ZOOLOGY

 Animal-like protists
 Invertebrates
 Vertebrates
 Animal Classifications

I. ANIMAL-LIKE PROTIST
Protozoan Homeostasis and Reproduction
- Protozoan homeostasis is maintained by specialized structures.
- A region analogous to a mouth is called a cytopharynx, which is involved in the intake
of food particles.
- Digestion can occur within food vacuoles, where enzymes break down the ingested
food.
- Wastes are removed from protozoa through egestion vacuoles or a cytopyge, which
expel indigestible materials or metabolic byproducts.
Protozoans can reproduce through various methods:
Binary fission: The simplest and most common form of asexual reproduction in
protozoa, where a single cell divides into two identical daughter cells.
Budding: A form of asexual reproduction where a small outgrowth or bud forms on the
parent cell and eventually separates to become a new individual.
Multiple fission: A form of asexual reproduction where a single cell undergoes
multiple divisions to produce multiple offspring simultaneously.
Schizogony: A type of asexual reproduction in which the nucleus undergoes multiple
divisions followed by cytokinesis, resulting in the formation of multiple daughter cells.
Sexual reproduction: Protozoa can also reproduce sexually, involving the fusion of
gametes from different individuals to produce offspring with genetic variation.
Protozoa can engage in symbiotic relationships, where both species involved
benefit:
 Symbiosis is a mutually beneficial relationship between two species.
 Parasitism is a type of symbiosis in which one organism, the parasite, lives in or on
another organism, called the host, and derives nutrients at the expense of the host.
 Many protozoa engage in parasitic interactions as part of their symbiotic
relationships.
Pseudopods- “fake feet”
- Cell membranes bulges outward and the cytoplasm rushes forward into the
bulge
- Used for locomotion and filter- feeding
- Ex. Amoeba and Sarcodines

Different forms of pseudopods include lobopodia, filopodia, reticulopodia, and

axopodia.
- Lobopodia can be cylindrical or flattened and are found in Amoeba proteus.
- Amoeboid movement involves contraction of the outer cytoplasm
(ectoplasm) and flow of the inner cytoplasm (endoplasm).
- Filopodia are thin, branched structures used for substrate movement, even
with a heavy test or shell.
- Reticulopodia are thin threads that form a dense network, aiding in prey
capture.
- Axopodia are complex pseudopods with flowing cytoplasm and
microtubules

Cilia - hair-like projection that moves in a wave-like pattern

- Used for locomotion
- Only active during the process of genetic exchange called Conjugation
- Ex. Ciliates

Flagella- whip-like structure that spin rapidly to drive the organisms through the water
- Ex. Giardia

II. INVERTEBRATES
Subphylum Cephalochordata and Subphylum Urochordata

Subphylum Cephalochordata (Lancelets):

- Cephalochordates are small, marine invertebrates commonly known as lancelets or
amphioxus.
- They exhibit chordate characteristics throughout their life cycle, making them important
in understanding vertebrate evolution.
- Lancelets have a fish-like appearance with a slender, elongated body and a notochord
that extends the length of their body.
- They lack a true vertebral column but possess a stiffening rod called the notochord.
- Cephalochordates are filter feeders, using ciliated tentacles called oral cirri to capture
small food particles from the water.
- They have a nerve cord, pharyngeal gill slits, and a post-anal tail, which are key
features of chordates.
- Cephalochordates are hermaphroditic, with both male and female reproductive organs
present in the same individual.

Subphylum Urochordata (Tunicates)

- Urochordates, also known as tunicates or sea squirts, are marine invertebrates.
- They exhibit a complex life cycle with distinct larval and adult stages.
- Adult urochordates typically have a sac-like body covered by a tough outer covering
called a tunic, from which they derive their common name.
- They are filter feeders, drawing water through an incurrent siphon, filtering out food
particles, and expelling water through an excurrent siphon.
- Urochordates possess an endostyle, a structure involved in filter feeding and iodine
metabolism.
- They have a nerve ganglion and a simple nerve cord in the larval stage, but these
structures are often reduced or absent in the adult stage.
- Tunicates are mostly hermaphroditic, although some species have separate sexes.
Fertilization typically occurs externally.
- Urochordates are considered to be the closest living relatives of vertebrates and
provide insights into the evolutionary transition from invertebrates to vertebrates.
 III. VERTEBRATES ( Phyla and Subclasses)

Phylum Porifera (Sponges):

- Porifera are multicellular, sessile organisms commonly known as sponges.
- They lack true tissues and organs and have a porous body structure with specialized
cells called choanocytes.
- Choanocytes generate water currents and filter food particles through their flagella.
- Porifera exhibit a wide range of body forms, including encrusting, vase-shaped, and
branching structures.
- No subclasses are present in the phylum Porifera.

Phylum Echinodermata (Echinoderms):

- Echinoderms are marine invertebrates characterized by radial symmetry as adults.
- They have a unique water vascular system, which aids in locomotion, respiration, and
capturing prey.
- Echinoderms include classes such as Asteroidea (sea stars), Ophiuroidea (brittle
stars), Echinoidea (sea urchins and sand dollars), Holothuroidea (sea cucumbers), and
Crinoidea (sea lilies and feather stars).

Phylum Cnidaria (Cnidarians):

- Cnidarians are diverse aquatic invertebrates, including jellyfish, sea anemones, corals,
and hydras.
- They exhibit radial symmetry and have specialized cells called cnidocytes, which
contain stinging structures called nematocysts.
- Cnidarians have two main body forms: the polyp, which is sessile, and the medusa,
which is free-swimming.
- Major subclasses in Cnidaria include Hydrozoa (hydras, Portuguese man o' war),
Scyphozoa (jellyfish), Anthozoa (corals, sea anemones), and Cubozoa (box jellyfish).
Phylum Hemichordata (Hemichordates):
- Hemichordates are marine invertebrates with a body plan resembling both chordates
and invertebrates.
- They are divided into two main classes: Enteropneusta (acorn worms) and
Pterobranchia (pterobranchs).
- Hemichordates possess pharyngeal gill slits, a dorsal nerve cord, and a structure
called the stomochord.
- They often live in burrows and feed on organic matter in the sediment.

Phylum Ctenophora (Ctenophores):

- Ctenophores, commonly known as comb jellies, are gelatinous marine invertebrates.
- They have a transparent, oval or elongated body with rows of cilia, called comb plates,
for locomotion.
- Ctenophores possess tentacles with specialized adhesive cells used for capturing
prey.
- No subclasses are present in the phylum Ctenophora.

Phylum Arthropoda (Arthropods):

- Arthropods are the largest and most diverse phylum of invertebrates, including insects,
spiders, crustaceans, and more.
- They have segmented bodies, jointed appendages, and an exoskeleton made of
chitin.
- Arthropods are divided into several major subclasses, including Insecta (insects),
Arachnida (spiders, scorpions), Crustacea (crabs, lobsters, shrimps), and more.

Phylum Mollusca (Mollusks):

- Mollusks are diverse invertebrates with a soft body often protected by a hard shell.
- They have a muscular foot for locomotion, a visceral mass containing internal organs,
and a mantle that secretes the shell.
- Major subclasses in Mollusca include Gastropoda (snails, slugs), Bivalvia (clams,
mussels), Cephalopoda (squids, octopuses), and more.
Phylum Platyhelminthes (Flatworms):
- Platyhelminthes are flatworms characterized by a flattened body shape.
- They can be free-living or parasitic and exhibit bilateral symmetry.
- Major subclasses in Platyhelminthes include Turbellaria (free-living flatworms),
Trematoda (flukes), and Cestoda (tapeworms).

Phylum Annelida (Annelids):

- Annelids are segmented worms with a cylindrical body divided into repeating
segments.
- They exhibit bilateral symmetry and possess a closed circulatory system.
- Major subclasses in Annelida include Polychaeta (marine bristle worms), Oligochaeta
(earthworms), and Hirudinea (leeches).

Phylum Nematoda (Nematodes):

- Nematodes, commonly known as roundworms, are unsegmented worms with a
cylindrical body shape.
- They have a protective cuticle and exhibit bilateral symmetry.
- Nematodes are found in diverse habitats, including soil, freshwater, and marine
environments.

IV. VERTEBRATES ( Animal Classification)

Fishes
- Fishes are aquatic vertebrates with gills and fins.
- They are ectothermic (cold-blooded) and have scales covering their bodies.
- Fishes can be divided into two main groups: jawless fishes (e.g., lampreys and
hagfish) and jawed fishes.
- Jawed fishes include cartilaginous fishes (e.g., sharks, rays) and bony fishes (e.g.,
tuna, salmon, goldfish).
Birds
- Birds are warm-blooded vertebrates characterized by feathers, beaks, and laying hard-
shelled eggs.
- They have forelimbs modified into wings, enabling flight in most species.
- Birds exhibit a wide range of adaptations for various habitats and diets.
- They are classified into numerous orders, such as Passeriformes (perching birds),
Falconiformes (birds of prey), and Strigiformes (owls).

Amphibians
- Amphibians are cold-blooded vertebrates that undergo metamorphosis from aquatic
larvae to terrestrial adults.
- They have moist skin, typically lay eggs in water, and undergo various degrees of
aquatic and terrestrial lifestyles.
- Amphibians include three main groups: frogs and toads (order Anura), salamanders
and newts (order Caudata), and caecilians (order Gymnophiona).

Reptiles
- Reptiles are cold-blooded vertebrates with dry, scaly skin and lay amniotic eggs.
- They have lungs for respiration and include various groups adapted to different
environments.
- Reptiles are divided into several orders, including Squamata (lizards and snakes),
Testudines (turtles and tortoises), Crocodylia (crocodiles and alligators), and
Sphenodontia (tuataras).

Mammals
- Mammals are warm-blooded vertebrates with hair or fur and mammary glands that
produce milk.
- They have specialized teeth and a highly developed brain.
- Mammals give birth to live young and provide parental care.
- Mammals encompass a wide range of species, including primates (e.g., humans,
monkeys), carnivores (e.g., lions, wolves), rodents (e.g., mice, squirrels), and cetaceans
(e.g., whales, dolphins).