Photoreception and Animal Skeletons

Lecture 10 Recap

Photoreception

  • Detection of light wavelengths: Organisms utilize photopigments to transduce light energy into bioelectric signals.

Eye Spot (Ocellus)

  • Definition: The simplest form of an eye that lacks a lens.

  • Structure: Composed of less than 100 photoreceptor cells.

  • Function: Detects changes in light and dark.

  • Occurrence: Common in many invertebrates including:

    • Planarians

    • Insects

    • Arthropods

    • Echinoderms

Compound Eyes

  • Structure: Contains multiple ommatidia.

  • Function: Utilizes rhodopsin to absorb light, leading to the formation of a motion-sensitive image.

  • Occurrence: Predominantly found in invertebrates, such as molluscs and insects.

Camera Eyes

  • Structure: Employs a lens to focus light onto the retina, which contains photoreceptors (rods and cones).

  • Rods: Detect black and white through rhodopsin.

  • Cones: Responsible for color detection using opsins.

  • Neurotransmission: Both rods and cones release neurotransmitters to interneurons.

Chemoreception

  • Definition: The process of detecting chemicals in the environment.

  • Difference in Receptors: In aquatic invertebrates, taste and smell occur via the same receptors, while terrestrial invertebrates utilize separate mechanisms.

Taste

  • Mechanism: Relies on physical contact with stimuli.

  • Receptor Location: Can be found on feet, antennae, and mouthparts.

  • Specificity: Different taste receptor cells are attuned to specific stimuli such as:

    • Salt

    • Sweet

    • Sour

    • Bitter

    • Umami

Smell (Olfaction)

  • Mechanism: Primarily relies on airborne chemical detection (e.g., pheromones).

  • Process: Binding of odors results in membrane depolarization.

  • Neural Correlation: Animals that depend heavily on olfactory capabilities generally possess a greater number of olfactory neurons.

Thermoreception

  • Definition: The ability to detect changes in environmental temperature.

  • Special Organs: Some animals, such as vampire bats, have specialized organs (e.g., pit organs, extra nasal folds) for identifying prey based on temperature variation.

Electroreception

  • Function: Enables organisms to sense electric fields in their environment.

  • Ancestral Trait: This ability has been lost in many lineages but remains crucial for detecting electric signals from prey or for navigation purposes.

BIOL 224 Animal Body Systems

Animal Locomotion – Part 1 – Skeletons

General Concepts – part 1

  • Skeleton Types: Different categories of animal skeletons.

  • Structural Groups of Skeletons: Analyze examples in various species including bats and sea stars.

Animal Skeletons

  • Definition: The framework through which the body moves.

  • Functions:

    • Provides physical support for the body.

    • Protects soft tissues, allowing bipedal locomotion (e.g., humans can stand and walk).

Types of Skeletons

  1. Hydrostatic Skeleton:

    • Structure: Consists of compartments with muscular walls filled with fluid.

    • Characteristics: Lacks rigid support structure; semi-rigid due to pressurized fluid.

    • Mechanism: Shape changes through muscle contractions (both longitudinal and circular muscles), allowing movement.

    • Examples:

      • Cnidarians (e.g., sea anemones)

      • Flatworms

      • Annelids (e.g., earthworms, leeches)

      • Human penis (via gelatinous fluid).

  2. Exoskeleton:

    • Structure: Rigid external covering.

    • Function: Provides support and protects delicate internal tissues.

    • Composition: Formed from secretions of underlying glands or epidermis (e.g., calcium carbonate shells in molluscs, chitinous cuticle in arthropods).

    • Characteristics: Incompressible; muscles exert force against it, enabling movement.

    • Functions:

      • Protection against dehydration.

      • Defense against predators.

      • Acts as levers for muscle contraction.

    • Note: While certain vertebrates (e.g., turtles) have shells, these shells are not classified as exoskeletons.

  3. Endoskeleton:

    • Definition: Refers to the primary skeletal system found in vertebrates.

    • Structure: Composed of rigid internal structures (bones) that protect internal organs.

    • Mechanism: Muscle contractions apply force against the bones to enable locomotion.

    • Protection: Skull protects the brain; ribs protect the heart and lungs.

    • Types Based on Composition:

    1. Calcium Carbonate and Protein Fibres:

      • Characteristics: Dermal support; limited durability; found in echinoderms.

    2. Calcium Phosphate and Protein Fibres:

      • Characteristics: Weight-bearing; greater strength; found in vertebrates (bones).

The Vertebrate Skeleton

  • Structural Groups:

    1. Axial Skeleton:

    • Description: Forms the long axis of the vertebrate body.

    • Function: Provides sites for muscle attachment; supports body weight.

    1. Appendicular Skeleton:

    • Description: Associated with limbs.

    • Function: Provides leverage for locomotion, as demonstrated by various species (e.g., monkeys, lemurs, raccoons).

Bones

  • Definition: Complex organs made from multiple tissues, including bone tissue, blood vessels, nerves, and adipose tissue.

  • Types:

    • Compact Bone: The outer surface; dense without spaces, containing microscopic canals called osteons.

    • Spongy Bone: The inner structure with larger spaces filled with marrow.

    • Red Marrow: Primary source of new red blood cells, found in flat bones (e.g., hips, ribs of mammals and birds).

    • Yellow Marrow: An adipose tissue source for white blood cells, found within the shaft of long bones (e.g., femur).

Bone Functionality

  • Mineral Storage: Plays a critical role in storing calcium (Ca2+) and phosphate (PO4-) ions, which are constantly deposited and withdrawn.

  • Homeostasis: Blood calcium levels are tightly regulated via endocrine negative feedback loops, affecting:

    • Nervous system functions (e.g., action potential conduction).

    • Muscular system operations (e.g., muscle contraction).

Lecture 11 Recap

  • Goal: Describe strategies for providing body support, locomotion, and protection through skeletal systems.

Skeleton Types Reviewed

  1. Hydrostatic Skeleton:

    • Limited protection; consists of muscular compartments filled with fluid.

    • Contraction and relaxation of circular and longitudinal muscles alters the animal's shape.

  2. Exoskeleton:

    • Rigid external covering formed by secretions of the underlying epidermis.

    • Functions to protect against dehydration, provide armor against predators, and serve as levers for muscle actions, requiring periodic shedding for growth (ecdysis).

  3. Endoskeleton:

    • Internal rigid structures (bones) against which muscle contractions act.

    • Composition types include calcium carbonate/protein fibres and calcium phosphate/protein fibres.

Vertebrate Skeleton Structure

  • Two primary structural groups:

    1. Axial Skeleton: Provides muscle attachment and supports weight.

    2. Appendicular Skeleton: Facilitates locomotion.

  • Bone Composition: Comprised of multiple tissue types.

    • Outer compact bone and inner spongy bone containing red marrow (source of red blood cells) and yellow marrow (source for white blood cells).

  • Mineral Storage: Provides calcium and phosphate that is deposited into or withdrawn from the bloodstream.

  • Regulation: Calcium levels are tightly controlled via endocrine negative feedback loops to maintain homeostasis.