kingdom protists part2

3. Binary fission
 It is the most common method of asexual
reproduction where in the parent divides into
two daughter individuals.
 It involves division of nucleus followed by the
division of the cytoplasm.
 The plane of fission differs in different
protozoans.

4. Types of binary fission
 Depending on the plane of fission binary fission is
of following types:
Irregular binary fission-
 Binary fission is irregular in some of the
protozoans which do not have defined body
shape.
 In these protozoans, there will be no defined
plane of fission either and hence the name
irregular binary fission. Example: Amoeba

6. Types of binary fission
Longitudinal binary fission-
 This type of fission process starts at the anterior end and
proceeds towards the posterior end.
 The plane of fission is parallel to the longitudinal axis of the
body of the organism. Example: Euglena, Vorticella

7. Types of binary fission
Transverse binary fission-
 The plane of fission in this type is at right angles to
the kineties.
 All the paramecia produced asexually by repeated
binary fission from a single parent constitute a
clone. Example: Paramecium

8. Types of binary fission
Oblique Binary fission-
 Oblique binary fission is common in some
protozoans like dinoflagellates.
 In this type the plane of fission is oblique to the
body axis of the organism. Example: Ceratium

9. Multiple fission
 It is the process of asexual reproduction in which
instead of 2 daughter cells, many daughter cells are
produced from the parent cell.
 In multiple fission, a protective covering called a cyst
develops over the cell.
 In this, the nucleus undergoes repeated division to
produce a large number of nuclei.
 Each nucleus along with little bit of cytoplasm forms
a membrane around it.
 All the daughter cells are equal sized and are
similar.

10. Multiple fission in plasmodium
Example of multiple fission can be seen in some protozoans
such as plasmodium (malaria parasites).

11. Plasmotomy
 A plasmotomy is a type of asexual reproduction in
which a multinucleate protozoan cell divided into two
or more multinucleate daughter-cells without the
occurrence of mitosis. Example: Opalina, Pleomyxa

17.  The kingdom Protista is divided into three groups:
 Animal-like protists: They are heterotrophs and
have the ability to move.
 Plant-like protists: They are autotrophs and have
the ability photosynthesize.
 Fungi-like protists: They are heterotrophs.
 Their cells have cell walls and have the ability to
reproduce by forming spores.

18. ANIMAL-LIKE PROTISTS
(PROTOZOANS)
 Protists that are close to animals are known
as protozoans.
 They are different from animals because they are
unicellular while animals are multicellular.
 They live in moist watery environments. The
characteristics that resemble that of animals are –
 They have the ability to move and
 They cannot produce their own food (heterotrophs).
Protozoans are classified into four categories (phyla)
on the basis of their mode of movement:
 Sacordinians – They use pseudopodia for the body
movement.
 Zooflagellates – They move using flagella.
 Ciliaphorans – They move by the cilia present all over
the body.
 Sporozoans – forms spores.

19. Phylum Sarcodina
 The sarcodinians show body movements by
extending cytoplasm in the form of lobes
known as pseudopodia.
 This pseudopoda is used for movement and
feeding. Example: Amoeba, Foraminiferans
(they are amoeba-like, single-celled protists,
characterized by an external shell, which has
holes or chambers).

20. Phylum Mastigophora
(Zooflagellata)
 The member protozoans of this group move with
the help of flagella.
 They are mostly parasitic.
 Many flagellates are found in the intestine of
humans, in termites and other animals.
 Some flagellates are harmful.
 Example: Trypanosoma gambiense
cause sleeping sickness in
cattle and human.

21. Phylum Ciliophora (Ciliates)
 These protozoans move with the hair-like
structures called cilia, which helps the
organism to move their body as well as taking
in the food particles.
 The movement of cilia is paddle-like, moving
back and forth for movement.
 Example: Paramecium, Lacrymaria, Coleps,
Stentor, Dileptus,

22. Phylum Sporozoa
 All members of this phylum are non-motile
and parasitic. They form spores, hence
termed as sporozoa.
 They lack locomotory structures, therefore,
they are carried in their hosts by their body
fluids.
 Many sporozoans cause serious diseases in
humans. Example: Plasmodium it causes
malaria in humans.

23. ALGAE
 These protists resemble the plants in having the
chlorophyll.
 The chlorophyll enables them to make food by
photosynthesis.
 They produce and release oxygen like the plants.
 Most of the supply of oxygen on Earth is
believed to be from plant-like protists.
 They are the major food source as well as primary
producers for water organisms.

24. Phylum Chlorophyta (Green Algae)
 The green algae comprise of unicellular and
multicellular algae.
 They are found in fresh water.
 Their cell wall is made of cellulose and pectin.
Example: Spirogyra; it is a unicellular green
alga, and grows as a green thread or filament.

25. Phylum Rhodophyta (Red
Algae)
 Red algae are named so, because of their bright red
color. Red algae are mostly large and multicellular.
 They are found in oceans and are generally referred to
as sea vegetables as they are used as food. Coralline
algae are red algae which secrete calcium carbonate
onto the surface of their cells and helps in forming coral
reefs.
 Agar, which is a gelatin-like substance is prepared
primarily from Gracilaria and Gelidium species and is
important as a culture medium for bacteria and fungi

27. Phylum Phaeophyta (Brown Algae)
 They are multicellular organisms.
 They grow on rocks of the sea.
 Large brown algae are called kelps.
 Kelps may grow densely in the sea and form kelp forests.
 They form important food sources for fish and invertebrates.
 The brown algae growing on rocks are known as rockweed.
Examples of Brown Algae include Sargassum, Laminaria,
Macrocystis, Nerocystis.
 Brown algae are an important source of algin, (a colloidal gel)
which is used as a stabilizer in the baking and ice-cream
industries.
 Some Brown Algae are used as fertilizer, and several are eaten
as a vegetable (e.g., Laminaria) in East Asia and elsewhere

29. Phylum Chrysophyta (Golden algae)
 ‘Chryso’ means ‘color of gold’.
 There are three types of golden-algae: yellow-green
algae, golden-brown algae, diatoms.
 They are found in both marine and fresh
waters. Diatoms are the most abundant and live
both in seawater and freshwater habitats.
 They are a major source of food for many aquatic
organisms.

37. Phylum Pyrrophyta (Fire Algae)
 Dinoflagellates are called fire algae because some forms of
these protists are bioluminescent.
 They store food in the form of starch and oils.
 Some species cause the ‘red tide phenomenon’.
 The Red tide is a phenomenon commonly termed as algae
bloom, caused by species of dinoflagellates and other algae.
 During this phenomenon, algae become so numerous that they
discolor coastal waters (hence the name “red tide”).
 The algal bloom may cause depletion in oxygen in the waters
and/or release toxins that may cause illness in humans and other
animals.


45. FUNGUS LIKE PROTISTS-
Slime Moulds
 Slime moulds are saprophytic protists.
 They are very bright in appearance.
 They live in moist soil, decaying plants, and trees.
 Slime mould is a name given to several kinds of unrelated
eukaryotic organisms that can live freely as single cells but
can aggregate together to form multicellular reproductive
structures.
 Phylum- Myxomycota

46. General features
 They are terrestial and occur in cool, moist and shady places on
decaying plant parts like leaves, logs, barks or other decaying organic
matter.
 The vegetative phase in their life cycle has no cell wall; this phase
consists of an aggregation of amoeba-like cells (pseudoplasmodium)
or a multinucleate slimy mass of protoplasm (plasmodium), both of
which do not have a definite shape.
 They exhibit amoeboid movement by putting forth pseudopodia-like
structures away from light, but towards moisture.
 The colony/vegetative phase exhibits various colours like grey, brown,
yellow, orange, etc., due to the pigment anthracene.
 Reproduction occurs by fragmentation of the vegetative phase, by the
formation of spores or by the formation of sclerotia or cysts (thick-
walled perennating structures.)
 Sexual reproduction occurs by gamete formation; it is isogamous or
anisogamous.

47. Acellular slime moulds
General Features
 These occur commonly on dead and decaying leaves, logs of wood
and other decaying organic matter, when the conditions are damp or
during rainy season.
 The vegetative phase is called plasmodium and it consists of a free-
living wall-less mass of multinucleate protplasm, surrounded by
slime (hence called slime moulds); the nuclei are diploid.
 The protoplasm is differentiated into an outer rigid part and an inner
fluid part, where the nuclei and cell organelles are present.
 The plasmodium shows colours like grey, greenish black, brown,
yellow, orange, etc., due to anthracene.
 The plasmodium shows creeping movement over the surface of the
substratum with the help of pseudopodia
 Nutrition is holozoic (phagotrophic) and some show saprotrophic
nutrition.

48. Asexual reproduction
(i) By formation of spores
 Asexual reproduction is by formation cells of spores in sporangia.
 The plasmodium is holocarpic/eucarpic, i.e , when it reaches a
certain stage of maturity, the plasmodium becomes contracted and
thickened and forms papilla that grows into a sessile or stalked
sporangium (fructification); each sporangium is multinucleate and is
surrounded by a hard, slimy and non-cellular layer, called peridium.
 Each of the diploid nuclei undergoes meiosis and the multinucleate
protoplasm undergoes cleavage into tiny uninucleate units; each of
them becomes surrounded by a wall to become a spore.
 The protoplasm of the sporangium also develops thread-like
structures called capillitium, that help in the dispersal of spores.

51.  When the spores are mature, the sporangial wall
bursts to liberate the spores, which arc dispersed by
wind.
 When they fall on a suitable substratum, each
germinates either into a biflagellate, spindle-shaped
swarm cell or a non-flagellate myxamoeba; they may
multiply in number.

52. Sexual reproduction
 The swarm cells or myxamoebae function as
gametes and ftlse in pairs.
 The swarm cells after swimming actively for a brief
period, start fusing in pairs by their posterior, non-
flagellated ends; the product of fusion is called a
zygote.
 The zygote shows creeping movement and
phagocytoses bacteria, yeast or organic matter and
grows in size.
 The diploid nuclcus undergoes repeated mitotic
divisions and forms a multinucleate plasmodium,
 Physarum, Stemoniles, Physarellu, Tubifera, etc.

53. B. Cellular slime moulds
General Features
 Cellular slime moulds are also known as pseudoplasmodial
slime moulds or Acrasiales.
 They are called communal slime moulds because the amoeba-
like cells in the colony retain their individuality and behave as
members of a community.
 These slime moulds occur on the upper layers of soil, rich in
organic matter.
 The thallus/vegetative phase, called pseudoplasmodium,
consists of amoeba-like, tminucleate, haploid cells, covered by
plasma membrane, (there is no cell wall).
 The thallus shows amoeboid movement and feeds on other
microbes by phagocytosis (ingestion).



54. Reproduction
(a) Asexual reproduction
 By spore formation
 The pseudoplasmodium differentiates to form a stalked
sporocarp, which bears a single sporangium at its tip; the
sporangium is naked.
 Each of the cells of the sporangium becomes rounded
and secretes a cellulosic cell wall to become a spore; the
spore is surrounded by mucilage .
 Each spore germinates to form an amoeba-like cell
(Myxamoeba).
 These myxamoebae multiply by mitosis and soon
aggregate around the chemical acrasin (hence called
aerasiales) and form pseudoplasmodium.

55. Cyst formation :
 If conditions are unfavourable, each amoeba-
like cell develops a cyst around it to form a
microcyst .
 Microcysts tide over the unfavourable
conditions and germinate during favourable
conditions, each producing a myxamoeba.

56. (b) Sexual reproduction
 It involves the fusion of two amoeba-like cells.
 One of the amoebae engulfs the other during plasmogamy; so
the process is anisogamous.
 It is followed by karyogamy and a diploid zygote is formed; the
zygote is much larger than any of the other cells in the thallus.
 The zygote undergoes meiosis (zygotic meiosis) to form haploid
amoebae, which start multiplying by mitotic divisions and
aggregate to form pseudoplasmodium
 If conditions are unfavourable, the zygote develops a thick wall
and forms a macrocyst, which helps in perennation and
germinates at the return of the favourable conditions, e.g.,
Dictyostelium, Piotostelium, etc.