Unit 4 Study Guide: Animal Diversity, Microbes, Circulatory, Immune, and Skeletal Systems

Animal Diversity

Major Animal Phyla

Animals are classified into several major phyla based on their body plans, developmental patterns, and other key features.

• Porifera: Sponges; lack true tissues, have porous bodies, filter feeders.

• Cnidaria: Jellyfish, corals, sea anemones; possess stinging cells (cnidocytes), radial symmetry, two tissue layers.

• Platyhelminthes: Flatworms; bilateral symmetry, no body cavity (acoelomate), simple digestive system.

• Annelida: Segmented worms; true coelom, segmented bodies, closed circulatory system.

• Mollusca: Snails, clams, squids; soft bodies, often with a hard shell, muscular foot, mantle.

• Nematoda: Roundworms; unsegmented, pseudocoelomate, complete digestive tract.

• Arthropoda: Insects, spiders, crustaceans; exoskeleton, jointed appendages, segmented bodies.

• Echinodermata: Sea stars, sea urchins; radial symmetry (as adults), water vascular system, endoskeleton.

• Chordata: Animals with a notochord; includes vertebrates and some invertebrates.

Classes within Major Phyla

• Mollusca:

  • Gastropods: Snails, slugs; single, often spiral shell.

  • Bivalves: Clams, oysters; two-part shell, filter feeders.

  • Cephalopods: Squids, octopuses; well-developed nervous system, tentacles.

• Arthropoda:

  • Arachnids: Spiders, scorpions; four pairs of legs, no antennae.

  • Millipedes & Centipedes: Many body segments, millipedes have two pairs of legs per segment, centipedes have one.

  • Crustaceans: Crabs, lobsters; two pairs of antennae, mostly aquatic.

  • Insects: Three body segments, six legs, usually wings.

• Chordata:

  • Lamprey & Hagfish: Jawless fish.

  • Chondrichthyes: Cartilaginous fish (sharks, rays).

  • Osteichthyes: Bony fish.

  • Amphibia: Frogs, salamanders; life cycle includes aquatic larval stage.

  • Reptilia: Snakes, lizards, turtles; amniotic eggs, scales.

  • Aves: Birds; feathers, flight adaptations.

  • Mammalia: Hair, mammary glands.

Chordate Characteristics

• Notochord: Flexible rod for support.

• Dorsal hollow nerve cord: Develops into the central nervous system.

• Pharyngeal slits: Openings near the throat; various functions.

• Post-anal tail: Tail extending beyond the anus.

Chordate Groups

• Vertebrates: Have a backbone.

• Urochordates: Tunicates; marine filter feeders.

• Cephalochordates: Lancelets; retain chordate features as adults.

Evolution of Tetrapods

• Tetrapods evolved from lobe-finned fish.

• Key adaptations: limbs with digits, lungs, changes in skeletal structure.

Mammal Diversity

• Unifying feature: Mammary glands for milk production.

• Monotremes: Egg-laying mammals (e.g., platypus).

• Marsupials: Pouched mammals (e.g., kangaroo).

• Placental mammals: Develop in uterus with placenta.

Microbes, Plants, and Fungi

Domains of Life

• Bacteria: Prokaryotic, cell walls with peptidoglycan, diverse metabolism.

• Archaea: Prokaryotic, unique membrane lipids, often extremophiles.

• Eukarya: Eukaryotic cells, includes protists, fungi, plants, animals.

Kingdom Comparisons

• Plantae: Multicellular, photosynthetic, cell walls of cellulose.

• Animalia: Multicellular, heterotrophic, no cell walls.

• Protista: Mostly unicellular, diverse nutrition and structure.

• Fungi: Mostly multicellular, heterotrophic by absorption, cell walls of chitin.

Bacteria

• Structure: No nucleus, single circular chromosome, cell wall, some have flagella or pili.

• Energy & Carbon Sources: Photoautotrophs, chemoautotrophs, heterotrophs.

• Roles: Decomposers, nitrogen fixation, pathogens, probiotics.

• Antibiotics: Target bacterial structures; resistance is a growing problem.

Archaea

• Often live in extreme environments (e.g., hot springs, salt lakes).

• Some are important for biotechnology and environmental processes.

Protists

• Animal-like: Protozoa (e.g., Amoeba).

• Fungi-like: Slime molds.

• Plant-like: Algae (e.g., Chlamydomonas).

Plants

• Characteristics: Multicellular, photosynthetic, alternation of generations.

• Evolution: From green algae; adaptations include cuticle, vascular tissue, seeds, flowers.

• Gymnosperms: Seed plants without flowers (e.g., conifers).

• Angiosperms: Flowering plants; seeds enclosed in fruit.

Fungi

• Characteristics: Eukaryotic, cell walls of chitin, heterotrophic by absorption.

• Anatomy: Hyphae (filaments), mycelium (network), fruiting bodies (e.g., mushrooms).

• Roles: Decomposers, symbionts (mycorrhizae), pathogens, food production.

Circulatory System

Types of Circulatory Systems

• Diffusion: Used by small/simple animals; direct exchange with environment.

• Open Circulatory System: Hemolymph bathes organs directly; found in arthropods, some molluscs.

• Closed Circulatory System: Blood confined to vessels; found in annelids, vertebrates.

Evolution of Vertebrate Circulatory Systems

• Fish: Two-chambered heart, single circuit.

• Amphibians: Three-chambered heart, double circuit (some mixing of blood).

• Reptiles: Incomplete septum in heart, less mixing.

• Birds & Mammals: Four-chambered heart, complete separation of oxygenated/deoxygenated blood.

Advantages: More efficient oxygen delivery supports higher metabolism.

Human Circulatory System

• Structures: Heart, blood vessels (arteries, veins, capillaries), blood.

• Blood Flow: Right atrium → right ventricle → lungs → left atrium → left ventricle → body.

• Cardiac Cycle: Sequence of heart contraction and relaxation.

Types of Blood Vessels

• Arteries: Carry blood away from heart; thick walls.

• Veins: Carry blood to heart; thinner walls, valves.

• Capillaries: Exchange of gases/nutrients; very thin walls.

Blood Pressure

• Force of blood against vessel walls; measured in mmHg.

• Normal adult: ~120/80 mmHg.

Atherosclerosis

• Build-up of plaques in arteries; restricts blood flow, increases risk of heart attack/stroke.

Blood Components

Component	Function
Red blood cells (erythrocytes)	Transport oxygen via hemoglobin
White blood cells (leukocytes)	Immune defense
Platelets (thrombocytes)	Blood clotting
Plasma	Transport nutrients, hormones, waste

Immune System

Types of Pathogens

• Bacteria, viruses, fungi, protozoa, parasites.

Three Lines of Defense

1. Barriers: Skin, mucous membranes, secretions.

2. Innate Immunity: Phagocytic cells, inflammation, fever.

3. Adaptive (Acquired) Immunity: Lymphocytes (B and T cells), antibodies, memory cells.

Specific Immune Response Sequence

1. Antigen presentation

2. Activation of helper T cells

3. Stimulation of B cells (antibody production) and cytotoxic T cells (destroy infected cells)

4. Formation of memory cells

Primary vs. Secondary Immune Response

• Primary: First exposure; slower, less antibody produced.

• Secondary: Subsequent exposure; faster, stronger response due to memory cells.

Active vs. Passive Immunity

• Active: Body produces its own antibodies (infection or vaccination).

• Passive: Antibodies acquired from another source (e.g., maternal antibodies, injection).

Immune System Problems

• Autoimmune: Immune system attacks self (e.g., lupus).

• Transplant rejection: Immune response against transplanted tissue.

• Allergies: Overreaction to harmless substances.

• Cancer: Immune evasion by abnormal cells.

Skeletal System

Types of Skeletal Systems

• Hydrostatic: Fluid-filled cavity (e.g., worms).

• Exoskeleton: External skeleton (e.g., arthropods).

• Endoskeleton: Internal skeleton (e.g., vertebrates).

Bone Components

• Compact bone: Dense outer layer.

• Spongy bone: Porous, contains marrow.

• Marrow: Red (blood cell production) and yellow (fat storage).

Functions of the Skeletal System

• Support, protection, movement, mineral storage, blood cell formation.

Human Bones and Articulation

• Major bones: skull, vertebrae, ribs, pelvis, limbs.

• Articulation: Joints where bones meet; e.g., humerus articulates with scapula and radius/ulna.

• Homologous bones in arms/legs: humerus/femur, radius/tibia, ulna/fibula.

Comparative Vertebrate Skeletal Anatomy

• Forelimbs and hindlimbs show evolutionary modifications for different functions (e.g., flight, swimming, running).

Bone Remodeling, Growth, and Healing

• Osteoblasts build bone; osteoclasts break down bone.

• Growth at epiphyseal plates; healing involves inflammation, callus formation, remodeling.

Risk Factors for Decreased Bone Density

• Aging, hormonal changes, poor nutrition, lack of exercise.

Types of Joints

• Immovable (synarthroses): e.g., skull sutures.

• Slightly movable (amphiarthroses): e.g., vertebral joints.

• Freely movable (diarthroses/synovial joints): e.g., knee, shoulder.

Synovial Joint Structure

• Articular cartilage, synovial cavity, synovial fluid, joint capsule, ligaments.

Shapes and Movements of Synovial Joints

Type	Shape	Movement
Ball-and-socket	Round head fits into cup	Multiaxial (e.g., shoulder, hip)
Hinge	Cylinder fits into trough	Uniaxial (e.g., elbow, knee)
Pivot	Rounded end fits into ring	Rotation (e.g., atlas/axis in neck)
Gliding	Flat surfaces	Sliding (e.g., wrist)
Saddle	Concave/convex surfaces	Biaxial (e.g., thumb)