Protists- Bio

Protists

A eukaryotic organism that cannot be classified as an animal, plant, or fungus.

Are protists considered a kingdom?

No, they are too similar to other species (plants, animals, fungi)

Are protists monophylectic

No

Characteristics of Protists

- nucleus

- Membrane enclosed organelles

- Well developed cytoskeleton

- some multicellular or colonial

colonial

single-celled organisms that live together in a closely interconnected group

Protists have the most ___ and ____ diversity

structural and functional

Unicellular protists are the most ___

complex

Nutritionally, some protists can be

photoautotrophs, heterotrophs, and mixotrophs

Photoautotrophs

Organisms that use light as a source of energy to synthesize organic substances.

Heterotrophs

An organism that obtains organic food molecules by eating other organisms or their by-products.

Mixotrophs

combine photosynthesis and heterotrophic nutrition

How do protists reproduce

sexually and asexually

Origin of flexible cell surface in protists

plasma membrane became flexible enough to fold inward and form membrane-bound compartments

Cytoskeleton

supports cell shape, move materials inside the cell, and help cell change shape

nuclear envelope

membrane folds surrounding the DNA that later became the nucleus

Digestive vacuoles

In protists, an organelle specialized for digesting food ingested by endocytosis.

Pros to flexible cell surface in protists

Cells could grow larger

infolding

the theory that the cell's outer membrane folded inward and became an organelle

4 diverse supergroups of eukaryotes

Excavata, SAR, Archaeplastida, Unikonta

Plastids

A group of membrane‐bound organelles commonly found in photosynthetic organisms and mainly responsible for the synthesis and storage of food.

endosymbiotic theory

Phagocytic eukaryotes engulfed proteobacteria that evolved into mitochondria

First function of mitochondria

To detoxify O2 by reducing it to water.

What feature of eukaryotes makes endosymbiosis possible?

flexible cell membrane

Alveolates

unicellular, contain alveoli (membrane bound sacs underneath plasma membrane), and photosynthetic

Falls under alveolates:

Dinoflagellates, apicomplexans, ciliates

Dinoflagellates

marine, photosynthetic, and sometimes parasites

Dinoflagellates can cause

red tides

Structure of dinoflagellates

two flagella, one equatorial groove, and one longitudinal groove

Apicomplexans

A type of parasitic protozoan. Can also have two different hosts & complex life cycles.

Apical complex

mass of organelles at one tip helps parasite enter host cells

Diseases caused by apicomplexans

malaria, toxoplasmosis

Ciliates

a type of protozoa that moves using hairlike cilia

Are ciliates heterotrophic or autotrophic?

heterotrophic

Structure of ciliates

complex body form and two types of nuclei

types of ciliates

Paramecium

Paramecium

A ciliated (it propels itself via cilia) protist that lives in fresh water and eats other tiny organisms for food.

Pellicle

A firm, flexible coating outside the plasma membrane

Function of pellicle

maintains shape while allowing movement

Organisms in fresh water are ____ to their environment

hypertonic

Contractile vacuoles

A membranous sac that helps move excess water out of the cell.

Protists that have contractile vacuoles

paramecium

Stramenopiles

Clade of protists with "hairy" flagellum includes oomycetes, diatoms, and brown algae

Structure of stramenopiles

two flagella with rows of tubular hairs on longer flagella

Diatoms

unicellular algae that have a unique glass-like wall made of silica

How do diatoms get their yellow color?

carotenoids

Many diatoms form ___

filaments

Major primary producers

Diatoms (produce 20%-40% of oxygen on Earth)

Dead diatom shells can accumulate as

diatomaceous earth (used in filters, abrasives, and insect-control products)

brown algae

group of marine, multicellular, autotrophic protists, the most common type of seaweed. Brown algae include the kelps.

What gives brown algae its color?

fucoxanthin pigment

Structures resembling roots, stems, and leaves in brown algae:

holdfasts, stipes, and blades (NOT true plant organs)

blades

A leaflike structure of a seaweed that provides most of the surface area for photosynthesis.

stipe

A stemlike structure of a seaweed.

Holdfast

A special structure used by an organism to anchor itself.

Oomycetes

water molds, downy mildews

Water molds are absorptive heterotrophs, meaning:

They secrete enzymes to digest large molecules into smaller molecules that can be absorbed

Saprobic

feed on dead organic matter

Oomycetes act as ___

decomposers

Rhizaria

Unicellular, aquatic organisms with long,

thin pseudopods.

Classified under rhizaria:

cercozoans, foraminiferans, and radiolarians

Cercozoans

-some are aquatic, others live in the soil.

-have diverse forms and habitats

foraminiferans

secrete shells of calcium carbonate

radiolarians

Amoebas with threadlike pseudopodia radiating from central body

Radiolarians are exclusively

marine

Pseudopods function

increase surface area for exchange of materials and help the cell float

Radiolarians have ____ internal skeletons

glossy

Excavata

clade characterized by its cytoskeleton

Excavata have an ____ ____ on the side of the cell body

excavated groove

Excavates include protists with ____ and ____

Modified mitochondria and unique flagella

Diplomonads and Parabasalids

lack mitochondria but have modified reduced version of mitochondria

Diplomonads

a protist (giardia lamblia) that has two nuclei and multiple flagella. A water-borne parasite that causes

intestinal disease.

Parabasalids have:

undulating membranes for locomotion

Trichomonas vaginalis

parabasalid that causes STI's in humans. Infects urogenital tract of males and females

Euglenozoans

a diverse clade that includes predatory heterotrophs, photosynthetic autotrophs, mixotrophs, and parasites

Main feature of euglenozoans

spiral or crystalline rod inside their flagella

Euglenozoans include

kinetoplastids and euglenids

Trypanasoma brucei

causes African sleeping sickness

Trypanosoma cruzi

causative agent of chagas disease (leads to congestive heart failure)

Why are trypanosomes difficult to control

they change their cell surface molecules frequently

Bait and switch defense

Trypanosomes evade immunity by changing surface proteins.

unikonta sub group

Amoebozoans

Amoebozoans

lobe shaped pseudopods used for locomotion

Causes amoebic dysentery

Entamoeba histolytica

How is Entamoeba histolytica transmitted?

contaminated water or food