Answers:
Examples: Jellyfish, Hydra, Sea anemone, Coral
Key Features: Diploblastic, acoelomate, radial symmetry, cnidocytes with stinging cells
Explanation: Starfish belong to the phylum Echinodermata. Their body is triploblastic, coelomate, and radially symmetrical in the adult stage.
Other Echinoderms: Sea urchin, Sea cucumber, Brittle star
Explanation: Intestinal worms are included in the Phylum Aschelminthes (Nematoda). Their bodies are triploblastic and pseudocoelomate.
Other Examples: Pinworms, Hookworms, Filarial worms
Explanation: Animals of the phylum Porifera, known as 'Sponges,' exhibit the simplest body structure. They feature numerous pores on their bodies.
Key Features: Cellular level organization, asymmetrical, aquatic, filter feeders
Answers:
- Simplest body structure among multicellular animals
- Body covered with pores (ostia and oscula)
- Aquatic organisms (mostly marine)
- Asymmetrical body organization
- Cellular grade of organization (no true tissues)
- Filter feeders using collar cells (choanocytes)
- Jointed appendages (arthros = joint, poda = legs)
- Triploblastic, coelomate, bilaterally symmetrical
- Segmented body (head, thorax, abdomen)
- Chitinous exoskeleton for protection
- Open circulatory system
- Tracheal system for respiration
- Aquatic, cold-blooded (poikilothermic)
- Streamlined (spindle-shaped) body to reduce water resistance
- Paired and unpaired fins for movement
- Caudal fin acts as steering organ
- Respiration through gills
- Two-chambered heart
- Warm-blooded (homeothermic) vertebrates
- Body streamlined for swimming (flightless bird)
- Forelimbs modified into flippers for swimming
- Exoskeleton of feathers for insulation
- Four-chambered heart
- Lightweight bones with air cavities
- Larval stage (tadpole): entirely aquatic, gill respiration
- Adult stage: can live on land and water
- Moist, glandular skin without scales
- Two pairs of limbs without claws
- Three-chambered heart
- External fertilization (amplexus)
- Cold-blooded (poikilothermic)
- Moves by creeping (body close to ground)
- Dry skin covered with scales/scutes
- Three-chambered heart (except crocodiles)
- Internal fertilization
- Terrestrial eggs with leathery shells
- Presence of mammary glands for feeding young
- Warm-blooded (homeothermic)
- Body divided into head, neck, trunk, and tail
- Digits protected by nails (in elephants, modified as hooves)
- Four-chambered heart
- Presence of hair/fur (reduced in elephants)
- Cylindrical or umbrella-shaped body (medusa form)
- Mostly marine, few freshwater species
- Radially symmetrical and diploblastic
- Tentacles with cnidoblasts (stinging cells)
- Cnidoblasts inject toxins for prey capture and defense
- Two body forms: polyp (sedentary) and medusa (free-swimming)
Answer:
The first documented attempt at classifying animals was carried out by the Greek philosopher Aristotle. His classification, known as the 'Artificial method,' categorized animals based on criteria like body size, habits, and habitats (land, water, air).
These scientists continued using artificial classification systems based on observable characteristics without considering evolutionary relationships.
This system used various criteria, such as body organization, cell types, chromosome structure, and biochemical properties to establish relationships between organisms.
They championed a classification system based on evolutionary relationships and common ancestry, moving beyond just physical characteristics.
Woese introduced a classification system based on ribosomal RNA differences, dividing life into three domains: Archaea, Bacteria, and Eukarya.
Currently the standard system. All multicellular animals are placed in Kingdom Animalia. This modern system relies on fundamental criteria including:
- Body organization
- Body symmetry
- Body cavity (coelom)
- Germinal layers
- Segmentation
Answer:
The level of structural complexity in animals, from simplest to most complex:
- Protoplasmic Grade: Found in unicellular organisms where all life functions occur within a single cell. Example: Amoeba, Paramecium.
- Cellular Grade: Multicellular animals without true tissue formation. Cells are loosely aggregated. Example: Phylum Porifera (Sponges).
- Cell-Tissue Grade: Cells group together to form tissues that perform specific functions. Example: Phylum Cnidaria (Jellyfish, Hydra).
- Tissue-Organ Grade: Tissues organize to form basic organs, but complete organ systems are absent. Example: Flatworms (Phylum Platyhelminthes).
- Organ-System Grade: Distinct organs combine to form specialized organ systems. Examples: Crab (Arthropoda), Frog (Chordata), Human (Chordata).
Describes how body parts are arranged around a central axis or plane:
- Asymmetrical: No plane can divide the body into two equal halves. Examples: Amoeba, Paramecium, most sponges.
- Radial Symmetry: Any imaginary cut through the central axis results in two equal halves. Body parts arranged around central axis like spokes of a wheel. Examples: Starfish (adult), Jellyfish, Hydra.
- Bilateral Symmetry: Only one specific plane (sagittal/mid-sagittal) divides the body into two equal mirror-image halves (left and right). Examples: Insects, fishes, frog, birds, humans.
- Biradial Symmetry: Combination of radial and bilateral symmetry. Example: Comb jellies (Ctenophora).
- Spherical Symmetry: Body can be divided into equal halves by any plane passing through the center. Example: Volvox (some protists).
Answers:
While "Pisces" is sometimes used as a class, modern classification often divides fish into multiple classes: Chondrichthyes (cartilaginous fish like sharks) and Osteichthyes (bony fish like rohu).
The presence of calcareous spines on the body surface gives these animals their name (echinos = spiny, derma = skin).
These animals are strictly found only in marine environments (oceans), never in freshwater or terrestrial habitats.
Adults exhibit radial symmetry (usually pentamerous), but larvae show bilateral symmetry. Triploblastic and coelomate.
Locomotion via tube feet powered by a unique water vascular system. Also used for feeding and respiration.
- Phylum: Arthropoda
- Body Covering: Chitinous exoskeleton
- Respiration: Tracheal system
- Circulation: Open circulatory system
- Wings: Membranous with scales
- Body Temperature: Cold-blooded
- Heart Chambers: Tubular heart
- Phylum: Chordata
- Body Covering: Skin with hair/fur
- Respiration: Lungs
- Circulation: Closed circulatory system
- Wings: Modified forelimbs with skin membrane
- Body Temperature: Warm-blooded
- Heart Chambers: Four-chambered heart
Phylum: Arthropoda
Possesses jointed legs and antennae (arthros = joint, poda = feet).
Body covered by a hard, protective exoskeleton made of chitin.
Triploblastic, coelomate, bilaterally symmetrical, and segmented body.
- Habitat Diversity: Found in diverse environments worldwide
- Reproduction: Sexual reproduction with separate sexes (unisexual)
- Respiration: Through tracheal system
- Circulation: Open circulatory system with dorsal heart
Answers:
The Class Amphibia is defined by animals that are obligatorily aquatic during their larval stage (tadpoles with gills), performing only aquatic respiration. They only gain the ability to live on land and perform aerial respiration as adults. This specific life cycle (metamorphosis) is not observed in tortoises. Tortoises are cold-blooded reptiles that lay amniotic eggs with shells on land. Therefore, based on their physiological, anatomical, and reproductive characteristics, they are correctly placed in the Class Reptilia, not Amphibia.
The jellyfish belongs to the phylum Cnidaria. These organisms have tentacles surrounding their mouth that bear specialized cells called cnidoblasts (nematocytes). These tentacles are used for capturing prey, while the cnidoblasts inject a neurotoxin (nematocyst venom) into the prey's body. They also serve as a mechanism for protection. When human skin comes into contact with the jellyfish, the release of this toxic substance causes skin irritation, redness, pain, and sometimes severe allergic reactions.
The Phylum Chordata is defined by the presence of a supportive skeletal structure called the notochord at some stage of life. The key difference lies in the fate of this notochord:
- Vertebrates: In subphylum Vertebrata, the embryonic notochord is replaced by a backbone (vertebral column) in adults.
- Other Chordates: In cephalochordates (e.g., Amphioxus), the notochord persists throughout life. In urochordates (e.g., sea squirts), the notochord is present only in larval stages.
Thus, every vertebrate must have been a chordate, but not every chordate develops vertebrae.
From an evolutionary standpoint, Balanoglossus (acorn worm) is viewed as a transitional organism linking non-chordates and chordates. It exhibits characteristics from both major groups:
- Chordate Traits: Possesses a notochord in larval stage, dorsal tubular nerve cord, and pharyngeal gill slits.
- Non-Chordate Traits: Has phosphagens (energy storage molecules) like invertebrates and a specific larval stage (tornaria larva) similar to echinoderms.
This combination of features suggests evolutionary relationships between the groups.
Reptiles are classified as poikilotherms (ectotherms), meaning they are cold-blooded animals. Cold-blooded organisms lack internal physiological mechanisms to maintain a stable, constant body temperature. Instead, their body heat is largely derived from the external environment through behavioral adaptations (basking in sun, seeking shade). This causes their body temperature to fluctuate based on the surrounding environmental temperatures, unlike warm-blooded (homeothermic) animals like birds and mammals that maintain constant internal temperatures through metabolic processes.
Answers:
Explanation: The specialized type of cells present in the body of sponges belonging to the Phylum Porifera are known as collar cells or choanocytes. These flagellated cells create water currents and capture food particles.
Explanation: Earthworms belong to the Phylum Annelida. They are triploblastic, bilaterally symmetrical, and possess a true coelom. Starfish (radial symmetry as adults), jellyfish (radial symmetry), and sponges (asymmetrical) do not exhibit bilateral symmetry.
Explanation: Starfish belong to the Phylum Echinodermata. Animals within this phylum have a strong ability for regeneration and can regrow lost arms or even an entire body from a single arm if it contains part of the central disc.
Explanation: Bats are warm-blooded and possess mammary glands, which are the defining characteristics of the Class Mammalia. Despite their ability to fly like birds, they are mammals with hair, give birth to live young, and produce milk.
Instructions:
When completing classification charts, remember to include:
- Kingdom: Animalia (for all animals)
- Phylum: Based on body organization, symmetry, coelom
- Class: Based on specific characteristics (for chordates)
- Key Features: Symmetry, coelom type, germ layers, segmentation
- Examples: Common representatives of each group
When sketching and labeling organisms, include:
- Tentacles with cnidocytes
- Mouth/aboral opening
- Gastrovascular cavity
- Radial symmetry
- Body segmentation (earthworm)
- Flat body (planaria)
- Pseudocoelom (roundworm)
- Bilateral symmetry
- Vertebral column
- Appendages (fins, limbs, wings)
- Respective class characteristics
- Key external features
When labeling diagrams, ensure you:
- Use clear, straight labeling lines
- Write labels horizontally for readability
- Include both external and internal structures as required
- Follow the specific instructions for each diagram
- Use proper biological terminology