M.Sc BT IInd sem,
A eukaryote is an organism whose cells
contain complex structures enclosed
within membranes. The defining membrane-
bound structure that sets eukaryotic cells apart
from prokaryotic cells is the nucleus,
or nuclear envelope, within which the genetic
material is carried.
The single celled eukaryotes are classified under
the kingdom “PROTISTA”.
It is a being a paraphyletic group.
They are first eukaryotes, having a well organized
nucleus and complex membranous organelles.
Protozoa; some unicellular algae,
phycomycetes; myxomycetes and yeasts come
under this kingdom.
The term protista was first used by Ernst
Haeckel in 1866.
The simplest protist is “Amoeba”.
They are microscopical, unicellular eukaryotes.
They are unicellular or colonial forms without
distinct division of labor.
They generally live in water.
They maybe heterotrophic or autotrophic.
They may use pseudopodia, flagella or cilia for
They showed mitosis and meiosis.
There are four phyla of Animal-like Protists
classified by how they move-
1.Zooflagellates – flagella.
2.Sarcodines - extensions of cytoplasm
3.Ciliates – cilia.
4.Sporozoans - do not move.
They move using one or two flagella
absorb food across membrane, eg-Leishmania
They moves using pseudopodia (false
feet),which are like extensions of the cytoplasm
They ingest food by surrounding and engulfing
food (endocytosis),creating a food vacuole.
They reproduce by binary fission.
contractile vacuole - removes excess water
can cause amebic dysentery in humans -
diarrhea and stomach upset from drinking
They move using cilia;has
two nuclei: macronucleus,
gathered through food
vacuole;anal pore is used
vacuole removes excess
(binary fission) or sexually
are always the same
shape,like a shoe.
They do not move on
They are parasitic.
infects the liver and
blood and causes
Fig. Plasmodium vivax
They contain chlorophyll and carry out
There are four phyla:
euglenophytes, chrysophytes, diatoms, dinofla
Their accessory pigments help absorb
light, and give them a variety of colors.
They live in water,have 2
photosynthesis, but turn
into heterotrophs if kept
in the dark,
has an eyespot used for
sensing light and dark
pellicle - like a cell
wall, helps maintain
produce thin cell
walls of silicon.
Often have two
Yeasts are eukaryotic, mostly unicellular micro-
reproduce asexually by budding, although a
few do so by mitosis. They are phylogenetically
diverse and are placed under phyla
Ascomycota and Basidiomycota. Yeasts
are chemorganotrophs. They usually reproduce
by budding or by meiosis and spore formation
(under stress conditions).
Nutrition in some different types of protists is
variable. In flagellates, for example, filter
feeding may sometimes occur where the
flagella find the prey. Other protists can engulf
bacteria and digest them internally, by
extending their cell membrane around the food
material to form a food vacuole. This is then
taken into the cell via endocytosis usually
phagocytosis; sometimes pinocytosis.
Phototrophs Sunlight Organic
llates or Euglena
reproduce sexually (conjugation), while others
reproduce asexually (binary fission).
Some species, for example Plasmodium
falciparum, have extremely complex life
cycles that involve multiple forms of the
organism, some of which reproduce sexually
and others asexually.
Protists form a broad base across the bottom of the
food chain, and they supply approximately one-half of
the world’s oxygen.
Protists, along with bacteria and fungi, are responsible
for decomposing and recycling nutrients.
Euglena are used to help treat sewage because of their
unique ability to switch from an autotrophic to a
heterotrophic nutritional mode, helping to maintain
oxygen levels in the balance.
Trichonympha which lives in the digestive system of
termites and produces cellulase, an enzyme that enables
termites to digest wood.
Products derived from protists are used in treatment of
ulcers, high blood pressure and arthritis.
Some protists are significant pathogens of
both animals and plants; for
example Plasmodium falciparum and P. vivax,
which causes malaria in humans,
and Phytophthora infestans, which causes potato
blight. Balantidium Coli and Entamoeba
Histolytica causes severe dysentry in animals,
eg-pigs and humans. Mastigophorites that
belong to the genus trypanosoma,causes
African Sleeping Sickness, a disease which
often leads to death.