Animal Biology Overview

General Concepts

• Animal = non-human animals, all members of the animal kingdom
• Animals are multicellular eukaryotes (lack cell walls)
• Animals are heterotrophs (obtain energy from consuming other organisms)
• Most animals are motile (able to move)
• Animals reproduce sexually or asexually
• Animals have nerves and muscles

Animal Characteristics

• Multicellular eukaryotes (lack cell walls)
• Heterotrophic
• Motile
• Sexual or asexual reproduction
• Nervous system
• Muscular system

Animal Diversity

• Diverse species
• Diverse habitats
• Diverse characteristics

Animal Origins

• Common ancestor for all animals = colonial flagellated protist in Precambrian
• Similarity to modern colonial flagellated species
• Morphological and molecular evidence

Animal vs Plant Cell

• Animal cells lack a cell wall and central vacuole, only vacuoles
• Plants have a cell wall and a central vacuole
• Cell wall provides tissue stability

Tissue Stability in Animals

• Animal cells do not have cell walls to provide stability like plant cells
• Animal tissues use extracellular junctions for stability
• Extracellular junctions maintain shape, structure, and function of cells
• Types of junctions:
  • Anchoring junctions: attach proteins to join cells together
  • Tight junctions: prevent things from passing through adjacent cells
  • Gap junctions: allow cell-cell communication and ion exchange

Classifying Animals

• Animal Body Plans (e.g., bilateral symmetry, radial symmetry, body cavity types) influence their structure and development pattern.
• Animal develop based on germ layers: endoderm, mesoderm, and ectoderm
• Protostomes: The mouth is developed first; anus is formed later.
• Deuterostomes: The anus is developed first; mouth is formed later.

Sexual Reproduction

• Germ line cells undergo meiosis to form haploid gametes (sex cells).
• Gametes fuse (fertilization) to form a diploid zygote.
• Most animals undergo some form of sexual reproduction.

Asexual Reproduction

• Examples include budding in hydra, fragmentation in echinoderms, and parthenogenesis in insects

Embryonic Development Differences

• Protostomes exhibit spiral cleavage; cell fate is determined early in development
• Deuterostomes exhibit radial cleavage; cell fate is not determined early in development

Body Cavity

• A body cavity is a fluid-filled space between the gut and the body wall.
  • Acoelomate animals lack a body cavity
  • Pseudocoelomate animals have a fluid-filled cavity between the endoderm and mesoderm
  • Coelomate animals have a fluid-filled cavity completely lined by mesoderm

Body Symmetry

• Radial symmetry can be divided equally by any longitudinal plane
• Bilateral symmetry can be divided along a vertical plane at the middle

Unifying Concepts

• Physiological processes must obey the laws of physics and chemistry
• Be tightly regulated usually (homeostasis)

Main Concept: Homeostasis

• The regulation of the body's internal environment at or near a stable level around a set point
• Important for optimal physiological performance
• Homeostatic methods include negative feedback loops, positive feedback loops, and feedforward mechanisms

Thermoregulation

• Maintaining body temperature at optimal levels to provide optimal physiological performance
• Endotherms: Obtain heat from internal reactions
• Ectotherms: Obtain heat from external environments

KEY TERMS FROM THIS LECTURE - Thermoregulation

• Organismal performance - Hypothalamus - Thermal acclimatization - Torpor - Vasoconstriction - Vasodilation

Main Concept: Animal Body Organization & Nervous System

• Organization of cells: specialized and organized into tissues
• Organization of tissues: groups of cells with the same structure and function
• Organization of organs: assembly of tissues integrated into a structure
• Organization of organ systems: group of organs that carry out related steps in a major physiological process
• Layers of organization: cells, tissues, organs, organ systems

Cell Properties in Tissue

• Acquire nutrients
• Synthesize molecules
• Sense and respond to the environment
• Protect the body
• Reproduce

Tissue Types

• Epithelial: sheetlike layers of cells, cover body surface, and lines cavities
• Connective: consists of cell networks and extracellular matrix, supports other body tissues, acts as a filter
• Muscle: long contractile cells, moves body parts and maintain posture, found in three types
• Nervous: neurons communicate information between body parts, glial cells

Connective Tissue

• Loose connective tissue: support, elasticity, diffusion
• Cartilage: support, flexibility, joint movement
• Adipose tissue: energy reserves, insulation, padding
• Fibrous Connective Tissue: strength, elasticity
• Bones: movement, support, and protection

Nervous Tissue

• Neurons: communicate information
• Glial cells: support, provide nutrients, electrical insulation

Glial Cells

• Support/provide nutrients to neurons
• Provide electrical insulation
• Scavenge foreign matter/debris

Neuron Structure

• Dendrites: receive signals, integrate, and transmit towards spike initiation zone (SIZ)
• Axons: conduct signals away from SIZ to another neuron or effector

Nervous System

• Consist of neurons and glial cells
• Nerves act as a common pathway between structures and the CNS
• CNS = ganglia and brains

Main Concept: Electrochemical Potentials in Neurons

• All cells are electrically polarized
• Have a membrane potential (MP), negative inside relative to outside
• Cell characteristics: all cells are electrically polarized, have membrane potential, negative inside relative to outside
• MP range: -10 to -90 mV
• Types of membrane potentials: resting membrane potentials (RMP), electrotonic potentials (EP), and action potentials (AP).
• Cell polarization: polarized refers to negative inside, depolarized refers to positive influx, hyperpolarized refers to increased negative inside
• Why?: needed to regulate max. cell function

Graded Potentials

• Changes in membrane potential due to changes in membrane permeability to ions.
• Part of integration; takes place in dendrites and cell bodies.
• Electrotonic Potentials: current travels along surface of membrane, can depolarize or hyperpolarize, only travels a short distance along membrane

Main Concept: Synaptic Transmissions

• Synapses: site where a neuron communicates with another neuron or effector
• Neurotransmitters: All bind to a receptor protein in post-synaptic membrane, have several different receptors, can stimulate or inhibit an effector cell.
• Receptor types: ionotropic and metabotropic
• Electrical Synapse: Gap junctions connect cytoplasm of each cell; ions flow directly between cells, rapid flow of current, excitatory only
• Chemical Synapse: Pre and postsynaptic separated by cleft; neurotransmitter stored in vesicles; neurotransmitter released; binds to receptors in postsynaptic membrane
• Release of Neurotransmitters: calcium influx, neurotransmitter release into cleft

Sensory Systems

• Environment detection
• Sensory inputs
• Sensory transduction
• Sensory receptors: Includes mechanoreceptors, photoreceptors, and chemoreceptors
• Sensory adaptation
• Perception: the conscious awareness of our external and internal environments
• Sensory Inputs

Chemoreceptors (Taste and Smell)

• Provide information about taste (gustation) and smell (olfaction)
• Work through membrane receptor proteins
• Stimulated when they bind to specific molecules
• Generate action potentials, leading to processing by the CNS

Sensory Receptors

• Respond to stimuli in their receptive fields
• Undergo a change in receptor potentials, this varies with the magnitude of the stimulus
• Change in receptor potential is caused by changes in rate of conduction of cations across plasma membrane

Nociceptors

• Detect damaging stimuli
• Located on body surface and interior
• Protective mechanisms adapt very little

Electroreceptors

• Detect electrical currents and fields

Magnetoreceptors

• Detect and use Earth's magnetic field as a source of directional information

Main Concept: Animal Locomotion; Skeleton and Muscles

• Types of animal skeletons (e.g., exoskeletons, endoskeletons, hydrostatic skeletons)
• Bone tissue
• Bone tissue (e.g., compact, spongy)
• Calcium regulation in bones
• Muscle types (e.g., skeletal, cardiac, smooth)
• Muscle structure
• Muscle physiology
• Muscle tissue types (skeletal, cardiac, smooth)
• Muscle structure (e.g., sarcomeres, myofilaments)