Overview and 28.1 Elyse SmilnakElyse Smilnak

Vocabulary Protists Protists Mixotrophs Mixotrophs Endosymbiosis Endosymbiosis Algae Algae Secondary endosymbiosis Secondary endosymbiosis

Overview Protists – incredibly small, unicellular group of eukaryotes Protists – incredibly small, unicellular group of eukaryotes First discovered by Dutch microscopist Antoni van Leeuwenhoek First discovered by Dutch microscopist Antoni van Leeuwenhoek Various shapes and forms Various shapes and forms Move with flagella or with blob-like appendages Move with flagella or with blob-like appendages Shaped like trumpets or strings of jewelry Shaped like trumpets or strings of jewelry Were once classified as their own kingdom: Protista Were once classified as their own kingdom: Protista

Most Eukaryotes are Single-celled Organisms Eukarya Domain Eukarya Domain Eukaryotes Eukaryotes Nucleus Nucleus Membrane-bounded organelles Membrane-bounded organelles Main Points: Main Points: Organisms in most eukaryotic lineages are protists Organisms in most eukaryotic lineages are protists Most protists are unicellular Most protists are unicellular

Structural and Functional Diversity in Protists Structurally and functionally diverse Structurally and functionally diverse Use some of the same organelles: nucleus, endoplasmic reticulum, Golgi apparatus, and lysosomes Use some of the same organelles: nucleus, endoplasmic reticulum, Golgi apparatus, and lysosomes Contractile vacuoles – pump excess water from the cell Contractile vacuoles – pump excess water from the cell Photoautotrophs, heterotrophs, and mixotrophs – combine photosynthesis and heterotrophic nutrition Photoautotrophs, heterotrophs, and mixotrophs – combine photosynthesis and heterotrophic nutrition Asexual, sexual Asexual, sexual

Endosymbiosis in Eukaryotic Evolution Endosymbiosis – the process in which certain unicellular organisms engulf other cells, which become endosymbionts and ultimately organelles in the host cell Endosymbiosis – the process in which certain unicellular organisms engulf other cells, which become endosymbionts and ultimately organelles in the host cell Eukaryotes acquired mitochondria by engulfing an aerobic prokaryote(alpha proteobacterium) Eukaryotes acquired mitochondria by engulfing an aerobic prokaryote(alpha proteobacterium) Algae – photosynthetic protists Algae – photosynthetic protists Red and green algae Red and green algae Secondary endosymbiosis – red and green algae is ingested in the food vacuoles and becomes endosymbionts themselves Secondary endosymbiosis – red and green algae is ingested in the food vacuoles and becomes endosymbionts themselves

Diversity of Plastids Produced by Endosymbiosis Diversity of plastids produced by endosymbiosis. Studies of plastid-bearing eukaryotes suggest that plastids evolved from a gram-negative cyanobacteria that was engulfed by an ancestral heterotrophic eukaryotic (primary endosymbiosis). That ancestor then diversified into red algae and green algae, some of which were subsequently engulfed by other eukaryotes (secondary endosymbiosis). Diversity of plastids produced by endosymbiosis. Studies of plastid-bearing eukaryotes suggest that plastids evolved from a gram-negative cyanobacteria that was engulfed by an ancestral heterotrophic eukaryotic (primary endosymbiosis). That ancestor then diversified into red algae and green algae, some of which were subsequently engulfed by other eukaryotes (secondary endosymbiosis).

Five Supergroups of Eukaryotes Excavata Excavata “excavated” groove on one side of the body “excavated” groove on one side of the body Chromalveolata Chromalveolata Include important pathogens and photosynthetic organisms such as brown algae Include important pathogens and photosynthetic organisms such as brown algae Rhizaria Rhizaria Contains many species of amoebas with thread-shaped pseudopodia Contains many species of amoebas with thread-shaped pseudopodia Archaeplastida Archaeplastida Includes red and green algae and land plants Includes red and green algae and land plants Unikonta Unikonta Ameobas with lobe- or tube-shaped pseudopodia, animals, and fungi Ameobas with lobe- or tube-shaped pseudopodia, animals, and fungi

Protistan Diversity