Animal Physiology: Core Concepts

• Zoology is the scientific study of animals, covering aspects like anatomy, physiology, behavior, genetics, and evolution.
• Animal physiology is a subdiscipline of zoology that focuses on the study of the functions and mechanisms within animal bodies.

Core Concepts in Animal Physiology

• Homeostasis is the maintenance of stable internal conditions despite changes in the external environment.
• Feedback loops are crucial for maintaining homeostasis, with negative feedback loops reducing the effect of the original stimulus and positive feedback loops amplifying it.
• Conformers allow their internal conditions to vary with external changes.
• Regulators use physiological mechanisms to maintain relatively constant internal conditions, regardless of external conditions.

Animal Form and Function

• Animal form (anatomy) and function (physiology) are closely correlated, reflecting adaptations to their environment and lifestyle.
• Tissues are groups of cells with similar structure and function, organized into organs.
• Organs work together to form organ systems, carrying out specific functions within the animal body.
• Epithelial tissue covers body surfaces and lines internal organs and cavities.
• Connective tissue supports, connects, and separates different types of tissues and organs in the body.
• Muscle tissue is responsible for movement, including skeletal, smooth, and cardiac muscle.
• Nervous tissue transmits and processes information in the form of electrical and chemical signals.

Key Physiological Systems

• The nervous system enables rapid communication and coordination via electrical and chemical signals.
• Neurons are the basic functional units of the nervous system, transmitting signals through action potentials and neurotransmitters.
• The endocrine system regulates body functions through the secretion of hormones into the bloodstream.
• Hormones travel to target cells and elicit specific responses, affecting growth, metabolism, reproduction, and behavior.
• The circulatory system transports oxygen, nutrients, hormones, and waste products throughout the body.
• Blood, heart, and blood vessels are key components of the circulatory system.
• The respiratory system facilitates gas exchange, taking in oxygen and releasing carbon dioxide.
• Gills in aquatic animals and lungs in terrestrial animals are specialized structures for gas exchange.
• The digestive system breaks down food into smaller molecules that can be absorbed and used by the body.
• The excretory system removes metabolic waste products from the body and regulates water and electrolyte balance.
• Kidneys are the primary organs of excretion in vertebrates, filtering blood and producing urine.
• The immune system defends the body against pathogens and other foreign invaders.
• Innate immunity provides rapid, nonspecific defense mechanisms, while adaptive immunity involves specific recognition and memory of pathogens.
• The reproductive system is responsible for producing offspring, involving either sexual or asexual reproduction.

Energy and Metabolism

• Metabolic rate is the amount of energy an animal uses per unit of time.
• Endotherms generate their own body heat, while ectotherms rely on external sources of heat.
• Basal metabolic rate (BMR) is the metabolic rate of an endotherm at rest, while standard metabolic rate (SMR) is the metabolic rate of an ectotherm at a specific temperature.
• Energy budgets allocate energy to different activities, such as growth, reproduction, and maintenance.

Osmoregulation and Excretion

• Osmoregulation is the process of maintaining water and solute balance in the body.
• Osmoconformers are isoosmotic with their surroundings and do not regulate their osmolarity.
• Osmoregulators control their internal osmolarity, regardless of the external environment.
• Nitrogenous wastes, produced from the breakdown of proteins and nucleic acids, are excreted as ammonia, urea, or uric acid.
• Excretory systems regulate solute movement between internal fluids and the external environment.

Animal Nutrition

• Animals are heterotrophs and obtain energy from consuming other organisms.
• Essential nutrients, including amino acids, fatty acids, vitamins, and minerals, must be obtained from the diet.
• Suspension feeders filter food particles from water.
• Substrate feeders live in or on their food source.
• Fluid feeders suck nutrient-rich fluids from living host.
• Bulk feeders eat relatively large pieces of food.
• Digestion involves mechanical and chemical breakdown of food.
• Absorption is the uptake of nutrients into body cells.
• Elimination is the passage of undigested material out of the body.

Circulation and Gas Exchange

• Open circulatory systems have hemolymph bathing the organs directly.
• Closed circulatory systems have blood confined to vessels.
• Arteries carry blood away from the heart, while veins carry blood back to the heart.
• Capillaries are the sites of gas and nutrient exchange between blood and tissues.
• Single circulation, found in fish, involves blood passing through the heart once in each complete circuit.
• Double circulation, found in amphibians, reptiles, and mammals, involves separate pulmonary and systemic circuits.
• Ventilation moves respiratory medium (air or water) over the respiratory surface.
• Partial pressure gradients drive the diffusion of oxygen and carbon dioxide across respiratory surfaces.

Animal Reproduction

• Asexual reproduction involves a single parent and produces genetically identical offspring.
• Sexual reproduction involves the fusion of gametes (sperm and egg) from two parents, resulting in genetically diverse offspring.
• External fertilization occurs outside the body, while internal fertilization occurs inside the body.
• Oviparous animals lay eggs, viviparous animals give birth to live young, and ovoviviparous animals have eggs that hatch inside the mother's body.

Animal Development

• Fertilization is the union of sperm and egg, forming a zygote.
• Cleavage is a series of rapid cell divisions that divide the cytoplasm of the zygote.
• Gastrulation is the process of cell movements that establishes the three germ layers: ectoderm, mesoderm, and endoderm.
• Organogenesis is the formation of organs from the germ layers.

Animal Behavior

• Ethology is the study of animal behavior.
• Innate behavior is genetically programmed and performed without prior experience.
• Learned behavior is modified by experience.
• Communication is the transmission and reception of signals between animals.
• Social behavior involves interactions between individuals of the same species.
• Mating behavior includes courtship rituals, mate choice, and parental care.

Sensing the Environment

• Sensory receptors detect stimuli from the external and internal environment.
• Mechanoreceptors sense physical deformation caused by stimuli such as pressure, touch, stretch, motion, and sound.
• Chemoreceptors detect chemicals, such as odors and tastes.
• Electromagnetic receptors detect electromagnetic energy such as light, electricity, and magnetism.
• Thermoreceptors detect changes in temperature.
• Pain receptors detect harmful stimuli.

Animal Movement

• Muscles produce movement by contracting and exerting force on the skeleton.
• Skeletal muscles are attached to bones by tendons.
• Muscle contraction is based on the sliding filament model, where actin and myosin filaments slide past each other.
• Different types of skeletons, such as exoskeletons, endoskeletons, and hydrostatic skeletons, support and protect the body.