.
Diatoms • Phylum Bacillariophyta • Photosynthetic • Unicellular • Double shelled • Move by secreting chemicals through holes in their shells, enabling them to glide • Sexual reproduction
Diatoms • Sexual reproduction involves separating the shell in halves, and each new diatom generates a new half. The shell becomes too small, after successive “halvings”. • Then the diatom slips out of its shell, grows to normal size, regenerates a new shell, and begins the cycle of reproduction again.
Flagellates • These are protists that move using flagella
Three kinds of Flagellates: • Dinoflagellates • Euglenoids • Kinetoplastids
Dinoflagellates • Freshwater and marine • Have an exterior coat made of cellulose • Various unusual shapes • Usually twin flagella, which beat within two grooves around the body at right angles to one another. • Responsible for “Red Tides” • Usually reproduce asexually • Can be heterotrophic or autotrophic, or both.
Euglenoids • Freshwater protists with two flagella. • About one-third of these are photosynthetic • The other two-thirds are heterotrophic • Has a light sensitive organ called the “eyespot” • Has a flexible protein scaffold called a pellicle, which allows it to change shape • Reproduce by mitosis
Kinetoplastids • Unicellular • Heterotrohpic • Have at least one flagella, but some have thousands • Most reproduce asexually, but some sexually • Example is the trypanosomes, like the one that causes African Sleeping Sickness
Ciliates • Have large numbers of cilia (short hair like projections from the cell membrane, which provide movement for the organism) • Unicellular heterotrophs • Also have a pellicle • Micronuclei and macronuclei • Reproduce sexually and asexually • Paramecium is an example
Protistan Molds: • These are heterotrophs with some mobility • Once thought to be fungi, because of their similar appearance • Contain different carbohydrates than fungal cell walls. • Carry out mitosis, unlike fungi
Cellular slime molds • Resemble amoebas • Move through the soil ingesting bacteria • During times of stress, they form aggregations called slugs • Then the aggregates form stalked structures which contain spores • These spores, when released, form new amoeba like organisms
Plasmodial slime molds • These stream along as a mass of cytoplasm that looks like an oozing slime • They feed on bacteria • Contains many nuclei, but they are not separated by cell walls • Also creates spores in unfavorable conditions • Spores can grow into amoeboid cells or flagellated cells, which can fuse into diploid zygotes
Other molds • Oomycetes is a phylum of water molds, white rusts, and downy mildews • Often grow on dead animals in freshwater • All members of the group are parasitic or detritivores (feed on dead organisms) • Unusual because they have two flagella, with one facing forward and the other facing backward.
Oomycetes • These organisms are responsible for the failure of potato crops in Ireland in 1845 – 1850 • This crop failure led to a famine that killed about 1 million people!
Sporozoans • Parasitic protists that form spores during their reproduction cycle • Nonmotile, unicellular • Malaria is a disease caused by sporozoans • Cryptosporidium is a sporozoan which causes disease, it infected water supplies in several cities in the US in 1980s and 1990s. It comes from pet feces.
