Lucture Notes: 2/4

Thursday Email by 8am if class if Lecture will be cancelled.

If lab is cancelled, both lab 2-3 will be done next Thursday

Protists:

  1. Found in moist terrestrial

  2. Found in fresh water (lakes, Ponds)

  3. Found in Marine environments (oceans, seas)

Supergroup Rhizarians: Are amoebas (

  • Amoebas are protists that move and feed using pseudopodia extensions of the cell surface

Radiolarians:

  • Have delicate, symmetrical internal skeletons typically made of cilica.

  • Pseudopodia renforced by micro tubules radiate from the central body

  • Prey are engulfed by cytoplasm in the pseudopodia and carried into the cell by cytoplasmic streaming

  • Most radiolarians are marine organisms

Forams:

  • Foraminiferans are named for their porous calcium carbonate shells called tests

  • Pseudopodia that extend through pores in the test

  • Live in the ocean and fresh water, and their fossils make up part of the marine sediments

  • Fossilized tests are used for correlating the age of sedimentary rocks in different parts of the world.

  • The magnesium content of fossilized tests is used to estimate the change in ocean temperature over time.

Cercozoans:

  • Amoeboid and flagellated protists that feed using threadlike pseudopodia

  • Found in Marine, fresh water, and moist soil.

  • Most are heterotrophic parasites or predators

  • Chlorarachniophytes are a small group of mixotrophs

  • Paulinella Chromatophora is a species known to be autotrophic

  • Does photosynthesis through structures called chromatophore

  • Derived from endosymbiosis with a Cyanobacteria different from the one that gave rise to plastids.

Supergroup Archaeplastids:

  • Plastids arose when a heterotrophic protist acquired a Cyanobacteria endosymbiosis

  • The photosynthetic descendants of this ancient protist evolved into red algae and green algae

  • Red and green algae are the closest relatives of plants

  • Plants are descended from the green algae

  • Archaeplastida is the supergroup for red algae, green algae, and plants.

Red Algae:

  • An accessory pigment called phycoerythrin masks the green of chlorophyll giving the red color

  • Color varies from greenish-red in shall water to dark red to black

  • Most are multicellular, we call seaweeds

  • Reproduce sexually in red algae life cycles often include alternation of generations

  • Common in coastal waters of tropical oceans

  • Some species are consumed by humans such as Porphyra (Nori) the wrap for sushi.

Green Algae:

  • Named for their green chloroplasts which are structurally and chemically similar to those in planets

  • Form a Paraphyletic group that includes the charophytes and the chlorophytes

  • Charophytes include the algae most closely related to plants.

  • Most Chlorophytes live in fresh water, but some life in marine and terrestrial.

  • Various unicellular species are free-living while others life symbiotically with other eukaryotes

  • Some live in environments exposed to intense visible and ultraviolet radiation.

  • Larger size and greater complexity evolved in green algae by three different mechanisms:

  1. Formation of colonies from individual calls (Pediastrum)

  2. Formation of true multicellular bodies by cell division and differentiation (Volvox & Ulva)

  3. Repeated division of nuclei with no cytoplasmic division (Caulerpa)

  • Most chlorophytes have complex life cycles with both sexual and asexual reproduction stages

  • Nearly all species have bifagellated gametes with sup-shaped chloroplasts

  • Alteration of generations has evolved in some species like the Ulva

  • Don’t have male & female, Shown as plus and minus for opposite sexes.

  • Video on alteration of generations of Ulva.

Charophytes: See Lab handout & photos

Supergroup: Unikonts

  • Includes animals, fungi, and some protists

  • Include protists that are closely related to fungi and animals

  • The two major clades of unikonts are the ameobozoans (tubulinids and relatives) and the opisthokonts (animals, fungi, and related protists)

  • The root of the eukaryotic tree is uncertain

  • One controversial hypothesis is that unikonts were the first to diverge from other eukaryotes groups. (Minority solution)

Ameobozoans:

  • Amoebas that have lobe- or tube- shaped

  • Tubulinids: Diverse group of ameobozoans with love or tube shaped pseudopodia

  • Common unicellular in

Slide Mold:

  • Slime mold, or mycetozoans, were once thought to be fungi due to their spore-producing fruiting bodies

  • This resemblance is a result of convergent evolution

  • Slime molds have diverged into two lineages, plasmodial slime molds and cellular slime molds.

  • MYCET prefix for fungi-like

  • Plasmodial slime Molds:

  • Brightly colored, often yellow or orange.

  • Large feedin mass called a plasmodium

  • Single “supercell” that contains many diploid nuclei undivided

  • “Smarter than slime mold video”

  • Mapping and memory capacity

  • Perform Chemotaxis to move faster. Grows a stalk so head of cells can use wind to fly away.

  • Altruism: Things that go against survival of the fittest but benefits the species as a whole.

  • Cellular slime molds:

  • For multicellular aggregates in which cells are sparated by plasma membranes

  • The feeding stage consists of solitary cells

  • Solitary cells unite to from a slug-like aggregate for migration when habitat conditions are poor

  • Ultimately, the aggregated cells form a fruiting body to give spores better disbursement.

  • Dictyostelium Discoideum is a model organism for the studying the evolution of multicellularity

  • Cells in the stalk of the fruiting body die without reproducing; cell s at the top survive to reproduce.

  • Some cells have a “cheat” mutation, giving them the reproductive advantage of not forming the stalk.

  • Why don’t all Dictyostelium cells cheat?

  • Cheating cells lack a specific surface protein recognized by noncheaters

  • Non-cheaters avoid exploitation by preferentially aggregating with other noncheaters

Entamoebas:

  • Genus of parasites of all classes of vertebrates and some invertebrates

  • Humans are host to at least six species, but only E. Histolytica is pathogenic

  • E. Histolytica causes amoebic dysentery, the third-leading cause of death due to eukaryotic parasites.

Opisthokonts

  • Diverse group discussed in mater chapters

Protists:

  • Diverse

  • Symbiotic: benefit their hosts. Live within polyps and nourish reef-building corals.

  • Plasmodium causes malaria in humans

  • Dinoflagellate that attaches and feed on the skin of fish

  • Others cause sudden oak death as happened in PA in 2021

  • Photosynthetic:

  • Either a producer or consumer

  • Photosynthetic protists are limited by nutrients (population size matches available food)

  • Population booms can have major ecological consequences, some good and some bad.

  • Growth and biomass of photosynthetic protists and prokaryotes have declined with increasing sea surface temperature

  • Phytoplankton communities rely on upwelling of cold, nutrient-rich water.

  • If sea surface temperature continues to warm due to global warming, this could effect fish

PBS Video: “Ancient Earth, Life Rising”

  • Early life thrived in superheated thermal vents

  • All land was made or basalt from a few small volcanic island

  • The islands were destroyed quickly by the closer moons aggressive seas

  • Plate tectonics: very controversial

  • Density differences and gravitational theories

  • Geology lead to asteroid impacts in ancient rock, perhaps causing the early shifts for plate tectonics

  • Data suggests one asteroid was 30 miles across (30x the ones that wiped out the dinosaurs)

  • Subduction: A plate is forced under another, bringing water underneath. This interacts and forms granite. Granite is less dense and floats on top of molten basalt.

  • Basalt has a slightly lower melting point than granite. Allowing for the granite to rise during cooling.