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Chapter 15 Protists !

! Protists live wherever there is water. So they have contractile vacuoles.

! Kingdom Protista is probably the most diverse group of living things.

! They can be plant-like, animal-like, or fungus-like.

! Protists range in size from microscopic algae to giant seaweeds.

! The one characteristic that they all have in common is that they are all eukaryotes.

! Most are unicellular."

! Some are colonial. A few colonies have evolved into multicellular organisms with specialized structures.

What is a Protist? !

The Biology of Protists - 1:12

! The most common way to group protists is by how they obtain nutrition.

! Plant-like - autotrophs

! Animal-like - heterotrophs

! Fungus-like - heterotrophs

! Animal-like are called protozoans.

! They are grouped according to their means of locomotion. (how they move)

Animal-like Protists – 1:48

! An example would be an Amoeba ! Some sarcodines are surrounded by a shell.

(foraminiferens and radiolarians)

! An amoeba extends lobes of cytoplasm called pseudopods to move and obtain food.

! When conditions become unfavorable an amoeba can develop into a cyst.

! A cyst can withstand drought, heat, famine, or ingestion by other organisms.

! When humans drink water contaminated with parasitic amoeba they can get amoebic dysentery.

Sarcodines - pseudopods ! Amoeba!

Amoeba – 1:51

Zooflagellates - flagella!! These protozoans use a whiplike flagella for

locomotion.

! They might use the flagella to swim in a certain direction or just to move in a spinning fashion.

! Some use their flagella to create currents to bring food.

! Some zooflagellates inhabit other organisms in a symbiotic relationship. Like Trichonympha living in the intestine of termites.

Ciliophorans - cilia!! The most numerous and diverse group.

! Ciliates are protozoans that are covered with cilia.

! Cilia are short hairlike projections used for movement.

! A paramecium is an example.

! A paramecium has a macronucleus (everyday functions) and a micronucleus(sexual reproduction).

! Most live in freshwater and can form cysts to survive unfavorable conditions.

Paramecium – 1:19

Sporozoans - nonmotile !! This group has no means of movement.

! Most are parasitic.

! Their life cycles are complex and involve both sexual and asexual phases.

!  In fact, their life cycle might include multiple hosts.

! An example would be Plasmodium. It is transmitted by mosquito and causes Malaria in humans.

Sporozoans !

Sporozoans – 1:44

! Plant-like are called algae.

! They are categorized as unicellular or multicellular.

Plant-like Protists – 3:47

Unicellular Algae !

! They are covered with cellulose plates.

! They use a pair of flagella for locomotion.

! Most are free-living marine organisms.

! One species causes a green glow in the ocean.

! One species causes “red tides”.

Dinoflagellates

Killer Algae – Pfiesteria Piscicida :3:21

Unicellular Algae !

! These are unicellular algae that look like and have the variety of snowflakes.

! They have glass-like cell walls containing silica.

! The walls have two parts that fit together like pill boxes.

! Pores in the cell walls allow materials to pass into and out of the diatom.

Diatoms

Unicellular Algae !

! They have thousands of different shapes and patterns.

! They are among the most abundant organisms in the ocean.

! They have a high oil content. ! When they die their shells accumulate at

the bottom of the ocean as diatomaceous earth.

Diatoms Diatoms!

Diatoms – 1:27

Unicellular Algae !

! They resemble both algae and protozoans.

! They lack rigid cell walls. ! They move about by using a flagella. ! They do have chloroplasts and carry out

photosynthesis.

Euglenoids

Euglenoids !

Euglenoids – 1:37

! Multicellular algae were once considered plants because they contained chloroplasts.

! They are now considered protists because few of them have true tissues.

! They also reproduce more like protists.

! We classify them according to the color of their pigments.

Chlorophyta - green algae !

! This group most closely resembles plants because of the cell wall and the structure of their chloroplasts.

! Some are unicellular like Chlamydomans, which grows abundantly in ponds and moist soils.

Chlorophyta - green algae !! Some are multicellular

like Ulva, which are made of flat, leaf-like sheets.

! Ulva is found in the ocean.

! Some are colonies like Volvox, which might include a thousand cells.

Colonial Protists – 1:11


! Some multicellular algae like Spirogyra, grow as filaments with cells linked end to end.

! Commonly found in ponds.


! Most green algae live in fresh water or in moist soil.

! Many green algae live in symbiotic relationships with other organisms.

! For example, a lichen, which is a green algae and a fungus.

Chlorophyta!

Green Protists - :54

Rhodophyta - red algae !

! They grow in warm, saltwater environments.

! Some live near the surface and some live as deep as 260 meters.

! At this depth, few wavelengths of light are available for photosynthesis.

Rhodophyta - red algae !

! Red algae contains an accessory pigment that enables them to use the available light.

! Their pigments can also appear green, orange or almost black.

Phaeophyta - brown algae !

! They are multicellular.

! They live in cool saltwater habitats.

! This group includes the largest organism in the Protista Kingdom.

! Giant Kelp

Phaeophyta - brown algae !! Giant kelp can grow to

100 meters and live in deep water beyond the intertidal zone.

! They have specialized structures called air bladders to keep the kelp afloat near the surface to absorb sunlight.

! Some multicellular algae have complex life cycles that alternate between a spore producing stage (called a sporophyte generation) and a gamete producing stage (called a gametophyte generation).

! This type of life cycle is called alternation of generations.

Fungus-like protists !! They are small and live in

damp or watery places.

! They break down dead organic material.

! A protist that acts as a decomposer is known as a mold.

! Most taxonomists divide the molds into three groups: Fungus-like Protists – 1:19

Fungus-like protists !! Plasmodial slime molds. ! Cellular slime molds.

! Slime molds have a shiny, wet appearance and a texture like gelatin.

! Water mold.

! Water molds are fungus-like and live mostly in the water.

Fungus-like protists !

! In its feeding stage it is called a plasmodium.

! It can weigh as much as 50 grams and grow as large as the palm of your hand.

! It is a single cell with many nuclei. (multinucleated)

Plasmodial slime mold


! When conditions become unfavorable a plasmodium either creeps to a different location or enters a different stage of its life cycle.

! It forms a structure called a fruiting body.

! The fruiting body produces spores, which are carried by wind or animals to different locations.



! They can remain dormant for years.

! When the conditions become favorable the spores release gametes that fuse to form a diploid zygote.

! This zygote develops into a new plasmodium.


Fungus-like protists !Plasmodial slime mold


! It also alternates between a spore producing, fruiting body form and an amoeba-like feeding form.

! The feeding stage consists of small, single cells that move, engulf and ingest food.

Cellular slime molds


! When conditions become unfavorable, the cells secrete a chemical attractant that causes nearby cells to clump together to form a pseudoplasmodium.

! It is still made of independent cells.

! The cells of a pseudoplasmodium are haploid, a plasmodial cell is diploid.

! Its fruiting bodies then produce spores.

Cellular slime molds

Fungus-like protists !Cellular slime molds


! They have the appearance of cotton or fluff.

! They are decomposers in freshwater ecosystems.

! They might decompose plants or animals.

! They have cell walls made of cellulose.

! When they reproduce asexually they produce spores with flagella.

Water molds

Fungus-like protists !Water molds

! Algae and protozoans are the most numerous organisms in the ocean.

! These organisms are the beginning of the aquatic food chains.

! Plankton are mostly microscopic organisms that float near the surface of oceans and lakes.

! Even one of the largest animals on the planet feeds on plankton.

! Plankton is made up of zooplankton and phytoplankton.

! Zooplankton is the protozoans.

! Phytoplankton is the algae.

! The phytoplankton carries out more than 70% of Earth’s photosynthesis.

! Many protozoans are predators of bacteria, keeping their numbers in check.

! Farmers use seaweed as livestock feed or fertilizer.

! We use diatomaceous earth in products such as insulation, filters, detergent, abrasives and polishing agents in toothpaste.

! Diatom shells are also used in road paint to make it reflect car headlights.

! Seaweed has three complex carbohydrates used in food products.

! Carrageenan - a thickner and flavor enhancer added to many dairy products, such as milkshakes and chocolate milk.

! Agar - is sometimes used to thicken soups, puddings and cake frostings.

! Algin - pie filling, ice cream, French dressing, syrups, toppings and purees.

! Some people eat seaweed for its mineral components especially iodine.

! In Japan, sheets of red algae called nori, are used to wrap sushi.

! Protozoans also make great bioindicators.

Diseases caused either directly or indirectly by Protists.!

! Plasmodium - malaria ! People with malaria often

experience fever, chills, and flu-like illness. Left untreated, they may develop severe complications and die.

! Each year 350-500 million cases of malaria occur worldwide, and over one million people die, most of them young children in sub-Saharan Africa.


! Trypansoma - African sleeping sickness ! The most common vector is the tsetse fly, which may

spread the parasite to humans and animals through bites"! Symptoms include headache, weakness, and joint pain in

the initial stages; anaemia, cardiovascular problems, and kidney disorders as the disease progresses; in its final stages, the disease may lead to extreme exhaustion and fatigue during the day, insomnia at night, coma, and ultimately death"


! Giardia - is the most frequent cause of non-bacterial diarrhea in North America.

! Normally illness lasts for 1 to 2 weeks. !  Ingestion of one or more cysts may cause disease. ! Signs posted in wilderness areas often warn

about Giardia in streams. Commonly found in wild animals such as the beaver, this graceful, flagellated organism may infect unwary hikers.


! Gonyaulax - is one of the dinoflagellates responsible for red tides.!

! During red tides, many fishes, whales, manatees, and shorebirds have died in massive numbers because of the toxic conditions produced by dinoflagellate blooms.!

! Gonyaulax gives us the gift of bioluminescence.!


! Phytophthora infestans - causes late blight in some vegatables.

! In the mid 1800’s a potato blight devastated the potato crop in Ireland.

The Value of Kelp – 3:04 Oil From Algae – 5:27

Protozoa – 20:51

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