Evolution of Protists Chapter 19 Section 1 p. 540

Between 2 and 1.8 billion years ago…… One type of prokaryotic cell grew large and evolved membranes around its organelles Some membrane formed nuclear envelope Result =eukaryotes Even more remarkable…some prokaryotic organisms entered this ancestral eukaryotic cell Symbiotic relationshipmutualism

The prokaryotes were special They had the ability to use oxygen to generate energy (ATP). Over time they evolved together Small cells became mitochondria and chloroplasts

What is a Protist? Protists are Eukaryotes! They have a membrane bound nucleus with membrane bound organelles This kingdom does not share any unique characteristics… Most protists are unicellular but some are multicellular! Many are microscopic but some can grow up to 70 meters long!

Protists continued Most protists need oxygen to survive but some are poisoned by it. Some protists are autotrophic and others are heterotrophic Three types of protists Plant like Animal like Fungus like Some reproduce asexually and other sexually Some can alternate between!

Classification Many protists have more in common with multicellular kingdoms such as fungi, animalia, and plant than they do with each other! They do not develop the multicellular structures found in those kingdoms so they must be classified on their own They are classified as what they are not An eukaryote that is not classified as a fungus, plant or animal is classified as a protist. Video

Evolution of Sexual Reproduction 300 million years after single-celled eukaryotes first appeared they started evolving quickly Sexually reproducing Lots of genetic variation After the evolution of sexual reproduction, adaptive radiation occurreddiverse

Living Protists – Autotrophic or Heterotrophic Algae – photosynthetic autotrophs that look and act like plants 30 to 40% of all photosynthesis performed by these protists ! Some are very small – some are as long as 70 meters (Giant kelp)

Here are two examples of a protist that can grow up to 70 meters in length and sometimes longer. What do you think it is? Where would you find it?

Algae Groups Euglenophyta Pyrrophyta Chrysophyta Chlorophyta Rhodophyta Phaeophyta UNICELLULAR MULTICELLULAR

Heterotrophic Protists (protozoans) All heterotrophic protists spend most of their lives as unicellular – some gather into groups Slime molds Heterotrophs live as predators, decomposers or parasites Sporazoa Complex parasites – can cause disease Plasmodium - malaria

Autotroph Heterotroph

How do Protists Reproduce? Euglenophyta reproduce only asexually All other phyla can reproduce sexually at least occasionally Slime molds can spend most of their lives like ameba-like cells but under certain conditions can gather into a slug-like mass

Fruiting body

Repro Continued Forms a fruiting body that releases spores that then develop into a slug-like mass Alternation of generations – sporophytes produce haploid spores Spores grow into male and female cells called gametophytes Gametophytes produce egg and sperm Fusion of these gametes produces a zygote which grows into a sporophyte again

Keys points to remember All protists are eukaryotic Algae are photosynthetic autotrophs Protozoans are heterotrophs Asexual repro occurs by mitosis Sexual repro occurs by fruiting bodies Alternation of generations between sexual and asexual stages

Slime mold travel Ant head NPR Encyclopedia of Life