Eukaryotes and Protozoans Overview

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Questions and Answers

What are the synapomorphies that define eukaryotes?

Membrane bound nucleus and endosymbiosis of organelles.

Describe the body plan and features common to protozoans.

Protozoans are acoelomate and can move using flagella, cilia, or pseudopodia; they may be autotrophic or heterotrophic and lack a cell wall.

How does ameboid movement occur?

Through pseudopodia where hydrostatic pressure of endoplasm pushes against ectoplasm, involving actin and actin-binding proteins.

What is the sliding filament hypothesis?

Dynein arms bind to tubulin, bend to move it up, release, and bind to the subunit below. Signup and view all the answers

Lobopodia are characterized by large extensions of and .

ectoplasm, endoplasm Signup and view all the answers

What is phagocytosis?

Ingestion of food particles. Signup and view all the answers

What does a contractile vacuole do?

Expulsion of water. Signup and view all the answers

Which of the following describes binary fission in protozoans?

Two identical individuals Signup and view all the answers

Which of the following is a method of sexual reproduction in protozoans?

Conjugation Signup and view all the answers

What is an example of an organism in the Phylum Euglenozoa?

Euglena Signup and view all the answers

What is the synapomorphy that defines Phylum Stramenopiles?

Two different flagella, one being tufted. Signup and view all the answers

What defines the Clade Alveolata?

Presence of alveoli and multinucleate cells in ciliates. Signup and view all the answers

Name an example of an organism in the Phylum Dinoflagellata.

Ceratium Signup and view all the answers

What is the main characteristic of the Phylum Apicomplexa?

Presence of an apical complex. Signup and view all the answers

What type of organism is radiolaria?

Amoeboid protists that are heterotrophic. Signup and view all the answers

What is an example of an organism in the Phylum Viridiplantae?

Volvox Signup and view all the answers

Study Notes

Defining Eukaryotes

Eukaryotes are defined by the presence of a membrane-bound nucleus and organelles.
Organelles are formed through endosymbiosis.

Protozoans

Protozoans are single-celled eukaryotic organisms with no cell wall, that are either autotrophic or heterotrophic.
Protozoans are generally categorized by their method of locomotion: flagella, cilia, or pseudopodia.
They can be free-living, sessile, colonial, commensal or parasitic.
Protozoans contain:
- nucleus
- mitochondria
- plastids
- extrusomes:
  - trichocyst: expel threads
  - toxicyst: expel filaments with toxins
  - ancoracyst: immobilize prey
Protozoans have an outer, selectively permeable cell membrane, which allows for the movement of molecules into and out of the cell.

Ameboid Movement

Ameboid movement occurs through pseudopodia (false feet).
The outer layer of the cell, the ectoplasm, is a gel-like substance that surrounds the more fluid inner endoplasm.
The hydrostatic pressure of the endoplasm pushes against the ectoplasm, which is made up of actin and actin-binding proteins.

Sliding Microfilament Model

The dynein protein arms bind to the tubulin subunits and bend to move the tubulin subunit upward.
The arms release and reattach to the subunit below, repeating the process rapidly by reverse.

Forms of Asexual Reproduction in Protozoans

Binary Fission: The parent cell divides into two identical daughter cells.
Budding: The offspring is smaller than the parent.
Schizogeny: Multiple individuals are formed through a process of multiple fission.
Sporogeny: Multiple fission occurs following the union of gametes to form spores or sporozoites.

Forms of Sexual Reproduction in Protozoans

Syngamy: One gamete fertilizes another.
Autogamy: Gametes arise and fuse within the parent cell.
Conjugation: The exchange of gamete nuclei occurs.

Phylum Euglenozoa

Synapomorphy: possess flagella, pellicle, and stigma.
Features: Some are autotrophic and some are parasitic.
Example: Euglena

Phylum Stramenopiles

Synapomorphy: possess 2 different flagella, one being tuffed.
Features: Some are autotrophic and some are parasitic.
Example: diatoms, brown algae

Clade Alveolata

Features: Alveolates have one or more alveoli, membrane-bound sacs below the cell membrane, which may play a role in providing structural support, osmoregulation, or other processes. They are generally heterotrophic and can be parasitic or free-living.

Phylum Ciliophora

Synapomorphy: Ciliates are all multinucleate (have multiple nuclei).
Features: All ciliates possess cilia, a pellicle, and some have trichocysts or toxicysts.
Example: Paramecium

Phylum Dinoflagellata

Synapomorphy: Possess two flagella, one being located in a transverse groove and the other in a longitudinal groove.
Features: Almost 50% are autotrophic and some are heterotrophic. They can be naked or contain cellulose plates and ornamentation. Some are bioluminescent. Dinoflagellates are responsible for harmful algal blooms and red tides.
Example: Ceratium

Phylum Apicomplexa

Synapomorphy: Have an apical complex consisting of distinctive organelles at one end, called the apex, used for penetrating host cells, and contains alveoli and a glideosome for movement.
Features: All are parasitic and possess a complex life cycle.
Example: Plasmodium

Clade Rhizaria

Features: Most are ameboid with filose pseudopods. All are heterotrophic and have tests.
Examples: Foraminifera and Radiolaria

Phylum Foraminifera

Synapomorphy: Heterotrophic and fossilize.
Features: Possess a calcium carbonate test that forms chambers, which are added as the organism grows. Some foraminiferans are important indicators of past environments.
Example: Globorotalia

Phylum Radiolaria

Features: Radiolaria produce elaborate siliceous skeletons that can be quite beautiful.

Phylum Amebozoa

Features: The Amoebozoa are a diverse group and are the most well-known group of amoeboids. They are characterized by amoeboid movement (using pseudopodia, and are mostly heterotrophic.
Examples: Amoeba, slime molds

Phylum Viridiplantae

Synapomorphy: Contain chlorophyll a and b, have cellulose cell walls.
Features: Photosynthetic.
Example: Volvox

Choanoflagellates

Choanoflagellates are solitary or colonial flagellated eukaryotes that are thought to be closely related to animals.
They are distinguished by a ring of microvilli surrounding a single flagellum, which creates a current to draw in food particles.
Choanoflagellates resemble the collar cells (choanocytes) found in sponges, which makes them important for understanding the evolution of multicellularity in animals.
They possess cell-to-cell signaling proteins that are common in multicellular animals.

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Description

This quiz covers the characteristics of eukaryotes and protozoans, including their organelles, locomotion methods, and cell structures. It delves into the details of ameboid movement and the functionality of various organelles in protozoans. Test your knowledge on these fascinating microorganisms!