Protozoan Groups

Protozoan Characteristics

They are found wherever life exits 

They are highly adaptable 

Easily moved from place to place

The required moisture

They may be sessile or free living 

They form a large part of the suspended plankton

They have to perform every function that they need to survive

Unicellular but many are colonial meaning they live close together

All symmetries found within the group

All feeding modes found in the group

What is the term denoting structures found within a cell?

Organelles-have specific functions

Aquatic Habitat

-Most are free-living

-Algae are the base of the food web and primary producers exposed to sunlight.

Parasitic protists

Complex life cycles with multiple habitats including multiple hosts.

Not free living.

Autotrophs like algae

Photosynthesizers-make their own energy through photosythesis

They also need- minerals/nutrients, water. CO2

Protozoa are heterotrophs

They consume other beings to get their nutrients and organic materials.

Phagocytosis

Ingest whole prey by engulfing them

Parasitic Protists nutrition

Consume resourses taken from their hosts

Unicellular Forms and Small Colonies

Comprise phytoplankton communities in oceans and lakes

Colonial Algae

Sometimes they can form large colonies for example, seaweed

Protozoan Vs Plants

Protozoans do not have roots and leaves and are composed of single cell organisms. They also can’t transport water and food.

Two Kinds of Asexual Reproduction for Protozoans

Binary Fission and Schizogany

Binary Fission

A form of mitotic division

A simple form of reproduction where one cell splits into two identical cells

Schizogany

repeated nuclear divisions followed by simultaneous cytokinesis

one cell divides many times to produce many new cells at once.

Two Kinds of Sexual Reproduction that occur in Protozoans

Syngamy and Conjugation

Syngamy

Fertilization of one haploid gamete by another they join together to form one cell

conjugation

mutual exchange of genetic material

Two cells join together exchange genetic material and become more genetically diverse, then break apart

Cilia

small, hairlike structures, usually very numerous

Flagella

long, whip-like, few in number

pseudopodia

fluid extensions of cell

lobopodia

Blunt and temporary-Amoeba

Axopodia

long, thin, with rigid rod (Prey)

reticulopodia

are branching, net-like (prey)

How does gas exchange occur in protozoans?

-simple diffusion from high to low concentration

-no special organelles or system-limits size

-diffusion occurs across the cell membrane this limits how large protozoans --can be because the surface-area-to-volume ratio decreases as they get bigger

-This is why very small/flat/skinny organisms don’t need specialized gas-exchange structures.

How does excretion occur in protozoans?

Simple diffusion from high to low concentration (because of high surface-area-to-volume ratio)

What is the major end product of protein metabolism in protozoans?

ammonia

What is osmoregulation?

Maintaining the appropriate solute/water balance (this is part of homeostasis)

What is the osmoregulatory challenge for freshwater protozoa

Water tries to push from the more concentrated area outside of the cell and the cell is saltier so water wants to go to the cell.

What is osmosis?

Movement of water form more higher concentration to lower concentration

what if the solute can’t move through a barrier (like a cell membrane)?

The water moves

What is exocytosis?

Contractile vacuoles gather and eject excess water

How do Contractile Vacuoles work?

“proton pumps” actively transport H+ and HCO3- ions, drawing water across lipid membrane of vacuole

How do marine protists cope with osmotic pressures?

-Most or all species are probably “osmoconformers”, not “osmoregulators”.

-This means their internal solute concentration matches seawater. Cope with it

-If they DO lose some water through osmosis, they can “drink” more in by forming vacuoles to take in water – this is called “pinocytosis”  (and then they have to force the excess salts out).

Phylum Euglenozoa

-Single Cell

-A thick outer membrane called a pellicle

-Flagellum locomotion

-have chlorophyll and red eyespot

-They are saprozoic (absorb nutrients) and many are autotrophic (photosynthesizers).

Trypanosoma

-A parasitic Euglenozoan

-causes African Sleeping Sickness in humans.

-Single cell parasites and rely on blood sucking vectors

-sickle-shape cell with an undulating membrane driven by a flagellum

Phylum Viridiplantae

-“plant-like” protists

-unicellular or colonial, autotrophic, very diverse; land plants arose from this group of algae

Volvox

Type of Viridiplantae

-displays the most primitive form of cell specialization, or division of labor:

-most cells have two flagella to propel the colony

-some have larger stigmata to detect light

-some form gametes, for sexual reproduction

Volvox reproduction

Volvox reproduces asexually in spring and summer, but sexually in the fall

To produce thick wall zygotes to survive harsh weather. They stay dormant until they can survive and better conditions.

Ameba

are not a monophyletic* group, so they are no longer in a single phylum.

-some are ”testate” (a “test” is a rigid outer structure)

-constantly changing shape

-locomotion on a substrate using lobopodia

-feeding via phagocytosis

Amoeba proteus

NON-testate ameba are characterized by the very common species

Entamoeba hystolitica

-A parasitic non-testate Ameba

-causes amoebic dysentery in humans and is transmitted via untreated drinking water.

-most prevalent in tropical regions and poorer regions without treated water

Testate Ameba

has a shell

Radiolaria

-Testate Ameba

-very abundant heterotrophs in the marine plankton worldwide

-They have skeleton-like tests made of silica

-They are divided inner and outer

-They significantly contribute to the composition of the ocean bed-form rocks

Foraminifera

-are also very abundant heterotrophs in marine plankton. Primarily marine.

-Limestone is ancient deposits of these tests.

-One-third of the seabed made up of test of single genus

-Cells are covered with locomotory cilia.

-Feeding is by ingestion (phagocytosis).

-Paramecium has two star-shaped Contractile vacuoles.

-Food enters through cytostome in the oral groove.

Conjugation vs Syngamy

conjucation-an exchange rather than a transfer of genetic information

Dinoflagellates

-They have an outer test and two distinctive flagella – one circling the cell and the other trailing from it (e.g., Fig 11.27).

-Toxins secreted by certain members of this group can build up and be toxic to fish and other marine life; what is this phenomenon called?

A:”red tide”

zooxanthellae

-live in a mutualistic association in the tissues of stony corals and other invertebrates

-only corals with (“) can build coral reefs because

(“) are photosynthesizers, providing sugars to the coral polyps

Giardia

-Phylum Retortamonada

-can occur in drinking water contaminated by fecal material and can cause severe diarrhea.

Phylum Apicomplexa

-includes parasitic protozoans with complex life cycles – many are pathogenic

Plasmodium

causes the most widespread infectious disease in the world

Malaria

Definitive Host

Where sexual maturity occurs and reproduce

Intermediate Host

an organism that harbors a parasite during its immature or larval stage

Plasmodium