Protozoa. Animal Like-Protista

1.

Protozoa

2.

Animal Like-Protista
(Protozoa)
• All are unicellular heterotrophs.
• Nutrition by ingesting other organisms or dead organic
material.
• Some organisms are parasitic, since they cannot actively
capture food. They must live in an area of the host organism
that has a constant food supply, such as the intestines or
bloodstream of an animal.

3.

Animal Like-Protista
(Protozoa)
The protozoans are grouped on the basis of their modes of
locomotion to:
Pseudopods
move by psedupodia
such as
Amoeba
Flagellates
move by flagella
such as
Giardia
Ciliates
move by cilia
such as
Paramecium
Sporozoans
do not move
such as
Plasmodium

4.

Protozoan Taxonomy:
• Phylum Sarcomastigophora
- Subphylum Mastigophora (e.g., Trypanosoma, African sleeping sickness)
- Subphylum Sarcodina (e.g., Entamoeba histolytica, dysentery)
• Phylum Apicomplexa (e.g., Plasmodium, malaria)
• Phylum Ciliophora (e.g., Paramecium)

5.

Sarcodina (Pseudopods)
e.g Amoeba
• Have no wall outside of their cell
membrane.
• Use extensions of their cell
membrane (called pseudopodia)
to move, as well as, to engulf
food.

6.

Sarcodina (Pseudopods)
e.g Amoeba
• Amoebas live in water, dissolved nutrients from the
environment can diffuse directly through their cell
membranes.
• Most amoebas live in marine environments, although some
freshwater species exist.
• Freshwater amoebas use contractile vacuoles to pump excess
water out of the cell.

7.

• Most amoebas reproduce asexually by
fission
• Amoebas may form cysts when
environmental conditions become
unfavorable.
• Two forms of amoebas have shells, made
of calcium carbonate or silica.

8.

Feeding:
• When the pseudopodium traps a bit of food, the cell
membrane closes around the meal, this forms a food vacuole.
• Digestive enzymes are secreted into the food vacuole, which
break down the food. The cell then absorbs the nutrients.

9.

Ciliophora (Ciliated Protozoa)
e.g Paramecium
• Move by the cilia covering their
bodies.
• They can be found almost
anywhere, in freshwater or
marine environments.
• Probably the best-known ciliate
is the organism Paramecium.

10.

Ciliophora (Ciliated Protozoa)
e.g Paramecium
• Paramecia have many well-developed organelles.
• Paramecia have two nuclei, a macronucleus and a
micronucleus.
• The larger macronucleus controls most of the metabolic
functions of the cell.
• The smaller micronucleus controls much of the pathways
involved in sexual reproduction.

11.

Ciliophora (Ciliated Protozoa)
e.g Paramecium
• Thousands of cilia appear through the pellicle, a tough,
protective covering surrounding the cell membrane.

12.

Feeding:
•Food enters the cell through the oral groove
(lined with cilia, to "sweep" the food into the
cell), where it moves to the gullet, which
packages the meal into a food vacuole.
•Enzymes released into the food vacuole break
down the food, and the nutrients are
absorbed into the cell.
•Wastes are removed from the cell through an
anal pore.
•Contractile vacuoles pump out excess water,
since paramecia live in freshwater
surroundings.

13.

Reproduction:
• Paramecia usually reproduce asexually, by transverse fission
• When conditions are unfavorable, however, the organism can
reproduce sexually.
• This form of sexual reproduction is called conjugation.
• During conjugation, two paramecia join at the oral groove,
where they exchange genetic material.
• They then separate and divide asexually

14.

15.

Apicomplexa (Sporozoans Protozoa)
e.g Plasmodium
•Sporozoans are all parasites e.g
Plasmodium
•Many of these organisms produce
spores, reproductive cells that can
give rise to a new organism.
• Sporozoans typically have complex
life cycles, as they usually live in more
than one host in their lifetimes.

16.

. Fig u re 28.18 Th e t w o -h o st lif e cy cle o f
Plasm od iu m , t h e ap ico m p lex an t h at cau ses
m alar ia.
1 An inf ect ed Anopheles
mosquit o bit es a person,
inject ing Plasmodium
sporozoit es in it s saliva.
? Are morphological differences between
sporozoites, merozoites, and gametocytes
caused by different genomes
or by differences in gene
expression? Explain.
M ast er in g Biology
Anim at ion: Lif e Cycle
of a M alaria Parasit e
Inside mosquit o
2 The sporozoit es ent er t he person’s
liver cells. Af t er several days, t he sporozoit es
undergo multiple mit ot ic divisions and become
merozoit es, w hich use t heir apical complex
t o penet rat e red blood cells (see TEM below ).
Inside human
Merozoite
0.5 o m
Sporozoites
(n)
Liver
8 An oocyst develops
f rom t he zygot e in t he w all
of t he mosquit o’s gut . The
oocyst releases t housands
of sporozoit es, w hich
migrat e t o t he mosquit o’s
salivary gland.
Liver cell
Oocyst
M EIOSIS
Zygote
(2n)
7 Fert ilizat ion occurs
in t he mosquit o’s
digest ive t ract , and a
zygot e f orms.
Red blood
cell
Merozoite
(n)
Red blood
cells
3 The merozoit es divide
asexually inside t he red
blood cells. At int ervals of
48 or 72 hours (depending
on t he species), large
numbers of merozoit es
break out of t he blood
cells, causing periodic chills
and f ever. Some of t he
merozoit es inf ect ot her
red blood cells.
FERTILIZATION
Gametes
Key
Haploid (n)
Diploid (2n)
6 Gamet es f orm f rom gamet ocyt es; each male
gamet ocyt e produces several slender male gamet es.
Apex
Gametocytes
(n)
4 Some merozoit es
f orm gamet ocyt es.
5 Anot her Anopheles mosquit o bit es t he inf ect ed person
and picks up Plasmodium gamet ocyt es along w it h blood.

17.

Some major protozoal diseases of
humans
• The host in which the sexual stage of the life cycle is completed is called the definitive host.
• The one with the asexual stage the intermediate host.