Practical Zoology
The Animal cell
The cell is the structural and functional unit of all living organisms. It is composed
of several compartment which include organelles and complex compounds . The
organelles , means plasma membrane bounded structures , whereas complex
compounds include several types of macromolecules , sugar , proteins, lipids ,……. .
- Plasma membrane: Separate a cell from its environment, it is a selective permeable
membrane composed of bilayer phospholipids with proteins.
- Mitochondria : It is the site for oxidative generation of energy (ATP) .
- Endoplasmic reticulum: Two types Rough (R.E.R.) which is the site for the synthesis
of proteins and Smooth (S.E.R) site for lipid synthesis.
- Golgi Apparatus : It is the organelle responsible for the sorting and modification of
proteins.
- Nucleus:- Surrounded by nuclear envelope and contains the Chromosomes (Genetic
material) and control all the cellular activities .
CELL CYCLE
Phase
Abbreviati
Description
on
1
Practical Zoology
Gap 0
G0
A resting phase where the cell has left the cycle and has stopped
dividing.
Gap 1
G1
Cell increases in size in Gap 1.
Synthesis S
DNA replication occurs during this phase.
Gap 2
G2
During the gap between DNA synthesis and mitosis, the cell will
continue to grow.
Mitosis
M
Cell growth stops at this stage and division starts.
The Shapes of Animal Cells
There are several shapes of animal cells:
1. Star –shape: Such as multipolar never cell.
2. Cubic – shape: Such as simple cuboidal epithelial tissue in the kidney tubules .
3. Oval – shape: Such Red Blood Cells (R.B.C.) of frog.
4. Polygonal – shape: Such as Squamous cells in Simple Squamous Epithelial tissue
in lung or inside walls of bloods vessels.
5. Biconcave discs – shaped: Such as erythrocytes or red blood cells of Human blood.
5
3
Histology
2
4
1
Practical Zoology
The tissue: is a collection of cells that frequently have the similar shape and
specialized in specific function .There are four basic tissues:
Epithelial T., Connective T., Muscular T. and Nervous T.
All these tissues are derived from 3 embryonic germ layers (ectoderm, mesoderm, and
endoderm).
First: Epithelial Tissues:
Layer ( or layers ) of cells attached tightly to each others and resting on basement
membrane , derived from all embryonic germ layers , these tissues classified
according to their structure and function to :
1) Glandular Epithelial Tissues:
Collections of cells specialized in secretion; the glands may be unicellular glands eg.
Goblet cells (in respiratory tract and intestine) or multicellular glands eg. Salivary
gland and frog skin.
2) Covering Epithelial Tissues:
These tissues covering the external surfaces or lining the internal surfaces of the
body , and classified according to the number of the layers to :
A) Simple Epithelial Tissues:
Simple Epithelium is made up of single layer of epithelial cells. It is found where
there is not much wear and tear or where diffusion or absorption occurs through a
membrane.
1. Simple Squamous Epithelial tissue: composed thin flat cells with round or oval
nuclei, found inside walls of blood vessesls (Endothelium), the body cavity, and
the lungs.
3
Practical Zoology
2. Simple Cuboidal Epithelial tissue : lines small ducts and tubules, such as kidney
tubules, salivary glands ,and mucous glands.
3. Simple Columnar Epithelium tissue: is found on highly absorptive surface such
as lining of the small intestine, and on secretive surfaces such as the lining of
the stomach.
4. Pseudo stratified Columnar Epithelial tissue: Pseudo Stratified Columnar tissue
is actually simple epithelium with all the cells resting on a basement membrane.
The cells have the appearance of stratified epithelium because they are not all
have the same height and their nuclei are located at different levels, some cells
don’t reach the surface ,Pseudo Stratified Columnar tissue lines the trachea and
bronchi.
B) Stratified Epithelial Tissues: composed of multilayer of cells, classified
according to the shape of the cells of their surface into:
1) Stratified Sequamous Epithelial Tissues: this tissue may be keratinized eg.
(Epidermis), or non- keratinized eg. (Esophagus).
2) Stratified Cuboidal Epithelial Tissues: eg. (Sweat gland).
3) Stratified Columnar Epithelial Tissues: eg. (Larynx).
4) Transitional Epithelial Tissues: : It is a form of stratified Epithelial Tissue
confined to the urinary tract bladder, when relaxed the epithelium appears to be
four or five cells thick, when stretched , it appears only two or three cells thick
,with the surface cells flattened.eg. (Urinary bladder).
Second: Connective Tissue
4
Practical Zoology
The connective tissues are tissue of mesodermal origin that provides structural
and metabolic support for the body. Despite the diversity of connective tissue, all are
composed of cells and extra cellular fibers embedded in a structureless ground
substance (also called matrix). Both the fibers and the ground substance are secreted
by the cells.
Classification of connective tissues:General connective tissue or Proper connective tissue:I ) Dense connective tissue:- distinguished by abundance of fibers in
corporate within the matrix:a- Dense irregular connective tissue:- unarranged fibers such as dermis.
b-Dense regular connective tissue:- fibers arranged , white fibers
connective tissue (Tendon) that join muscle to bone and Elastic
connective tissue (Ligaments)that join bone to bone.
II ) Loose connective tissue:- classified to :1- Mesenchyme connective tissue.
2- Areolar connective tissue:- most widespread of all the connective tissue.
It is found fastening down the skin it consist of a clear jelly like matrix,
various cells,and all three types of fibers(White, Elastic, Reticular
fibers).Found in subcutaneous layer and mucous membranes, and around
blood vessels, nerves and organs.
3- Mucoid connective tissue .
4- Adipose connective tissue: Specialized for the storage of lipids each cell
contains a single lipid droplet. The cytoplasm and nucleus have been
pushed to one side of the cell by the lipid dropt.Found in subcutaneous
layer, around organs and in the yellow marrow of long bones.
5- Reticular connective tissue.Found in liver, spleen and lymph nodes
Special connective tissue:5
Practical Zoology
A-) Skeletal connective tissue: Special type of connective tissue, composed of
cells and matrix, the matrix consist of ground substance containing fibers
,cartilage and bone are different chemically as well as structurally.
1- Cartilage :it forms the skeleton of early mammalian fetuses but it is gradually
replaced in the growing individual by bone, and only remnants of it are
encountered in the skeleton after maturity. At that time cartilage is one of the
least prevalent constituents of the human body.
 Hyaline cartilage :the most common form of cartilage it is found on the
ends of long bones and in the nose, trachea and other places, Its ground
substance is firm but flexible scattered through it lacunae , little cavities
each containing at least one cell. The cells secret the ground substance
and some collagen fibers.
 Fibro cartilage: found in the intervertebral discs, the ground substance
contains many inelastic fibers.
 Elastic cartilage: found in places such as the external ear, epiglottis, and
larynx contains many elastic fibers.
2- Compact bone: is the most specialized of supporting connective tissue, it not
only supports, but it also protects vital organs by means of bony
frameworks, and it forms the red blood cells and most of white blood
cell.
Bone matrix is heavily infiltrated with calcium and phosphate salts.
A long bone such as the femur, consist of a shaft of compact bone
surrounding a bone marrow cavity .
Compact bone is made up of series of osteons, each one built around a
narrow canal containing blood vessels, the bone-forming cells,
osteoblasts, become arranged in the matrix around the blood vessels in
6
Practical Zoology
layers called lamellae .Each osteoblasts occupies space called a lacuna
.The cell have branching, thus forming tiny channels, called canaliculi
through which nourishment can reach the cell from the blood supply.
B-) Vascular connective tissue:
Blood and lymph are often considered to be connective tissue having a
variety of cells types (corpuscles) suspended in fluid matrix (plasma) and flowing
within a system of blood vessels .Vascular tissue transports nutritive substances,
oxygen, and hormones to the tissues and carries away wastes.The cells in blood
include erythrocytes, leukocytes and blood platelets.
1.
)Erythrocytes(Red corpuscles) or R.B.C.(Red Blood Cell):In the human and other mammals erythrocytes are round,biconcave
discs that don’t have nuclei. They average about (7µm ) in diameter
but are very thin .Oval-shaped erythrocytes with large granular nuclei
are found in most other vertebrates.Vertebrate red corpuscles are
packed with the respiratory pigment hemoglobin,which function to
transport oxygen and carbon dioxide between the lungs and the body
tissues.
2. ) Leukocytes(White corpuscles) or W.B.C. (White Blood Cell):There are several types of leukocyte in vertebrate blood ,all with
large ,darkly,staining nuclei,in human blood they are larger than the red
cells; in other vertebrate they are smaller .By means of their amoeboid
movement they can pass through capillary walls and surround ingest
foreign particles and invading organisms(a process called phagocytosis).
7
Practical Zoology
Monocytes and neutrophil are the most active phagocytes,
lymphocytes play a key role in all immuno- responses. Leukocytes
perform their protective functions outside the blood vessels in
connective tissue.The pus that forms in and around an infection
consists largely of dead white blood cells.
3) Blood platelets:
Platelets are disc-shaped,tiny (2 to3 µm in diameter) ,very fragile, clot
promoting bodies found only in mammalian blood.
Third: Muscular tissue:
Muscular tissues are derived from mesoderm and in few instances from ectoderm,
they are responsible for body movement .according to their morphology and function
there are three types of muscles:
a) Smooth muscles: have fusiform, non –striated cells, have central nucleus, and
they are not under the voluntary control.
b) Skeletal muscles: have unbranched cylindrical striated cells with peripheral
nuclei, they are under the voluntary control.
c) Cardiac muscles: have branched cylindrical striated cells with central nuclei,
and there are intercalated discs between the cells, they are not under the
voluntary control.
Fourth: Nervous tissues:
These tissues derived from ectoderm, and composed of nerve cells and neuroglia.
The nerve cell composed of:
a) Cells body: (which contain the nucleus and nissl granules).
b) Processes: (which include the dendrites and the axon).
8
Practical Zoology
And according to the size and the shape of their processes, the nerve cells are
classified to: multipolar neurons, bipolar neurons, unipolar neurons.
In most instances the axon surrounded by a fatty myelin sheath composed of
Schwann cells ,this sheath is not continuous , and forming the nodes of Ranvier,and so
this axon called myelinated fiber .
The Kingdom Animalia
Animals are eukaryotic, multicellular (sometimes unicellular), heterotrophs whose
cells do not have cell walls. More than 1 million species are known, most of them
invertebrates. Animals differ in development and body form. Distinguishing
characteristics include number of primary germ layers (diploblastic, or triploblastic),
presence and type of body cavity (coelomate, acoelomate, and psedeucoelomate), and
body symmetry (radial symmetry with oral or aboral ends, or bilateral symmetry with
cephalization).
Animal Phyla:
1. Phylum Protozoa:
Protozoa are unicellular eukaryotic organisms, may classified in kingdom called
(Protista). They are found in moist habitates, and they include free-living and parasitic
forms. Most species of protozoa are heterotrophic organisms that obtain nutrients by
process of phagcytosis. The protozoa may be classified into groups (classes) include:
Class-1: Sarcodina: consists of protozoa that move by pseudopodia, most sarcodina
are free-living like (Ameoba) or parasitic eg. (Entamoeba histolytica) which cause
the disease (amebic dysentery).
Ameoba: the amoeba cell has irregular shape, contain ectoplasm (the outer portion of
the cytoplasm), and endoplasm (the inner portion of the cytoplasm), it moves by
9
Practical Zoology
amboid movement (by pseudopodia), which also are used for feeding (surrounds the
food with its pseudopodia forming food vacuole in process called endocytosis). Also
contains (contractile vacuole) an organelle that expels fluid from the cell. And it
reproduces asexually by binary fission.
Class-2: Ciliophora: consists of protozoa that move by cilia eg. Paramecium, its
cell contains macronucleus, micronucleus, food vacuole, contractile vacuole, anal
pore, and pellicle. And it reproduces by binary fission as well as by sexual
reproduction.
Class-3: Zoomastigophora: consists of protozoa that move by flagella, eg.
Trypanosoma
a
species
that
cause
African
sleeping
sickness
called
(Trypanosomasis) which transmitted by Tse-tse fly, and Leishmania donovani
which is transmitted by sand fly and causes the Leishmaniasis, and Giardia lamblia
causes Giardiasis.
Class-4: Sporozoa: which unable to move in the adult form, the sporozoa have
complex life cycles in which they develop a spore, and all sporozoa are parasites in
humans or other animals eg. Plasmodium which causes the disease malaria that
transmitted by Anopheles mosquito, this parasite causes extensive damage to red
blood cells in a victim.
2- Phylum Porifera: it's made up of sponges, sessile invertebrates that have no
true tissues or organs. Simplest sponges are hollow cylinders, the body wall of a
sponge is composed of two layers of cells, the body supported by a skeleton made of a
network of protein fibers called sponging, and spicules (tiny hard particles of calcium
carbonate or silicon dioxid, its shape like spine), collar cells lining the inside of
sponge having flagella, drawing a current of water into the sponge through pores in
body wall, water leaves through the osculum an opening at the top of the sponge.
Sponges feed by filtering small organisms and organic matter out of the water that
10
Practical Zoology
passes through their body. Nutrients are distributed through the body amebocytes
which crawl about within the body wall. Sponges can reproduce asexually, through
budding or regeneration, as well as sexually, most sponges are hermaphrodite (single
animal can produce both ova and sperms).
3. Phylum Cnidaria: this animals can be either sessile polyps or swimming
medusae. Some cnidaria alternate between polyp and medusae stages during their life
cycles. The body of a cnidarian is diploblastic (consists of two cell layers, an outer
epidermis and an inner gastrodermis separated by jelly like mesoglea. Cnidarians have
cells called cnidocytes, which contain organelles known as nematocysts, when a
cnidocyte is stimulated, its nematocyst ejects a filament that can paralyze or ensnare
prey. Cnidarians feed by capturing small animals with their nematocysts and pushing
the animal into their gastro vascular cavity with their tentacles.
Class: Hydrozoa: Live as polyps, medusae, or mixed colonies of polyps and
medusae. eg. Hydra exist only as polyps, they live in fresh water, range from 1 to 4
cm in length they attach to rocks or water plants by their sticky base. Generally Hydra
reproduces asexually by budding, or sexually (the Hydra is hermaphrodite).
11
Practical Zoology
Entamoeba histolytica Trophozoite
12
Entamoeba histolytica Cyste
Practical Zoology
Trypanosoma
13
Practical Zoology
Giardia lamblia
Porifera (Sponge)
14
Porifera (Sponge)
Practical Zoology
Hydra
4. Phylum : Platyhelminthes (flat worms)
Their bodies are triploblastic ( develop from three germ layers), they have
bilaterally symmetrical bodies, with dorsal and ventral surface, right and left sides,
and anterior and posterior ends, since flat worms don't have a hollow cavity between
the endoderm and the mesoderm they belong to acoelomates. Most flat worms have a
gastrovascular cavity, a gut with single opining, these cephalized animals also have
excretory, nervous, and reproductive system.
Class: Trematoda: consists of parasitic fluckes, which have complex life cycles in
which they alternate between two types of hosts: a primary host, from which the
adults drive their nourishment and in which sexual reproductive occurs, and an
intermediate host, from which the larvae drive their nourishment, some fluckes live in
the internal organs of their host, while others live on the external surface of their host.
15
Practical Zoology
Example : Fasciola hepatica (sheep liver flucke): this worm look like a plant leaf,
the mouth lies in the center of anterior muscular disc called (oral sucker) near to it in
the ventral side there is another disc called ventral sucker (which connects the worm
with the host body). The worm is hermaphrodite, and it reproduce asexually (forming
sporocysts in the Lamnaea a snail), and sexually (cross-fertilization in the liver of the sheep).
5. Phylum : Aschelminthes
Class: Nematoda: The nematodes are pseudocoelomates, they have hollow, fluidfilled cavity called pseudocoelom between mesoderm and endoderm, they also have a
digestive tract with a mouth (surrounded by 3 lips) at anterior end, and an anus at
posterior end. This class consists of round worms, which may be free living or
parasites eg. Ascaris lumbricoids which infects the intestine of human, the adult
female can reach length of up to 30 cm, with straight posterior end, the smaller male
has hooked posterior end.
6. Phylum :Annelida
Have a true coelom and a body that is divided into many segments. Most annelids
have external bristles called setae.
Class: Oligochaeta: eg. Allolobophora (Earth worm) which lives in the moist soil
and feeds on organic matter of the soil, its body is divided into more than 100
segments, it has circular and longitudinal muscles. It has prostomium, and the mouth
lies in the peristomium (the first segment), the clitellum (a noticeable swelling around
the reproductive organs composed of 8 or 9 segments), earth worms have a closed
circulatory system, they exchange gases through their skin and eliminate cellular wastes and
excess water through excretory tubules called nephridia. Each segment contains setae,
nephridia, a pair of excretory pores found in the ventral side of every segment, the worm is
hermaphrodite, there are two female genital pores in the fourteenth segment, and two
male genital pores in the fifteenth segment.
16
Practical Zoology
7. Phylum :Molluska
Mollusks have a true coelom; their body is divided into the head-foot and the
visceral mass, which contain the internal organs. Most mollusks have at least one
shell, which is secreted by a layer epidermis called the mantle. Aquatic mollusks have
gills through which they exchange gases with water. The main feeding adaptation of
most mollusks is the radula, a tongue-like structure that is modified in different
species for scraping or drilling.
Class-1: Gastropoda: eg. Helix (snail): has open circulatory system move by wave
like muscular contractions of the foot.
Class-2: Lamellibranchiata: eg. Anodonata (The oysters)
Class-3: Cephalopoda: eg. Octopus
8. Phylum Arthropoda:
Are segmented animals that have jointed appendages, an exoskeleton, a high
degree of cephalization, a ventral nerve cord, and an open circulatory system. To
grow, an arthropod must shed its exoskeleton periodically in a process called molting.
Class: Crustacea: have branched antennae and a pair of chewing mouth parts called
mandibles, most crustaceans are aquatic, respire with gills, and a nouplius larval stage
during development. eg. Penaeus (prawn): the body composed of two regions:
cephalothorax and abdomen. The cephalothorax coverd with carapace, its anterior
part called rostrum. The abdomen composed of 6 segments with terminal segments
called telson. The prawn has 8 pairs of thoracic appendages (3 pairs are maxillipeds,
5 pairs are periopods), and 6 pairs of abdominal appendages and 5 pairs of cephalic
appendages (2 pairs of antenna, a pair of mandibles and 2 pairs of maxillae).
Class: Arachnia: includes spiders, scorpions, mites, and ticks, their bodies are
divided into a cephalothorax and an abdomen, and they usually have 6 pairs of jointed
17
Practical Zoology
appendages: one pair of chelicerae, one one pair of pedipalps, and 4 pairs of
periopods. The scorpions have pincerlike pedipalps and a venomous stinger at the end
of their abdomen.
Class: Insecta: the insects body is divided into 3 regions: the head has mandibles and
one pair of un branched antennae; the thorax has 3 pairs of jointed legs, and in many
species, one or two pairs of wings; the abdomen has 9 to 11 segments but neither
wings nor legs in adults.
Insects lived in most every terrestrial and fresh water environment, factors responsible
for their success include their ability to fly, exoskeleton, jointed appendages, small
size, and short life span.
Insects have open circulatory system, gas exchange occurs by spiracles (an external
opening of a trachea), insect sersory structures include simple and compound eyes,
and antennae. Most insects go through metamorphosis. eg.:
Order: Odonata: eg.: Dragonflies.
9. Phylum Echinodermata:
Class: Asteroidea: eg.: Astropecto (sea star): are radially symmetrical with 5-part
body plan, most forms have a water vascular system with tube feet for locomotion.
Sea stars are lack circulatory, excretory, and respiratory systems and they have no
head or brain, they use skin gills for gas exchange and waste excretion, most have
separate sexes.
18
Practical Zoology
10. Phylum Chordata:
Bilaterally symmetrical; deuterostomes coelom present; have a notochord, a dorsal
nerve cord, pharyngeal slites, and a tail in some stage of life; aquatic and terrestrial.
The chordates include 3 subphyla:
Subphylum-1: Urochrdata: eg. Tunicates
Small animals, the body with saclike covering or tonic, these animals are
hermaphrodites, cross-fertilization.
Subphylum-2: Cephalochordata:
eg. Amphioxus (lancelet):
It’s a blade shape eyeless small animal live partially buried in the sand, and they can
swim from place to place, ingests particles suspended in the water using ciliated
structures around its mouth, these animals have separated sexes, external fertilization,
and ciliated larval stage.
Subphylum-3: Vertebrata:
The notochord replaced by a spinal column composed of vertebrae that protect the
dorsal nerve cord; recognizable head containing a brain. Vertebrates include:
Class-1: Chondrichthyes: fishes with jaws and paired fins, gills present, cartilaginous
skeleton eg. Sharks.
Class-2: Osteichthyes: fresh water and marine fishes with gills attached to gill arch;
jaws and paired fins, bony skeleton, eg. bony fishes.
Class-3: Amphibia: fresh water or terrestrial, gills present at some stages, skin is
often slimy and lacking scales, have 4 legs, egg typically laid in water and fertilized
externally; eg. the frog Rana ridibunda.
19
Practical Zoology
Class-4: Reptilia: exothermic terrestrial or semi aquatic vertebrates; breathe with
lungs at all stages; the body covered by scales, eg. crocodile, lizards, snakes, and
turtles (which have a shell composed of a bony plates, the vertebrae and ribs are fused
to the interior surface of the shell).
Class-5: Aves (birds): body covered with feathers, forelimbs modified into wings, 4chambered heart, endothermic, eg.: order: Columbiformes eg.: the pigeons.
Class-6: Mammalia:
Hair on at least part of the body, young nourished with milk secreted by mammary
glands, endothermic, breathe with lungs. eg.:
Order-1: Rodentia: eg. Mice, Rats
Order-2: Lagomorpha: eg. Rabbits
Order-3: Chiroptera eg. Bats
Order-4: Primates
Family: Hominidae
Homo sapiens
A. Lecturer: Raad AL-Harmoosh
20