Kingdom Protista

What is a Protist?There is much debate about this very diverse group of organisms. Scientists have been arguing for years over how best to classify these organisms. Eventually the protists may be divided into many separate kingdoms. For now, we will consider the protists as a single kingdom.

A protist is any organism that is

not:a plant, an

animal, a fungus or a prokaryote.

Protists are __________ that are not members of the

kingdoms:Plantae, Animalia, or Fungi.

eukaryotes

The range and variety of organisms in this kingdom is huge. It is thought that this

group may contain over _______ different species.

200,000

Most protists are _________, but a few are _______ and a few

are ___________.

unicellularcolonial

multicellular

Because most protists are unicellular they are considered the simplest eukaryotic organisms, but their cells are extremely complex. They must carry out within a single cell all the _____________ performed by __________ cells, such as:digestion, gas exchange, circulation and excretion.

basic functionsspecialized

In multicellular organisms, essential

biological functions are carried out by organs.

Unicellular protists carry out the same

essential functions, but they do so using

subcellular organelles, rather than with

multicellular organs.

Classification of Protists

One way to classify the protists is according to…..…..the way they obtain their nutrition.

The heterotrophs are called animal-like protists.The photosynthetic autotrophs are called plant-like protists.A few obtain their food by external digestion and are called fungus-like protists.

Some protists are ____________, some are ___________, and some are __________.

Mixotrophs are capable of combining……photosynthesis and heterotrophic nutrition.

heterotrophicautotrophic mixotrophs

Protists can be divided into three categories:

Protozoa:Ingestive

animal-like protists

Algae: Photosynthetic

plant-like protists

Slime Molds:

Absorptive, fungus-like

protists.

The protists were the first _________ cells, and they evolved 1.5

billion years ago.

eukaryotic

The evolution from prokaryotes to the first eukaryotes was one of the big evolutionary

transitions, second in importance only to the origin of life.

One theory is that larger, more complex cells evolved partly as a result of certain prokaryotes taking up residence inside other cells.

These prokaryotes that began to live inside other cells became the ____________ of that cell. This theory is referred to as _____________.

The first eukaryotes acquired mitochondria by….

…..engulfing aerobic prokaryotes.

mitochondriaendosymbiosis

Chloroplasts were formed by a similar

fashion.

_________________ prokaryotes captured and trapped ______________ prokaryotes and these became the ___________ inside the cell.

Nonphotosynthetic

photosynthetic

chloroplasts

The Evidence

Mitochondria and chloroplasts carry out their own replication by a splitting process similar to binary fission.

Chloroplasts and mitochondria contain their own DNA.

The DNA is a single, circular molecule of DNA like the one found in the bacteria.

Mitochondria and chloroplasts contain ribosomes that resemble those of the bacteria.

Many of the enzymes contained in the cell membrane of bacteria are found in

mitochondria and chloroplast membranes.

They are the appropriate size to be descendants of bacteria.

Both of these (mitochondria and chloroplasts) are

types of symbiosis known as

endosymbiosis.

Endosymbiosis: A hypothesis about the origin of the _________ cell, maintaining that the forerunners of eukaryotic cells were _________ associations of __________ cells living inside larger ___________. Mitochondria originated as symbiotic, aerobic bacteria.

eukaryoticsymbiotic

prokaryotic prokaryotes

THE PLANT-LIKE PROTISTS: THE ALGAE

Algae are a very diverse group of protists. They

range in size from microscopic single-celled

organisms to largemulticellular seaweeds.

All of the algae are __________. They are __________,

have __________, and make their

own food by ______________.

autotrophseukaryoticchloroplasts

photosynthesis

Algae are producersin the food chain. They are responsible

for much of the atmospheric oxygen.

They are classified by color. They all contain

chlorophyll, but the green chlorophyll may be maskedby other pigments. There are green algae, red algae,

brown algae, golden brown, and yellow algae.

In the past, the algae were classified as plantsand placed in the Kingdom Plantae.

They are now classified as protists and are no longer a

part of the plant kingdom for the following reasons:

Algae lack the specialized tissues that are found in the true plants.

Algae lack vascular tissue that is found in the true plants.

Algae lack true roots, stems and leaves.

Algae are divided and classified into several phyla, based on the following characteristics:

1. Their color:

All algae contain chlorophyll a, which is required for photosynthesis.Some phyla have accessory pigments that give them a characteristic color.

REDBROWN

GOLDEN

GREEN

These algae consist of a single cell.Most unicellular algae are aquatic and compose the “phytoplankton”of aquatic ecosystems. Phytoplankton are the….…..unicellular, photosynthetic organisms in aquatic ecosystems that form the foundation of aquatic food chains.The phytoplankton produce almost ____ of the world’s ____________ and are the major producers of ______ in the atmosphere.

half carbohydrates

oxygen

Colonial algae have a structure that consists of….….groups of cells acting in a coordinate manner.

It is believed by many scientists that the green algae gave rise to the land plants.

Evidence supporting this theory includes:

a) Both groups of organisms have chloroplasts that contain chlorophylls a and b.

b) Both store their food as starch.

c) Both have cell walls composed of cellulose.

Plant- Like Protists

Unicellular Algae

20-3

Diatoms

Euglena Dinoflagellates

Although these types of unicellular protists are motile, they are considered plant-like because they are autotrophic.

Diatoms are unicellular algae that have….

…. a unique glass-like wall made of silica.

The wall consists of two parts that overlap like a shoebox and its lid. The walls are able to withstand great pressure and offer protection from the crushing jaws of predators.

Most reproduce by binary fission. Sexual reproduction is not common.

There are over 100,000 different species.

They are the major component of phytoplankton,

making them very important producers in both freshwater

and salt water ecosystems.

They are an essential source of nutrition for microscopic

heterotrophs such as protists and invertebrates.

As producers, they release an abundance of oxygen into

the atmosphere.

The dinoflagellates are characterized by cells that are…….reinforced by cellulose plates.

They have two flagella that make them spin in the water as they move.

Dinoflagellates are abundant components of both marine and freshwater plankton, forming the basis

of the food chain.

Many are photosynthetic. Others are…

…mixotrophs or heterotrophs.

Some dinoflagellates bloom in the ocean and create red tides. They have an abundance of carotenoids turning the water a reddish color. They produce toxins which can kill fish and invertebrates in the area.

Some species can produce bioluminescence, a display of light that can be seen at night.

Euglenophytes are flagellated, unicellular algae that exhibit……both plant-like and animal-like characteristics.

A euglenoid has a pocket at one end of the cell from which…….one or two flagella emerge.

A familiar euglenoid is Euglena. Euglena are __________. In sunlight they are __________, but when sunlight is unavailable, they can become ____________, absorbing nutrients from their environment.

mixotrophsautotrophic

heterotrophic

Label the structures of the Euglena:

1 – Cell

membrane

2 – Pellicle

3 – Flagella

4 – Contractile

vacuole

5 – Nucleus

6 – Chloroplast

7 – Eyespot

Euglena have both plant and animal characteristics:

Animal – like Characteristics:

a) They are highly motile and move with a flagella.

b) They can take in food through the cell membrane.

c) There is no cell wall.

Plant – like Characteristics:

a) They have chloroplasts and carry out photosynthesis.

The eyespot is red and is sensitive to light. Euglena seek out bright areas. The cell is also sensitive to touch, heat and chemicals.

Pellicle:Transparent

protein bands beneath the

plasma membrane that provide strength

and flexibility. There is no cell wall.

Contractile vacuoles help to rid the cell of

excess water.

They swell with water and contract when full to send the water out of the cell.

Euglena reproduce asexually only by:

binary fission.

20-2 THE ANIMAL-LIKE PROTISTS: THE PROTOZOANS

Protozoa means "first animals". They perform all the processes of

multicellular organisms such as digestion, excretion, and

respiration except that in the protozoa all processes take place

inside a single cell.

Most are heterotrophic and obtain their nutrients by ingesting small molecules or cells.

These particles are digested inside food vacuoles. A food vacuole is….

….a membrane-bound sac that contains digestive enzymes.

They may live in ponds, streams, oceans, mud, soil, in or on certain plants and animals.

Some species live as parasites inside the body cavity of certain worms, termites, and humans.

They make up zooplanktonand form the basis of the food chain in aquatic environments.

They can cause diseases such as….….malaria, African sleeping sickness, and dysentery.

All are capable of asexualreproduction, usually by binary fission. A few species can reproduce sexually by conjugation.

Pseudopodia (Sarcodines)

Cilia (Ciliates)

Flagella (Zooflagellates)

No movement

(Sporozoans)

The protozoa are generally classified into four groups based on their method of movement.

Methods of movement include:

This group includes hundreds of species of

amoebas.The amoeba is a shapeless mass of

protoplasm surrounded by a plasma membrane.

The amoeba moves by pseudopodia or "false

feet".

The oxygen necessary for life diffuses through the cell membrane from the water. Wastes pass out in the same way.

Water enters the ameba by osmosis. If the ameoba did not have a way of getting rid of the excess water, it would burst.Contractile vacuole: When this vacuole fills up with water, it contracts and expels the excess water.

Food Getting and Digestion

Amoeba eat……algae or other

protozoans.

The particle of food is surrounded by the pseudopodia and engulfed into the cell by phagocytosis.The food is digested by enzymes in the food vacuole.The digested food is absorbed by the cytoplasm and used as a source of energy.The wastes are excreted through the cell membrane.

Reproduction

They reproduce:asexually by simple cell

division.

They reproduce:sexually by conjugation

Diseases caused by Sarcodines:

Many people become infected with a species of Entamoebawhich causes the disease known as ameobic dysentery.

These amoeba live in the intestine where they absorb

food from the host. The host may experience

severe diarrhea and bleeding from damage caused to the

intestinal wall.

Cilia are….….short, hair like projections that line the cell membrane. The cilia beat in synchronized waves across the surface of the cell.

Ciliates are a large, varied group of protists named for their use of cilia to move and feed.

1 – Contractile vacuole

2 – Oral groove

3 – Mouth

4 – Gullet

5 – Food vacuole

6 – Anal pore

7 – Micronucleus

8 – Macronucleus

9 – Cilia

10 – Trichocyst

Label the structures of the

Paramecium:

The Paramecium has a definite shape and size. It does not change shape like the ameba.

The Paramecium has two nuclei:a) Macronucleus:

This is the large nucleus. This nucleus regulates nutrition and activities of the cell.

b) Micronucleus: This is the small nucleus. This nucleus functions only during reproduction.

The paramecium moves with cilia, which are hair like structures

arranged in rows. They beat back and forth to

cause movement.

The paramecium has the pellicleunder the cell membrane.

A pellicle consists of…… bands of protein that provide support to the cell membrane.

Food Getting:a) The oral groove is lined with cilia,

which force food particles into the mouth.

b) The mouth opens into the gullet. c) When the end of the gullet becomes

full, it breaks off and becomes a food vacuole where the food is digested.

d) The wastes pass out of the cell through the anal pore.

Oxygen enters through the cell membrane by

diffusion.

Sensitivitya) The paramecium has no specialized sense

organs, but they are sensitive to touch, heat, chemicals, and light.

b) Except when feeding, they swim constantly. When they bump into something, they reverse, and swim off in another direction. This kind of trial and error response is called the “avoiding reaction”.

Trichocysts are found just under the cell membrane. Trichocysts are used for defense. When a paramecium is confronted by danger, the trichocysts release stiff projections that protect the cell.

Reproduction

Asexual by binary fission.

Sexual by conjugation. Two paramecia exchange micronuclei, and then continue to

divide by fission. They have exchanged genetic information.

The Zooflagellates

The 2500 species found in this group are characterized by the presence of one or more flagella. Flagella are….…. long, hair like structures that whip back and forth propelling the cell through the water.This group contains some of the most primitive of the protozoa.

The Trypanosomes are flagellatesthat cause African sleeping sickness.

Trypanosomes are found in the blood of jungle animals and are transmitted to man by the bite

of the tsetse fly.

Early symptoms are headache and fever.

Advanced symptoms are coma and death.

Trypanosomes evade the host’s immune system with a “bait and switch” tactic. The surface of the trypanosome is coated with millions of copies of a single protein.

Just as the host’s immunesystem learns to recognize this pathogen and launch

an attack, new generations of the

trypanosome switch to another surface protein

with a different molecular structure.

These frequent changes in the surface protein prevent the

host from developing immunity.

Found in the bloodstream

Characteristics include:1. No method of movement.2. Reproduce asexually by

spores.3. Always are parasitic.4. They live by absorbing food

from the cells of the host.5. Cause malaria in man.6. Requires two hosts: man

and the Anopheles mosquito.

Life cycle of the Malarial Parasite, Plasmodium:

1. Mosquito bites a human who has malaria.

2. The plasmodium from the humanenters the stomach of the mosquito.

3. Plasmodium travels to the salivary glands of the mosquito.

4. Mosquito bites another human and the plasmodium enters the bloodstream of man.

5. Plasmodium enters the red blood cells where they produce spores. Since they live inside the red blood cell, they are hidden from the host’s immune system. Infected red blood cells burst, releasing the spores to infect other red blood cells.

6. Healthy mosquito bites a malaria victim and the cycle continues.

Both the Plasmodium and the Anopheles mosquito have become resistant to drugs and pesticides.

In recent years there has been a resurgence of malaria, killing 2 million people a year.

These organisms have unique life cycles that set them apart from the algae, the protozoa,

and the fungi. They are….

…eukaryotic, multicellular, heterotrophic organisms with

very little tissue specialization.

The fungus-like protists include the:

slime molds and the water molds.

Water Mold

Slime Mold

SLIMEM

OLD

SSlime molds are typically found

growing on damp soil, rotting logs,

or decaying leaves.

They appear as glistening masses of slime that may be white, red or yellow.

They spend part of their life in a mobile, amoeba-like feeding form, engulfing organic materials, and part of their life in a stationary reproductive stage.

The slime molds play a key role in the recyclingof organic material.