Presentation on theme: "Eukaryotic Diversity Chapter 28. Protists Protists – eukaryotes; more complex than prokaryotes. 1 st – unicellular - called protists – in 1 big kingdom."— Presentation transcript:
Eukaryotic Diversity Chapter 28
Protists Protists – eukaryotes; more complex than prokaryotes. 1 st – unicellular - called protists – in 1 big kingdom (Protista) Protista - unicellular eukaryotes that are not plants, fungi, or animals.
Protists diverse; few characteristics that all have in common. Some heterotrophs, some autotrophs, some both. Euglena use light (if available) to produce food or find food themselves (if no light)
Protists divided into 3 categories. 1 Protozoa- ingestive, animal-like. 2 Absorptive, fungus-like protists. 3 Algae -- photosynthetic, plant-like protists. Most move with flagella, cilia at some time in life cycle. Flagella - extensions of cytoplasm.
Cilia shorter, more numerous than flagella. Both move cell with rhythmic power strokes, like oars of boat. Reproduction and life cycles highly varied among protists.
Some reproduce asexual; can shuffle genes through syngamy (union of 2 gametes. Others primarily asexual; can reproduce sexually occasionally. Many protists form resistant cells (cysts) - can survive harsh conditions.
Protists found wherever there is water (oceans, ponds, lakes); also damp soil, leaf litter, moist terrestrial habitats. Protists - important parts of plankton, communities of organisms that drift passively or swim weakly in water.
Many protists symbionts that inhabit body fluids, tissues, or cells of hosts. Relationships could be mutualistic or parasitic.
Origin Evolution of eukaryotic cell led to development of unique cellular structures and processes. Smallness of prokaryote limited amount of metabolic activity. Evolution of multicellular prokaryotes - cells specialized for different functions.
Some form groups that had specialty or have compartments for each activity (evolution of eukaryotes) Plasma membrane infolded, creating organelle membranes in eukaryotes. Chloroplasts, mitochondria evolved from endosymbiotic relationships.
Serial endosymbiosis - mitochondria and chloroplasts - small prokaryotes living within larger cells. Ancestors of mitochondria - aerobic heterotrophic prokaryotes. Ancestors of chloroplasts - photosynthetic prokaryotes.
Evolved a mutualistic relationship. Over time - became more interdependent. Close similarity between bacteria and chloroplasts + mitochondria of eukaryotes.
Mitosis/meiosis - result of evolution. Mitosis - could reproduce large genomes in eukaryotic nucleus. Meiosis - essential process in eukaryotic sex.
Mitochondria, plastids contain DNA - not genetically self-sufficient. Some protein encoded by organelles’ DNA. Some of genome got transferred as relationship went from parasitic to interdependent.
Plastids diversified because of endosymbiotic relationships. Secondary endosymbiosis - heterotrophic protist engulfed algae containing plastids. Led to diversification of plastids (including chloroplasts).
Domain archaea - more closely related to eukaryotes than prokaryotes. Modern archaea have genes of bacterial origin.
3 domains arose from ancestral community of primitive cells that swapped DNA.
Every diversification allowed for future ones. Range from very simple to very complex.
1 Flagellates Diplomonads have multiple flagella, 2 separate nuclei, simple cytoskeleton, no mitochondria or plastids.
Parabasalids include trichomonads. Spread through sexual contact.
2 Euglenoids Euglenoids (Euglenophyta) - characterized by anterior pocket from which 1 or 2 flagella emerge. Most autotrophic; can be heterotrophic or mixotrophic.
3 Kinetoplastids Kinetoplastids (Kinetoplastida) have single large mitochondrion associated with unique organelle (kinetoplast) Kinetoplastids symbiotic, include pathogenic parasites. Trypanosoma causes African sleeping sickness.
4 Alveolata Alveolata - flagellated protists (dinoflagellates), parasites (apicomplexans), ciliated protists (ciliates). Members have aveoli, small membrane-bound cavities, under cell surface.
Example – dinoflagellates - big components of phytoplankton. Each dinoflagellate species has characteristic shape, reinforced by internal plates of cellulose - hard- shelled.
Red tides caused by dinoflagellates in bloom. Color comes from pigment they produce. Produce toxins deadly to predators and humans. 1 species - carnivorous; produces toxin to stun fish, then eats flesh.
Some dinoflagellates form mutualistic symbioses with cnidarians, animals that build coral reefs. Some are bioluminescent.
5 Apicomplexans Apicomplexans - parasites of animals; some cause serious human diseases. Spores (sporozoites) - infectious. Plasmodium - protist that causes malaria; spends part of life cycle in mosquitoes, part in humans.
6 Ciliates Ciliophora (ciliates) named for use of cilia to move and feed. Most ciliates live as solitary cells in freshwater. Ciliates - 2 types of nuclei, large macronucleus, several tiny micronuclei.
Paramecium - cilia along oral groove draw in food engulfed by phagocytosis. Paramecium expels accumulated water from contractile vacuole.
Ciliates reproduce via conjugation - micronuclei that have gone through meiosis exchange genetic information.
7 Stramenopila Includes heterotrophic and photosynthetic protists; presence of numerous fine, hairlike projections on flagella. Heterotrophic stramenopiles – oomycotes - water molds, white rusts, downy mildews.
Water molds important decomposers, mainly in fresh water. Form cottony masses on dead fish. Some water molds parasitic, growing on skin, gills of injured fish. White rusts and downy mildews parasites of terrestrial plants.
8 Heterokont algae Diatoms (Bacillariophyta) - glasslike walls composed of hydrated silica embedded in organic matrix. Reproduce mostly asexually; form cysts during certain parts of year.
Golden algae named for pigments (yellow and brown carotene and xanthophyll) Some mixotrophic; can form cysts that will last decades.
Brown algae (Phaeophyta) - largest and most complex algae. Most multicellular, unlike other members of group. Brown or olive color - accessory pigments in plastids. Found in temperate waters.
9 Seaweed Largest marine algae - brown, red, and green algae - seaweeds. Inhabit intertidal and subtidal zones of coastal waters. Body of seaweed – thallus - consists of rootlike holdfast + stemlike stipe - supports leaflike photosynthetic blades.
Some brown algae have floats to raise blades toward surface.
Algae - many uses including thickener for foods. Seaweed popular food item in Asian countries.
Multicellular brown, red, and green algae show complex life cycles with alternation of multicellular haploid and multicellular diploid forms. Evolved convergent in life cycle of plants.
Diploid individual (sporophyte) produces haploid spores (zoospores) by meiosis. Haploid individual (gametophyte) produces gametes by mitosis that fuse to form diploid zygote.
10 Rhodophyta Red algae - no flagellated stages in life cycle. Red coloration visible due to accessory pigment phycoerythrin. Red algae (Rhodophyta) - most common seaweeds in warm coastal waters of tropical oceans.
Some species that live down deep have special pigments - allow them to absorb blue and green wavelengths (only ones that penetrate bottom). Most red algae multicellular - some reaching size large enough to be “seaweeds.”
Life cycles of red algae especially diverse. In absence of flagella, fertilization depends entirely on water currents to bring gametes together.
11 Chlorophyta Green algae (chlorophytes) named for grass-green chloroplasts - similar to plants. Most of the species chlorophytes live in freshwater. Most green algae have both sexual and asexual reproductive stages.
3 groups of protists use pseudopodia, cellular extensions, to move and feed. Most heterotrophic; some parasitic. Rhizopods (amoebas) - unicellular - use pseudopodia to move and feed.
Amoeba extends pseudopod, anchors tip, streams more cytoplasm into pseudopodium. Pseudopodia activity not random - directed toward food.
Amoebas inhabit freshwater and marine environments. Most free-living heterotrophs. Some important parasites, including dysentery in humans.
Most heliozoans (“sun animals”) live in fresh water. Skeletons made of glass. Foraminiferans, (forams) almost all marine. Shells have pores in them. Pseudopodia extend through pores for swimming, shell formation, feeding.
12 Mycetozoa Mycetozoa (slime molds or “fungus animals”) neither fungi nor animals - protists. Slime molds feed and move via pseudopodia but comparisons of protein sequences place slime molds close to fungi and animals, not amoeba.
Cellular slime molds (Dictyostelida) straddle line between individuality and multicellularity. Feeding stage consists of solitary cells. When food scarce, cells form aggregate (“slug”) - functions as unit. Dominant stage - haploid stage.