Zoology Chapter 11 Protozoa

1
Zoology Chapter 11Protozoa
2
Characteristics of Protozoans

• 1. unicellular with some colonial and
  multicellular stages.
• 2. most are microscopic.
• 3. all symmetries are present.
• 4. no germ layers are present.
• 5. they include free-living, mutualistic,
  commensal and parasitic forms.

3

• 6. they move by pseudopodia, flagella, cilia and
  they can direct cell movements.
• 7. all types of nutrition are present
  autotrophic, heterotrophic and saprozoic.
• 8. they are ecologically diverse, widely
  dispersed, but many are limited to narrow
  environmental ranges.
• 9. reproduction is asexual by fission, budding
  or cysts sexual by conjugation of syngamy of
  gametes.

4
Form and Function

• A. Nucleus and cytoplasm
• The nucleus is membrane bound and contains DNA in
  the form of chromosomes.
• Nucleoli are often present inside the nucleus.
• Cytoplasm may be divided into a granular
  endoplasm and a transparent gel ectoplasm.

5

• B. Locomotor organelles cilia and flagella
• C. Pseudopodia chief means of locomotion in
  Sarcodina, many flagellates and ameboid cells of
  many invertebrates and vertebrates.
• Lobopodia are large blunt extensions containing
  both endoplasm and ectoplasm
• In the limax form, the whole body moves rather
  than sending out arms.
• Filopodia are thin extensions of ectoplasm
• Reticulopodia repeatedly rejoin to form a
  netlike mesh.

6

• D. Excretion and Osmoregulation
• 1. excretion of metabolic wastes is by
  diffusion, although many ciliates have a point of
  expulsion of wastes, called a cytoproct.
• 2. contractile vacuoles fill and empty to
  maintain osmotic balance.

7

• E. Nutrition
• 1. Autotrophs synthesize their own food and
  heterotrophs obtain organic molecules made by
  others.
• 2. Phagotrophs or holozoic feeders ingest food
  particles while osmotrophs or saprozoic feeders
  ingest soluble food.
• 3. Most protozoans use more than one nutritional
  strategy.

8

• F. Reproduction
• 1. Asexual reproduction
• Fission
• Budding
• Multiple fission (schizogony)

9

• 2. Sexual reproduction
• Fertilization of one gamete by another is
  syngamy this is the stantard form of sexual
  reproduction.
• Isogametes look alike anisogametes (like egg
  and sperm) are dissimilar.
• Autogamy is when gametic nuclei arise by meiosis
  and fuse to form a zygote inside the parent
  organism.
• Conjugation is exchange of gametic nuclei between
  paired organisms, common in Paramecium.

10

• G. Encystment and Excystment
• 1. protected only by a delicate membrane,
  protozoa are successful in changing and harsh
  environments.
• 2. Cysts are dormant forms that shut down
  metabolism and have a resistant material
  covering.
• 3. cysts often resist cold or hot temperatures
  some tolerate acidity but not sunlight.
• 4. once under favorable conditions again, the
  organism escapes from the cyst.

11
Representative Types

• Trichomonas vaginalis infects the urogenital
  tract of humans and is sexually transmitted.

12

• Euglena

13

• Volvox

14

• Trypanosoma brucei gambiense

15

• Trypanosoma cruzi

16

• Leishmania

17

• Amoeba proteus

18

• Entamoeba histolytica

19

• Toxoplasma gondii

20

• Plasmodium

21

• Paramecium