BIOL1030_W22_Lecture12_Part1.pdf

Chapter 28 Lecture 20 Exploring protist diversity https://www.expii.com/t/eukaryotic-cell-definition-examples-10021  Protists are diverse! The Eukarya – 4 supergroups! Excavata SAR:...

Chapter 28 Lecture 20 Exploring protist diversity https://www.expii.com/t/eukaryotic-cell-definition-examples-10021  Protists are diverse! The Eukarya – 4 supergroups! Excavata SAR: Stramenopile Alveolate Rhizaria Archaeplastida Unikonta What is a protist? Protists are a Diverse Group of Eukaryotes that Span All Four Super groups Protists are eukaryotes and are very diverse (both structurally and functionally) Eukaryotic cells have organelles and are more complex than prokaryotic cells It is important to bear in mind that: The organisms in most eukaryotic lineages are protists, and (highlighted in yellow) Most protists are unicellular but there are some colonial and multicellular species Feeding and reproductive strategies vary iClicker question The protists are an example of A) A monophyletic group because protists include all of the ancestor species and their descendants B) A paraphyletic group because protists consists of the ancestor and all of their descendants **might be paraphyletic** C) A polyphyletic group because protists include distantly related species but not their common ancestor D) A polyphyletic group because protists include closely related species and their common ancestor E) A paraphyletic group because protists consists of an ancestral species and none of their descendants Mitochondria arose only once (happened in ancestor of plants and animals) Below is plastid endosymbiosis  The protists - Excavata Some members of this supergroup have an “excavated” feeding groove on one side of the cell body. Diplomonads, parabasalids, euglenozoa The euglenozoans have flagella that differ in structure from those of other organisms. Cork screws The euglenozoans vary from predators and parasites eg: Trypanosomas - the cause of sleeping sickness, and to photosynthetic autotrophs eg: Euglena Purple ribbon-shaped cells among the red blood Interested in parasitology? BIOL 3270 cells are the trypanosomes  Diplomonads and parabasalids Diplomonads Modified mitochondria called mitosomes Lack electron transport chain – cannot use oxygen Live in anaerobic environments Many are parasites Multiple flagella and 2 nuclei one note stops here Giardia Parabasalids Modified mitochondria called hydrogenosomes Release hydrogen as a byproduct Many parasites Interested in parasitology? BIOL 3270  Euglenids not part of euniglenous - single cell - can be parasites Some of these organisms are photosynthetic (autotrophic) when light is available, or heterotrophic feeding when there is no access to light. This is known as mixotrophy Unicellular freshwater organism No cell wall Membrane-bound nucleus Contractile vacuole Kinetoplastids (relative) Euglenids - have one or two Single, large mitochondria flagella that emerge from a Can feed on prokaryotes or be pocket at one end of cell, parasites mixotrophs The protists – the SAR clade The SAR clade is a highly diverse group of protists defined by DNA similarities hardened mineralized exoskeleton The “SAR” clade is named for the first letters of its three major clades: stramenopiles, alveolates, and rhizarians The stramenopiles - Diatoms Diatoms are unicellular algae with a unique two-part, glass-like wall of silicon dioxide (protection) Diatoms are a major component of phytoplankton and are highly diverse (found in the ocean and the lakes) Fossilized diatom walls compose much of the sediments known as diatomaceous earth So abundant that photosynthesis impacts climate CO2 As diatoms die and fall in ocean, CO2 is ‘pumped’ to floor (carbon sink) huge component for sand/glass The stremenopiles – brown and golden algae Golden algae: Brown algae: Yellow and brown Large complex multicellular carotenoids structures Simple structure Kelps, giant seaweed Mostly colonies of unicellular organisms Plant-like structures: holdfast anchors the algae, stipe supports leaflike blades The similarities between algae and plants are examples of analogous structures The Life Cycle of the Brown Alga Laminaria: an Example of Alternation of Generations A variety of life cycles have evolved among multicellular algae The most complex life cycles include an alternation of generations the alternation of multicellular haploid and diploid forms Heteromorphic generations are structurally different Isomorphic generations look similar (but still differ in 2n versus n) The protists – the alveoates Membrane bound sacs (alveoli) just under plasma membrane Function is unknown still The alveolates - dinoflagellates Dinoflagellates Body made up of cellulose ‘armour’ Phytoplankton ~half are strict heterotrophs Blooms (explosive growth) results in ‘red tide’ Toxins produced by dinoflagellates causes massive kills of invertebrates and fishes