Chapter 25

rhizarians

unicellular organisms with long thin pseudopods

1. cercozoans

2. foraminiferans

3. radiolarians

foraminiferans

• secrete CaCO₃ shells and form limestone over millions of years

• some plankton, some at sea bottom

• threadlike branched pseudopods extend through pores in shell, capture plankton in sticky net

  • plankton: autotrophic

  • zooplankton: heterotrophic

radiolarians

marine; radial symmetry; thin stiff pseudopodia made by microtubules

• pseudopods increase SA for material exchange/floating

• SiO₂ elaborate glassy internal skeleton

  • color → sometimes endosymbiotic dinoflagellates

excavates

diverse, some lack mitochondria

1. diplomonads

2. parabasalids

3. heteroloboseans

4. euglenids

5. kinetoplastids

diplomonads and parabasalids

• lack mitochondria (derived trait)

• Giardia lamblia: diplomonad with 2 nuclei + multiple flagella

  • water parasite cause internal disease

• parabasalids: undulating membrane; membrane extension for locomotion

• Trichomonas vaginalis: Parabasalids STD

heteroloboseans

• amoeboid body form

• ex: naegleria “brain-eating amoeba” - fatal NS disease

euglenids

• spiral protein strips under plasma membrane, controls shape

• can switch btwn photosynthetic + heterotrophic

• unicellular, flagella w/ crystalline road (light detector)

• mitochondria w/ disc shape cristae

• binary fission

kinetoplastids

• parasites - 2 flagella + 1 mitochondria

• kinetoplast in mitrochondria: multiple circular DNA+protein

• unicellular, flagella w/ crystalline road (light detector)

• mitochondria w/ disc shape cristae

• binary fission

examples

• Trypanosoma brucei (sleep sickness)

• Trypanosoma cruzi (chagas disease)

• Trypanosomes: pathogen that frequently change surface proteins, difficult to control

amoebozoans

lobe shaped pseudopods for locomotion

1. loboseans

2. plasmodial slime molds

3. cellular slime molds

loboseans

• unicellular, dont aggregate

• predators, parasites, scavengers

• feed by phagocytosis

• bottoms of lakes/ponds

• Testate amoebas: secrete shells/glue sand grains to form casing

plasmodial slime molds

• no cytokenisis, just increase cytoplasm and nuclei without dividing

• coenocytes: vegetative feeding stage; wall-less cytoplasm mass with many diploid nuclei

• plasmodium: mass streams over substrate in network of strands

  • extend pseudopodia, engulf by phagocytosis, grow

  • no nutrients = resting spore

primary producers

• photosynthesis to make own energy + food for self/others

• phytoplankton: PP of oceans

  • diatoms: perform 1/5 of photosynthetic C fixation;

  • aquatic heterotrophs depend on bc major PP

pathogens

• cause disease

• plasmodium: apicomplexan cause malaria

  • ½ life in RBC host

  • ½ life in Anopheles mosquito host

  • transfer by bite

• diatoms/dinoflagellates massive reproduction in favorable conditions

  • red tides: nerve toxins

  • too much dinoflagellates in on area = low O₂

endosymbionts

• organisms lives in/on another organisms

• microbial eukaryotes; radiolarians + photosynthetic

• host gives nutrients and protection

• endosymbiont given carbon components

commercial use

• diatoms: petroleum and diatomaceous Earth

  • store oil for energy / for floating

  • die → sink to ocean floor → oil produce petroleum + gas

  • insulation, filtration, metal polishing, insecticides

• foraminiferans: mitosis; daughter abandons parents to make own shells

  • limestone deposits

  • sands on beaches

  • shells preserved in marine sediment used for rock classification/dating and temperature estimates when shells formed