BSCC 1011: General Biology 2 - Protists Overview

Characteristics of Protists =========================== - **Classification: Domain Eukarya, Kingdom? MANY. Usually classified into eukaryotic supergroups** - **Polyphyletic:** Not a monophyletic group - **Common ancestor = ancestor of all Eukaryotes** - **Structure:** Structu...

Characteristics of Protists =========================== - **Classification: Domain Eukarya, Kingdom? MANY. Usually classified into eukaryotic supergroups** - **Polyphyletic:** Not a monophyletic group - **Common ancestor = ancestor of all Eukaryotes** - **Structure:** Structurally simplest eukaryotes - Most are **unicellular**; Some are **colonial** (live in groups) or truly **multicellular** - Have support structures - Many have **shells or cell walls** - All have an internal cytoskeleton - **Microfilaments/Actin filaments**: thinnest in diameter, made from actin subunit polymerization - **I**nteract with cell membrane via additional proteins - Have other functions in some cells (ex: animal muscle) - Myosin proteins can pull on them to generate movement - **Microtubules**: thickest in diameter, made from tubulin subunit polymerization - Functions - Used as "roadways" in the cell (motor proteins walk along these and pull vesicles/organelles) - "Spindle fibers" of mitosis/meiosis - Move eukaryotic cilia and flagella - Kinesins and dyneins can pull on them/walk on them to generate movement - Note: eukaryotic intermediate filaments only found in cells of some animal groups - Have **nucleus & other membrane-bound organelles** - **Endosymbiotic Theory** (see also week 2) - **Mitochondria**: Proteobacterium species ingested/not destroyed by ancestor of all eukaryotic organisms EARLY in eukaryotic evolution - **Chloroplasts and other plastids** - **Primary (1°) Endosymbiosis:** Cyanobacterium ingested/not destroyed by ancestor of Archaeplastids (red algae, green algae, & plants) - **Secondary (2°) Endosymbiosis:** unicellular red or green alga ingested/not destroyed by other protists - Occurred many times independently - **Invagination Theory** (see also week 2) - Membrane folded in to form nucleus, ER, Golgi, etc. - Likely occurred after mitochondrial endosymbiosis - **Selective advantage of organelles** - **Compartmentalization of cellular functions** allows many chemical pathways to simultaneously occur without interfering with one another - More metabolically efficient, allows for more rapid growth/larger cell - **Movement:** Many are **motile** (can move themselves) at some point in their life cycles - Three main structures that different protists use to move - **Pseudopodia** ("false feet"): Microfilaments/actin filaments of cytoskeleton push cell membrane out to form "feet" that can pull the cell in a given direction. (Example: Amoebas) - **Flagella**: Long, **whip-like tail(s)** containing microtubules; allow cell to swim. (Example: Euglenoids) - **Cilia**: Short, **hair-like structures** containing microtubules; usually found all over cell surface to allow cell to swim (like oars on a boat). (Example: Ciliates) - **Axoneme**: arrangement of microtubules, motor proteins (dyneins), and accessory proteins along length of a cilium or flagellum. **Microtubules in 9 + 2 array:** axoneme: inner pair of singlet microtubules in center. 9 Outer doubles of microtubules (1= complete and 1 = partial) surround the periphery. dynein arms are attached to each outer doublet to connext to neighbor doublet. cell membrane surrounds all of it. - Dynein arms pull on outer doublets when hydrolyzing ATP for energy to cause movement. - **Habitat: Most are** **aquatic** (marine or freshwater) - Many are **critical** members of aquatic ecosystems (ex: many = phytoplankton or zooplankton) - **Plankton:** organisms that are carried/moved by tides/currents in water or wind in air. Can be from any major groups of organisms, not just protists. - Some live in **damp soils or other organisms (as symbionts)** - **Symbionts can be mutualistic or parasitic (see below)** - **Nutritionally diverse** group - Either **anaerobic** or **aerobic** - Some are **photoautotrophs (have chloroplasts)** - **\~30% global photosynthesis by photosynthetic protists (aquatic mainly)** - **Remaining 20% by photosynthetic bacteria, 50% by land plants** - **Phytoplankton: photosynthetic protists & other photosynthetic plankton** - **Symbiotic dinoflagellates provide food for host corals (mutualism)** - Some are **chemoheterotrophs, including** - **Decomposers:** absorb organic matter from environment/decompose dead organisms - **Predators**: eat other living organisms (often unicellular organisms) - **Parasites/pathogens**: feed off of or live in other living organism and extract nutrients from them - Some **protistan diseases**: *Plasmodium* (**Malaria),** *Trichomonas* (**Trichomoniasis),** *Giardia* (**Giardia),** *Trypanosoma* (**Sleeping sickness & other diseases)** - **Mutualists**: get food from host organism and provide benefit to host - **Ex**: protists in termite guts - Some are **mixotrophs**: can switch back and forth between different nutrition modes - **Life Cycles** - Most spend the majority of their lives **haploid** (n) and reproduce **asexually** by mitosis - Many can enter **diploid (2n)**, **sexual** stages - Some sexually **exchange nuclei** in horizontal gene transfer - Many form **cysts**: dormant cells that can withstand extreme environmental conditions **\ ** **Protist Diversity/Systematics\ ** - **Controversial/changes frequently** - MANY Eukaryotic supergroups with subgroupings. **We'll focus on 4 major supergroups:** Table 1. Eukaryotic Supergroups covered in this course +-----------------------------------+-----------------------------------+ | **Eukaryotic Supergroup** | **Key | | | Characteristics/Subgroupings** | +===================================+===================================+ | **SAR** (Stramenopila, Alveolata, | - **Stramenopiles** = | | Rhizaria) | photosynthetic diatoms & | | | brown algae plus fungus-like | | | oomycetes | | | | | | - Many have **hairy | | | flagellum** | | | | | | - **Alveolates** = | | | dinoflagellates, | | | apicomplexans, & ciliates | | | | | | - Have **sacs (alveoli)** | | | under membrane | | | | | | - **Rhizarians** = **Cercozoans | | | & Shelled amoebas | | | (radiolarians & | | | foraminiferans)** | +-----------------------------------+-----------------------------------+ | **Archaeplastida** | - Includes **photosynthetic** | | | | | | - **Red Algae** | | | | | | - **Green Algae** | | | (chlorophytes & | | | charophytes) | | | | | | - **Kingdom Plantae** | | | (plants- most closely | | | related to charophytes) | +-----------------------------------+-----------------------------------+ | **Excavata** | - Includes | | | | | | - **Metamonads | | | (parabasalids & | | | diplomonads**) with | | | reduced mitochondria | | | | | | - Flagellated | | | **Euglenozoans (Euglenids | | | and Kinetoplastids**) | | | | | | - Many have **groove** | | | (excavation) on cell surface | +-----------------------------------+-----------------------------------+ | **Amorphea** (Unikonta in your | - Includes | | textbook) | | | | - **Amoebozoans** (fungus | | | like **slime molds, | | | tubulinids** (incl. true | | | amoebas), **& | | | entamoebas**) | | | | | | - **Opisthokonts**, | | | including: | | | | | | - **Nucleariids & | | | Kingdom Fungi** | | | | | | - **Choanoflagellates & | | | Kingdom Animalia** | +-----------------------------------+-----------------------------------+  1. SAR protists ============ SAR phylogeny. Outgroup is archaeplastida (protists & plants). Within the SAR: alveolata and stramenopila are closer relatives than rhizaria. - **Stramenopiles (Diatoms, Brown Algae, & Oomycetes)** - Most have a **"hairy" flagellum (*stramenopilos*)** often paired with a smooth one - Diatoms: flagella present in male gametes - Brown algae & oomycetes: flagella present in spores  Table 2. Stramenopile protists covered in this course +-----------------------------------+-----------------------------------+ | **Subgroup** | **Description** | +===================================+===================================+ | **Diatoms** | - **Unicellular & very | | | diverse** | | | | | | - **Not motile** | | | | | | - **Photoautotrophs** | | | | | | - **Chloroplasts (with 4 | | | membranes: 2° | | | endocytosis)** contain a | | | **brownish pigment | | | (fucoxanthin)** to trap | | | light energy | | | | | | - **Very important for | | | global photosynthesis** | | | | | | - Hard **silica (SiO~2~) double | | | shells** (cell walls) that | | | last long after the organism | | | dies diatomaceous earth | | | | | | - Shells can withstand | | | [extreme] | | | pressure! | +-----------------------------------+-----------------------------------+ | **Brown Algae** | - **Multicellular** | | | | | | - **Not motile** | | | | | | - **Photoautotrophs** | | | | | | - **Chloroplasts (with 4 | | | membranes: 2° | | | endocytosis)** contain a | | | **brownish pigment | | | (fucoxanthin)** to trap | | | light energy | | | | | | - Includes **kelp**, which make | | | up forests in the Pacific | | | ocean along the North | | | American Coast | | | | | | - **Appearance = analogous | | | to plants** | | | | | | - **Stipes:** Stem or | | | trunk-like structures | | | | | | - **Blades:** Leaf-like | | | structures | | | | | | - **Floats**: | | | Gas-filled structures | | | that help kelp float | | | in water | | | | | | - **Holdfasts**: anchor | | | alga to sediment | | | | | | - No true tissues or | | | organs, chains of | | | cells with connected | | | cytoplasm (hyphae), | | | similar to fungi | | | | | | - **Alternation of | | | Generations**: alternate | | | between haploid & diploid | | | multicellular stages similar | | | to plants | +-----------------------------------+-----------------------------------+ | **Oomycetes** | - **Multicellular** | | | | | | - **Not motile** | | | | | | - **Chemoheterotrophs | | | (decomposers or parasites, | | | much like fungi)** | | | | | | - **Fungus-like bodies (strands | | | of multinucleate hyphae | | | (mitosis without cytokinesis) | | | that make up mass called | | | mycelium)** | | | | | | - **Unlike fungi: have | | | cellulose cell walls | | | (like plants)** | | | | | | - **Water molds, white rusts, & | | | downy mildews** | | | | | | - **Water molds mostly | | | decompose dead organisms | | | in freshwater** | | | | | | - **White rusts/ downy | | | mildews mainly plant | | | parasites** | +-----------------------------------+-----------------------------------+ - **Alveolates (Dinoflagellates, Apicomplexans, & Ciliates)** - Contain membrane enclosed sacs (**alveoli)** just under cell membrane\ Alveolate phylogeny. Outgroup is stramenopila. Within the alveolates: dinoflagellates and apicomplexans are closer relatives than ciliates Table 3. Alveolate protists covered in this course +-----------------------------------+-----------------------------------+ | **Subgroup** | **Description** | +===================================+===================================+ | **Dinoflagellates** | - **Unicellular** | | | | | | - **Motile with 2 flagella (sit | | | in grooves in cellulose | | | plates of armored cell | | | wall)** | | | | | | - **Some mixotrophs, some | | | photoautotrophs, some | | | chemoheterotrophs** | | | | | | - **Likely photosynthetic | | | common ancestor, 2° | | | endosymbiosis for | | | chloroplasts** | | | | | | - **Carotenoids | | | (red/orange): Most common | | | photopigments in | | | photosynthetic | | | dinoflagellates** | | | | | | - **Found in marine and | | | freshwater** | | | | | | - **Red tides: algal blooms | | | of dinoflagellates | | | (population surges) | | | release high | | | concentrations of toxins | | | & change color of water** | | | | | | - **Some dinoflagellates | | | are endosymbionts of | | | corals** | | | | | | - **Provide food from | | | photosynthesis to | | | coral host; coral | | | houses them & gives | | | them usable | | | nitrogen** | | | | | | - **Coral bleaching: | | | disturbed corals | | | eject dinoflagellates | | | and later die** | +-----------------------------------+-----------------------------------+ | **Apicomplexans** | - **Unicellular** | | | | | | - **Motile via gliding | | | mechanism (involves | | | microfilaments & adhesion | | | proteins)** | | | | | | - **Chemoheterotrophs: obligate | | | intracellular parasites of | | | animals** | | | | | | - **Sporozoite cells = | | | infectious & have apex | | | (tip) with organelles for | | | infections** | | | | | | - **Most have complex life | | | cycles with 2 different | | | hosts** | | | | | | - **Ex: Malaria caused by | | | (*Plasmodium falciparum*) | | | cycles between mosquitos | | | & human host. Leading | | | cause of human death due | | | to parasite.** | +-----------------------------------+-----------------------------------+ | **Ciliates** | - **Unicellular** | | | | | | - **Motile with cilia** | | | | | | - **Some covered in cilia, | | | some have localized | | | cilia** | | | | | | - **Chemoheterotrophs: mostly | | | predators of bacteria or | | | other unicellular protists** | | | | | | - Mostly **free-living in | | | freshwater** | | | | | | - Cell structures: | | | | | | - **Cilia** | | | | | | - **Macronucleus** and a | | | **Micronucleus** (can | | | exchange micronuclei | | | sexually: conjugation) | | | | | | - **Macronucleus used | | | for regular | | | functions, | | | disintegrates during | | | mitosis, micronuclei | | | form new | | | macronucleus** | | | | | | - **Contractile vacuole | | | (fills with water from | | | hypotonic environment by | | | osmosis, then expels it | | | forcefully) & Pellicle | | | (flexible protein under | | | membrane)** | | | | | | - **Oral groove and | | | gullet** for feeding by | | | phagocytosis ingested | | | into **food vacuole | | | (fuses with lysosome** | | | for digestion) | +-----------------------------------+-----------------------------------+ - **Rhizarians (Cercozoans, Radiolarians, & Foraminiferans)** - Many = amoebas (generic name for protists that move **with pseudopodia**) - Radiolarians & Foraminiferans (forams) also called **shelled amoebas** - Rhizarian pseudopodia are thread-like (filopodia) & can be used for movement and/or feeding - Some have flagella for movement and use pseudopodia for feeding  Table 4. Rhizarian protists covered in this course +-----------------------------------+-----------------------------------+ | **Subgroup** | **Description** | +===================================+===================================+ | **Radiolarians** | - **Unicellular** | | | | | | | | | | | | - **Not motile** | | | | | | - **Chemoheterotrophs: | | | predators of bacteria or | | | other unicellular protists** | | | | | | - **Feed with pseudopodia | | | that protrude out through | | | silica skeleton/shell** | | | | | | | | | | | | - Most are **marine** | +-----------------------------------+-----------------------------------+ | **Foraminiferans (forams)** | - **Unicellular** | | | | | | | | | | | | - **Motile with pseudopodia** | | | | | | - **Chemoheterotrophs: | | | predators of bacteria or | | | other unicellular protists** | | | | | | - **Feed with pseudopodia | | | that protrude out through | | | calcium carbonate shells | | | (tests)** | | | | | | | | | | | | - Most are **marine (fossil | | | tests often used to estimate | | | sediment ages and changes in | | | ocean temperatures over | | | time)** | +-----------------------------------+-----------------------------------+ | **Cercozoans** | - **Unicellular** | | | | | | | | | | | | - **Motile with flagella** | | | | | | | | | | | | - **Most = Chemoheterotrophs: | | | parasites or predators of | | | bacteria or other unicellular | | | protists that feed with | | | pseudopodia** | | | | | | - **Some mixotrophs or | | | photoautotrophs** | | | | | | | | | | | | - Found in marine & freshwaters | | | and Soil | +-----------------------------------+-----------------------------------+ 2. Archaeplastid protists ========================= - **Photoautotrophic algae (red and green): chloroplasts due to 1° endosymbiosis of cyanobacteria in ancestor** - **Include unicellular, colonial, and multicellular species** - **Land plants (Kingdom Plantae) descended from charophyte green algae** Archaeplastid tree. SAR is outgroup. Red algae branch off next. Then Chlorophytes, then charophytes and plants. Note that plants are not protists Table 5. Archaeplastid protists covered in this course +-----------------------------------+-----------------------------------+ | **Subgroup** | **Description** | +===================================+===================================+ | **Red Algae** (aka Rhodophytes) | - **Most Multicellular (some | | | Unicellular or Colonial)** | | | | | | | | | | | | - **Not motile** | | | | | | - **Photoautotrophs with red | | | pigment (phycoerythrin): | | | hides green of chlorophyll** | | | | | | - **Absorbs blue/green | | | light (penetrate deeper | | | into water)** | | | | | | | | | | | | - Mainly **marine (many in | | | warm, tropical coastal | | | waters)** | | | | | | - **Reproduce sexually with | | | alternation of generations**: | | | alternate between haploid & | | | diploid multicellular stages | | | similar to plants | +-----------------------------------+-----------------------------------+ | **Chlorophytes** (green algae) | - **Some unicellular (ex: | | | *Chlamydomonas*), some | | | colonial (ex: *Pediastrum*), | | | some multicellular (ex: *Ulva | | | or Volvox*)** | | | | | | - **Some motile with flagella, | | | some sessile** | | | | | | - **Photoautotrophs with | | | Chlorophyll A as primary | | | photopigment in | | | chloroplasts** | | | | | | - **Have cellulose cell walls | | | and store starch in plastids | | | (like plants)** | | | | | | - **Most live in freshwater, | | | some marine or terrestrial** | | | | | | - Most reproduce **asexually | | | and sexually** (complex life | | | cycles) & have | | | **biflagellated gametes** | | | with cup shaped chloroplasts | | | of opposite mating strains | | | (+/-) | | | | | | - Some have **alternation | | | of generations** (see | | | above) | +-----------------------------------+-----------------------------------+ | **Charophytes** (also green | - **Some unicellular, some | | algae) | colonial, some | | | multicellular** | | | | | | - **Sessile** | | | | | | - **Photoautotrophs with | | | Chlorophyll A as primary | | | photopigment in | | | chloroplasts** | | | | | | - **Have cellulose cell walls | | | and store starch in plastids | | | (like plants)** | | | | | | - **Most live in freshwater** | | | | | | - **Use phragmoplast cell | | | division (like plants) for | | | cell plate formation** | | | | | | - **Complex life cycle | | | (haplontic): all stages | | | haploid except diploid | | | zygote** | | | | | | - **One branch gave rise to | | | Kingdom Plantae** | | | | | | - **"Green algae" and | | | Charophytes both | | | paraphyletic** | +-----------------------------------+-----------------------------------+ Excavata protists ================= - **Many have feeding groove on cell surface (excavation)** - **Paraphyletic supergroup** - **2 Main groups** - **Metamonads: Diplomonads & Parabasalids** - **Have reduced mitochondria & mostly anaerobic** - **Euglenozoans** (aka Discobans)**:** Kinetoplastids & Euglenids - Have flagella with central rod with spiral or crystalline structure  Table 6. Excavate protists covered in this course +-----------------------------------+-----------------------------------+ | **Subgroup** | **Description** | +===================================+===================================+ | **Metamonads: Diplomonads** | - **Unicellular** | | | | | | - **Motile with multiple | | | flagella** | | | | | | - **Chemoheterotrophs (many = | | | parasites, ex: *Giardia | | | species)*** | | | | | | - **Have reduced | | | mitochondria (mitosomes) | | | that lack electron | | | transport chains** | | | | | | - **Mainly rely on | | | anaerobic fermentation** | | | | | | - **Cells each have 2 equal | | | sized nuclei (dikaryotic)** | +-----------------------------------+-----------------------------------+ | **Metamonads: Parabasalids** | - **Unicellular** | | | | | | - **Motile with flagella** | | | | | | - **Chemoheterotrophs** | | | | | | - **Have reduced | | | mitochondria | | | (hydrogenosomes) that can | | | make some ATP | | | anaerobically, releasing | | | H~2~ gas** | | | | | | - **Includes STI parasite of | | | Trichomoniasis: *Trichomonas | | | vaginalis*** | +-----------------------------------+-----------------------------------+ | **Euglenozoans: Kinetoplastids** | - **Unicellular** | | | | | | - **Motile with flagella** | | | | | | - **Chemoheterotrophs | | | (predators of prokaryotes or | | | parasites)** | | | | | | - **One large mitochondrion | | | per cell (kinetoplast) | | | with large DNA mass** | | | | | | - **Parasite ex: | | | *Trypanosoma:* African | | | sleeping sickness | | | (transmitted by tsetse | | | fly bites)** | | | | | | - **Evades human immune | | | system by changing | | | surface proteins in | | | membrane regularly** | +-----------------------------------+-----------------------------------+ | **Euglenozoans: Euglenids** | - **Unicellular** | | | | | | - **Motile with flagella** | | | | | | - **Some mixotrophs, others | | | chemoheterotrophic | | | predators** | | | | | | - **Mixotrophs:** Have an | | | **eyespot & light | | | detector**, which | | | together detect light | | | | | | - Important **freshwater** | | | organisms | | | | | | - **Pellicle**: layer of | | | elastic proteins under | | | the cell membrane, but no | | | cell wall | | | | | | - Have a **contractile | | | vacuole**, which collects | | | water that enters the | | | cell & then contracts & | | | releases water when it is | | | full | +-----------------------------------+-----------------------------------+ Amorphea **(aka Unikonta)** protists ==================================== - **Amoebozoa: Slime molds, Tubulinids, & Entamoebas (Polytomy)** - **Opisthokonta: Nucleariids & Fungi and Choanoflagellates & Animals** Amorphea tree. Excavates are outgroup. Then splits into 2 groups: amoebozoa and Opisthokonta. AMoebozoa has polytomy to tubulinids, slime molds, and entamoebas. Osithokonta splits to fungi and nucleariids vs. choanoflagellates and animals. Table 7. Amorphea protists covered in this course +-----------------------------------+-----------------------------------+ | **Subgroup** | **Description** | +===================================+===================================+ | **Amoebozoa: Slime molds** | - **As a group: similar to | | | fungi by convergence. Use | | | "fruiting bodies" to release | | | spores** | | | | | | - **Motile via crawling** | | | | | | - **Amoeboid stages use | | | pseudopodia** | | | | | | - **Aggregate or plasmodium | | | stages crawl in similar | | | manner** | | | | | | - **Chemoheterotrophic** | | | | | | **[Plasmodial Slime | | | molds]** | | | | | | - **Not truly multicellular: | | | multinucleate diploid | | | crawling plasmodium = | | | continuous cytoplasm that can | | | be streamed throughout the | | | organism** | | | | | | - **Mitotic divisions | | | without cytokinesis** | | | | | | - **Dry conditions: grow | | | sporangia: make haploid | | | spores by meiosis** | | | | | | - **Have amoeboid and | | | flagellated gametes (2 | | | different sets)** | | | | | | - **Decomposers in | | | soil/mulch/rotting logs** | | | | | | - **Often yellow to orange | | | color\ | | | ** | | | | | | **[Cellular Slime | | | molds]** | | | | | | - **Unicellular as | | | bacteria-hunting amoebas | | | (haploid)** | | | | | | - **Aggregate into | | | multicellular haploid | | | migrating slug when food | | | supply low & grow sporangia | | | to make asexual spores.** | | | | | | - **Have asexual and sexual | | | life cycles** | | | | | | - **Sexual fertilization by | | | haploid amoeboid cell | | | fusion makes zygote, | | | which divides by | | | meiosis** | | | | | | - **Haplontic: all stages | | | haploid except diploid | | | zygote** | +-----------------------------------+-----------------------------------+ | **Amoebozoa: Tubulinids** | - **Unicellular** | | | | | | - **Motile with pseudopodia | | | (lobe/tube shaped)** | | | | | | - **Chemoheterotrophs that use | | | phagocytosis (most are | | | predators of unicellular | | | organisms; some detritivores: | | | eat dead/decaying matter)** | | | | | | - **Common in soil, freshwater, | | | & marine habitats** | | | | | | - **Includes true amoebas | | | (Genus *Amoeba*)** | +-----------------------------------+-----------------------------------+ | **Amoebozoa: Entamoebas** | - **Unicellular** | | | | | | - **Motile with pseudopodia** | | | | | | - **Chemoheterotrophs: | | | symbiotic parasites of | | | animals** | | | | | | - **Includes *Entamoeba | | | histolytica*: cause of | | | amoebic dysentery (3^rd^ | | | leading cause of human death | | | due to eukaryotic parasite)** | +-----------------------------------+-----------------------------------+ | **Opisthokonta: Nucleariids** | - **Unicellular** | | | | | | - **Motile with pseudopodia** | | | | | | - **Chemoheterotrophs: feed on | | | algae & bacteria by | | | endocytosis** | | | | | | - **Amoebas that are closest | | | living relatives of Kingdom | | | Fungi** | +-----------------------------------+-----------------------------------+ | **Opisthokonta: | - **Unicellular & Colonial** | | Choanoflagellates** | | | | - **Motile with flagella: also | | | used to draw food toward | | | cell** | | | | | | - **Chemoheterotrophs: ingest | | | bacteria and debris by | | | phagocytosis** | | | | | | - **Have "collar" of microvilli | | | (membrane foldings)** | | | | | | - **Look and behave | | | identical to collar cells | | | of sponges (Kingdom | | | Animalia, Phylum | | | Porifera)** | | | | | | - **Closest living relatives of | | | Kingdom Animalia** | +-----------------------------------+-----------------------------------+