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UF / Biological Sciences / BSC 2011 / How did the modern eukaryotic cell arise?

How did the modern eukaryotic cell arise?

How did the modern eukaryotic cell arise?


School: University of Florida
Department: Biological Sciences
Course: Integrated Principles of Biology 2
Professor: Norman douglas
Term: Fall 2016
Tags: Biology, Bio, notes, Biology 2, bio 2, eukaryotes, Chapter 20, archaea, and Bacteria
Cost: 25
Name: Chapter 20: The Origin and Diversification of Eukaryotes
Description: Principles of Life 2nd Edition
Uploaded: 01/10/2016
8 Pages 296 Views 1 Unlocks


The Origin and Deversification of

Eukaryotes Don't forget about the age old question of What allow us to understand the evolution of complex traits?

vocab words/ definitions We also discuss several other topics like What leads to osmotic pressure?
Don't forget about the age old question of What refers to the amount of mass packed into volume?

Tconcept 1 Eukaryotes Acquired Features from I 20.1 I Both Archaea + Bacteria We also discuss several other topics like the vertical distance between the total revenue line and the total expense

main to pies / subtitles important information We also discuss several other topics like cse helproom msu

. eukaryotes that are not plants, animals, or fungi have traditionally 4, "protist" doesn't describe a taxa group We also discuss several other topics like What is Entropy based on?

been called protists. L convenient term for all the eukaryotes that are not plants, animals..

or fungi

• eukaryotes are monophyletic + single eukaryotic ancestor diversified into many diff. protist


• mitochondria + chloroplasts of euka. → derived from bacterial lineages

cages - split from /of Eukarya from Archaea was followed by the endosymbioses

w/ bacterial lineages that led to the origin of mitochondria chloroplasts.

because of *origin of eukaryotes as the fusion of lineages


• the environment went through HUGE change - low to high amounts of Oz' Do The Modern Eukaryotic cell arose in several steps: → several events important in origin of the modern eukaryotic cell [lo origin of a flexible cell wall/surface

2. origin of a cytoskeleton 3. origin of a nuclear envelope → enclosed DNA in to chromosomes

4. appearance of digestive vacuoles | 5. addition of some organelles because of endosymbiosis


• ancien+ prokaryotes had firm cell walls. List step to eukaryotes was the loss of cell wall - as a cell grows, its surface area- to-volume ratio decreases

bat some point, cell volume will reach maximum limit




BUT if the cell's surface is flexible, it can fold inward and create more surface area Callows for more gas + nutrient exch *infoldings important for the evolution of bigger eukaryotic cells

CHANGES IN CELL STRX AND FXN: Other steps important for evolution that involved increased compartmentalization

. more complex cy to skeleton . formation of ribosone-studded membranes (endoplasmic reticulum)

• DNA inside the nucleus + enclosed

• flagellum from microtubules of the cytoskeleton Lo digestive vacuoles - Cytoskeletons evolved before origin of eukaryotes

- greater development of microfilaments and microtubules helps :

a) manage changes in shape b) distribute daughter chromosomes c) and move materials d) also allowed to develop characteristic eukaryotic flagellum


• Nuclear envelope ist appeared in eukaryote lineage . Next step was phagocytosis: ability to engulf + digest other cells


• cyano bacteria were creating / generating O2 → because of photosynthesis

Oz levels increased so high some organisms didn't adapt + went extinct - only some prokaryotes evolved to use the Qu + also some phagocytic eukaryotes * thus endosymbioses began to play a role in eukaryote evolution

• Theory of Endosymbiosis: proposes that certain organelles are the descendants of

prokaryotes engulfed, but not digested, by ancient eukaryotic cells. * important event was incorporation of a proteo bacterium that evolved into the mitochondrion

• Photosynthetic eukaryotes are result of another endosymbiotic step:

Lo the incorporation of a prokaryote related to today's cyanobacteria. Do Chloroplasts have been transferred among eukaryotes several times:

• groups leukaryote clades) differ in the photo synthetic pigments their chloroplasts contain.

- not all chloroplasts are limited to a pair of surrounding membranes — 3+ for some * all chloroplasts can go back to ancestry of engulfment of one cyano bacterium by a larger

eukaryotic cell

•primary endosymbiosis: step that ist gave rise to the photosynthetic eukaryotes

- original chloroplasts had 2 membranes : inner touter membranes of the cyanobacterium .hoto Synthetic euglenids derived their chloroplasts from secondary endosymbiosis.

Le reason for 3rd membrane of the euglenido chloro plasts . tertiary endo symbiosis: when a dinoflagellate apparently lost its chloroplast, took up another

protist that had quired its chloroplast through secondary endosymbiosis.

Sconcept7 Major Lineages of Eukaryotes L 20.2 s Diversified in the Precambrian: . 8 major clades → started to change 1.5 BYA.

1. alveolates

4. Plants

7. fungi

2. excavates

1 5. rhizarians 8. animals 3. stramenopiles 6. amoe bozoans 5 major groups of protists: will be covered in next pages - unicellular species of protists: microbial eukaryotes 4 of the origins of multicellularity resulted in large familiar organism: plants, brown algae, blast group are strameno piles

fungi, and animals unicellular species keep individual identities → but associate in

large multicellular


D Alveolates have sacs under their cell membranes :

Lo named because they possess sacs, called alveoli, just beneath their cell membranes >> play a role in supporting cell surface.

all unicellular, most photo synthetic but diverse in body form -groups considered: Dinoflagellates, Apicomplexons, + ciliates.

DINOFLAGELLATES: by most marine + photosynthetic - important primary producers of organic matter in oceans.

La fewer species in fresh water - chloroplasts are a golden brown color o some dinoflagellates cause red tides while others are photosynthetic endosymbionts Doors

• others nonphotosynthetic naka are parasites

Lo they are within cells of other organisms

example: CORALS - HAVE dinstinct appearance

L2 Flagella: 1 in equatorial groove; other

in longitudinal groove

• some dinoflagellates can have different forms

including amoeboid ones ex. Priesteria pisci ceda (2 dozen forms)


derive name from apical complex: a mass of organelles contained in the apical end (tip) of the cell. - they help the Apicomplexan enter host's tissue

o are obligate parasites > Thus they have complex life cyclesiasexual + Sexual reproduction

example: Taxoplasma can apicomplexan) infects rats + makes them forget their fear of cats, so the rat will be eaten to then infect the cat.


their - to named after numerous hair-like cilia shorter than eukaryotic flagella

. have 2 types of nuclei

• most are heterotrophio, but some photosynthetic endosymbionts - pellicle: strx composed principally of an outer membrane and an inner layer of closely packed,

membrane-enclosed sacs Calveoli) - trichocysts : defensive organelles (also present)

cilio provide locomotion o coordinate the beating of its cilia to propel itself either forward or backward in a spiraling


• organisms living in fresh H2O are hypertonic to their environment. Lo fix problem of fresh H2O by contractile vacuoles • excrete the excess H2O the organisms constantly

take in by osmosis.

• engulf solid food by endo cytosis form a digestive vacuole Do Stramenopiles typically have 2 unequal flagella, one wy hairs

stramenopiles: possession of rows of tubular hairs on the longer of their 2 Flagella - some lack flagella Stramenopiles are : a) diatoms + algae: which are photosynthetic

6) comycetes: not photo synthetic





DIATOMS: * ALL are unicellular → altho some group together in filaments - caretenoids in their chloroplasts → makes them yellow or brown color


show either * ALL Synthesize carbohydrates + oils

Iradial lack flagella except in male gametes

& symmetry cell wall of diatom is made of 2 pieces : one overlapping the other

bilateral I made of silica : cool patterns

like a petri dish


(left-right s for each specie

reproduce both sexually t asexual

constrained by - l done by binary fission( cell wall

• found

because of this the "new" cell will be smaller in the ocean, & in big numbers

than the parent cell a major photosynthetic producers

• also common in fresh water ZA BROWN ALGAE:

- a type of I name from their colors pigment

o carotenoid fucoxanthin reason for their Cin the chloroplast)

• ALL are multicellular

mainly exclusive marine . hold fast: a specialized Strx that gives to rocks

gle" is alginic acid, a polymer of sugar acids found in the walls of brown algal cells OO MYCETES:

consist of water molds + terrestial relatives lex: downy mildews)

filamentous + Stationary

• are absorptive heterotrophs: secrete enzymes that digest large food molecules into small ones

they can absorb

all aquatic + saprobic: feed on dead matter

Rhizarians typically have long, thin pseudo pods: 3 main groups of rhizarians: I cercozoans 1 unicellular


and 3 radiolarians mainly aquatic I have long, thin pseudopods / contrast with the broad, lobelike pseudopods of amoebozoans

.contribute to ocean sediments

CERCOZOANS: diverse group with many forms + habitats

some aquatic, some terrestial 1. one group have chloroplasts derived from green alga lendo symbiosis)


secrete external shells of calcium carbonate

• produce much of the world's limestone o live as plankton or on the seafloor

• have long, thread-like branched pseudopods to catch smaller plankton



y recognizable by their thin, Stiff pseudo pods → reinforced by microtubules . pseudopods 4 Cocronym for increase) the surface area of the cell,+ help it stay afloat * recognizable by their distinctive radial symmetry (BEST way to identify)

• secrete glassy endoskeletons (internal skeletons)

beach different like snowflakes (not one is the same)

• some are the largest unicellular eukaryotes D Excavates began to diversify about 1.5 BYA :

a number of diverse groups that began to split from one another right after the origin

• many lack mitochondrias

of eukaryotes. I belief that they lost/ reduced them in time with evolution

* shows that eukaryotic life is possible without mitochondria

i an

DIPLOMONADS AND PARABASALIDS: ounicellular + lack mitochondria

→ one diplomonad (Giardia lamblia): parasite that contaminates H,0 F 2 2 nuclei bounded by nuclear envelopes, cytoskeleton, & many flagella

paraba salids have this and undulating membranes

that contribute to the cell's locomotion ZA HETEROLOBOSE ANS :

their body forms is similar to that of lobo seans (amobo zoean group) . AMOEBAS bhave 2-stage life cycle — I with amoebid cells, the other with flagellated cells A EUGLE NIDS AND KINETOPLASTIDS:

both constitute a clade of unicellular excavates with flagella mitochondria → have disc-shaped cristal

flagella have a crystalline rod (not found in any other org.)

• reproduce asexually by binary fission . flagella of euglenids arise from a pocket at the anterior end of the cell.

some are photosynthetic example: Euglena leuglenid) → propels w2 Flagella that can also serve as anchors

2nd flagellum usually more basic

1 *when kept in the dark, they7 o euglenids have diverse nutritional requirements → heterotrop

lose pigment + eat dead

matter, but if put back Gothers autotrophic in sunlight

in the light autotrophic

• kineto plastids are unicellular parasites WI 2 flagella and one mitochondria

again ]


of them

contains a kinetoplast; a stry housing multiple circular include pathogenic trypanosomes

DNA molecules + associated proteins So some of these DNA molecules encode

"guide proteins" De Amoebozoans use lobe-shaped pseudopods for locomotion :

derived from other eukaryotes about 1.5 BYA o not clear if more closely related to opisthokonts or eukaryotes

love shaped pseudo pods ->hall mark of amoe boid body form 3 amoebozoan groups: O loboseans + slime molds Groups)

LOBOSEANS: small amoebozoans that feed on small org. + dead matter by phagocytosis -> W

eat them my

coudonnas adapted to live in the bottom of lakes, ponds, t other bodies of H,O . have a creeping locomotion . have a rich supply of sedentary org. + particles . most exist as parasites, predators, + scavengers

some produce caisings ] - testate amoebas: (group of loboseans) live inside of shells by Sticking sand together

PLASMODIAL SLIME MOLDS: nucleus of an amoeba begins mitotic division, with î in cytoplasm & organelles but no cytokinesis. end result will be an org. like a plasmodial slime mold

it moves blo . coenocyte! Many nuclei enclosed

of its plasmodium,

a network of Tin feeding stage) is a wall-less mass in a single cell membrane

- Strandst of astoplasm w/ numerous diploid o outer cytoplasm is less fluid than the interior one


7 Plasmodium b gives structural rigidity

Siione mold

hisloos 'pretzel) plasmodial slime molds move by cytoplasmic streaming.

EDIDOS mold")

they sometimes Outer cytoplasmic region becomes more fluid

leave strands in some places & the cytoplasm rushes in behind Stretching the plasmodium.

(like a snail & their


• microfilaments + a contractile protein produce the streaming movement plasmodium enguits food by endocytosis: mainly bacteria, yeasts, fungi, plant remains, dead,


• can grow anywhere + D, as long as there is food, pH and moisture are okay. IF conditions are not okay... o they form an irregular mass of hardened cell-like strx, but becomes a plasmodium again when conditions are okay again. @can transform into spore-bearing fruiting strx's.

sporangia h sporangia: one or more knobs, develop on the stalk. eventually they shed the pone's spores germinate into wall-less, haploid cells called Swarm cells can divide into more haploid

cells or fun as gametes

• Swarm cells can live as seperate individual cells that move by Flagella or pseudopods

Gor can become walled

• 2 swarm cells can fuse to form a diploid zygote which forms a new coenytic plasmodium Z CELLULAR SLI ME MOLDS: . amoe boid cell is the vegetative unit of the cellular slime mold

eact by cells called my xamoebas → have a single haploid nuclei, reproduce by mitosis + binary fission, endocytosis . when conditions NOT okay : will aggregate + form fruiting strx's

individual myxa moebas, aggregate into a mass called a slug or pseudoplasmodium

single ones retain their cell membranes & their identity slugs may migrate over a substrate ocells developed into thick-walled spores → spores germinare releasing my xamoebas o the cycle is asexual o also have a sexual cycle when 2 my xamoebus fuse



Concep+7 Protists Reproduce sexually

| 20.3 ) and Asexually

• several asexual reproductive processes have been observed among the protists:

- equal splitting of one cell into 2 by mitosis & then cytokinesis - splitting of one cell into multiple (< than 2) - outgrowth of a new cell from the surface of an old one (called budding) - formation of specialized cells (spores) that are capable of developing into new individuals

(known as sporulation)

• asexually reproduced groups saka clonal lineages

Some Protists have reproduction wout sex + sex wlout reproduction: micronuclei (typical eukaryotic nucleil are essential for genetic recombination

• macronucleus contain many copies of the genetic information very few genes each unit

• Paramecia have a sexual behavior called conjugation : 2 individuals line up Hightly

against each other & fuse in the oral groove region of the body. exchange of nuclei is fully reciprocal

each of the paramecia gives + receives an equal amount of DNA De some pro tist life cycles feature alternation of generations:

his a type of life cycle found in many multicellular

protists, all land plants, t some fungi.



. a multicellular, diploid, spore-producing organism gives rise to a multicellular, haploid, gamete

producing organism. imay reproduce asexually

heteromorphic alternation of generations, the 2 generations differ morphologically

L but in isomorphic alternation of generations, they don't.

• Specialized cells of the diploid sporé producing org., called sporocytes, divide meiotically

to produce 4

• gametes, unlike spores, can produce new org. only by fusing w/ other haploid spores.

I Concepty Protists are critical components | 20.4 J of Many Ecosystems: protists are food for marine animals, while others are poisonous some have nutritional value, & others are human pathogens

Phyto plankton are primary producers: So

• single protist clade, the diatoms, perform is of all photosynthetic carbon fixation on Earth hy same amount as all of Earth's rainforests

sun *

• are the predominant component of phyto plankton

protist C

• "floating photosynthesizers" gateway for energy from the sun to all other animals - bare primary producers #autotrophs eaten by heterotrophs

Some microbial eukaryotes are deadly! malaria is one of the world's 3 most serious infectuous diseases

Ginfects 350 m ppl.


• Plasmodium (malaria) is a difficult pathogen to attack its life cycle best broken by removal of stagnant water (where mosquitoes breed)


by some microbial eukaryotes are endo symbionts : o endo Symbiosis is common among the microbial eukaryotes oradiolarians appear green or golden, depending on the type of endosymbiont they contain.

by mutually beneficial: radiolarian can use the carbon compounds produced by the endosymbiont c' guest


. dinoflagellates → are common endosymbionts

protists y found in both Nonis & animals

must but not all are photosynthetic coral bleaching: when corals expel their dinoflagellates b/c of stress (ex: global warming)

De we rely on the remains of ancient marine protists: odiatoms store oil as an energy reserve & to keep from sinking

major source of petroleum + natural gas

Short Hand: with w/ and + without w/out increase because b/c decrease → V

@ forever structure strx.

fxn function

structures - Stix's.


P years ago


My million

water H2O

BYA - billion

Std S

organism — Org.

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