PROTOZOAPROTOS-FIRSTZOON-ANIMAL

Eucaryotic, unicellular microorganism

Occurrence• Almost all habitat• Sea, soil, fresh water, polar regions and very high

altitude

Ecology• Free living• Symbiotic –

parasitic-mutualistic

Free living-Factors affecting the distribution and the no.-1. light- photosynthetic protozoa have

chromatophore. Some are present in absence oflight.

2. pH- 3.2-8.7 (6-8 is optimal for metabolism)

Factors affecting the distribution and thenumber of protozoa

3.a. Nutrients-water rich in oxygen and low in organicmatter (mountain springs, ponds)b. some require water rich in mineralsc. some grow well in water where there is activeoxidation and degradation of organic matter (eg.Ciliates)d. Salt watere. fresh waterf. in less oxygeng. presence of bacteria, protozoa for holozoic protozoaThe nutrient supply is a major determining factor inthe distribution and number of protozoa

Factors affecting the distribution and thenumber of protozoa

4. Temperature – 16-250 c (optimum), 36-400c(maximum)The encysted stage will thrive high temperature. Sotheir no will be more in warm environment

Symbiotic protozoa• Commensalism-the host is neither harmed nor

benefitted-1.Ectocommensalism- protozoa attaches themselves

to a host’s body2.Endocommensalism- when protozoan is inside the

host eg. The protozoa inside the gut of the host• Mutualism- both the parasite and the host are

benefitted. Eg, the flagellates in the gut of termitedigest woody materials consumed by termites.These are converted into glycogenous substancesused by the host. In absence of each other bothperish

Symbiotic protozoa• Parasitism- the parasite lives at the expense of

other. The parasite feeds on others with the helpof pseudopodia or cytosome.

• Hyperparasitism- parasitic protozoa parasitizes

MorphologySize an shape- variable, 2mm to 15 cmIntracellular structure-

Cytoplasm• Homogeneous, show colours (green, brown, blue ,

purple due to pigment• Has submicroscopic protein fibrils (myonemes,

microtubules)• Arranged in parallel• Divided in two portions- ectoplasm & endoplasm• Ectoplasm- more gel like and endoplasm is

voluminous and fluid• Cell organelles are present (ER, ribosomes, golgi

complex, mitochondria, food vacuole, contractilevacuole, kinetosome)

plasmalemma

Nucleus• Eucaryotic nucleus- has chromosomes, the

nucleolar substance, the nuclear membrane,nucleoplasm

• one or many• Some have two-a. Macronucleus- large in size, controls the metabolic

the metabolic activities and regenerationprocesses

b. Micronucleus- small in size concerned withreproductive activity

Plasmalemma & other coveringsCell membrane or plasmalemma- outermost layer,semi permeable

Functions-a. protectionb. site of perception of chemical and mechanicalstimulic. transport

Compound coverings• Combinations of membranes, also called pellicle• Simplest is plasmalemma eg, Amoeba• Some have mucopolysaccharide on plasmalemma

plays an important role in pinocytosis andadhesion

• Can be thick, ridged and sculputured, nodularthickening,

Additional coverings• Diverse• Egs. thecae, shells, tests or loricae• Thecae- directly secreted by the organism• Others are the loose coverings• Made up of organic and inorganic materials

(calcium carbonate and silica)

thecae

Feeding structures• Pseudopodia- in Amoeba• Tentacular feeding tubes- in suctorians• Mouth (cytosome)- in ciliates

a. simple round openingb. a slit like- remains open all the time in some andsome have slit which can be opened and closed andalways located anteriorly

• Oral groove- an indentation in the pellicle , guidesfood toward the cytosome and act as a concentratingdevice

• Peristome- this an oral groove with membanelles• Cytopharynx- it is a region through which the food

must pass and is enclosed in the food vacuole.

Feeding structurespseudopodia Tentacular feeding tubes

cysts• Resistant structure• Able to survive an adverse conditions like

dessication, low nutrient supply, lack of oxygenetc.

• Cyst stage is an infective stage for intestinalpathogens

• Cyst is important mean of asexual reproduction

Other protective structures• Mucocyst- membrane bound vesicle secrete

mucilage• Trichocyst- harpoon like weapon used by some

protozoa to defend• Toxicyst- tubular thread like structure, secrets

toxin to paralyze and capture prey• Haptocyst- used to contact and immobilize prey.

They are present in the tentacles of suctorian.

Locomotor organellesPseudopodia- it is a temporary projection of part ofthe cytoplasm of some protozoa not having rigidpellicle

• It is the characteristic of amoebas• Used for capturing and engulfment of food

Flagella -• fine filamentous extension of the cell, 9+2

arrangement• 1-8 per cell

Locomotor organellescilia-• thinner and shorter than flagella• Apart from locomotion helps in ingestion of food• Tactile organelle• Arranged in longitudinal, oblique, or spiral rows

Undulating membrane-

Reproduction (Asexual reproduction)Asexual reproduction-Binary fission- two daughter cells are formed

Reproduction (Asexual reproduction)Multiple fission- many daughter cells are formed

Reproduction (Asexual reproduction)Budding-

Exogenous-

Endogenous-

Sexual reproduction-• Syngamy or gametogamy

Life cycle of amoeba

Importance of Protozoa• Important link in the food chain in aquatic

environment eg. Marine water

I. LIGHT PHYTOPLANKTON ZOOPLANKTON(primary producer) (pri. consumer)

CARNIVORESsec. consumer

Dead bodies of producers and consumers and theirexcreta including faeces

Decomposed by fungi and bacteria

Ingestion of bacteria by protozoa

Importance of Protozoa

1. Sewage treatment (biological)-aerobic andanaerobic protozoa

2. Industrial waste treatment- rich in nitrates andphosphates. In the settling tank illumination isdone to increase the growth of algae andprotozoa.