Title: Henry Hsieh
1Chapter 28The Origins of Eukaryotic Diversity
- By
- Henry Hsieh
- Perry Huang
- Kevin Kim
- Joon Park
- Period 6
2(No Transcript)
3Introduction to the Protists
- Protists existed at least a billion years ago,
before the origin of plants, fungi, and animals - They were the earliest descendants of prokaryotes
- Oldest fossils called acritarchs Precambrian
objects about 2.1 billion years old
4Protists are the most diverse of all eukaryotes
- All protists are eukaryotes
- About 60,000 known species of unicellular
protists, few colonial and multicellular species - Incredibly complex at cellular level because a
single cell would have to perform many functions
5Protists are the most diverse of all eukaryotes
(cont.)?
- Protists are metabolically diverse
- Most are aerobic in their metabolism and use
mitochondria for cellular respiration - 3 categories of nutritional diversity1.
protozoa (animal-like protists)2. absorptive
(funguslike) protists3. algae (photosynthetic
plantlike protists)?
6Protists are the most diverse of all eukaryotes
(cont.)?
- Most protists are motile, can have flagella or
cilia- Eukaryotic flagella and cilia are
extensions of the cytoplasm, with bundles of
microtubules covered by the plasma membrane - Some protists are asexual, others can reproduce
sexually with meiosis and syngamy (the union of 2
gametes)?
7Protists are the most diverse of all eukaryotes
(cont.)?
- Resistant cells called cysts are formed at some
point in life cycle - Protists can be found almost anywhere with water
- Important constituents of plankton the
communities of organisms that drift near water
surface that are the bases of most marine and
freshwater food webs
8Symbiosis was involved in the genesis of
eukaryotes from prokaryotes
- The endomembrane system of eukaryotic cells the
nuclear envelope, endoplasmic reticulum, Golgi
apparatus, and related structures-- may have
evolved from infoldings of the plasma membrane of
an ancestral prokaryote - Endosymbiosis led to mitochondria, chloroplasts,
and other features of eukaryotic cells
9Symbiosis was involved in the genesis of
eukaryotes from prokaryotes (cont.)?
- Serial endosymbiosis proposes that mitochondria
and chloroplasts were formerly small prokaryotes
living within larger cells. - All eukaryotes have mitochrondria
- Only photosynthetic eukaryotes have chloroplasts
- Mitochondria is proposed to have evolved before
chloroplasts
10Protist Systematics and PhylogenyMonophyletic
taxa are emerging from modern research in protist
schematics
- Unicellular eukaryotes assigned to Kingdom
Protista - Later included some multicellular organisms, such
as seaweeds - Kingdom Protista is polyphyletic (members derived
from two or more ancestral forms not common to
all members)? - For now, divide into 5 groups of Protists
Archaezoa, Euglenozoa, Alveolata, Stramenopila,
Rhodophyta.
11Fig 28-1. Too diverse for one kingdom a small
sample of protists.
12Members of candidate kingdom Archaezoa lack
mitochondria and may represent early eukaryotic
lineages
- Several protists lack mitrochondria, leads to the
hypothesis that the lineages of these organisms
diverged before the endosymbiotic event that gave
rise to mitochondria - Protists that lack mitochondria located in
Kingdom Archaezoa - Diplomonads subgroup of archaezoans have
flagella, two separate nuclei, no mitochondria,
no plastids, and a simple cytoskeleton
13Members of candidate kingdom Archaezoa lack
mitochondria and may represent early eukaryotic
lineages (cont.)?
- A diplomonad parasite called Giardia lamblia
infects human intestines - Giardia and others are living relics of an early
lineage of eukaryotes evidence indicates that
their genes once coded for mitochondria. This
indicates that their ancestors once possessed
mitrochondria, but have lost them over
evolutionary history.
14Giardia lamblia
15Candidate kingdom Euglenozoa includes both
autotrophic and heterotrophic flagellates
- Flagellates- A term that is not used in formal
taxonomy. - -Molecular indicates that two groups of
flagllates - euglenoids and kinetoplastids make up the
monophyletic candidate kingdom Euglenozoa. - Euglenoids-(Englena and its close relatives) are
characterized by an anterior pocket, or chamber,
from which one or two flagella emerge. - Paramylum, a glucose ploymer that functions as a
storage molecule, is also characteristic of
euglenoids. - Euglena is chiefy autotrophic, absorbing organic
molecules from their surroundings or engulfing
prey by phagocytosis. - The kinetoplastids have a single large
mitochondrion associated with unique organelle,
the kinetoplast, that houses extranulear DNA.
16Subsurface cavities(alveoli) are diagnostic of
candidate kingdom Alveolata
Another monophyletic candidate kingdom that is
emerging from molecular systematics, -The
Alveolata, -draws together a group of
photosynthetic flagellates ( the
dinoflagellates), -a group of parasites
(apicomplexans), -and a a distinctive group of
eukaryotes that move by means of cilia( the
cilates). -Alveolates have a small
membrane-bounded cavities (alveoli) under their
cell surfaces, functions are unknown may help
stabilize the cell surface and regulate the
cells water and ion content
17Dinoflagellata (Dinoflagellates) Apicomplexa
(Apicomplexans)?
- Dinoflagellates are abundant components of the
vast aquatic pastures of phytoplankton that are
suspended near the water surface and provide the
foundation of most marine and many freshwater
food webs. There are also heterotrophic species
of dinoflagellates. - Apicomplexans are parasites of animals,
- Some cause serious human diseases
- The parasites disseminate as tiny infectious
cells called sporozoite
18Fig 28-13. The two-host life history of
Plasmodium , the apicomplexan that causes
malaria. (Colors are not true to life.)?
19Ciliophora (Ciliates)?
- This diverse group of protists is named for their
use of cilia to move and feed
20Ciliophora (Ciliates) Con.
- Most ciliates live as solitary cells in fresh
water. In contrast to most flagella, cilia are
relatively short. They are associated with a
submembrane system of microtubules that may
coordinate the movement of the thousands of
cilia. - Some ciliates are completely covered by rows of
cilia, whereas others have their cilia clustered
into fewer rows or tufts. - The specific arrangements adapt the ciliates for
their diverse lifestyles. Some species, for
instance, scurry about on leglike structures
constructed from many cilia bonded together. - A unique feature of ciliate genetics is the
presence of two types of nuclei, - a large macronucleus and usually several tiny
micronuclei. - The genes are not distributed in typical
chromosomes but are instead packaged into a much
larger number of small units, each with hundreds
of copies of just a few genes. - The macronucleus controls the everyday functions
of the cell by synthesizing RNA and is also
necessary for asexual reproduction. - Ciliates generally reproduce by binary fission,
- The sexual shuffling of genes occurs during the
process known as conjugation
21Fig 28-15. Conjugation and genetic recombination
in Paramecium caudatum .
22A diverse assemblage of unicellular eukaryotes
move by means of pseudodia
- The three gropus we discuss in this section
represent some of the immense diversity of
unicellular eukaryotes that move and often feed
by means of cellular extensions called
pseudpopdia. - Most of these organisms are heterotrophs that
actively seek and consume bacteria, other
protists, and detritus (dead organic matter).
There are also symbiotic species, including some
parasites cause human diseases. - Little is known about their phylogeny.
-
23Rhizopods (Amoebas)?
- Are all unicellular and use pseudopodia to move
to feed. - The cytoskeleton, consisting of microtibules and
microfilaments - Functions in amoeboid movement
- Meiosis sex are NOT known to occur in amoebas.
- Reproduce asexually by various mechanisms of cell
division. - Inhabit both freshwater marine environments and
are also abundant in soils - The majority of amoebas are free-living, but some
are important parasites, including Entamoeba
histolytica - Cause amoebic dysentery in humans
- (These organisms spread via contaminated drinking
water, food, or eating utensils)? -
24Actinopods (Heliozoans Radiolarians)?
- Means ray foot
- A reference to the slender pseudopodia called
axopodia that radiate from these exceptionally
beautiful protists. - Each axopodium is reinforced by a bundle of
microtubules cover by thin layer of cytoplasm - Most actinpods are planktonic
- Their projections place an extensive area of
cellular surface in contact with the surrounding
water, help the organism float and feed
25Actinopods (Heliozoans Radiolarians) con.
- Heliozoan(sun animals)- living in freshwater.
- Skeletons consist of siliceous(glassy) or
chitnous unfused plates. - Radiolarian(not used in formal taxonomy)-refers
to several groups of mostly marine actinopods
w/skeleton fused into one delcate piece-commonly
made of silica - After actinopods die, their skeletons settle
settle to the seafloor, where they have
accumlated as an ooze that is hundreds of meters
thick in some locations -
26Foraminiferans (Forams)?
- Are almost all marine.
- Most live in sand or attach themselves to rocks
algae, but some are abundant in plankton - Named for their poruous shells
- The shells generally multichambered and consist
of organic material hardened w/calcium carbonate. - Strands of cytoplasm(pseudopodia) extend through
the pores - Functioning-swimming, shell formation, and
feeding. - (Many also derive nourishment from the
photosynthesis of symbiotic algae that live w/in
the shells)?
27Slime molds have structural adaptations and life
cycles that enhance their ecological role as
decomposers
- 2 groups of protists called slime molds
- Resemble fungi in appearance and lifestyle
- Similarities are convergence
- In their cellular organization, reproduction and
life cycles - Slime molds depart from the true fungi is partly
due to convergent evolution of filamentous body
structure - A morphological adaptation that increase exposure
to the environment and enhances the ecological
role of these organisms as decomposers - Slime molds have complex life cycles that are
adaptations that contribute to survival in
changing habitats and facilitate dispersat to new
food sources
28Plasmodial Slime Molds (Myxomycota)?
- Are more attractive than their name implies.
- Many brightly pigmented, usually yellow or
orange, but all are heterotrophic. - The feeding stage of the cycle is an amoeboid
mass called a plasmodium - Plasmodium are not multicellular
- The cytoplasmic streaming apparently helps
distribute nutrients oxygen - The plasmodium engulfs food particles by
phagocytosis as it grows by extending pseudopodia
through moist soil, leaf mulch, or rotting logs. - If the habitat of slime mold dried out or no food
left, the plasmodium ceases growth and
differentiates into a stage of the life cycle
that function in sexual reproduction
29Cellular Slime Molds(Acrasiomycota)?
- Pose a semantic question what it means to be an
individual organism. - Although the feeding stage of the life cycle
consists of solitary cells that function
individually - When food is depleted the cells form an aggregate
that function as a unit - Though the mass of cells resembles a plasmodial
slime mold - The distinction is that the cells of a cellular
slime mold maintain their identity and remain
separated by their membranes. - Cellular Slime molds also differ from Plas. Slime
molds in being haploid organisms - Cellular Slime molds have fruiting bodies that
function in asexual reproduction. - Most of Cell. Slime mold have no flagellated
stages