BIOLOGICAL SCIENCE REVIEWER.docx

**BIOLOGICAL SCIENCE** **MODULE 1** **Cell Structure Reviewer** **Key Components of Cells** 1. **DNA and Genes** - **DNA**: Contains the genetic information for cellular functions and survival. - **Gene**: A specific DNA segment directing a cell to perform particul...

**BIOLOGICAL SCIENCE** **MODULE 1** **Cell Structure Reviewer** **Key Components of Cells** 1. **DNA and Genes** - **DNA**: Contains the genetic information for cellular functions and survival. - **Gene**: A specific DNA segment directing a cell to perform particular tasks. 2. **Cytoplasm and Plasma Membrane** - **Cytoplasm**: Gel-like substance filling the cell, aiding in shape and material transport. - **Plasma Membrane**: Encloses the cytoplasm, controlling substance entry and exit, maintaining cell integrity. **Cell Theory** - All living things are composed of cells. - The cell is the fundamental unit of life. - Cells arise from the division of pre-existing cells. **Notable Contributors**: - Matthias Schleiden - Theodor Schwann - Rudolf Virchow **Types of Cells** 1. **Based on Number of Cells** - **Unicellular**: Single-celled organisms reproducing asexually (e.g., bacteria). - **Multicellular**: Organisms with many cells performing specialized functions (e.g., plants, animals). 2. **Based on Function** - **Somatic Cells**: Body cells (diploid), involved in metabolism, growth, and repair. - **Gametes**: Reproductive cells (haploid), involved in producing offspring (e.g., sperm, egg). 3. **Based on Structure** - **Prokaryotic Cells**: Lack membrane-bound organelles (e.g., bacteria). - **Eukaryotic Cells**: Have membrane-bound organelles, including a nucleus (e.g., plants, animals). **Organelles** - **Organelles**: Specialized structures within cells performing distinct functions (e.g., nucleus, mitochondria). **Comparison Chart: Eukaryotic vs. Prokaryotic Cells** **Feature** **Eukaryotic Cell** **Prokaryotic Cell** --------------------------------- ------------------------------- ---------------------- **Nucleus** Present Absent **Number of Chromosomes** More than one One (plasmids) **Cell Type** Usually multicellular Usually unicellular **True Membrane-bound Nucleus** Present Absent **Lysosomes and Peroxisomes** Present Absent **Microtubules** Present Absent **Endoplasmic Reticulum** Present Absent **Mitochondria** Present Absent **Cytoskeleton** Present Absent **Ribosomes** Larger Smaller **Vesicles** Present Present **Golgi Apparatus** Present Absent **Chloroplasts** Present (in plants) Absent **Cell Wall** Only in plant cells and fungi Chemically complex **Vacuoles** Present Present **Cell Size** 10-100µm 1-10µm **Examples** Animals, plants Bacteria, archaea **Differences between Plant and Animal Cells** - **Mitochondria**: Both have mitochondria; only plant cells have chloroplasts for photosynthesis. - **Vacuoles**: Plant cells have one large vacuole; animal cells have multiple smaller vacuoles. - **Cell Wall**: Plant cells have a cell wall and membrane; animal cells only have a membrane. **Plant Cell Anatomy Glossary** - **ATP**: High-energy molecule for energy storage. - **Cell Membrane**: Thin layer controlling substance passage. - **Cell Wall**: Rigid structure providing support. - **Centrosome**: Microtubule organizing center, no centrioles. - **Chlorophyll**: Molecule for photosynthesis. - **Chloroplast**: Organelle where photosynthesis occurs. - **Cytoplasm**: Jellylike material outside the nucleus. - **Golgi body**: Packages proteins and carbohydrates. - **Granum**: Stack of thylakoid disks. - **Mitochondrion**: Converts glucose to ATP. - **Nuclear Membrane**: Surrounds the nucleus. - **Nucleolus**: Produces ribosomal RNA. - **Nucleus**: Contains DNA, controls cell functions. - **Photosynthesis**: Converts sunlight to energy. - **Ribosome**: Protein synthesis sites. - **Rough ER**: Transports materials, produces proteins. - **Smooth ER**: Transports materials, digests lipids. - **Stroma**: Part of the chloroplast. - **Thylakoid Disk**: Contains chlorophyll. - **Vacuole**: Large storage space. **Animal Cell Anatomy Glossary** - **Cell Membrane**: Thin layer controlling substance passage. - **Centrosome**: Microtubule organizing center. - **Cytoplasm**: Jellylike material outside the nucleus. - **Golgi body**: Packages proteins and carbohydrates. - **Lysosome**: Digests cell nutrients. - **Mitochondrion**: Converts glucose to ATP. - **Nuclear Membrane**: Surrounds the nucleus. - **Nucleolus**: Produces ribosomal RNA. - **Nucleus**: Contains DNA, controls cell functions. - **Ribosome**: Protein synthesis sites. - **Rough ER**: Transports materials, produces proteins. - **Smooth ER**: Transports materials, digests lipids. - **Vacuole**: Storage spaces inside the cell. **MODULE 2** **ntroduction to Cells:** Cells are the fundamental units of life, discovered and studied with the advent of the microscope. Cytology, the study of cells, encompasses their structure, function, and processes. All living organisms are composed of cells, each containing genetic material and various organelles enclosed by a membrane. **Structure of a Cell:** 1. **DNA:** - Genetic material that carries all necessary information for cell function and reproduction. - Genes are specific segments of DNA that instruct cells in performing tasks. 2. **Cytoplasm:** - Gel-like substance where genetic material resides, maintaining cell shape and facilitating material transport. 3. **Plasma Membrane:** - Surrounds the cytoplasm, separating internal cell components from the external environment. **Cell Theory:** - Proposed by Matthias Schleiden, Theodor Schwann, and Rudolf Virchow. - States that all organisms are composed of cells, cells are the basic units of life, and cells arise from pre-existing cells. **Classification of Cells:** - Based on: a. **Number of Cells:** - **Unicellular:** Single-celled organisms capable of independent existence (e.g., bacteria). - **Multicellular:** Organisms composed of multiple specialized cells (e.g., plants, animals). - **Somatic Cells:** Maintain the organism\'s life processes (e.g., metabolism, growth). - **Gametes:** Reproductive cells responsible for offspring production (e.g., egg and sperm cells). - **Prokaryotic:** Lack membrane-bound organelles, found in bacteria. - **Eukaryotic:** Have a distinct nucleus and membrane-bound organelles, found in plants and animals. **Comparison: Eukaryotic vs. Prokaryotic Cells:** - Highlighting differences in nucleus presence, organelles, size, and complexity. **Differences between Plant and Animal Cells:** - Both are eukaryotic but differ in organelles: - **Plant Cells:** Have chloroplasts for photosynthesis, a cell wall for structural support, and a large central vacuole. - **Animal Cells:** Lack chloroplasts and cell walls, with multiple smaller vacuoles. **Organelles:** - Defined as membrane-bound structures within cells performing specific functions: - Includes mitochondria (energy production), endoplasmic reticulum (protein synthesis), and Golgi apparatus (protein processing). **MODULE 3** Cell division is essential for reproduction, growth, and repair. It involves splitting a single cell into new cells, distributing genetic information from parent cells to daughter cells. The process includes an ordered set of events known as the cell cycle, resulting in two identical daughter cells. The Cell Cycle -------------- The cell cycle is the regular sequence of growth and division that eukaryotic cells undergo, divided into three main stages: 1. **Interphase**: The cell grows, makes a copy of its DNA, and prepares for division. 2. **Mitosis**: The cell's copied DNA is distributed into each daughter cell. 3. **Cytokinesis**: The cytoplasm divides, distributing organelles into the two new cells. ### Interphase Interphase consists of three parts: - **G1 (Growth Phase)**: The cell doubles in size and produces structures necessary for its functions. - **S (DNA Copying Phase)**: The cell makes a copy of its DNA (replication) to ensure the new cell has the directions for its function and survival. - **G2 (Preparation Phase)**: The cell prepares for division by producing structures needed for cell division. Chromosomes and Chromatids -------------------------- Human somatic cells have 23 pairs of homologous chromosomes, one from each parent. Chromatin (DNA and proteins) condenses into chromosomes during the S phase of interphase, forming an "X" shape. Each chromosome consists of two identical sister chromatids attached by a centromere. ### Chromosome Structure - **Chromatin**: Indistinguishable mass of DNA and proteins. - **Chromatids**: Identical parts of a chromosome attached by a centromere. Mitosis ------- Mitosis results in two genetically identical daughter cells and is divided into four stages: 1. **Prophase**: Chromosomes condense and become visible. The nuclear envelope disappears, centrioles move to opposite poles, and spindle fibers form. 2. **Metaphase**: Chromosomes line up in the middle of the cell, and spindle fibers connect centromeres to cell poles. 3. **Anaphase**: Centromeres split, and sister chromatids separate, moving to opposite poles. 4. **Telophase**: Chromosomes uncoil, nuclear envelopes reform around chromosomes, spindle fibers dissolve, and cytokinesis begins. ### Cytokinesis Cytokinesis is the division of the cytoplasm, resulting in two separate daughter cells with identical nuclei. Meiosis ------- Meiosis is the process of cell division producing four gametes with half the number of chromosomes. It consists of two rounds of division: Meiosis I and Meiosis II. ### Unique Features of Meiosis 1. **Synapsis**: Homologous chromosomes pair along their length after replication. 2. **Crossing Over**: Exchange of genetic material between homologous chromosomes during synapsis, causing genetic variation. 3. **Reduction Division**: Chromosomes are not copied between divisions, resulting in haploid cells. ### Meiosis I - **Prophase I**: Chromosomes become visible, homologous chromosomes pair, and crossing over occurs. - **Metaphase I**: Homologous chromosomes line up in the cell center. - **Anaphase I**: Spindle fibers shorten, separating homologous chromosomes (sister chromatids remain paired). - **Telophase I**: Nuclear membrane reforms, resulting in two haploid cells, each with two sister chromatids. ### Meiosis II - **Prophase II**: Nuclear membrane breaks down again. - **Metaphase II**: Chromosomes line up in the cell center. - **Anaphase II**: Spindle fibers shorten, and sister chromatids move to opposite poles. - **Telophase II**: Nuclear envelope reforms around daughter chromosomes. ### End of Meiosis II - Results in four haploid cells, each with one copy of each chromosome (23 chromosomes in humans). Key Terms --------- - **Cell Cycle**: Sequence of growth and division in eukaryotic cells. - **Interphase**: Phase of growth and DNA replication. - **Mitosis**: Division of genetic material into two daughter cells. - **Cytokinesis**: Division of the cytoplasm. - **Meiosis**: Division process producing gametes with half the chromosomes. - **Synapsis**: Pairing of homologous chromosomes. - **Crossing Over**: Exchange of genetic material between homologous chromosomes. - **Reduction Division**: Division resulting in haploid cells. **MODULE 4** **Introduction to Genetics** - **Definition**: Genetics is the study of heredity and variation, investigating how genes and traits are passed from parents to offspring. - **Genetic Information**: Located in the cell nucleus, cells undergo division and reproduction, passing genes from parents to offspring. **Gregor Mendel\'s Experiment** - **Foundation**: Mendel\'s experiments with garden pea plants established the basic rules of inheritance. - **Reasons for Using Pea Plants**: 1. Small and easy to cultivate. 2. Short generation time (\~90 days). 3. Ability to self-fertilize and cross-pollinate. 4. Seven distinct contrasting traits. **Characteristics of Pea Plants** **Trait** **Dominant** **Recessive** ----------------- -------------- --------------- Stem Height Tall Short Seed Shape Round Wrinkled Seed Color Yellow Green Flower Color Purple White Pod Shape Inflated Constricted Pod Color Green Yellow Flower Position Axial Terminal **Mendel's Experiment Process** 1. **Purebred Plants**: Produced purebred plants (P1 generation) with specific traits. 2. **Hybridization**: Cross-pollinated purebred plants to create hybrids (F1 generation). 3. **Self-Fertilization**: Allowed F1 generation to self-fertilize, producing the F2 generation. 4. **Results**: Observed that 75% of F2 generation had dominant traits, while 25% had recessive traits. 5. **Conclusion**: Traits are determined by genes, with dominant and recessive forms. **Key Terms and Concepts** - **Genes**: Segments of DNA determining traits. - **Alleles**: Different forms of a gene. - **Dominant Allele**: Fully expressed form. - **Recessive Allele**: Masked when paired with a dominant allele. - **Genotype**: Genetic makeup (e.g., RR, Rr, rr). - **Phenotype**: Physical expression of traits. - **Homozygous**: Identical alleles (e.g., RR or rr). - **Heterozygous**: Different alleles (e.g., Rr). **Mendel's Laws of Inheritance** 1. **Law of Segregation**: Alleles separate randomly during meiosis, with each gamete receiving one allele. 2. **Law of Independent Assortment**: Traits are inherited independently, allowing for different combinations of alleles. 3. **Law of Dominance**: Dominant alleles mask recessive alleles in heterozygous individuals. **Genetic Predictions** - **Punnett Square**: A tool to predict the probability of genotypes and phenotypes in offspring. - **Monohybrid Cross**: Involves one trait (e.g., RR x rr). - **Dihybrid Cross**: Involves two traits (e.g., TtRr x TtRr). **Pedigree Analysis** - **Definition**: A chart showing how traits are inherited within a family. - **Symbols**: - Circle: Female - Square: Male - Shaded: Trait present - Unshaded: Trait absent - Half-shaded: Carrier - **Uses**: Identifies genetic disorders and tracks inheritance patterns. **Karyotype** - **Definition**: A photograph of chromosomes showing structure, shape, and size. - **Uses**: Detects chromosomal abnormalities. **Extensions of Mendel's Laws** - **Incomplete Dominance**: Neither allele is fully dominant, resulting in a blended phenotype. - **Codominance**: Both alleles are fully expressed. - **Multiple Alleles**: More than two alleles control a trait. - **Polygenic Traits**: Traits controlled by multiple gene pairs. **Sex-Related Traits** - **Sex Chromosomes**: X and Y chromosomes determine sex. - **Sex-Linked Traits**: Traits determined by genes on sex chromosomes. **Mutation** - **Definition**: Permanent change in genetic makeup. - **Causes**: Natural factors (e.g., replication errors) and mutagens (e.g., chemicals, radiation). - **Types**: - **Chromosome Mutation**: Changes in chromosome structure. - **Nondisjunction**: Failure of chromosomes to separate, leading to abnormal chromosome numbers. **Genetic Disorders** - **Sex Chromosome Mutations**: Turner Syndrome, Klinefelter Syndrome, etc. - **Autosome Mutations**: Down Syndrome, Edward Syndrome, Patau Syndrome. **MODULE 5** **Charles Darwin and Evolution** - **Charles Darwin**: Father of modern evolution; spent years observing and analyzing to develop the theory of evolution. - **Evolution**: Gradual change of organisms over time, where modern organisms descend from ancient ones, replacing them in ecological niches. - **Populations**: Evolution occurs in populations, not individuals. Populations are interbreeding groups of a species in a geographic area with a shared gene pool. - **Gene Pool**: Collection of genes within a population; changes in the gene pool drive evolution. **Mechanisms of Evolution** 1. **Mutation** - **Definition**: Random changes in DNA that introduce new alleles. - **Impact**: Source of genetic variation; can be harmful or beneficial (e.g., producing enzymes to utilize new food sources). 2. **Gene Flow** - **Definition**: Movement of genes between populations through migration. - **Impact**: Increases genetic similarity between populations (e.g., seeds carried by wind, animals migrating). 3. **Genetic Drift** - **Definition**: Random changes in gene frequencies, particularly in small populations. - **Impact**: Can lead to significant differences from the original population (e.g., isolated fish population evolving differently). 4. **Natural Selection** - **Definition**: Differential survival and reproduction based on environmental adaptation. - **Impact**: The fittest organisms pass on their genes, leading to a population better adapted to the environment. - **Selective Forces**: Environment (e.g., avoiding predators, disease resistance, obtaining food). **Types of Natural Selection** - **Stabilizing Selection**: Eliminates extreme traits, favoring average traits. - **Disruptive Selection**: Favors extreme traits, leading to multiple populations. - **Directional Selection**: Favors one extreme trait, leading to gene group replacement (e.g., antibiotic-resistant bacteria). **Species Development and Speciation** - **Species**: Group of interbreeding individuals with common features and a shared gene pool. - **Speciation**: Evolution of new species due to geographic or reproductive isolation. - **Geographic Barriers**: Isolation by physical barriers (e.g., Australia, Galapagos Islands). - **Reproductive Barriers**: Anatomical or behavioral differences preventing interbreeding. **Phylogeny and Systematics** - **Phylogeny**: History of species and their relationships. - **Systematics**: Methods to discover species history. - **Adaptation**: Characteristics increasing fitness (ability to survive and reproduce) that become more common over generations. **The Geologic Time Scale** - **Stratigraphy**: Study of Earth\'s layers (strata) to understand its history. - **Geologic Time**: Divided into Eons, Eras, Periods, Epochs, and Ages, based on significant events and fossil records. **Time Divisions** 1. **Eons**: Largest intervals, lasting hundreds of millions of years. 2. **Eras**: Subdivisions of eons (e.g., Cenozoic, Mesozoic, Paleozoic). 3. **Periods**: Subdivisions of eras (e.g., Permian, Devonian). 4. **Epochs**: Subdivisions of periods, finer divisions for recent history (e.g., Holocene). 5. **Ages**: Smallest units of geologic time. **Geologic Time Scale Structure** - **Present at the top**: Progressively older time divisions as one reads down. - **Naming**: Based on life forms and significant geological events (e.g., \"Cenozoic\" for \"new life\"). **Importance of Fossil Records** - **Fossils**: Evidence of ancient life, providing insights into evolutionary changes and environmental conditions. - **Dating Rocks**: Fossils help geologists date and compare rock layers across geologic time. **Stratigraphy and Geologic Time Units** - **Eons**: Largest time intervals (e.g., Phanerozoic Eon). - **Eras**: Subdivisions of eons (e.g., Cenozoic Era). - **Periods**: Subdivisions of eras (e.g., Cambrian Period). - **Epochs**: Subdivisions of periods, notable in the Cenozoic Era (e.g., Holocene Epoch). - **Ages**: Subdivisions of epochs, smallest time units. **MODULE 6** - **Classification** is the arrangement of organisms into orderly groups based on their similarities. - It is also known as **taxonomy**. - **Taxonomists** are scientists that identify and name organisms. ### Benefits of Classifying - Accurately and uniformly names organisms. - Prevents misnomers such as starfish and jellyfish that aren\'t really fish. - Uses the same language (Latin or Greek) for all names. Historical Background --------------------- ### Early Taxonomists - **Aristotle** (2000 years ago): First taxonomist who divided organisms into plants and animals and subdivided them by their habitat (land, sea, or air dwellers). ### Carl Linnaeus (Carl von Linné) - 18th-century taxonomist. - Classified organisms by their structure. - Developed the modern system of naming known as **binomial nomenclature** (two-word name: Genus & species). - Known as the "Father of Taxonomy". Modern Classification System ---------------------------- ### Hierarchical System - **Domain**: The largest classification category. - The three domains that include all living things on Earth are: 1. **Bacteria** 2. **Archaea** 3. **Eukarya** ### Taxonomic Groups - **Domain** - **Kingdom** - **Phylum** (Division for plants) - **Class** - **Order** - **Family** - **Genus** - **Species** ### The Six Kingdoms 1. **Archaebacteria** 2. **Eubacteria** 3. **Protista** 4. **Fungi** 5. **Plantae** 6. **Animalia** Domains and Kingdoms -------------------- ### Domains 1. **Bacteria**: Single-celled microorganisms without a nucleus. 2. **Archaea**: Single-celled microorganisms without a nucleus, often found in extreme environments. 3. **Eukarya**: Organisms with DNA contained within a nucleus, including four kingdoms: Protista, Fungi, Plantae, and Animalia. ### Kingdoms #### Protista - Mostly unicellular. - Some are multicellular. - Some are autotrophic; others are heterotrophic. - Aquatic environments. #### Fungi - Multicellular (except yeast). - Absorptive heterotrophs (digest food outside their body and then absorb it). - Cell walls made of chitin. #### Plantae - Multicellular. - Autotrophic. - Absorb sunlight to make glucose (photosynthesis). - Cell walls made of cellulose. #### Animalia - Multicellular. - Ingestive heterotrophs (consume food and digest it inside their bodies). - Feed on plants or animals. #### Archaebacteria - Found in extreme environments (hot boiling water, thermal vents, acidic conditions with no oxygen). - Anaerobic, with unique DNA in their ribosomes. - Includes methanogens, thermophiles, and halophiles. #### Eubacteria - Diverse in shape, chemical composition, nutritional requirements, and biochemical activities. - Important decomposers in the ecosystem, recycling nutrients. Scientific Nomenclature ----------------------- ### Rules for Scientific Names - Organisms are identified by their **binomial name** (genus and species). - **Genus name** is capitalized; **species name** is not. - Both names are italicized or underlined. - Genus names can be abbreviated by their first letter (e.g., Phyllopteryx eques can be written as *P. eques*). - Unknown species are referred to with the abbreviation **sp.** (e.g., *Hippocampus sp.*). ### Importance of Scientific Names - Provides useful information about evolutionary history and relationships. - Acts as shorthand for describing plants or animals. - Developed using Latin and Greek, which were common languages of educated people when the system was created. Conclusion ---------- - **Classification** helps organize and understand the vast diversity of life. - **Taxonomy** provides a structured system to name and categorize living organisms. - Understanding the classification system and scientific nomenclature is crucial for studying relationships and evolutionary history among organisms. **MODULE 7** ### Cells A cell is the basic unit of structure and function in living things. In multicellular organisms, cells are often specialized, each uniquely suited to perform specific functions. ### Tissues A tissue is a group of cells that perform a single function. There are four basic types of tissue in the human body: 1. **Epithelial Tissue**: Includes glands and tissues that cover interior and exterior body surfaces. 2. **Connective Tissue**: Provides support for the body and connects its parts. 3. **Nervous Tissue**: Transmits nerve impulses throughout the body. 4. **Muscle Tissue**: Along with bones, enables the body to move. ### Organs An organ is a group of different types of tissues that work together to perform a single function. For example, the eye is an organ composed of epithelial, nervous, muscle, and connective tissues, all working together to enable sight. ### Organ Systems An organ system is a group of organs that perform closely related functions. For instance, the brain is part of the nervous system, which gathers information about the external world and coordinates the body\'s response. The eleven organ systems of the human body work together to maintain homeostasis. Nervous System -------------- ### Function Recognizes and coordinates the body's response to changes in internal and external environments. ### Structures - Brain - Spinal cord - Peripheral nerves The nervous system carries electrical signals called impulses, transmitted by neurons. Neurons are classified into three types: 1. **Sensory Neurons**: Carry impulses from sense organs to the spinal cord and brain. 2. **Motor Neurons**: Carry impulses from the brain and spinal cord to muscles and glands. 3. **Interneurons**: Connect sensory and motor neurons and carry impulses between them. ### Divisions The nervous system is divided into the central nervous system (CNS) and the peripheral nervous system (PNS). #### Central Nervous System (CNS) The CNS, comprising the brain and spinal cord, acts as the control center of the body. It relays, processes, and analyzes information. ##### Brain The brain has approximately 100 billion neurons and weighs about 1.4 kilograms. It includes several key regions: - **Cerebrum**: The largest region, responsible for voluntary activities, intelligence, learning, and judgment. It is divided into two hemispheres connected by the corpus callosum and consists of gray matter (cerebral cortex) and white matter. - **Cerebellum**: Coordinates and balances muscle actions. - **Brain Stem**: Connects the brain and spinal cord, controlling vital functions like blood pressure, heart rate, breathing, and swallowing. It includes the pons and medulla oblongata. - **Thalamus and Hypothalamus**: The thalamus relays sensory information to the cerebrum, while the hypothalamus controls hunger, thirst, fatigue, anger, body temperature, and coordination of the nervous and endocrine systems. ##### Spinal Cord The spinal cord is the main communication link between the brain and the body, with 31 pairs of spinal nerves branching out to connect the brain to different body parts. It also processes certain reflexes. #### Peripheral Nervous System (PNS) The PNS includes all nerves and associated cells outside the CNS. It is divided into the sensory division (transmits impulses from sense organs to the CNS) and the motor division (transmits impulses from the CNS to muscles or glands). ##### Motor Division The motor division is further divided into: - **Somatic Nervous System**: Regulates activities under conscious control, such as skeletal muscle movement and certain reflexes. - **Autonomic Nervous System**: Regulates involuntary activities, controlling functions like heart rate, blood flow, and digestion. It is subdivided into the sympathetic and parasympathetic nervous systems, which have opposing effects to maintain homeostasis. Circulatory System ------------------ ### Function Brings oxygen, nutrients, and hormones to cells; fights infection; removes cell wastes; helps regulate body temperature. ### Structures - Heart - Blood vessels - Blood The heart, a muscular organ about the size of a clenched fist, pumps blood through a system of vessels. It consists of four chambers (two atria and two ventricles) and is divided by a septum to prevent mixing of oxygen-rich and oxygen-poor blood. ### Blood Circulation Blood flows through two main pathways: 1. **Pulmonary Circulation**: Right side of the heart pumps blood to the lungs to exchange carbon dioxide for oxygen. 2. **Systemic Circulation**: Left side of the heart pumps oxygen-rich blood to the rest of the body and returns oxygen-poor blood to the right side. ### Blood Vessels Blood circulates through arteries, capillaries, and veins. Arteries carry oxygen-rich blood from the heart, capillaries facilitate nutrient and gas exchange, and veins return blood to the heart. ### Blood Pressure Blood pressure, the force exerted by blood on artery walls, is measured using a sphygmomanometer and consists of systolic (pressure during heart contraction) and diastolic (pressure during heart relaxation) readings. A typical healthy reading is 120/80 mmHg. Integumentary System -------------------- ### Function Serves as a barrier against infection and injury; helps regulate body temperature; provides protection against UV radiation. ### Structures - Skin - Hair - Nails - Sweat and oil glands The skin, the body's largest organ, consists of the epidermis (outer layer) and dermis (inner layer). The epidermis provides a protective barrier and contains melanocytes, which produce melanin. The dermis contains collagen fibers, blood vessels, nerve endings, and glands that help regulate body temperature and produce sebum. Skeletal System --------------- ### Function Supports the body; protects internal organs; allows movement; stores minerals; provides a site for blood cell formation. ### Structures - Bones - Cartilage - Ligaments - Tendons Muscular System --------------- ### Function Works with the skeletal system to produce voluntary movement; helps circulate blood and move food through the digestive system. ### Structures - Skeletal muscle - Smooth muscle - Cardiac muscle **GOODLUCK GAIZZ!!!**