2/29  Evidence of endosymbiosis

Spring Break plans  Ecology Unit!

3/1  Singled cell Eukaryotes and the environment  Single Celled Eukaryotes and humans  Bacteria transformation, transduction, recombination, and conjugation  R plasmids  F Plasmids

animated-timeline-earth-history  How did eukaryotes ever show up? shows/monsters-inside- me/videos/african-sleeping- sickness/

 How did eukaryotes ever show up?

 Mitochondria have their own DNA… its circular weirdddddddddddd

 Mitochondria has its own membrane…  what a eukaryote’s cell membrane was not good enough!?

 Mitochondria have enzymes and transport system on their inner membranes similar to prokaryotes alive today

 Mitochondria divide themselves  THERE IS NO WAY TO MAKE MORE Mitochondria if you remove them from a cell

 Mitochondria have their own ribosomes

 All of the above also applies to chloroplasts and other “plastids”

 Chloroplasts and mitochondria are nearly the exact same size as bacteria

The theory of endosymbiosis  Some bacteria engulfed other bacteria  Instead of digesting the bacteria, the two lived together and each was benefitted  How we think eukaryotes came to be

Endosymbiosis  Protists formed by endosymbiosis  Protists are presumably the ancestors of all multicellular organisms

Origin of Mitochondria and Plastids  Endosymbiont theory proposes that mitochondria and plastids were formerly small prokaryotes that began living within larger cells  An endosymbiont is a cell that lives within a host cell  Prokaryote ancestors to mitochondria and plastids probably entered the host cell as undigested prey or internal parasites © 2014 Pearson Education, Inc.

 The relationship between endosymbiont and host cells was mutually beneficial  Anaerobic host cells benefited from endosymbionts’ ability to take advantage of an increasingly aerobic world  Heterotrophic host cells benefited from the nutrients produced by photosynthetic endosymbionts  In the process of becoming more interdependent, the host and endosymbionts would have become a single organism © 2014 Pearson Education, Inc.

 Serial endosymbiosis supposes that mitochondria evolved before plastids through a sequence of endosymbiotic events © 2014 Pearson Education, Inc.

Figure 25.3 Cytoplasm DNA Nucleus Engulfing of aerobic bacterium Engulfing of photo- synthetic bacterium Mitochondrion Mito- chondrion Plastid Plasma membrane Endoplasmic reticulum Nuclear envelope Ancestral prokaryote Ancestral heterotrophic eukaryote Ancestral photosynthetic eukaryote

 DNA sequence analysis indicates that mitochondria arose from an alpha proteobacterium  Eukaryotic mitochondria descended from a single common ancestor  Plastids arose from an engulfed cyanobacterium  Some photosynthetic protists may have been engulfed to become endosymbionts themselves © 2014 Pearson Education, Inc.

 The ancestral host cell may have been an archaean or a “protoeukaryote,” from a lineage related to, but diverged from, archaeal ancestors © 2014 Pearson Education, Inc.

Overview: Shape Changers  Protist is the informal name of the diverse group of mostly unicellular eukaryotes  Some protists, like the ciliate Didinium, are able to perform dramatic shape changes due to the structural complexity of their cells © 2014 Pearson Education, Inc.

Figure 25.1

Concept 25.1: Eukaryotes arose by endosymbiosis more than 1.8 billion years ago  Early eukaryotes were unicellular  Eukaryotic cells have organelles and are structurally more complex than prokaryotic cells  A well-developed cytoskeleton enables eukaryotic cells to have asymmetrical forms and to change shape © 2014 Pearson Education, Inc.

The Fossil Record of Early Eukaryotes  Chemical evidence for the presence of eukaryotes dates back to 2.7 billion years ago  The earliest fossils of eukaryotic cells are 1.8 billion years old © 2014 Pearson Education, Inc.

 Initial diversification of eukaryotes occurred 1.8 to 1.3 billion years ago  Novel features of eukaryotes, including complex multicellularity, sexual life cycles, and photosynthesis, arose 1.3 billion to 635 million years ago  The first large, multicellular eukaryotes represented by the Ediacaran biota evolved 635 to 535 million years ago © 2014 Pearson Education, Inc.

Figure bya mya 1.8 bya1.5 bya1.3 bya1.2 bya 20  m 25  m (a)A 1.8-billion- year-old fossil eukaryote (b)Tappania, a 1.5-billion-year-old fossil that may represent an early alga or fungus (c)Bangiomorpha, an ancient red alga 20  m (d)Proterocladus, classified as a green alga (e)Bonneia, a vase-shaped eukaryote (f) An early member of the Ediacaran biota (g)Spriggina floundersi, an early animal with many body segments 750 mya635 mya600 mya 550 mya 535 mya 1 cm 0.5 cm

© 2014 Pearson Education, Inc. Table 25.1

Origin of Mitochondria and Plastids  Endosymbiont theory proposes that mitochondria and plastids were formerly small prokaryotes that began living within larger cells  An endosymbiont is a cell that lives within a host cell  Prokaryote ancestors to mitochondria and plastids probably entered the host cell as undigested prey or internal parasites © 2014 Pearson Education, Inc.

 Serial endosymbiosis supposes that mitochondria evolved before plastids through a sequence of endosymbiotic events © 2014 Pearson Education, Inc.

Figure 25.3 Cytoplasm DNA Nucleus Engulfing of aerobic bacterium Engulfing of photo- synthetic bacterium Mitochondrion Mito- chondrion Plastid Plasma membrane Endoplasmic reticulum Nuclear envelope Ancestral prokaryote Ancestral heterotrophic eukaryote Ancestral photosynthetic eukaryote

 DNA sequence analysis indicates that mitochondria arose from an alpha proteobacterium  Eukaryotic mitochondria descended from a single common ancestor  Plastids arose from an engulfed cyanobacterium  Some photosynthetic protists may have been engulfed to become endosymbionts themselves © 2014 Pearson Education, Inc.

 The ancestral host cell may have been an archaean or a “protoeukaryote,” from a lineage related to, but diverged from, archaeal ancestors © 2014 Pearson Education, Inc.

Concept 25.2: Multicellularity has originated several times in eukaryotes  The evolution of eukaryotic cells allowed for a greater range of unicellular forms  A second wave of diversification occurred when multicellularity evolved and gave rise to algae, plants, fungi, and animals © 2014 Pearson Education, Inc.

Multicellular Colonies  The first multicellular forms were colonies, collections of cells that are connected to one another but show little or no cellular differentiation  Multicellular colonies consist of simple filaments, balls, or cell sheets  Colonial cells may be attached by shared cell walls or, in cells that lack rigid walls, held together by proteins that physically connect adjacent cells © 2014 Pearson Education, Inc.

Figure 25.5 Pediastrum

Independent Origins of Complex Multicellularity  Multicellular organisms with differentiated cells originated multiple times over the course of eukaryotic evolution  Genetic and morphological evidence indicates that lineages of red, green, and brown algae, plants, fungi, and animals arose independently from different single-celled ancestors © 2014 Pearson Education, Inc.

 Volvox is a multicellular green algae that forms a monophyletic group with a single-celled alga (Chlamydomonas) and several colonial species  Volvox and all colonial members of this group have proteins homologous to those found in the cell wall of Chlamydomonas  Multicellularity in Volvox may have originated through evolution of increasingly complex colonial forms descended from a single-celled common ancestor © 2014 Pearson Education, Inc. Video: Chlamydomonas

© 2014 Pearson Education, Inc. Figure 25.6 Flagellum Cytoplasm Outer cell wall Inner cell wall Outer cell wall Cytoplasm Extracellular matrix (ECM) Chlamydomonas Gonium Pandorina Volvox

 Only a few novel genes account for morphological differences between Volvox and Chlamydomonas  The transition to multicellularity may result from changes in how existing genes are used rather than the origin of large numbers of novel genes © 2014 Pearson Education, Inc.

Steps in the Origin of Multicellular Animals  Choanoflagellates are the closest living relatives of animals  The common ancestor of choanoflagellates and living animals may have resembled present-day choanoflagellates © 2014 Pearson Education, Inc.

Figure 25.7 Individual choanoflagellate Choano- flagellates Other animals Collar cell (choanocyte) Sponges Animals OTHER EUKARY- OTES

 The origin of multicellularity in animals required mechanisms for cells to adhere to each other and to communicate with each other (cell signaling)  Molecular similarities in domains of proteins functioning in cell adherence (cadherins) and cell signaling have been found between modern choanoflagellates and representative animals © 2014 Pearson Education, Inc.

Nutritional and Metabolic Adaptations  Prokaryotes can be categorized by how they obtain energy and carbon  Phototrophs obtain energy from light  Chemotrophs obtain energy from chemicals  Autotrophs require CO 2 as a carbon source  Heterotrophs require an organic nutrient to make organic compounds

 Energy and carbon sources are combined to give four major modes of nutrition  Photoautotrophy  Chemoautotrophy  Photoheterotrophy  Chemoheterotrophy

 The transition to multicellularity in animals involved new ways of using proteins encoded by genes found in choanoflagellates rather than the evolution of many novel genes © 2014 Pearson Education, Inc.

Concept 25.4: Single-celled eukaryotes play key roles in ecological communities and affect human health  The majority of the eukaryotic lineages are composed of protists  Protists exhibit a wide range of structural and functional diversity © 2014 Pearson Education, Inc.

 Protists are found in diverse aquatic environments  Some protists reproduce asexually, while others reproduce sexually, or by the sexual processes of meiosis and fertilization © 2014 Pearson Education, Inc.

 Protists show a wide range of nutritional diversity, including  Photoautotrophs, which contain chloroplasts  Heterotrophs, which absorb organic molecules or ingest larger food particles  Mixotrophs, which combine photosynthesis and heterotrophic nutrition © 2014 Pearson Education, Inc.

Photosynthetic Protists  Many protists are important producers that obtain energy from the sun  In aquatic environments, photosynthetic protists and prokaryotes are the main producers  In aquatic environments, photosynthetic protists are limited by nutrients  These populations can explode when limiting nutrients are added © 2014 Pearson Education, Inc.

Figure Other consumers Herbivorous plankton Carnivorous plankton Protistan producers Prokaryotic producers

 Diatoms are a major component of the phytoplankton  After a diatom population has bloomed, many dead individuals fall to the ocean floor undecomposed  This removes carbon dioxide from the atmosphere and “pumps” it to the ocean floor © 2014 Pearson Education, Inc.

 The biomass and growth of photosynthetic protists and prokaryotes have declined as sea surface temperature has increased  Warmer surface temperatures may prevent nutrient upwelling, a process critical to the growth of marine producers © 2014 Pearson Education, Inc.

 If sea surface temperature continues to warm due to global warming, this could have large effects on  Marine ecosystems  Fishery yields  The global carbon cycle © 2014 Pearson Education, Inc.

Figure NI SI S SP SA EA NA A EP NP Sea-surface temperature (SST) change (  C) −2.50− (a)(b) Southern (S) South Pacific (SP) Equatorial Pacific (EP) North Pacific (NP) South Indian (SI) North Indian (NI) South Atlantic (SA) Equatorial Atlantic (EA) North Atlantic (NA) Arctic (A) Chlorophyll change (mg/m 2 yr) −0.02−

Figure 25.24a Sea-surface temperature (SST) change (  C) −2.50− SA SP EA NA A EPNP NI SI S (a)

Figure 25.24b −0.02− Southern (S) South Pacific (SP) Equatorial Pacific (EP) North Pacific (NP) South Indian (SI) North Indian (NI) South Atlantic (SA) Equatorial Atlantic (EA) North Atlantic (NA) Arctic (A) Chlorophyll change (mg/m 2 yr) (b)

Symbiotic Protists  Some protist symbionts benefit their hosts  Dinoflagellates nourish coral polyps that build reefs  Wood-digesting protists digest cellulose in the gut of termites © 2014 Pearson Education, Inc.

10  m Figure 25.25

 Some protists are parasitic  Plasmodium causes malaria  Pfiesteria shumwayae is a dinoflagellate that causes fish kills  Phytophthora ramorum causes sudden oak death  Phytophthora infestans causes potato late blight © 2014 Pearson Education, Inc.

Effects on Human Health  Protists that cause infectious disease can pose major challenges to human immune systems and public health  Trypanosoma is an excavate that causes sleeping sickness in humans © 2014 Pearson Education, Inc.

 Trypanosomes evade immune responses by switching surface proteins  A cell produces millions of copies of a single protein  The new generation produces millions of copies of a different protein  These frequent changes prevent the host from developing immunity © 2014 Pearson Education, Inc.

 Entamoebas are amoebozoan parasites of vertebrates and some invertebrates  Entamoeba histolytica causes amebic dysentery, the third-leading cause of human death due to eukaryotic parasites © 2014 Pearson Education, Inc.

 Apicomplexans are alveolate parasites of animals, and some cause serious human diseases  Most have sexual and asexual stages that require two or more different host species for completion © 2014 Pearson Education, Inc.

Figure  m Apex Red blood cell Merozoite Liver cell Red blood cells Merozoite (n) Zygote (2n) Oocyst MEIOSIS Sporozoites (n) Inside mosquito Inside human FERTILIZATION Gametes Gametocytes (n) Key Haploid (n) Diploid (2n)

Genetic Recombination  Genetic recombination, the combining of DNA from two sources, contributes to diversity  Prokaryotic DNA from different individuals can be brought together by transformation, transduction, and conjugation  Movement of genes among individuals from different species is called horizontal gene transfer

Transformation and Transduction  A prokaryotic cell can take up and incorporate foreign DNA from the surrounding environment in a process called transformation  Transduction is the movement of genes between bacteria by bacteriophages (viruses that infect bacteria)

Figure Phage infects bacterial donor cell with A  and B  alleles. Donor cell A  B  Phage DNA

Figure Phage infects bacterial donor cell with A  and B  alleles. Phage DNA is replicated and proteins synthesized. Donor cell AA BB A  B  Phage DNA

Figure Phage infects bacterial donor cell with A  and B  alleles. Phage DNA is replicated and proteins synthesized. Fragment of DNA with A  allele is packaged within a phage capsid. Donor cell AA AA BB A  B  Phage DNA

432 1 Phage infects bacterial donor cell with A  and B  alleles. Phage DNA is replicated and proteins synthesized. Fragment of DNA with A  allele is packaged within a phage capsid. Phage with A  allele infects bacterial recipient cell. Recipient cell Crossing over Donor cell A − B − AA AA AA BB A  B  Phage DNA Figure

Figure Phage infects bacterial donor cell with A  and B  alleles. Incorporation of phage DNA creates recombinant cell with genotype A  B . Phage DNA is replicated and proteins synthesized. Fragment of DNA with A  allele is packaged within a phage capsid. Phage with A  allele infects bacterial recipient cell. Recombinant cell Recipient cell Crossing over Donor cell A  B − A − B − AA AA AA BB A  B  Phage DNA

Conjugation and Plasmids  Conjugation is the process where genetic material is transferred between prokaryotic cells  In bacteria, the DNA transfer is one way  In E. coli, the donor cell attaches to a recipient by a pilus, pulls it closer, and transfers DNA

Figure Sex pilus 1  m

 The F factor is a piece of DNA required for the production of pili  Cells containing the F plasmid (F + ) function as DNA donors during conjugation  Cells without the F factor (F – ) function as DNA recipients during conjugation  The F factor is transferable during conjugation

Figure One strand of F  cell plasmid DNA breaks at arrowhead. Bacterial chromosome Bacterial chromosome F plasmid Mating bridge F  cell (donor) F − cell (recipient)

Figure One strand of F  cell plasmid DNA breaks at arrowhead. Bacterial chromosome Bacterial chromosome F plasmid Mating bridge F  cell (donor) F − cell (recipient) Broken strand peels off and enters F − cell.

Figure One strand of F  cell plasmid DNA breaks at arrowhead. Bacterial chromosome Bacterial chromosome F plasmid Mating bridge F  cell (donor) F − cell (recipient) Broken strand peels off and enters F − cell. Donor and recipient cells synthesize complementary DNA strands.

Figure One strand of F  cell plasmid DNA breaks at arrowhead. Bacterial chromosome Bacterial chromosome F plasmid Mating bridge F  cell (donor) F − cell (recipient) F  cell F  cell Broken strand peels off and enters F − cell. Recipient cell is now a recombinant F  cell. Donor and recipient cells synthesize complementary DNA strands.

Four Supergroups of Eukaryotes  It is no longer thought that amitochondriates (lacking mitochondria) are the oldest lineage of eukaryotes  Many have been shown to have mitochondria and have been reclassified  Our understanding of the relationships among protist groups continues to change rapidly  One hypothesis divides all eukaryotes (including protists) into four supergroups © 2014 Pearson Education, Inc.

Figure 25.9 Stramen- opiles Diplomonads Parabasalids Euglenozoans Excavata Alveo- lates Rhiza- rians Diatoms Brown algae Dinoflagellates Apicomplexans Ciliates Forams Cercozoans “SAR” clade Green algae Amoebo- zoans Red algae Chlorophytes Charophytes Land plants Archaeplastida Opisthokonts Unikonta Gymnamoebas Slime molds Nucleariids Fungi Choanoflagellates Animals 100  m 50  m “SAR” Clade Excavata 5  m Archaeplastida 20  m 50  m Unikonta 100  m

© 2014 Pearson Education, Inc. Figure 25.9a Stramen- opiles Diplomonads Parabasalids Euglenozoans Excavata Alveo- lates Rhiza- rians Diatoms Brown algae Dinoflagellates Apicomplexans Ciliates Forams Cercozoans “SAR” clade Green algae Amoebo- zoans Red algae Chlorophytes Charophytes Land plants Archaeplastida Opisthokonts Unikonta Gymnamoebas Slime molds Nucleariids Fungi Choanoflagellates Animals

© 2014 Pearson Education, Inc. Figure 25.9aa Stramen- opiles Diplomonads Parabasalids Euglenozoans Excavata Alveo- lates Rhiza- rians Diatoms Brown algae Dinoflagellates Apicomplexans Ciliates Forams Cercozoans “SAR” clade

© 2014 Pearson Education, Inc. Figure 25.9ab Green algae Amoebo- zoans Red algae Chlorophytes Charophytes Land plants Archaeplastida Opisthokonts Unikonta Gymnamoebas Slime molds Nucleariids Fungi Choanoflagellates Animals

© 2014 Pearson Education, Inc. Figure 25.9b Excavata“SAR” Clade Archaeplastida 50  m 20  m 5  m Unikonta 100  m

© 2014 Pearson Education, Inc. Figure 25.9ba Giardia intestinalis, a diplomonad parasite 5  m

© 2014 Pearson Education, Inc. Figure 25.9bb Diatom diversity 50  m

© 2014 Pearson Education, Inc. Figure 25.9bc Globigerina, a rhizarian in the SAR supergroup 100  m

© 2014 Pearson Education, Inc. Figure 25.9bca Globigerina, a rhizarian in the SAR supergroup 100  m

© 2014 Pearson Education, Inc. Figure 25.9bcb

© 2014 Pearson Education, Inc. Figure 25.9bd Volvox, a multicellular freshwater green alga 20  m 50  m

© 2014 Pearson Education, Inc. Figure 25.9bda Volvox, a multicellular freshwater green alga 50  m

© 2014 Pearson Education, Inc. Figure 25.9bdb 20  m

© 2014 Pearson Education, Inc. Figure 25.9be 100  m A unikont amoeba

Excavates  The supergroup Excavata is characterized by its cytoskeleton  Some members have a feeding groove  This monophyletic group includes the diplomonads, parabasalids, and euglenozoans © 2014 Pearson Education, Inc.

Figure 25.UN02 Diplomonads Parabasalids Euglenozoans Excavata SAR clade Archaeplastida Unikonta

Diplomonads and Parabasalids  These two groups lack plastids and have modified mitochondria, and most live in anaerobic environments  Diplomonads  Have reduced mitochondria called mitosomes  Derive energy from anaerobic biochemical pathways  Are often parasites, for example, Giardia intestinalis  Move using multiple flagella © 2014 Pearson Education, Inc.

 Parabasalids  Have reduced mitochondria called hydrogenosomes that generate some energy anaerobically  Include Trichomonas vaginalis, a sexually transmitted parasite © 2014 Pearson Education, Inc.

Figure The parabasalid parasite, Trichomonas vaginalis (colorized SEM) Undulating membrane Flagella 5  m

Euglenozoans  Euglenozoa is a diverse clade that includes predatory heterotrophs, photosynthetic autotrophs, and parasites  The main feature distinguishing them as a clade is a spiral or crystalline rod inside their flagella  This clade includes the euglenids and kinetoplastids © 2014 Pearson Education, Inc. Video: Euglena Motion Video: Euglena

© 2014 Pearson Education, Inc. Figure Euglenozoan flagellum Ring of microtubules (cross section) Crystalline rod (cross section) 8  m 0.2  m Flagella

© 2014 Pearson Education, Inc. Figure 25.11a Ring of microtubules (cross section) Crystalline rod (cross section) 0.2  m

 Euglenids have one or two flagella that emerge from a pocket at one end of the cell  Some species can be both autotrophic and heterotrophic © 2014 Pearson Education, Inc.

 Kinetoplastids have a single mitochondrion with an organized mass of DNA called a kinetoplast  They include free-living consumers of prokaryotes in aquatic ecosystems and parasites of animals, plants, and other protists  This group includes Trypanosoma, which causes sleeping sickness in humans © 2014 Pearson Education, Inc.

Figure Trypanosoma, the kinetoplastid that causes sleeping sickness 9  m

The “SAR” Clade  The “SAR” clade is a diverse monophyletic supergroup named for the first letters of its three major clades, stramenopiles, alveolates, and rhizarians © 2014 Pearson Education, Inc.

Figure 25.UN03 Archaeplastida Unikonta SAR clade Rhizarians Alveolates Stramenopiles Excavata Diatoms Brown algae Dinoflagellates Apicomplexans Ciliates Forams Cercozoans

Stramenopiles  The subgroup stramenopiles includes the most important photosynthetic organisms on Earth  Diatoms and brown algae are members of the stramenopiles clade  Diatoms are highly diverse, unicellular algae with a unique two-part, glass-like wall of silicon dioxide © 2014 Pearson Education, Inc. Video: Various Diatoms Video: Diatoms Moving

© 2014 Pearson Education, Inc. Figure The diatom Triceratium morlandii (colorized SEM) 40  m

 Brown algae are the largest and most complex algae  All are multicellular, and most are marine  Brown algae include many species commonly called “seaweeds” © 2014 Pearson Education, Inc.

 Brown algal seaweeds have plantlike structures: the rootlike holdfast, which anchors the alga, and a stemlike stipe, which supports the leaflike blades  Similarities between algae and plants are examples of analogous structures © 2014 Pearson Education, Inc.

Figure Blade Stipe Holdfast

Alveolates  The alveolates are a subgroup of the SAR clade that have membrane-bounded sacs (alveoli) just under the plasma membrane  Dinoflagellates and ciliates are members of the alveolata clade © 2014 Pearson Education, Inc.

Figure Flagellum Alveoli Alveolate 0.2  m

© 2014 Pearson Education, Inc. Figure 25.15a Flagellum Alveoli 0.2  m

 Dinoflagellates have two flagella, and each cell is reinforced by cellulose plates  They are abundant components of both marine and freshwater phytoplankton  They are a diverse group of aquatic phototrophs, mixotrophs, and heterotrophs  Toxic “red tides” are caused by dinoflagellate blooms © 2014 Pearson Education, Inc. Video: Dinoflagellate

© 2014 Pearson Education, Inc. Figure Flagella Pfiesteria shumwayae, a dinoflagellate 3  m

 Ciliates, a large varied group of protists, are named for their use of cilia to move and feed  Most ciliates are predators of bacteria or small protists © 2014 Pearson Education, Inc. Video: Paramecium Cilia Video: Paramecium Vacuole Video: Vorticella Cilia Video: Vorticella Habitat Video: Vorticella Detail

© 2014 Pearson Education, Inc. Figure Contractile vacuole Cilia Oral groove Cell mouth Micronucleus Food vacuoles Macronucleus 50  m

© 2014 Pearson Education, Inc. Figure 25.17a 50  m

 Many species of rhizarians are amoebas  Amoebas move and feed by pseudopodia; some but not all belong to the clade Rhizaria  Forams and cercozoans are members of the rhizarian clade Rhizarians © 2014 Pearson Education, Inc.

 Foraminiferans, or forams, are named for porous shells, called tests  Pseudopodia extend through the pores in the test  Many forams have endosymbiotic algae  Forams include both marine and freshwater species © 2014 Pearson Education, Inc.

 Cercozoans include amoeboid and flagellated protists with threadlike pseudopodia  They are common in marine, freshwater, and soil ecosystems  Most are heterotrophs, including parasites and predators © 2014 Pearson Education, Inc.

 Paulinella chromatophora is an autotroph with a unique photosynthetic structure called a chromatophore  This structure evolved from a different cyanobacterium than the plastids of other photosynthetic eukaryotes © 2014 Pearson Education, Inc.

Figure  m Chromatophore

Archaeplastids  Plastids arose when a heterotrophic protist acquired a cyanobacterial endosymbiont  The photosynthetic descendants of this ancient protist evolved into red algae and green algae  Land plants are descended from the green algae  Archaeplastida is the supergroup that includes red algae, green algae, and land plants © 2014 Pearson Education, Inc.

Figure 25.UN04 Archaeplastida Unikonta SAR clade Excavata Chlorophytes Charophytes Red algae Green algae Land plants

Red Algae  Red algae are reddish in color due to an accessory pigment called phycoerythrin, which masks the green of chlorophyll  The color varies from greenish-red in shallow water to dark red or almost black in deep water  Red algae are usually multicellular; the largest are seaweeds  Red algae are the most abundant large algae in coastal waters of the tropics  Red algae reproduce sexually © 2014 Pearson Education, Inc.

Figure Bonnemaisonia hamifera 8 mm Red algae Nori

© 2014 Pearson Education, Inc. Figure 25.19a Bonnemaisonia hamifera 8 mm

© 2014 Pearson Education, Inc. Figure 25.19b Nori

© 2014 Pearson Education, Inc. Figure 25.19c

Green Algae  Green algae are named for their grass-green chloroplasts  Plants are descended from the green algae  Green algae are a paraphyletic group  The two main groups are charophytes and chlorophytes  Charophytes are most closely related to land plants © 2014 Pearson Education, Inc.

 Most chlorophytes live in fresh water, although many are marine and some are terrestrial  Nearly all species of chlorophytes reproduce sexually  Some unicellular chlorophytes are free-living while others live symbiotically within other eukaryotes  Larger size and greater complexity are found in multicellular species including Volvox and Ulva © 2014 Pearson Education, Inc.

Figure (a) Ulva, or sea lettuce (b) Caulerpa, an intertidal chlorophyte Multicellular chlorophytes 2 cm

© 2014 Pearson Education, Inc. Figure 25.20a (a) Ulva, or sea lettuce 2 cm

© 2014 Pearson Education, Inc. Figure 25.20b (b) Caulerpa, an intertidal chlorophyte

Unikonts  The supergroup Unikonta includes animals, fungi, and some protists  This group includes two clades: the amoebozoans and the opisthokonts (animals, fungi, and related protists)  The root of the eukaryotic tree remains controversial  It is unclear whether unikonts separated from other eukaryotes relatively early or late © 2014 Pearson Education, Inc.

Figure 25.UN05 Unikonta Archaeplastida SAR clade Excavata Gymnamoebas Slime molds Nucleariids Fungi Animals Choanoflagellates

© 2014 Pearson Education, Inc. Figure Results Common ancestor of all eukaryotes Choanoflagellates Animals Fungi Amoebozoans Unikonta Excavata Diplomonads SAR clade Euglenozoans Stramenopiles Alveolates Rhizarians Plants Green algae Red algae Archaeplastida DHFR-TS gene fusion

Amoebozoans  Amoebozoans are amoebas that have lobe- or tube-shaped, rather than threadlike, pseudopodia  Most amoebozoans are free-living, but those that belong to the genus Entamoeba are parasites © 2014 Pearson Education, Inc.

 Slime molds are free-living amoebozoans that were once thought to be fungi  DNA sequence analyses indicate that slime molds belong in the clade Amoebozoa © 2014 Pearson Education, Inc.

 Dictyostelium is an example of a cellular slime mold  Cellular slime molds consist of solitary cells that feed individually but can aggregate to form a fruiting body © 2014 Pearson Education, Inc.

Figure Spores (n) Fruiting bodies (n) Emerging amoeba (n) Solitary amoebas (feeding stage) (n) ASEXUAL REPRODUCTION SEXUAL REPRODUCTION MEIOSIS FERTILIZATION Zygote (2n) Amoebas (n) Aggregated amoebas 600  m Migrating aggregate 200  m Key Haploid (n) Diploid (2n)

© 2014 Pearson Education, Inc. Figure 25.22a-1 Solitary amoebas (feeding stage) (n) SEXUAL REPRODUCTION FERTILIZATION Zygote (2n) Key Haploid (n) Diploid (2n)

© 2014 Pearson Education, Inc. Figure 25.22a-2 Solitary amoebas (feeding stage) (n) SEXUAL REPRODUCTION MEIOSIS FERTILIZATION Zygote (2n) Amoebas (n) Key Haploid (n) Diploid (2n)

© 2014 Pearson Education, Inc. Figure 25.22a-3 Solitary amoebas (feeding stage) (n) ASEXUAL REPRODUCTION SEXUAL REPRODUCTION MEIOSIS FERTILIZATION Zygote (2n) Amoebas (n) Aggregated amoebas Key Haploid (n) Diploid (2n)

© 2014 Pearson Education, Inc. Figure 25.22a-4 Fruiting bodies (n) Solitary amoebas (feeding stage) (n) ASEXUAL REPRODUCTION SEXUAL REPRODUCTION MEIOSIS FERTILIZATION Zygote (2n) Amoebas (n) Aggregated amoebas Migrating aggregate Key Haploid (n) Diploid (2n)

© 2014 Pearson Education, Inc. Figure 25.22a-5 Spores (n) Fruiting bodies (n) Emerging amoeba (n) Solitary amoebas (feeding stage) (n) ASEXUAL REPRODUCTION SEXUAL REPRODUCTION MEIOSIS FERTILIZATION Zygote (2n) Amoebas (n) Aggregated amoebas Migrating aggregate Key Haploid (n) Diploid (2n)

© 2014 Pearson Education, Inc. Figure 25.22b 200  m

© 2014 Pearson Education, Inc. Figure 25.22c 600  m

Opisthokonts  Opisthokonts include animals, fungi, and several groups of protists © 2014 Pearson Education, Inc.

Figure 25.26a 0.5  m Apex Red blood cell Merozoite

© 2014 Pearson Education, Inc. Figure 25.UN01

© 2014 Pearson Education, Inc. Figure 25.UN06