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Protista: Learning Objectives
Three-Domain Classification
•
What features are common to the members
of kingdom Protista?
• Diversity among Protists
Eukaryote Phyla
Six-Kingdom Classification
Sizes of Protists
•
A unicellular protist
Mostly unicellular eukaryotic organisms that
live in aquatic environments
•
•
•
•
Unicellular organisms (most)
•
microscopic
Colonies
•
loosely connected groups of cells
Coenocytes
•
multinucleate masses of cytoplasm
Multicellular organisms
•
composed of many cells
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Locomotion
Diversity in the Kingdom Protists.
•
Classification based on:
• means of locomotion
• modes of nutrition
• interactions with other organisms
• habitats
• modes of reproduction
•
Pseudopodia
Flagella
• Cilia
• Some are nonmotile
•
Nutrition
Interactions
•
•
•
•
Protists are free-living or symbiotic
Symbiotic relationships vary
- A close relationship between 2 unrelated
organisms
Mutualism + +
Commensalism + Parasitism + -
Protists are:
Heterotrophs
• Autotrophs
Habitats
•
•
Most protists live in
• ocean
• freshwater ponds
• lakes
• streams
Reproduction
•
Many protists reproduce both sexually and
asexually
•
Others reproduce only asexually
Parasitic protists live in body fluids of hosts
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Relationships Among Protists
Chloroplast Evolution
•
Protist kingdom
• paraphyletic group:
- group of orgs with common ancestor
and some but not all of its descendents
• Determined by
• ultrastructure (electron microscopy)
• comparative molecular data
Eukaryote Phyla
Giardia
Protists are descendants of early eukaryotes
Discicristates
Trichonympha – live in
gut of termites
Nucleus
Flagella
50 µm
Fig. 25-5b, p. 536
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Ciliates
Cilliates - Conjugation
Dinoflagellates
Plasmodium
A Water Mold
Diatoms: some form floating plankton
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Heterokonts: Golden Algae
Heterokonts: Brown Algae
•
Multicellular - important in cooler ocean
waters
•
Kelps (largest brown algae)
•
•
•
•
•
Brown Algae
Foraminiferans
Cercozoa: Actinopods
Plants
Mostly marine
plankton
•
Monophyletic group including
•
•
•
Obtain food
with axopods
•
leaflike blades
stemlike stipes
anchoring holdfasts
gas-filled bladders for buoyancy
slender
cytoplasmic
projections
•
•
red algae
green algae
land plants
Based on
•
•
molecular data
presence of chloroplasts bounded by outer
and inner membranes
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Red Algae: Mostly multicellular seaweeds
important in warm tropical ocean waters
Green Algae
•
Wide diversity in size, structural
complexity, and reproduction
•
Botanists hypothesize that ancestral green
algae gave rise to land plants
–
–
Green Algae
–
ASEXUAL
–
REPRODUCTION
(by mitosis)
–
4 Four haploid
cells emerge, +
two (+)
and two
–
–
(-).
5 Both mating types reproduce
asexually by mitosis; only (-)
strain is shown.
Zoospores
1 Gametes are
produced by
mitosis.
–
SEXUAL
REPRODUCTION
+
HAPLOID (n)
GENERATION
–
–
+
from a different
strain
DIPLOID (2n)
GENERATION
+
Fertilization
Meiosis
3
Meiosis
occurs.
Zygote (2n)
Amoebazoa: Amoebas
2 (+) and (-)
gametes fuse,
forming a
diploid zygote.
Fig. 25-17, p. 547
Amoebas: Use cytoplasmic extensions (pseudopodia) to move and obtain
food by phagocytosis
Green alga
•
Entamoeba histolytica
•
•
parasitic amoeba
causes amoebic dysentery
Pseudopodia
100 µm
Fig. 25-22, p. 549
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Plasmodial Slime Molds
Omoebozoa:
•
Feeding stage is multinucleate plasmodium
Slime molds
Opisthokonts: Choanoflagellates
•
•
•
single posterior flagellum in flagellate cells
collar of microvilli surrounds base of flagellum
Choanoflagellates
•
are related to fungi and animals
Choanoflagellate
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