Zoology Past Paper PDF

**TAXONOMY: KINGDOM ANIMALIA AND PORIFERA** **Taxonomy** - It is a branch of biology that deals with the classification and naming of all living things. - It is the practice of identifying different organisms, classifying them into categories and naming them with a unique scientific n...

**TAXONOMY: KINGDOM ANIMALIA AND PORIFERA** **Taxonomy** - It is a branch of biology that deals with the classification and naming of all living things. - It is the practice of identifying different organisms, classifying them into categories and naming them with a unique scientific name (Basic Biology, 2019) **Father of Taxonomy** - ***In the 18th century, the Swedish scientist Carolus Linnaeus developed the modern system of taxonomy and classification.*** - ***With his invention of the widely used system of classification, Carolus Linnaeus is considered to be the 'FATHER OF MODERN TAXONOMY'.*** **Modern Taxonomy** - **The 10th revision of Systema Naturæ in 1758 marked the official start of modern taxonomy and the first formal biological classification.** - **This book became the standard of contemporary scientists of Linnaeus, not just with classifying organisms but as well as with the standard way of naming them.** **The Linnaean System of Classification** 1. ***Domain*** 2. ***Kingdom*** 3. ***Phylum*** 4. ***Class*** 5. ***Order*** 6. ***Family*** 7. ***Genus*** 8. ***Species*** **Domains and Kingdoms of Life** **How do we name organisms?** - **Binomial Nomenclature** - **the word nomenclature is derived from to Latin words *nomen*, which means "name" and *clare*, means to call R** - **The system of naming introduced by Linnaeus is also referred as A Two-Part Naming System.** - ***[Step 1: Genus Identification]*** - **The first part of the name indicates the genus and is always capitalized.** - **Example: *\'Homo'*** - ***[Step 2: Species Designation]*** - **The second part specifies the species, written in lowercase.** - **Example: *\'sapiens\'*** - **Golden Rules:** - **Writing the Scientific Names of organisms may be done in to formats:** 1. ***Typewritten Format*** - **The full name should be italicized to maintain clarity and emphasis.** 2. ***Handwritten Convention*** - **the full name should be [underlined] to indicate its significance.** **Kingdom Animalia** - **also known as Metazoa, is a kingdom which includes all animals** - **regarded as the kingdom with the most number of species** - **animals are [multicellular, eukaryotic organisms] which are [heterotrophic ]** - **most animals are capable of complex behavioral responses and rapid movement**  **Invertebrates** - ***Characterized by neither the possession nor development of a vertebral column or a [backbone.]*** - ***Recognized as the largest group present in the Animal Kingdom: 97% of animal species are all invertebrates.*** - ***Invertebrates are considered to be [successful] organisms due to their rapid capacity to reproduce.*** - ***They are classified based upon [their body structure, life cycle, and evolutionary history.]*** **Vertebrates** - ***Also called Craniata, are members of the subphylum Vertebrata, under the Phylum Chordata of the Kingdom Animalia.*** - ***Comprise all species of animals that have a spinal cord surrounded by either cartilage or bone; the word is derived from the vertebrae, which is the set of bones that make up the spine.*** - ***Characterized by a muscular system consisting primarily of bilaterally paired masses and a central nervous system partly enclosed within the backbone.*** - ***There are approximately [40,000] identified species of vertebrates*** 1. ***Fish*** - ***Cold-blooded*** - ***Breathe underwater using gills, not lungs*** - ***Live in water*** - ***Have scales and fins (no hair of fur)*** - ***Lay [many] eggs***  2. ***Amphibians*** - ***It means "double life"*** - ***Cold-blooded*** - ***Live on land and water*** - ***Webbed feet*** - ***Breathe with lungs and gills*** - ***Moist smooth skin, (no hair or fur)*** - ***4 legs (sometimes none)*** - ***Lay many eggs***  3. ***Reptiles*** - ***Cold-blooded*** - ***Have scales, not fur*** - ***Have dry skin*** - ***Usually lay eggs, sometimes live young*** - ***Ear holes instead of ears*** - ***4 legs or no legs***  4. ***Birds*** - ***Warm-blooded*** - ***Have feathers and wings*** - ***Lay eggs*** - ***Have 2 legs*** - ***Ear holes instead of ears*** 5. ***Mammals*** - ***Warm-blooded*** - ***Have hair or fur*** - ***Give birth to 'live young'*** - ***Mammal mothers nurse their young with milk*** - ***Have lungs and need air to breathe*** - ***Mammals that live on land have 4 legs, and ears that stick out***  **Phylum Porifera** - commonly referred to as **sponges** - derived from two Latin terminologies, **"porus",** which means pore; and **"fera"**, which means to bear; species classified under this Phylum are primarily **marine pore-bearing animals comprised of loosely-organized cells** **Characteristics** - oldest animal group - simplest multicellular organisms - most are **asymmetrical,** while some are superficially radially **symmetrical** - composed of loosely organized cells - even though they are multicellular, they do not have tissues nor organs - depict a **cellular grade of organization**, in which all cells are specialized for the performance of a specific function - absence of a specialized digestive, nervous, or circulatory system; instead, they have a **water** **transport or canal system,** which achieves the functions of digestion, excretion and also an exchange of gases - mostly reside in **aquatic habitat**, particularly in a marine environment; though a few species are found in freshwater - composed primarily of [three kinds of cells:] (1) pinacocytes; (2) amoebocytes; and (3) choanocytes - possesses a central cavity, or a series of branching chambers, through which water circulates during feeding **Anatomy of Phylum Porifera**  **Pinacocyte** - thin, flat cells which line the pinacoderm\* (outermost layer of the sponge) may be mildly contractile, and this contraction has the capacity to change the entire shape and form of some sponges - in a number of sponges, some pinacocytes are transformed into porocytes **Porocyte** - specialized, tube-like pinacocytes which is responsible for water regulation amongst sponges - tubular cells which make up the opening of the sponge - openings through porocytes are pathways for water moving through the body wall **Amoebocytes** - **amoeboid cells,** also referred to as mesenchyme cells are located in the **mesohyl** and can perform various functions - **mesohyl**: derived from two Greek words: "meso", which means middle; and "hyl", which means matter; it is a jelly-like, gelatinous layer located just below the pinacoderm and acts like the matrix of the sponge - **Functions** - storing and transporting food; - delivering nutrients from the choanocytes to other cells within the sponge; - secreting various skeletal elements; - releasing of egg cells for sexual reproduction; and - forming contractile rings around the openings of the sponge wall **Choanocytes** - derived from the two Greek words: **"choane**", which means tunnel; and **"cyto"**, which means cell - have a collar-like ring of **microvilli** surrounding a **flagellum,** this collar is responsible for the filtration of microscopic food particles - flagellated cells that line the choanoderm\* (innermost layer of the sponge) - The **flagellum** creates water current through the sponge, and the **collar** filters microscopic food particles from the water to be absorbed by the sponge. **Spicules** - microscopic, **needle-like spikes** which serve as support in sponges - formed by **amoeboid cells** or the **amoebocytes** and are located in the **mesohyl** - made of either **calcium carbonate** or **silica**, can take on a variety of shapes - alternatively, spicules can be comprised of **spongin\***, a [fibrous protein made up of collagen ] - acts as the **skeletal framework** of the sponge **Passageways** 1. ***Ostium / Ostia*** - ***commonly known as the pores present on sponges*** - ***number of pores in the wall of a sponge through which water is drawn in*** - ***opening of the porocytes*** 2. ***Spongocoel*** - ***large, central cavity of sponge*** - ***water enters the spongocoel through hundreds of tiny pores and exits through the larger opening*** 3. ***Osculum*** - ***single large opening at the top of the sponge*** - ***excretory structure from which water is expelled after passing through the spongocoel*** - ***carries away the wastes manufactured by the sponge*** **Classification of Phylum Porifera** **Class Calcarea** - Also known as **"calcareous sponges"**, composed of spicules which are made up of [calcium carbonate] - spicules are **needle-shaped** or have **three** or **four** rays - all reside in [marine environment] and are found in [shallow, tropical waters] - take a wide range of shapes, including irregular massive forms, **vase-shaped** bodies on a stalk or **meshwork** of thin tubes  **Class Hexactinellida** - Commonly referred to as **"glass sponges"** - spicules consisted of **silica** and **six-rayed**; often fused into an **intricate lattice** - found in [deep water] and [marine environment] - typically pale in color and resembles the shape of a cup or a basket  **Class Demospongiae** - Sometimes called as **"demosponges"** - Brilliantly-colored sponges made up of **four-rayed** siliceous spicules or spongin or both. - acknowledged as the **most diverse class under Phylum Porifera**, including 76% of all species of sponges - their geographic distribution in the marine environment is from the **intertidal\*** (marine shoreline that is exposed to air during low tide) to the **abyssal zone\*** (deepest layer of the ocean); while some species inhabit freshwater  **Class Homoscleromorpha** - Homoscleromorpha is now recognized as the fourth class of sponges. - Fossil records are extremely poor due to their tiny spicules and encrusting forms, which rarely preserve well. - They have a small **"tetraxon"** spicules. - They are exclusively marine sponges that tend to encrust on other surfaces at shallow depths.  **Body Forms of Sponges / Morphology of Phylum Porifera** **Ascanoid** - The **simplest and least common body form** - Ascon sponges are vase-like - **Passageway of water:** - ostia are the outer openings of porocytes and lead directly to a chamber called the spongocoel - choanocytes line the spongocoel, and their flagellar movements draw water into the spongocoel through the ostia - water exits the sponge through the osculum, which is a single, large opening at the top of the sponge - [classes with ascanoid forms:] [ ] **some calcarean**  **Syconoid** - Characterized by the presence of folding patterns in the sponge wall - **Passageway of water:** - water enters through openings called dermal pores or ostia - pores in the body wall connect incurrent canals to radial canals, and the radial canals lead to the spongocoel - choanocytes line radial canals and moves water from the ostia, through incurrent and radial canals, to the spongocoel, and out the osculum - [classes with syconoid forms:] [ ] **some calcarean and few hexactinellida**  **Leuconoid** - Composed of extensive branched canal systems - **Passageway of water:** - water enters the sponge through ostia and moves through branched incurrent canals, which lead to choanocytes-lined chambers - canals leading away from the chambers are called excurrent canals - proliferation of chambers and canals has resulted in the absence of spongocoel, and often, multiple exit points (oscula) for water leaving the sponge - [classes with leuconoid forms:] [ ] **some calcarean, few hexactinellida, Demospongiae,** and **homoscleromorpha** **Physiology of Phylum Porifera** 1. ***Nutrition*** - ***Food is primarily consisted of bacteria, microscopic algae, protists, and other suspended organic matter; eats prey and obtains nutrition through filtration*** - ***Choanocytes filter small, food suspended particles by trapping the food into its collar moving it along the microvilli where the food will be incorporated into a food vacuole*** - ***Digestion begins in the food vacuole by lysosomal enzymes, while partially digested food is passed to amoebocytes, which will distribute it to other cells*** 2. ***Reproduction*** - ***Sponges are considered to be monoecious\* but do not self-fertilize because individual sponges produce egg and sperm cells at different times*** - ***Choanocytes undergo meiosis to form flagellated sperm, while other choanocytes and amoebocytes form egg cells*** - ***[Fertilization occurs in ocean water,] and planktonic larvae develop*** - ***The larva breaks free, and water currents carry the larva out of the parent sponge; after no more than two days, the larva settles into a substrate and begins to develop into its adult body form***