Lecture 6

Question 1

What is a protozoan ?

Answer 1

Distinctly animal like : no cell wall at leat 1 motile stage in life cycle
Most ingest their food
- not a monophyletic clade
- completely contained within 1 plasma membrane

Question 2

axoneme

Answer 2

9 pairs around central pair (9+2) arrangement.

Question 3

kinetosome

Answer 3

9 triplets (basal body)

Question 4

How do we classify protozoa ?

Answer 4

•constantly under revision due to new molecular data

• will focus on clades rather than taxonomic levels

Question 5

Important organelles .
1) nucleus

Answer 5

• membrane - bound structure containing genetic material (DNA) as chromosomes
• nucleoli also often present

Question 6

Mitochondria ?

Answer 6

• used in energy acquisition using oxygen
• also contains DNA (former prokaryote?)
• form of internal membranes (cristae)

can serve to group into clades.

Question 7

Hydrogenosomes ?

Answer 7

substitutes where oxygen is absent

Question 8

Kinetoplast?

Answer 8

Derivatives of mitochondria

Question 9

Golgi apparatus ?

Answer 9

•part of secretory system

Question 10

Parabasal bodies ?

Answer 10

They are structures with similar function to golgi apparatus
- secretory function

Question 11

Plastids ?

Answer 11

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•organelles containing photosynthetic pigments
-e.g. chloroplasts
• via ancestral engulfment of cyanobacteria

Question 12

Extrusomes

Answer 12

•membrane-bound organelles used to

extrude something from the cell

Question 13

Cilia & flagella

Answer 13

•same ultrastructure but different actions
differ in beating patterns
Ø flagellum with undulating motion (force generated in same direction as flagellum axis)

Ø cilia like oars (power & recovery strokes perpendicular)

Question 14

The structure of cilia and flagella.

Answer 14

•both consist of microtubules
Ø 9 pairs around central pair (9+2) arrangement (axoneme) covered with continuous membrane

• different arrangement at entrance to cell

Ø 9 triplets ( kinetosome /basal body)

Question 15

How do cilia & flagella propel protozoans ?

Answer 15

sliding microtubule hypothesis

Question 16

Pseudopodia ( 2nd mode of movement)

Answer 16

• temporary protrusions of cytoplasm
• locomotion & ingestion in protozoa & other ameboid cells (e.g. leukocytes)
• Exist in several forms.

Question 17

filipodia

Answer 17

thin extensions containing only ectoplasm

Question 18

reticulopodia

Answer 18

Ørepeatedly rejoin to form net-like mesh

Question 19

Axopodia

Answer 19

Øsupported by axial rods of microtubules

Question 20

protozoans are categorize into 2 groups for nutrition type

Answer 20

1) autotroph
2) heterotrophs

Question 21

Autotrophs

Answer 21

Synthesize own organic molecules

Question 22

Heterotrophs

Answer 22

must obtain organic molecules from others
•heterotrophs either ingest visible food particles via phagocytosis (phagotrophs/holozoic feeders) or ingest food in soluble form (osmotrophs/saprozoic feeders).

Question 23

Excretion & osmoregulation of protozoans

Answer 23

•taken care of by contractile vacuoles.
Ø usually in ectoplasm, act as pumps

Question 24

Reproduction of protozoans

Answer 24

They can reproduce either asexually or sexually

Question 25

Asexual reproduction

Answer 25

•cell multiplication producing genetically identical individuals via fission

Ø binary fission most common

Question 26

multiple fission are called …

Answer 26

schizogony

Question 27

Sexual reproduction

Answer 27

•all protozoans reproduce asexually but there can still be genetic recombinant

Ø sexual processes may proceed asexual processes but embryos do not result

Question 28

synagmy

Answer 28

•fertilization of 1 individual gamete by another
Ø but not all protozoans produce gametes

Question 29

Autogamy

Answer 29

•gametic nuclei result from meiosis & fuse to form a zygote within the same individual

Question 30

conjugation

Answer 30

•exchange of gametic nuclei occurs between paired organisms

Question 31

Encystment & excystment of protozoans ?

Answer 31

•ability to form cysts
Ø dormant forms with resistant covering

Ø arrested metabolism

• also important to many parasitic forms for transmission

• triggered by environmental conditions in free-living species

•excystment triggered by return to favourable conditions
Ø specific host cues stimulate parasitic excystment

Question 32

Heterokont

Answer 32

2 different flagella located at anterior end