BIOL 201: Invertebrate Zoology

Chapter 2: Introduction to Protozoa

Rob SwatskiAssistant Professor of Biology

HACC-York

Eukaryotes

Domain Eukarya

Protozoa are animal-like

protists

Classification continually

changes

Membrane-bound nucleus

& organelles2

Protozoa

Most unicellular

Some colonial (ancestors of

plants & animals)

Most motile

Incredible diversity

3

Eukaryotic Cells

Diversity of specialized organelles

Cell membrane & cytoplasm

Double-membranednucleus,

mitochondria, & chloroplasts

Internal membrane system

4

5

Cytoplasm

Fluid enclosed by cell

membrane

Ectoplasm: outer, stiff

portion

Endoplasm: inner, fluid

portion6

Cell Membrane

Phospholipidbilayer with

proteins

Barrier to the external

environment

Selective passage of molecules

Glycocalyx

Endocytosis & exocytosis

7

8

Internal Membrane

System

Compartmentalizes the cell

Endoplasmic reticulum (ER)

Golgi bodies

Lysosomes

9

10

Cytoskeleton

Cytoskeleton

3-D network of protein fibers

Microfilaments(actin)

Microtubules

Dynamic

11

12

Microfilaments

Microtubules13

Functions of the Cytoskeleton

Cell motility: cilia, flagella, pseudopodia

Maintains cell shape

Regulates cell division

Vesicular transport

14

15

Cell Motility

Motor molecules (dynein) change shape in the presence of ATP

Dynein arms grab, move, & release outer

MT’s

MT doublets flex, bending cilium or

flagellum

Treadmilling

16

17

18

Cilia & FlagellaBoth made of MT core (axoneme) sheathed by plasma membrane

(9x2)+2 MT arrangement

Arises from & anchored to cell by basal body (9x3)+0

Motor protein (dynein) drives

bending movement

Cilia

Many

Short

Sweep materials across

cell (oar-like)

Flagella

Fewer

Long

Move entire cell (whip-like)

19

20Cilia

Cilia

21

22

Basal body

Cilium or Flagellum

(9x2)+2

23

Flagella

24

Base-to-tip wave propagation

Longitudinal forces provide forward thrust

Flagellarpropulsion 25

Ciliarypropulsion Metachronal waves

26

27

Cell motility using actin

Pseudopodia

Used for locomotion, feeding, & endocytosis

Dynamic disassembly & assembly of actin

Ectoplasm (gel) converted into

endoplasm (fluid)

Contractile ectoplasm provides force to move

cytoplasm forward

28

29Amoeboid movement

30

Protozoan Physiology

Same rules as in metazoans

Environmental effects may be

more significant

Ectothermic

Large surface area-to-volume ratio

31

Uptake By Cells

Endocytosis: extracellular uptake

Micropinocytosis: water, ions, small

molecules

Macropinocytosis: proteins &

macromolecules

Phagocytosis: bacteria & protozoans

in food vacuoles

32

33

34Micropinocytosis

35Macropinocytosis

36

Phagocytosis

Intracellular Digestion

Engulfment(phagocytosis): food vacuoles fuse with

lysosomes

Intracellular Digestion: mechanical/chemical

Absorption into cytoplasm: products are metabolized or stored

Elimination of indigestible material via

exocytosis37

Cell Circulation

Cytoplasmiccirculation needed in

larger cells

Streaming: directional transport within cell

or pseudopodium

Shuttling: the movement of vesicles

along a MT

Cyclosis: flow travels in a circuit

(Paramecium)38

39

Endosymbiosis

Heterotrophs often form mutualistic symbioses

with autotrophs

Zoochlorellae: photosynthetic symbiontssuch as unicellular green

algae or diatoms

Zooxanthellae: photosynthetic symbiontssuch as nonmotile yellow or brown dinoflagellates

Evolutionary value

40 Stentor

41

Zoochlorellae (in Paramecium bursaria)

42

Zoochlorellae(in giant green sea anemone)

43

Zooxanthellae (in coral)

44

Endosymbiosis

45

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