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pt 2
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What challenges do animals face in different environments, and how does this affect movement and body support?
Aquatic animals:
Buoyancy helps support the body
Must overcome drag when moving through water
Terrestrial animals:
Must support body weight against gravity
Must overcome friction and terrain challenges
Amphibious / dual-environment animals:
Balance aquatic drag with terrestrial support needs
Other challenges for all animals:
Protecting body surfaces from abrasion, ions, and predation
✅ Key idea: Animal body support and movement are shaped by the physical properties of their environment.
What are the animal support systems, and what roles do they play?
Support systems involve:
Epithelial layers / epidermis → produce protective layers
Fluids in body cavities → hydrostatic support
Skeletal muscles → enable movement
Connective tissues → fibrous tissue, cartilage, bone
Functions of support systems:
Structural support → maintain body shape
Anchor for muscles → allow contraction and movement
Protection → from predators, pathogens, desiccation, and abrasion
Three basic types of skeletal systems:
Hydrostatic skeleton → fluid-filled cavities provide support
Exoskeleton → external rigid covering (e.g., arthropods)
Endoskeleton → internal rigid support (e.g., vertebrates)
✅ Key idea: Animal support systems integrate structure, protection, and movement in diverse environments.
What is the role of muscle tissue in animal locomotion, and what are the main types?
Muscle function:
Contraction and relaxation of fibers → shortens/lengthens cells
Movement roles:
Skeletal muscle → locomotion (e.g., swimming, walking)
Smooth muscle → moves food through digestive tract
Cardiac muscle → pumps blood in heart
Antagonistic muscle groups: muscles that work in opposition to control movement
Three types of muscle tissue:
Skeletal → voluntary, striated, moves skeleton
Smooth → involuntary, non-striated, lines internal organs
Cardiac → involuntary, striated, heart contractions
✅ Key idea: All muscle tissue enables movement, and antagonistic pairs allow precise control.
What is the integument, and how does it provide protection in vertebrates?
Integument = outer protective covering
Function:
Protects inner tissues from physical damage, predators, and abrasion
Vertebrate integument:
Epidermis: surface layer → often produces scales, feathers, or hair
Dermis: deeper layer → supports epidermis and contains connective tissue, blood vessels, glands
Evolutionary significance:
Changes in integument are linked to endoskeleton evolution and locomotion adaptations
✅ Key idea: The integument provides physical protection and is integrated with structural and locomotor systems in vertebrates.
What are the main connective tissues that provide support, and what are their functions?
Connective tissue functions:
Bind tissues together
Provide structural support
Types of connective tissue involved in support:
Fibrous connective tissue
Parallel bundles of collagen fibers
Maximizes non-elastic strength
Found in tendons and ligaments
Cartilage connective tissue
Contains chondrocytes in a rubbery ground substance
Flexible cartilage: outer ear, nose, vertebrate embryos, some skeletons
Hyaline cartilage: non-fibrous, harder, lines ends of long bones at joints
✅ Key idea: Connective tissues provide strength, flexibility, and support for animal bodies, forming critical parts of the skeleton and joints.
What is bone connective tissue, and what are hydrostatic skeletons?
Bone connective tissue:
Found in endoskeletons and teeth
Osteoblasts → deposit collagen matrix + ions → forms hardened bone
Structure:
Compact bone made of osteons → mineralized rings around a central cavity with blood vessels and nerves
Cells:
Chondrocytes → cartilage cells
Osteocytes → mature bone cells
Tendons and ligaments:
Tendons → connect muscle to bone
Ligaments → connect bone to bone
Hydrostatic skeletons:
Fluid-filled compartments of fixed volume
Muscle contraction in one area + relaxation in another → changes compartment shape → movement
Found in cnidarians (jellyfish, sea anemones)
✅ Key idea:
Bone provides rigid support and protection, while hydrostatic skeletons use fluid and muscle interaction for movement.
How do hydrostatic skeletons function in earthworms, and what are the main types of exoskeletons?
Hydrostatic skeleton in earthworms:
Body structure: fluid-filled coelom, thin chitin cuticle, circular & longitudinal muscle layers
Chaete (setae): short chitin spines for traction
Muscle action:
Circular muscles → constrict diameter
Longitudinal muscles → shorten body length
Locomotion: variation in muscle contraction + hydrostatic pressure in coelomic compartments changes body shape → movement
Septa: divide coelom into compartments → local pressure control
Exoskeletons:
Earthworm cuticle: simple, chitinized layer (supports hydrostatic skeleton)
Molluscan shells: calcium carbonate + proteins, secreted by mantle, protects soft body; some reduced/lost
Arthropod exoskeletons: rigid, segmented, chitin + sometimes CaCO₃, provides protection and muscle attachment
✅ Key idea: Hydrostatic skeletons use fluid pressure and muscle contraction for movement, while exoskeletons provide external support and protection.
What are the features of arthropod exoskeletons, and how do they affect locomotion?
Composition:
Chitin, proteins, and calcium carbonate, secreted by epidermis
Covers the entire body
Thickness varies by function:
Thin at flexible joints → movement
Thick/spiny where protection needed
Diversity & locomotion:
Aquatic arthropods (horseshoe crabs, crayfish, lobsters, shrimp) → heavier exoskeletons; water supports body
Barnacles → heaviest exoskeleton; sessile (no movement)
Terrestrial arthropods (spiders, ticks) → lighter, flexible exoskeletons
Insects → lightest exoskeletons for flight
Key idea: The size, shape, and material of the exoskeleton is adapted to each animal’s locomotion strategy
Question: Phyla with both hydrostatic skeletons AND exoskeletons?
Example: Annelida (earthworms: hydrostatic + cuticle)
✅ Key idea: Arthropod exoskeletons balance protection, support, and movement, optimized for habitat and behavior.
What are the features of sponge endoskeletons?
Composition:
Fibers and spicules made of proteins, calcium carbonate, and silica
Embedded in mesohyl → tough but pliable connective tissue-like material
Function:
Provides structural support for the sponge body
Maintains shape while allowing some flexibility
Supports water flow through sponge canals
✅ Key idea: Sponge endoskeletons are internal, rigid yet flexible, using spicules and fibers for support and structure.
What are the features and functions of echinoderm and chordate endoskeletons?
Echinoderm endoskeletons:
Composed of calcified plates (ossicles) beneath soft epidermis
Flexibility: soft tissue between ossicles allows body wall movement
Spines: vary by species, e.g., sea urchins have long spines for predator defense
Diversity: sea stars → short spines; sea urchins/sand dollars → ossicles encase body
Chordate endoskeletons:
Notochord: internal skeletal rod, precursor to vertebral column
Location: ventral to nerve cord (e.g., Amphioxus)
Function:
Provides internal support
Anchors trunk muscles for undulatory swimming
Continuous notochord → ancestral condition in jawless fishes
✅ Key idea: Both endoskeletons provide internal support, but echinoderms rely on ossicles + soft tissue, while chordates rely on the notochord for muscular anchoring and locomotion.