Animal Kingdom is a vast and diverse group of multicellular organisms that share key characteristics:
- Heterotrophs: They obtain energy from consuming other organisms.
- Lack Cell Walls: Unlike plants, they don’t have rigid cell walls.
- Eukaryotes: Their cells have a nucleus and membrane-bound organelles.
- Tissue Level of Organization: They have specialized cells organized into tissues, performing specific functions.
Classification of Animals
Animals are classified based on several characteristics, including:
- Level of Organization: From cellular (sponges) to organ system (vertebrates).
- Symmetry: Asymmetrical (sponges), radial (cnidarians), or bilateral (most animals).
- Presence of Coelom: A body cavity lined by mesoderm (coelomates, pseudocoelomates, or acoelomates).
- Segmentation: Body divided into segments (annelids, arthropods).
- Notochord: A dorsal supporting rod present at some point in development (chordates only).
Major Phyla
The Animal Kingdom is divided into several major phyla, each with unique characteristics:
- Porifera: Sponges, simple multicellular animals with no true tissues.
- Cnidaria: Jellyfish, corals, and anemones, with radial symmetry and stinging cells.
- Platyhelminthes: Flatworms, acoelomate animals with a dorsoventrally flattened body.
- Nematoda: Roundworms, pseudocoelomate animals with a cylindrical body.
- Annelida: Segmented worms, coelomate animals with a closed circulatory system.
- Arthropoda: Insects, crustaceans, spiders, and more, with jointed appendages and an exoskeleton.
- Mollusca: Snails, clams, and octopuses, with a soft body often enclosed in a shell.
- Echinodermata: Starfish, sea urchins, and sea cucumbers, with radial symmetry and a spiny exoskeleton.
- Chordata: Vertebrates and a few invertebrate groups, characterized by a notochord, dorsal nerve cord, pharyngeal slits, and a post-anal tail.
Key Points
- The Animal Kingdom is incredibly diverse, with over 1.5 million described species.
- Animals have evolved to adapt to various habitats and lifestyles.
- Understanding the classification of animals helps us appreciate their diversity and evolutionary relationships.
Exercise
1. What are the difficulties that you would face in classification of animals, if common fundamental features are not taken into account?
Ans : The Animal Kingdom is a diverse group of multicellular organisms that can be classified based on their level of organization, symmetry, coelom, segmentation, and notochord. Major phyla include Porifera, Cnidaria, Platyhelminthes, Nematoda, Annelida, Arthropoda, Mollusca, Echinodermata, and Chordata. Common features are crucial for accurate classification and understanding evolutionary relationships.
2. If you are given a specimen, what are the steps that you would follow to classify it?
Ans :
- Observe and Record Physical Characteristics: I would carefully examine the specimen’s physical features, including its size, shape, color, symmetry, and any distinctive structures. I would also note the presence or absence of specific features, such as a notochord, segmentation, or radial symmetry.
- Identify Level of Organization: I would determine the level of organization of the organism. Is it cellular, tissue, organ, or organ system level?
- Determine Symmetry: I would observe whether the organism exhibits asymmetry, radial symmetry, or bilateral symmetry.
- Identify Presence of Coelom: I would examine the presence or absence of a body cavity (coelom) and its type (coelomate, pseudocoelomate, or acoelomate).
- Observe Segmentation: I would check if the body is divided into segments.
- Examine Notochord: If present, I would identify the notochord, a dorsal supporting rod found in chordates.
- Compare to Known Groups: I would compare the observed characteristics to those of known animal groups. This could involve using identification keys, comparing to reference specimens, or consulting taxonomic literature.
- Consider Evolutionary Relationships: I would consider the evolutionary relationships between the observed characteristics and known groups. This might involve examining phylogenetic trees or analyzing shared derived traits.
- Place Specimen in a Phylum: Based on the analysis of these characteristics, I would place the specimen in the appropriate phylum.
- Further Classification: Within the phylum, I would continue to classify the specimen based on more specific characteristics, such as class, order, family, genus, and species.
3. How useful is the study of the nature of body cavity and coelom in the classification of animals?
Ans : The study of the body cavity and coelom is essential for understanding the evolutionary relationships, body plans, and internal structures of animals. It is a key feature used in the classification of animals into different phyla and helps us appreciate the diversity and complexity of the animal kingdom.
4. Distinguish between intracellular and extracellular digestion?
Ans :
| Feature | Intracellular Digestion | Extracellular Digestion |
| Location | Inside cells | Outside cells in specialized organs |
| Process | Phagocytosis/endocytosis, enzyme breakdown in vacuoles | Mechanical and chemical digestion in digestive tract |
| Organisms | Single-celled organisms, specialized cells | Most multicellular animals |
5. What is the difference between direct and indirect development?
Ans :
| Feature | Direct Development | Indirect Development |
| Growth Pattern | Continuous | Metamorphosis |
| Larval Stage | No larval stage | Distinct larval stage |
| Parental Care | Extensive | Less |
| Reproductive Strategy | Fewer offspring, greater investment | Larger number of offspring, less investment |
| Examples | Mammals, birds, reptiles | Insects, amphibians, marine invertebrates |
6. What are the peculiar features that you find in parasitic platyhelminthes?
Ans :
1.Dorsoventrally Flattened Body: This shape allows for maximum surface area for nutrient absorption from the host’s body.
2. Hooks and Suckers: These structures help them attach firmly to the host’s internal organs, ensuring a secure feeding position.
3. Thick Tegument: Their outer covering is tough and resistant to the host’s digestive enzymes, protecting them from being digested.
4. Developed Reproductive System: Parasitic flatworms often have complex reproductive systems to produce large numbers of offspring, ensuring the continuation of their species.
5. Absence of Specialized Organs: They lack specialized organs like a circulatory system, respiratory system, and digestive tract, as they absorb nutrients directly from the host’s body.
6. Presence of Flame Cells: These specialized cells help in osmoregulation, regulating the water balance within their body.
7. Life Cycles: Many parasitic flatworms have complex life cycles involving multiple hosts, often involving intermediate hosts where they reproduce asexually before infecting the final host.
7. What are the reasons that you can think of for the arthropods to constitute the largest group of the animal kingdom?
Ans :
Exoskeleton: Their hard, external skeleton provides protection, structure, and support, enabling them to thrive in diverse habitats.
Jointed Appendages: These specialized limbs allow for efficient movement, locomotion, and various functions like feeding, reproduction, and defense.
Segmentation: Their bodies are divided into segments, providing flexibility, specialization, and efficient movement.
Efficient Respiratory System: Arthropods have diverse respiratory systems, including gills, tracheae, and book lungs, allowing them to breathe in various environments.
Diverse Feeding Strategies: They exhibit a wide range of feeding strategies, from herbivory and carnivory to parasitism and detritivory, enabling them to exploit various food sources.
High Reproductive Potential: Arthropods have high reproductive rates, producing large numbers of offspring, which contributes to their abundance and diversity.
Rapid Adaptation: Their short life cycles and genetic diversity allow them to adapt quickly to changing environmental conditions, ensuring their survival.
8. . Water vascular system is the characteristic of which group of the following:
(a) Porifera (b) Ctenophora (c) Echinodermata (d) Chordata
Ans : The water vascular system is a characteristic of the Echinodermata phylum.
9. “All vertebrates are chordates but all chordates are not vertebrates”. Justify the statement.
Ans :
The statement “All vertebrates are chordates but all chordates are not vertebrates” is true.
Here’s a breakdown of why:
- Chordates: Chordates are a phylum of animals characterized by having a notochord, a dorsal nerve cord, pharyngeal slits, a post-anal tail, and an endostyle (a groove in the ventral wall of the pharynx) at some point in their development.
- Vertebrates: Vertebrates are a subphylum of chordates. They are distinguished by the presence of a vertebral column, which replaces the notochord during development. Vertebrates also have a well-developed brain, closed circulatory system, and paired appendages.
10. How important is the presence of air bladder in Pisces?
Ans The air bladder is a crucial organ in many fish species, serving several vital functions such as buoyancy regulation, sound production, gas exchange, and hydrostatic support. It’s an important adaptation that has contributed to the success and diversity of many fish groups.
11.What are the modifications that are observed in birds that help them fly?
Ans :
Feathers: Feathers provide insulation, lift, and control during flight. They are lightweight, aerodynamic, and arranged in a way that maximizes lift.
Hollow Bones: Birds have hollow bones that reduce their weight without compromising strength.
Powerful Wings: Their wings are large, muscular, and shaped for efficient flight. The muscles attached to the wings generate the necessary lift and propulsion.
Lightweight Skeleton: Birds have a lightweight skeletal system, further reducing their weight for flight.
Efficient Respiratory System: Birds have a highly efficient respiratory system that allows them to take in and expel oxygen quickly, providing the energy needed for flight.
Streamlined Body: Birds have a streamlined body shape that reduces air resistance and improves their ability to fly.
Large Chest Muscles: The pectoral muscles, which are attached to the sternum and wings, are powerful and allow birds to flap their wings vigorously for flight.
12. Could the number of eggs or young ones produced by an oviparous and viviparous mother be equal? Why?
Ans : No, the number of eggs or young ones produced by an oviparous and viviparous mother is generally not equal.
Oviparous animals compensate for the higher risk of offspring mortality by producing a larger number of eggs, while viviparous animals invest more resources in a smaller number of offspring, increasing their chances of survival.
13. Segmentation in the body is first observed in which of the following: (a) Platyhelminthes (b) Aschelminthes (c) Annelida (d) Arthropoda
Ans : The correct answer is (c) Annelida.
14. Match the following:
(a) Operculum (i) Ctenophora
(b) Parapodia (ii)Mollusca
(c) Scales (iii)Porifera
(d) Comb plates (iv)Reptilia
(e) Radula (v) Annelida
(f) Hair (vi)Cyclostomata and
Ans :
(a) Operculum – (vi) Cyclostomata
(b) Parapodia – (v) Annelida
(c) Scales – (iv) Reptilia
(d) Comb plates – (i) Ctenophora
(e) Radula – (ii) Mollusca (f) Hair – (iii) Porifera
15. Prepare a list of some animals that are found parasitic on human beings.
Ans :
Protozoa:
- Plasmodium falciparum (malaria)
- Trypanosoma brucei (sleeping sickness)
- Leishmania species (leishmaniasis)
Helminths:
- Taenia solium (pork tapeworm)
- Fasciola hepatica (liver fluke)
- Ascaris lumbricoides (roundworm)
- Ancylostoma duodenale (hookworm)
Arthropods:
- Pediculus humanus capitis (head lice)
- Pediculus humanus corporis (body lice)
- Phthirus pubis (pubic lice)
- Culex quinquefasciatus (mosquito, vector for malaria and other diseases)
- Ixodes scapularis (deer tick, vector for Lyme disease)
