Protist #2 Life cycles Algae Dichotomous key

Human life Cycle

Gametes (unicellular) are only haploid cells Alternation of generations: BOTH diploid and haploid multicellular stages Individual haploid spores divide by mitosis (rather than fusing together). Gametes produced by mitosis fuse to make zygote (inc. some algae) Zygote (1 cell) is only diploid cell

Generalized alternation of generation life cycle 2 copies of each chromosome 1 copy of each chromosome

Algae is not a taxon Algae (informal term) = photosynthetic protist – 1.5 b.y.o. – Previously organized by color (photosynthetic pigment) Red, green, brown, golden – Description based on ecological role as a producer Form base of fresh water and marine food chains

If humans had alternation of generations 2n n n n n n n n n n n

Figure 28.2a Diplomonads Parabasalids Euglenozoans Excavata Diatoms Golden algae Brown algae Dinoflagellates Apicomplexans Ciliates Forams Cercozoans Radiolarians “SAR” clade Stramenopiles Alveolates Rhizarians Green algae Red algae Chlorophytes Charophytes Land plants Archaeplastida Slime molds Tubulinids Entamoebas Nucleariids Fungi Unikonta Choanoflagellates Animals Amoebozoans Opisthokonts Primary endocytosis of cyanobacteria Secondary endocytosis of red algae

Figure 28.3 Cyanobacterium Nucleus Membranes are represented as dark lines in the cell Heterotrophic eukaryote One of these membranes was lost in red and green algal descendants. Red alga Green alga Primary endosymbiosis Secondary endosymbiosis Dinoflagellates Plastid Stramenopiles Plastid Euglenids Chlorarachniophytes Secondary endosymbiosis

Figure 28.3a Cyanobacterium Nucleus Membranes are represented as dark lines in the cell. 1 (from euk) 2 (outer cell wall lipid layer—lost) 3 (plasma membrane of bacteria) Heterotrophic eukaryote One of these membranes was lost in red and green algal descendants. Primary endosymbiosis Red alga Green alga mitochondria divergence

Figure 28.3b Red alga Secondary endosymbiosis Dinoflagellates Plastid Stramenopiles 4 membranes & neucleomorph

Figure 28.2a Diplomonads Parabasalids Euglenozoans Excavata Diatoms Golden algae Brown algae Dinoflagellates Apicomplexans Ciliates Forams Cercozoans Radiolarians “SAR” clade Stramenopiles Alveolates Rhizarians Green algae Red algae Chlorophytes Charophytes Land plants Archaeplastida Slime molds Tubulinids Entamoebas Nucleariids Fungi Unikonta Choanoflagellates Animals Amoebozoans Opisthokonts Primary endocytosis of cyanobacteria Secondary endocytosis of red algae

Archaeplastida Red Algae (rhodophyta) Green algae (chlorophyta and charophyta) Land plants Share a common eukaryotic ancestor that obtained plastid through endosymbiosis of cyanobacteria Primary endosymbiosis Green algae Red algae Chlorophytes Charophytes Land plants Archaeplastida

Red Algae (rhodophytes) Mostly marine, mostly multicellular, concentrated in warm tropical waters Pigments: – Chlorophyll – Phycoerythrin (erythr = red) Absorbs blue and green light (most penetrating wavelengths) Shallower water = less phycoerythrin  greenish red Deeper water = more phycoerythrin  very dark (almost black) red Genus Porphyra = nori Reproduce asexually and sexually (w/ alt. of generations). Gametes not flagellated agar, carrageenan

Color of pigment = color NOT absorbed Absorbed = energy to make organic molecules

Green Algae Mostly freshwater (but some marine and terrestrial) Range of complexity – Unicellular, colonial/filamentous, & multicellular Chloroplasts to land plants – Chlorophyll Most have both sexual and asexual stages. Mostly by biflagellated gametes Alternation of generation in some

Chlamydomonas Isogamous = same shape Poor env. syngamy Resistant zygospore

spirogyra Conjugation Sexual reproduction Different strains - Strain nucleus moves to + strain and nuclei (isogametes) fuse  zygote  zygospore

Volvox Differentiated cells Haploid “adult” Asexual reproduction  daughter colonies Sexual reproduction w/ oogamy Oogamy – Small, motile sperm fertilize large non-motile egg

Ulva multicellular green alga w/ alternation of isomophic generation

SAR Algae Diatoms Golden algae Brown algae Dinoflagellates Apicomplexans Ciliates Forams Cercozoans Radiolarians “SAR” clade Stramenopiles Alveolates Rhizarians

Brown Algae (phaeophytes) All multicellular Mostly marine – Common in temperate and cold water Can have specialized structures (e..g. holdfast, blades, stipes, etc) Important habitat—kelp forests Food (kombu) Algin in cell walls Some alternation of generations

A brown alga life cycle

Golden Algae Mostly unicellular Freshwater and marine phytoplankton – Some mixotrophic yellow-brown carotenoid pigments Biflagellated Can form protective cysts that can survive for decades under poor conditions

Diatoms Unicellular Cell wall (frustule) of silica (silicon dioxide, glass like) – Protects – two overlapping halves Important phytoplankton Large deposits on the ocean floor and form sedimentary deposits known as diatomaceous earth Blooms uptake & sequester large amounts of CO2 Only limited number of species have flagella, most are planktonic (drifters)

Dinoflagelates Unicellular, mostly marine A number have cell walls of cellulose, two flagella at right angles Important phytoplankton – but many species are heterotrophic and many are mixotrophic Dinoflagellate blooms produce red-tides – (carotenoid pigments create colors) – toxins Symbionts in cnidarians (e.g., corals, jellies, and anemones) Bioluminesence

1a. Organism is square…………………go to 3 1b. Organism is not square……………. Go to 2 2a. Organism has stripes……………….. go to 4 2b. Organism has no stripes……………. Go to 5 3a. Organism has legs ………………… Right walky 3b. Organism has no legs……………... Right sitty 4a. Organism has antennae…………….. Roundy feely 4b. Organism has no antennae………….go to 6 5a. Organism is happy …………………. Go to 7 5b. Organism is not happy……………… Plain grumpy 6a. Organism has arms………………….Touchy feely 6b. Organism has no arm ………………. Roundy touchy 7a. Organism has 2 or less toes per foot…………. Plain footys 7b. Organism has 3 or more toes per foot ………..Plain toesies Dichotomous Key