Circulatory System

Overview of the Circulatory System

The circulatory system is responsible for transporting nutrients, gases, hormones, and wastes throughout the body. It consists of the heart, blood vessels, and blood, and is essential for maintaining homeostasis in multicellular organisms.

• Blood: The fluid that carries oxygen, nutrients, hormones, and waste products.

• Heart: The muscular organ that pumps blood through the circulatory system.

• Blood Vessels: Include arteries, veins, and capillaries, each with distinct structures and functions.

Blood Vessels: Structure and Function

• Arteries: Thick-walled vessels that carry blood away from the heart under high pressure.

• Veins: Thinner-walled vessels that return blood to the heart; contain valves to prevent backflow.

• Capillaries: Microscopic vessels where exchange of gases, nutrients, and wastes occurs between blood and tissues.

• Example: Capillaries in the lungs allow oxygen to enter the blood and carbon dioxide to be removed.

Heart Structure and Function

• Atrium: Upper chamber(s) of the heart that receive blood.

• Ventricle: Lower chamber(s) that pump blood out of the heart.

• Atrioventricular (AV) Valves: Prevent backflow from ventricles to atria.

• Semilunar Valves: Prevent backflow from arteries into ventricles.

• Pulmonary Artery: Carries deoxygenated blood from the right ventricle to the lungs.

• Aorta: Main artery carrying oxygenated blood from the left ventricle to the body.

• Pulmonary Veins: Return oxygenated blood from the lungs to the left atrium.

• Coronary Artery: Supplies blood to the heart muscle itself.

• Vena Cava: Large veins (superior and inferior) that return deoxygenated blood to the right atrium.

Circulation Types

• Single Circulation: Blood passes through the heart once in each complete circuit (e.g., fish).

• Double Circulation: Blood passes through the heart twice per circuit (pulmonary and systemic circuits; e.g., mammals).

• Pulmonary Circuit: Carries blood between the heart and lungs for gas exchange.

• Systemic Circuit: Carries blood between the heart and the rest of the body.

Cardiac Cycle and Regulation

• Systole: Contraction phase of the heart, pumping blood out.

• Diastole: Relaxation phase, heart fills with blood.

• Cardiac Cycle: Sequence of events in one heartbeat, including systole and diastole.

• Pacemaker (SA Node): Specialized tissue in the right atrium that initiates the heartbeat and sets the pace.

• Blood Pressure: The force exerted by blood on vessel walls; measured in mmHg.

Blood Components

• Plasma: Liquid matrix of blood, containing water, proteins, ions, nutrients, and wastes.

• Erythrocytes (Red Blood Cells): Transport oxygen using hemoglobin.

• Leukocytes (White Blood Cells): Defend against pathogens.

• Platelets: Cell fragments involved in blood clotting.

Immune System

Overview of Immunity

The immune system protects organisms from pathogens through innate and adaptive mechanisms. It involves a complex network of cells, tissues, and molecules.

• Innate Immunity: Non-specific, immediate defense present in all animals.

• Adaptive Immunity: Specific, acquired defense found in vertebrates; involves memory.

• Pathogen: Disease-causing organism (e.g., bacteria, viruses).

Innate Immunity

• Physical Barriers: Skin, mucous membranes prevent pathogen entry.

• Internal Defenses: Phagocytic cells (macrophages, neutrophils), natural killer cells, inflammation, antimicrobial proteins (interferons, cytokines).

• Phagocytosis: Engulfment and digestion of pathogens by cells like macrophages and neutrophils.

• Inflammatory Response: Localized response to infection or injury, involving mast cells, cytokines, and increased blood flow.

Adaptive Immunity

• Lymphocytes: B cells (produce antibodies) and T cells (mediate cellular responses).

• Antigen: Foreign molecule recognized by immune cells.

• Antigen Receptor: Protein on lymphocytes that binds specific antigens.

• Antibody (Immunoglobulin): Protein produced by B cells that binds antigens.

• Major Histocompatibility Complex (MHC): Cell surface proteins presenting antigens to T cells.

• Helper T Cells: Activate other immune cells via cytokines.

• Cytotoxic T Cells: Destroy infected or abnormal cells.

• Memory Cells: Long-lived cells that provide immunological memory.

Immune Responses

• Humoral Immune Response: Involves B cells and antibody production; defends against extracellular pathogens.

• Cell-Mediated Immune Response: Involves T cells; defends against infected or abnormal cells.

• Clonal Selection: Process by which lymphocytes proliferate in response to specific antigens.

• Cytokines: Signaling proteins that coordinate immune responses.

• Immunological Memory: Enhanced response to previously encountered antigens.

Plant Diversity and Angiosperm Reproduction

Evolution and Diversity of Plants

• Charophytes: Green algae most closely related to land plants.

• Derived Traits of Plants: Alternation of generations, multicellular dependent embryos, walled spores, apical meristems.

• Alternation of Generations: Life cycle alternating between multicellular haploid (gametophyte) and diploid (sporophyte) stages.

• Gametophyte: Haploid generation producing gametes by mitosis.

• Sporophyte: Diploid generation producing spores by meiosis.

• Haploid vs. Diploid: Haploid (n) has one set of chromosomes; diploid (2n) has two sets.

Plant Reproductive Structures

• Antheridium: Male gametangium producing sperm.

• Archegonium: Female gametangium producing eggs.

• Sporangium: Structure where spores are produced.

• Sporopollenin: Durable polymer in spore and pollen walls.

• Monoecious vs. Dioecious: Monoecious plants have both male and female organs on the same plant; dioecious have them on separate plants.

Vascular Tissues and Plant Groups

• Xylem: Conducts water and minerals from roots to shoots; contains lignin for support.

• Phloem: Transports sugars and organic nutrients.

• Homospory: Production of one type of spore.

• Heterospory: Production of microspores (male) and megaspores (female).

Seed and Flower Structure

• Seed: Contains embryo, food supply, and seed coat.

• Ovule: Structure that develops into a seed after fertilization.

• Pollen Grain: Male gametophyte; contains generative cell (forms sperm) and tube cell (forms pollen tube).

• Double Fertilization: One sperm fertilizes egg (forms zygote), another fuses with polar nuclei (forms endosperm).

• Embryo Sac: Female gametophyte in angiosperms; contains egg, synergids, antipodal cells, and polar nuclei.

Flower and Fruit Structure

• Flower Parts: Sepals, petals, stamens (anther, filament), carpels (stigma, style, ovary, ovule).

• Fruit: Mature ovary; types include simple, aggregate, multiple, and accessory fruits.

• Monocot vs. Dicot: Monocots have one cotyledon, parallel leaf veins, scattered vascular bundles, fibrous roots, and flower parts in multiples of three. Dicots (eudicots) have two cotyledons, netted veins, ringed vascular bundles, taproots, and flower parts in multiples of four or five.

Plant Form and Function

Plant Organs and Systems

• Shoot System: Aboveground parts (stems, leaves, flowers).

• Root System: Belowground parts (roots and associated structures).

Root Structure and Types

• Primary Root: First root to emerge from seed.

• Taproot: Main vertical root (common in dicots).

• Fibrous Root: Many thin roots (common in monocots).

• Root Hairs: Increase surface area for absorption.

• Root Zones: Root cap, zone of cell division (apical meristem), zone of elongation, zone of differentiation (maturation).

• Specialized Roots: Prop roots, pneumatophores, strangling aerial roots, buttress roots, storage roots.

• Lateral Roots: Branch from the pericycle.

• Endodermis: Regulates movement of substances into vascular tissue.

Shoot and Leaf Structure

• Stem: Supports leaves and flowers; contains nodes (leaf attachment) and internodes (between nodes).

• Apical Bud: Growth at tip of stem.

• Axillary Bud: Can form branches or flowers.

• Vascular Bundle: Contains xylem and phloem.

• Stem Modifications: Stolons, tubers, rhizomes, bulbs, thorns.

• Leaf: Main photosynthetic organ; parallel veins (monocots), branched veins (dicots).

• Leaf Modifications: Spines, tendrils, storage leaves, reproductive leaves.

Plant Tissues

• Dermal Tissue: Epidermis, cuticle, periderm, trichomes.

• Vascular Tissue: Xylem and phloem.

• Ground Tissue: Pith and cortex.

Plant Growth

• Determinate Growth: Growth stops after reaching a certain size.

• Indeterminate Growth: Growth continues throughout life.

• Primary Growth: Lengthening of roots and shoots (apical meristems).

• Secondary Growth: Increase in girth (lateral meristems: vascular cambium, cork cambium).

• Wood: Secondary xylem.

• Bark: Secondary phloem plus periderm.

• Heartwood: Older, non-conducting xylem.

• Sapwood: Younger, conducting xylem.

Plant Nutrition, Resource Acquisition, and Transport

Water and Nutrient Uptake

• Root Hairs: Absorb water and minerals from soil.

• Apoplast Pathway: Movement through cell walls and intercellular spaces.

• Symplast Pathway: Movement through cytoplasm via plasmodesmata.

• Casparian Strip: Waxy barrier in endodermis forcing substances through cell membranes.

Transport Mechanisms

• Transpiration: Loss of water vapor from leaves, driving water movement.

• Cohesion-Tension Mechanism: Explains ascent of water in xylem due to cohesion of water molecules and tension from transpiration.

• Stomata: Pores for gas exchange; regulated by guard cells.

• Turgor Pressure: Pressure of cell contents against cell wall; maintains rigidity.

• Bulk Flow: Movement of fluid due to pressure differences.

• Source vs. Sink: Source (site of sugar production, e.g., leaves); sink (site of sugar use/storage, e.g., roots, fruits).

• Phloem Sap: Solution of sugars transported in phloem.

Soil and Plant Nutrition

• Soil Horizons: Layers of soil (topsoil, subsoil, etc.).

• Humus: Organic component of soil.

• Macronutrients: Required in large amounts (e.g., nitrogen, potassium).

• Micronutrients: Required in trace amounts (e.g., iron, zinc).

• Essential Element: Required for plant growth and reproduction.

Nitrogen and Symbioses

• Nitrogen Fixation: Conversion of atmospheric nitrogen () to ammonia () by bacteria.

• Rhizobacteria: Soil bacteria that promote plant growth.

• Legumes: Plants that form mutualistic relationships with nitrogen-fixing bacteria.

• Nodules: Structures on roots housing nitrogen-fixing bacteria.

• Mycorrhizae: Fungi that form mutualistic associations with plant roots, enhancing nutrient uptake.

Adaptations to Nutrient-Poor Environments

• Epiphytes: Grow on other plants but are not parasitic.

• Carnivorous Plants: Obtain nutrients by digesting insects.

• Parasitic Plants: Obtain nutrients from other living plants.

Comparison Table: Xylem vs. Phloem

Additional info: This study guide covers key concepts and terminology from the Circulatory System, Immune System, and Plant Biology, including plant structure, reproduction, and nutrition. For exam preparation, review the definitions, processes, and examples provided, and practice applying these concepts to new scenarios.