Pg:- 10,11,12,13
Arthropods are a diverse and highly successful group of invertebrates characterized by their jointed appendages, segmented bodies, and exoskeletons made of chitin.
Characteristics of Arthropods
Exoskeleton:
Made of chitin, providing structural support and protection.
It must be periodically shed and replaced through a process called molting (ecdysis).
Segmented Body:
Typically divided into distinct regions: head, thorax, and abdomen.
Segments can be specialized for different functions.
Jointed Appendages:
Legs, antennae, and other appendages are jointed, allowing for a wide range of movements.
Bilateral Symmetry:
Symmetrical body plan with a distinct head and tail end.
Open Circulatory System:
Hemolymph (blood equivalent) is pumped into an open body cavity.
Nervous System:
Consists of a brain and a ventral nerve cord with segmental ganglia.
Major Groups of Arthropods
Insects (Class Insecta):
Largest class of arthropods.
Three-part body: head, thorax, and abdomen.
Three pairs of legs, one pair of antennae, and usually two pairs of wings.
Examples: Butterflies, beetles, ants, bees.
Arachnids (Class Arachnida):
Two-part body: cephalothorax and abdomen.
Four pairs of legs and no antennae.
Examples: Spiders, scorpions, ticks, mites.
Crustaceans (Subphylum Crustacea):
Primarily aquatic.
Two pairs of antennae, variously specialized appendages.
Examples: Crabs, lobsters, shrimp, barnacles.
Myriapods (Subphylum Myriapoda):
Elongated bodies with many segments.
Examples: Centipedes (one pair of legs per segment) and millipedes (two pairs of legs per segment).
Ecological Importance
Decomposers: Many arthropods break down organic matter, recycling nutrients.
Pollinators: Insects like bees play crucial roles in pollinating plants.
Pest Control: Predatory arthropods help control pest populations.
Food Source: An important part of the food chain, serving as prey for many animals.
Vertebrates are a subgroup of the phylum Chordata, characterized by having a backbone or spinal column. They represent the most complex organisms in the animal kingdom.
Characteristics of Vertebrates
Vertebral Column:
Composed of vertebrae, replacing the notochord in adults.
Provides support and protects the spinal cord.
Endoskeleton:
Internal skeleton made of bone or cartilage.
Allows for greater size and complexity of body structures.
Complex Nervous System:
Well-developed brain and spinal cord.
Advanced sensory organs.
Closed Circulatory System:
Heart pumps blood through a network of vessels.
More efficient nutrient and gas exchange.
Paired Appendages:
Limbs, fins, or wings that are often paired.
Bilateral Symmetry:
Body plan with a distinct head (cephalization) and tail end.
Major Groups of Vertebrates
Fishes:
Jawless Fishes (Class Agnatha): Primitive fishes like lampreys and hagfishes.
Cartilaginous Fishes (Class Chondrichthyes): Sharks, rays, and skates with skeletons made of cartilage.
Bony Fishes (Class Osteichthyes): Most fish species, with bony skeletons.
Amphibians (Class Amphibia):
Dual life stages (aquatic larvae and terrestrial adults).
Moist skin for gas exchange.
Examples: Frogs, toads, salamanders.
Reptiles (Class Reptilia):
Dry, scaly skin.
Lay shelled eggs on land.
Examples: Snakes, lizards, turtles, crocodiles.
Birds (Class Aves):
Feathers and wings.
Warm-blooded with high metabolic rates.
Lay hard-shelled eggs.
Examples: Eagles, sparrows, penguins.
Mammals (Class Mammalia):
Hair or fur.
Mammary glands for feeding young.
Warm-blooded with complex brains.
Examples: Humans, whales, elephants, bats.
Ecological Importance
Ecosystem Balance: Vertebrates occupy various ecological niches and help maintain ecosystem balance through predation, herbivory, and other interactions.
Pollination and Seed Dispersal: Some vertebrates, like birds and bats, are important pollinators and seed dispersers.
Biodiversity Indicators: The presence and health of vertebrate species often indicate the overall health of ecosystems.
Human Uses: Vertebrates are sources of food, clothing, medicine, and companionship.