Animal Taxonomy

• In the five-kingdom system of classification, the eukaryotes were distributed among four kingdoms: Protista, Plantae, Fungi, and Animalia.

22 - -Kingdom ProtistaKingdom Protista((Eukaryotic uni-/multi-cellularEukaryotic uni-/multi-cellular))

EukaryotaEukaryota

11 22

33

332211

prokaryotic

• Protists are eukaryotes and thus are much more complex than the prokaryotes.

• The first eukaryotes were unicellular.

• eukaryotic and multi-cellular animals originated from protists

22 - -Kingdom ProtistaKingdom Protista((Eukaryotic uni-/multi-cellularEukaryotic uni-/multi-cellular))

EukaryotaEukaryota

11 22

33

332211

prokaryotic

• Protista (mostly unicellular eukaryotes) ranging from uni-celled microscopic members, simple multi-cellular forms, and complex giants like seaweeds.

• Still,“protist” is used as a term for a great diversity of eukaryotic kingdoms.

• Most of the 60,000 known protists are unicellular, but some are colonial and others multi-cellular.

• Many protists form resistant cells (cysts) that can survive harsh conditions.

ProtistsProtists

• Most protists are aerobic, with mitochondria for cellular respiration.

• Some protists are photoautotrophs with chloroplasts.

• Still others are heterotrophs that absorb organic molecules or ingest larger food particles.

• A few are mixotrophs, combining photosynthesis and heterotrophic nutrition.

• Protists may include photosynthetic species, heterotrophic species, and mixotrophic species.

Characters of ProtistsCharacters of Protists

A)- NutritionA)- Nutrition::

• Most protists move with flagella or cilia during some time in their life cycles.

• The eukaryotic flagella are not homologous to those of prokaryotes.

• The eukaryotic flagella are extensions of the cytoplasm with a support of the 9 + 2 microtubule system.

• Cilia are shorter and more numerous than flagella.

• Cilia and flagella move the cell with rhythmic power strokes, analogous to the oars of a boat.

• Reproduction and life cycles are highly varied among protists.• Mitosis occurs in almost all protists. • Some protists are asexual .• Others are primarily asexual but can also reproduce sexually

occasionally.

B(- MovementB(- Movement::

C(- C(- ReproductionReproduction::

• Many protists are symbionts that inhabit the body fluids, tissues, or cells of hosts.

• These symbiotic relationships span the continuum from mutualism to parasitism.

• Some parasitic protists are important pathogens of animals, including those that cause potentially fatal diseases in humans.

F(- Importance:F(- Importance:

Protists )Protists )1-1-EuglenaEuglena((

Systematic PositionKingdom :Protista Phylum : SarcomastigophoraSubphylum : MastigophoraClass : PhytomastigophoraGenus : Euglena

Eyespot which is sensitive to light and

helps the euglena find light.

Light detector near the base of long

flagellum function to detect light that is not

blocked by eyespot.

protein bands beneath the plasma

that provide strength and flexibility

Contractile Vacuole holds excess water and

removes it from the cell.

MovementMovement::

• Euglena use Euglena use flagellaflagella ((flagellates) for movement for movement• The euglena can glide and swim using their flagella

• A single-celled mixotrophic protist, • Can use chloroplasts to undergo photosynthesis if light is available • or live as a heterotroph by absorbing organic nutrients from the environment.• Sometimes form resistant cells (cysts) that can survive harsh conditions.

Nutrition:Nutrition:

Reproduction:Reproduction:

• Euglena Reproduce asexually by binary fission

The Summary

• Most protists are aerobic, with mitochondria for cellular respiration.

• Some protists are photoautotrophs with chloroplasts.

• Still others are heterotrophs that absorb organic molecules or ingest larger food particles.

• A few are mixotrophs, combining photosynthesis and heterotrophic nutrition.

• Protists may include photosynthetic species, heterotrophic species, and mixotrophic species.

NutritionNutrition::

• Most protists move with flagella or cilia during some time in their life cycles.

• The eukaryotic flagella are not homologous to those of prokaryotes.

• The eukaryotic flagella are extensions of the cytoplasm with a support of the 9 + 2 microtubule system.

• Cilia are shorter and more numerous than flagella.

• Cilia and flagella move the cell with rhythmic power strokes, analogous to the oars of a boat.

• Reproduction and life cycles are highly varied among protists.

• Mitosis occurs in almost all protists.

• Some protists are asexual .

• Others are primarily asexual but can also reproduce sexually occasionally.

MovementMovement::

ReproductionReproduction::• Many protists are symbionts that inhabit the body fluids, tissues, or cells of hosts.

• These symbiotic relationships span the continuum from mutualism to parasitism.

• Some parasitic protists are important pathogens of animals, including those that cause potentially fatal diseases in humans.

ImportanceImportance::

Kingdom Protista

)Eukaryotic

uni-/multi-cellular(