Animal Anatomy of Invertebrates: Reproductive & Digestive Systems

Types of Reproduction:
- Asexual (budding, fragmentation, parthenogenesis)
- Sexual (most invertebrates exhibit sexual reproduction with distinct male and female)
Reproductive Organs:
- Ovaries and testes common in many phyla (e.g., annelids, mollusks)
- External fertilization prevalent in aquatic species (e.g., echinoderms)
- Internal fertilization seen in terrestrial invertebrates (e.g., insects, spiders)

Types of Digestive Systems:
- Incomplete (single opening for intake and excretion; e.g., cnidarians)
- Complete (two openings, mouth and anus; e.g., annelids, mollusks)
Feeding Mechanisms:
- Herbivorous, carnivorous, detritivorous, and filter feeders
- Specialized structures (e.g., radula in mollusks, mandibles in arthropods)
Digestive Adaptations:
- Varied gut lengths and complexities based on diet
- Symbiotic relationships with microorganisms for digestion (e.g., in termites)

Basic Organization:
- Ranges from simple nerve nets (e.g., cnidarians) to advanced centralized systems (e.g., arthropods)
Types:
- Radial symmetry (e.g., echinoderms) may have decentralized nervous systems
- Bilateral symmetry shows a more centralized nervous system with a brain and nerve cords (e.g., annelids, arthropods)
Sensory Structures:
- Simple receptors (e.g., light-sensitive cells) to complex eyes (e.g., compound eyes in insects)

Body Plans:
- Variation in symmetry (radial vs. bilateral)
- Protective structures (e.g., exoskeletons in arthropods, shells in mollusks)
Specialized Appendages:
- Adaptations for locomotion (e.g., fins in cephalopods, legs in insects)
- Feeding adaptations (e.g., spatulae in bivalves for filter feeding)
Habitat Adaptations:
- Modifications for terrestrial (e.g., exoskeleton for water retention) or aquatic environments (e.g., streamlined bodies)

Types of Muscles:
- Smooth muscles for involuntary movements (e.g., in soft-bodied invertebrates)
- Striated muscles for voluntary movements (e.g., in arthropods)
Locomotive Mechanisms:
- Hydrostatic skeletons in soft-bodied invertebrates using coelomic fluid
- Rigid structures (exoskeletons) in arthropods, facilitating joint movement
Movement Coordination:
- Muscles often work in antagonistic pairs (e.g., flexors and extensors)
- Primitive systems use hydraulic pressure for movement (e.g., in annelids)

Invertebrates reproduce both asexually and sexually.
Asexual reproduction methods include budding, fragmentation, and parthenogenesis.
Sexual reproduction is dominant in most invertebrates, with distinct male and female individuals.
Organs like ovaries and testes are common in many phyla, such as annelids and mollusks.
External fertilization is prevalent in aquatic invertebrates, such as echinoderms.
Internal fertilization occurs in terrestrial invertebrates, like insects and spiders.

Two types of digestive systems in invertebrates are:
- Incomplete digestive systems, with one opening for both intake and excretion (e.g., cnidarians).
- Complete digestive systems, with two openings, a mouth and anus (e.g., annelids, mollusks).
Feeding mechanisms vary widely, including herbivorous, carnivorous, detritivorous, and filter feeding.
Specialized structures for feeding include radula in mollusks and mandibles in arthropods.
Digestive tract length and complexity adapt according to diet.
Invertebrate digestive systems exhibit symbiosis with microorganisms, like in termites for digesting wood.

Nervous systems in invertebrates range from simple nerve nets (cnidarians) to advanced centralized systems (arthropods).
Radial symmetry (echinoderms) often means decentralized nervous systems.
Bilateral symmetry usually indicates a centralized nervous system with a brain and nerve cords (annelids, arthropods).
Invertebrates possess various sensory structures: simple receptors, such as light-sensitive cells, and complex eyes, such as the compound eyes of insects.

Invertebrates exhibit diverse body plans, including radial and bilateral symmetry.
Protective structures are common, such as exoskeletons in arthropods and shells in mollusks.
Specialized appendages for locomotion include fins in cephalopods and legs in insects.
Feeding adaptations include spatulae in bivalves for filter feeding.
Invertebrates show habitat adaptations: exoskeletons for water retention in terrestrial environments and streamlined bodies for aquatic environments.

Invertebrates possess both smooth and striated muscles:
- Smooth muscles for involuntary movements (e.g., in soft-bodied invertebrates)
- Striated muscles for voluntary movements (e.g., in arthropods)
Locomotion is achieved through hydrostatic skeletons in soft-bodied invertebrates, using coelomic fluid, and rigid structures (exoskeletons) in arthropods, facilitating joint movement.
Muscles often work in antagonistic pairs, like flexors and extensors, to control movement.
Primitive systems in invertebrates utilize hydraulic pressure, such as in annelids, for movement coordination.