Functions of Body Systems and Homeostasis, Osmoregulation and Digestive Systems in Animals, Comparative Physiology: Respiration and Circulation, Vertebrate Groups and Their Characteristics, Types and Functions of Epithelial Tissue, Overview of Invert…

Nervous tissue

Nervous tissue is responsible for electrical and chemical communication. Neurons have dendrites that receive signals and axons that send them.

Integumentary system

It encloses internal body structures and has a lot of sensory receptors (e.g. hair, skin, nails).

Skeletal system

Supports the body and helps with movement (includes cartilage, bones, joints).

Muscular system

Enables movement, helps maintain body temperature (includes skeletal muscles and tendons).

Cardiovascular system

Delivers oxygen and nutrients to tissues and helps regulate body temperature (includes heart and blood vessels).

Respiratory system

Removes carbon dioxide and delivers oxygen to the blood (includes nasal passages, trachea, lungs).

Digestive system

Processes food and removes waste (includes stomach, liver, gallbladder, large and small intestines).

Urinary system

Controls water balance and removes waste from the blood (includes kidneys and urinary bladder).

Male reproductive system

Produces sex hormones and gametes, and delivers gametes to the female (includes testes and epididymis).

Female reproductive system

Produces sex hormones and gametes, supports embryo/fetus, and produces milk for infants (includes mammary glands, ovaries, uterus).

Homeostasis

The process of maintaining equilibrium in the body; regulated by the nervous and endocrine systems.

Negative feedback loop

A mechanism that counters internal changes to maintain balance (e.g. blood glucose, pH, gas concentration, blood pressure).

Positive feedback loop

A mechanism that strengthens the response to a stimulus (e.g. uterine contractions during birth).

Body temperature regulation

It's important for enzyme and protein activity.

Ectotherms vs Endotherms

Ectotherms depend on the environment for body temp (e.g. most reptiles). Endotherms generate heat through metabolism (e.g. birds, mammals).

Main types of tissues

Epithelium, Connective, Muscular, and Nervous.

Epithelial tissue

It lines body surfaces and cavities, protects, absorbs, and secretes. Cells are tightly packed with polarity and high regeneration capacity; avascular.

Connective tissue

Connects different tissues, gives body structure, and is the most abundant tissue type. It contains cells (like fibroblasts) in an extracellular matrix, usually with protein fibers.

Muscular tissue

Controls movement. Includes: Smooth: involuntary (found in internal organs, digestive tract); Cardiac: involuntary (heart); Skeletal: voluntary (attached to bones).

Surface area to volume ratio

A larger surface area to volume ratio allows for a greater rate of exchange. Smaller objects exchange materials faster.

Glucose homeostasis

The regulation of blood glucose levels to provide energy. Insulin lowers glucose by promoting uptake into cells and liver storage. Glucagon raises glucose by releasing it from liver stores.

Diabetes mellitus

A disorder resulting from impaired insulin function or secretion.

Oxygen homeostasis

Maintaining stable oxygen levels in the blood. Controlled by erythropoietin (EPO), released by kidneys when O₂ levels are low, stimulating red blood cell production in bone marrow.

Hormones in endocrine control

Hormones are long-distance chemical messengers that travel through circulation and bind to target cell receptors.

Osmoregulation

The process of maintaining water and salt balance in the body to keep cells in an isotonic environment (equal solute concentration inside and outside).

Hypotonic environment

Water moves into cells → cells may swell or burst.

Hypertonic environment

Water moves out of cells → cells shrink.

Freshwater fish water/salt balance

Live in hypotonic water; Gain water through gills and skin; Kidneys excrete dilute urine; Gills pump salts into body.

Saltwater fish water/salt balance

Live in hypertonic water; Lose water through gills and skin; Kidneys excrete isotonic urine; Gills pump salts out; Fish drink water to compensate.

Terrestrial animals water balance

Lose water via evaporation, urine, feces; Gain water and electrolytes from diet; Kidneys adjust urine volume/concentration to stay balanced.

Marine birds and reptiles adaptation

Salt glands near eyes/nose excrete salty solution. Ex: Marine iguanas 'sneeze' out salt.

Nitrogenous wastes

Waste products from protein/nucleic acid breakdown — mostly ammonia (NH₃), which is toxic.

Aquatic animals nitrogen waste handling

They excrete ammonia directly into water (very toxic, but easily diluted). Ex: Bony fish, aquatic inverts, tadpoles.

Mammals and amphibians nitrogen waste handling

Convert ammonia into urea (less toxic, needs less water to excrete).

Birds, reptiles, and insects nitrogen waste handling

Convert ammonia into uric acid (least toxic, excreted as paste/powder to save water).

Trade-off with urea and uric acid

Less toxic = safer storage, but requires more energy to make.

Functions of the digestive system

Digest food into monomers (ex. starch → glucose); Absorb nutrients into the bloodstream; Eliminate waste.

Incomplete vs complete digestive systems

Incomplete: One opening (food/waste go same way) - e.g. flatworms, cnidarians; Complete: Two openings (mouth → anus), more advanced.

Nutrient absorption in digestive system

The small intestine — uses villi and microvilli to increase surface area.

Mammal teeth adaptation

Carnivores: Sharp canines to tear flesh; Herbivores: Broad molars for grinding plants.

Birds adaptation for diet

Beaks — shaped for their specific diet.

Herbivores digesting cellulose

They can't do it alone — they house microbes in specialized gut chambers to help.

Ruminants adaptation

Four-chambered stomach, Rumen holds microbes to break down cellulose; They regurgitate and chew it again (ruminate).

Rabbits and horses adaptation

Have a large cecum with microbes; Rabbits eat feces (coprophagy) to re-digest fiber and get more nutrients.

Physiology

The study of how living organisms, tissues, and cells function—how the body works when healthy and what happens when it gets sick.

Oxygen in Animal Cells

For aerobic cellular respiration to generate ATP; they also produce CO₂ as waste.

Respiratory and Circulatory Systems

Respiratory surfaces/organs exchange gases with the environment, while the circulatory system transports those gases to/from tissues.

Complexity of Respiratory Systems

Affected by body size, surface-area-to-volume ratio (SA:V), and metabolic rate (ectotherm vs. endotherm).

Types of Respiratory Surfaces/Organs

Skin, gills, and lungs.

Gas Exchange in Small Animals

Through direct diffusion across their skin—no circulatory system needed.

Gas Exchange in Earthworms and Amphibians

They have capillary networks close to the skin surface, which must stay moist for efficiency.

Gills

Highly folded/branched organs with thin membranes used by mollusks, crustaceans, and fish for gas exchange in water.

Efficiency of Gills

They have high surface area and very thin membranes for diffusion.

Insect Breathing

Through a tracheal system—tiny tubes (tracheae) bring oxygen directly to tissues, bypassing circulation.

Spiracles

Openings in an insect's exoskeleton where air enters the tracheal system.

Lungs

Used by terrestrial vertebrates (amphibians, reptiles, mammals, birds); lungs are internal to stay moist and protect from dry environments.

Efficiency of Mammal and Bird Lungs

They have huge surface area (alveoli in mammals, parabronchi in birds) and thin respiratory membranes.

Components of Circulatory Systems

Circulatory fluid (like blood), pump(s) (like the heart), and vessels.

Oxygen Delivery Efficiency

Higher oxygen-carrying capacity and faster fluid flow rate.

Hemoglobin

A pigment that carries oxygen in vertebrates—each molecule can carry four oxygen molecules (1 per heme group).

Hemoglobin vs. Hemocyanin

Hemoglobin (red) is used by vertebrates; hemocyanin (blue) by some invertebrates like arthropods and mollusks.

Pressure and Flow Rate in Blood Vessels

Greater pressure difference (ΔP) increases flow rate; larger vessels reduce resistance.

Open Circulatory System

Blood (hemolymph) flows into open body cavities (hemocoel); found in most mollusks and arthropods; lower pressure/flow.

Closed Circulatory System

Blood stays in vessels; higher pressure/flow; found in vertebrates, annelids, cephalopods.

Fish Circulatory System

2-chambered heart, 1 circuit (gills → body); low pressure/flow to tissues.

Amphibians and Reptiles Circulatory System

3-chambered heart, 2 circuits (lungs/skin + body); medium pressure/flow.

Mammals and Birds Circulatory System

4-chambered heart, 2 circuits (lungs + body); highest pressure/flow due to strong left ventricle.

Efficiency of Bird and Mammal Systems

They are endothermic (high metabolism), needing lots of O₂—so they evolved high lung surface area (alveoli/parabronchi), very thin respiratory membranes, and four-chambered hearts with high systemic pressure.

Endotherm Oxygen Demand

To support high oxygen demands for constant body heat and activity.

Jawless fish (Superclass Agnatha)

No jaws, no paired fins, no bones or scales, cartilage skull.

Hagfish

Slimy, no vertebrae, scavengers, rasping tongue, produce slime for defense.

Lampreys

Parasitic as adults, feed on blood, have cartilage skeleton and simple vertebrae.

Cartilaginous fish (Class Chondrichthyes)

Sharks, rays, skates; strong sense of smell, skeleton made of cartilage, internal fertilization, two-chambered heart.

Ray-finned fish

Fins supported by long, flexible rays; bony skeleton.

Lobe-finned fish

Bone structure in fins, lungs for air breathing, gave rise to tetrapods (land vertebrates).

Amphibians

Live on land but need water to reproduce, tetrapods (4 limbs), 3-chambered heart, external fertilization in water, smooth moist skin.

Examples of amphibians

Frogs, salamanders.

Reptiles

Dry, scaly skin; amniotic eggs; ectothermic; 3-chambered heart (except for crocodilians).

Groups considered reptiles

Lizards, snakes, turtles, alligators, crocodiles.

Defining traits of birds

Endothermic, feathers (for flight and insulation), hollow bones, adaptations for flight.

Bird fertilization

Internal fertilization with amniotic eggs.

Key characteristics of mammals

Mammary glands, hair or fur, endothermic, specialized teeth adapted to diet.

Three major groups of mammals

Monotremes (Prototheria): Lay eggs, no placenta, e.g., platypus. Marsupials: Young develop in pouch, short gestation. Placentals (Eutherians): Complex placenta, long gestation.

Examples of monotremes

Platypus, echidna.

Mammal tooth adaptations

Biting teeth, gnawing teeth, tusks, grasping teeth.

Function of mammal hair/fur

Insulation, camouflage, defense (e.g., quills), sensory.

Amniotic egg

Allows animals to reproduce on land; contains membranes like the amnion, yolk sac, allantois, and chorion for protection, nourishment, and gas exchange.

Functions of epithelial tissue

Protection, absorption, secretion, filtration, and forming boundaries.

Classification of epithelial tissue

By the number of cell layers and the shape of the cells.

Simple epithelium

A single layer of cells; involved in absorption, secretion, and filtration.

Stratified epithelium

Multiple layers of cells; mainly for protection.

Squamous epithelium

Flat, thin cells; ideal for diffusion and filtration (e.g., in lungs and blood vessels).

Cuboidal epithelium

Cube-shaped cells; involved in secretion and absorption (e.g., kidney tubules, glands).

Columnar epithelium

Tall, column-shaped cells; good for absorption and secretion (e.g., digestive tract lining).

Simple squamous epithelium location

Alveoli in lungs, lining of blood vessels (endothelium).

Simple cuboidal epithelium location

Kidney tubules, ducts of glands.

Simple columnar epithelium location

Lining of stomach and intestines; may have microvilli or goblet cells.

Stratified squamous epithelium location

Skin (keratinized), mouth, esophagus (non-keratinized).

Pseudostratified columnar epithelium

Appears layered but is a single layer; often ciliated; found in respiratory tract.

Transitional epithelium

Stretches and changes shape; found in the bladder and urinary tract.