Science QTR1 Reviewer Notes - Respiratory, Circulatory, Genetics, Biodiversity, Photosynthesis, Cellular Respiration, Endosymbiotic Theory

Respiratory System

  • Nose
    • Functions (5 total):
    • Serves as an air passageway. 5 functions overall.
    • Warms and moistens inhaled air before it enters deeper into the system.
    • Cilia and mucus trap dust, pollen, bacteria, and foreign matter.
    • Contains olfactory receptors to detect smells.
    • Aids in phonation and affects the quality of voice.
  • Pharynx (throat)
    • Dual role: part of both the respiratory and digestive systems.
    • Receives air from the nasal cavity and air, food, and water from the oral cavity.
    • Functions (3):
    • Serves as a passageway for air.
    • Serves as a passageway for food.
    • Aids in phonation by changing its shape.
  • Larynx (voice box)
    • Routes air and food into proper channels.
  • Trachea (windpipe)
    • Approximately 4-inch-long tube that connects the larynx with the bronchi.
    • Provides a safe, sturdy passageway for air to travel from the mouth or nose to the lungs.
  • Lungs
    • Main structure of the respiratory system.
    • Contain alveoli where gas exchange with the blood occurs.
  • Diaphragm
    • Dome-shaped muscle beneath the lungs.
    • Contracts and relaxes to change chest cavity volume, enabling breathing.
  • Bronchi
    • Two main tubes branching from the trachea into each lung.
    • Direct air into progressively smaller branches.
  • Bronchioles
    • Smaller branches of the bronchi.
    • Distribute air to all parts of the lungs.
  • Alveoli
    • Tiny air sacs where gas exchange occurs: oxygen enters the blood and carbon dioxide leaves it.
  • Circulatory System (overview)
    • Primary role: transport blood, gases, nutrients, and hormones; collect waste materials; help regulate body temperature.
    • Interaction with nervous system to regulate breathing and circulation.

Nervous System and Circulation

  • Medulla Oblongata
    • Bottom-most part of the brain, part of the brainstem.
    • Controls vital processes like heartbeat, breathing, and blood pressure.
  • Heart
    • Pumps blood throughout the body.
    • Right side pumps deoxygenated blood to the lungs to pick up oxygen.
    • Left side pumps oxygenated blood to the body.
  • Four chambers of the heart
    • Atria (upper two chambers):
    • Right atrium: receives deoxygenated blood from the body.
    • Left atrium: receives oxygen-rich blood from the lungs.
    • Ventricles (lower two chambers):
    • Right ventricle: pumps deoxygenated blood to the lungs via the pulmonary artery.
    • Left ventricle: pumps oxygen-rich blood to the entire body via the aorta.
  • Septum
    • Muscle that divides the heart into right and left halves.
  • Valves (4 types)
    • Tricuspid Valve
    • Pulmonary Semilunar Valve
    • Mitral (Bicuspid) Valve
    • Aortic (Semilunar) Valve
  • Blood composition
    • Blood is composed of 45 ext{%} cells and 55 ext{%} plasma.
    • Erythrocytes – Red blood cells
    • Leukocytes – White blood cells
    • Thrombocytes – Platelets
  • Blood vessels
    • Arteries – move blood away from the heart.
    • Veins – move blood back to the heart.
    • Capillaries – exchange tissues with blood; connect arteries and veins.
  • Types of blood circulation
    • Coronary circulation – blood within the heart tissue.
    • Pulmonary circulation – flow of blood between the heart and lungs.
    • Systemic circulation – flow of blood between the heart and all body cells.

Genetics

  • Genetics overview
    • Genetics is the study of genes and how they are passed from generation to generation.
    • Gene – basic unit of heredity; region of a DNA strand containing instructions for body development.
    • Genome – entirety of genetic material in an organism.
    • Alleles – alternative versions of a gene.
    • Phenotype – outward appearances or characteristics.
    • Genotype – genetic makeup of an organism.
    • Homozygous – two identical alleles.
    • Heterozygous – two different alleles.
    • Polyallelic concept: Multiple alleles – more than two alleles can exist in a population; an individual can inherit only two alleles at a time.
    • Punnett square – shows possible outcomes of genetic crosses.
  • Classical Mendelian genetics (dominance and segregation)
    • Law of Dominance – dominant alleles mask recessive alleles in a heterozygous genotype.
    • Law of Segregation – offspring inherit one allele from each parent; one allele per gamete; two alleles per individual.
    • Law of Independent Assortment – alleles of different genes assort independently of one another.
  • Non-Mendelian and complex inheritance patterns
    • Codominance – both phenotypes express simultaneously when both alleles are present (e.g., heterozygous).
    • Incomplete dominance – heterozygotes show an intermediate phenotype between the two homozygotes.
    • Sex-linked inheritance – alleles located on sex chromosomes (XX female, XY male).
    • Sex-linked traits – traits carried on X or Y chromosomes; prevalence may differ by sex.
    • Sex-influenced traits – expressed differently in males vs females even though the genotype is the same.
    • Autosomal traits – related to autosomes (non-sex chromosomes).
  • Other terminology
    • Monohybrid – cross involving a single gene; common Punnett square examples.
    • Dihybrid – cross involving two genes.
  • Concepts to remember
    • Gene – sequence of DNA with instructions for phenotype.
    • Genotype vs Phenotype differentiation.
    • Genotype can be homozygous or heterozygous; alleles from each parent.

Biodiversity

  • Biodiversity definition and levels
    • Biodiversity = vast array and variety of life.
    • Three levels:
    • Genetic Diversity – range of inherited traits within a species (varieties of the same genes within a species).
    • Species Diversity – variety of species within an ecosystem.
    • Ecological (Community) Diversity – variety of habitats and ecosystems within the biosphere.
  • Taxonomy and classification
    • Taxonomy – classification of organisms; assigning names to organisms.
    • Classic taxonomy: Kingdom, Phylum, Class, Order, Family, Genus, Species (KPCOFGS).
  • Key terms
    • Population – group of organisms of the same species living in a particular area.
    • Threatened species – population decline rapidly toward endangerment.
    • Habitat diversity, ecological niches, and genetic diversity contribute to resilience.
  • Notable individuals
    • Karl Landsteiner – immunologist; Father of Immunology.
  • Biodiversity benefits
    • (Note: this section title appears but details are not fully listed in the transcript.)
  • Causes of biodiversity loss
    • Pollution
    • Loss of tropical forests
    • Urban spread
    • Warfare
    • Large dam constructions
    • Road building
    • Tourism
    • Loss of traditional lifestyles
  • Consequences of biodiversity loss
    • Loss of food resources
    • Decrease in biomass
    • Collapse of food webs
    • Loss of keystone species
    • Reduced ecosystem efficiency and productivity
    • Diminished medicinal resources
    • Increased vulnerability to disease and predation

Photosynthesis

  • Key pigments
    • Carotenoids (carotene and xanthophyll) – absorb light regions not absorbed by chlorophyll; transfer energy to chlorophyll.
    • Chlorophyll – principal pigment; located in chloroplasts; absorbs violet-blue and red light; reflects green, hence leaves look green.
  • What is photosynthesis?
    • The process by which light energy is converted to chemical energy stored in glucose (a sugar).
    • Often described as the most important chemical reaction on Earth due to energy capture and basis of food chains.
  • Requirements for photosynthesis
    • Water (H₂O)
    • Carbon dioxide (CO₂)
    • Light
    • Chlorophyll
  • Chloroplasts and related structures
    • Chloroplasts – site of photosynthesis.
    • Thylakoids – stacked internal membranes; each stack is called a granum (plural grana).
    • Stroma – fluid surrounding the thylakoids inside the chloroplast.
  • Major events of photosynthesis
    • Event 1: Light energy is captured and converted into chemical energy (ATP and NADPH).
    • Event 2: Water is split to release O₂ (photolysis) and supply electrons.
    • Event 3: CO₂ is fixed into sugars (glucose) via the Calvin cycle.
  • Chemical equation (overall)
    • 6CO2 + 6H2O + light
      ightarrow C6H{12}O6 + 6O2

Cellular Respiration and Endosymbiotic Theory

  • Cellular respiration (overview)
    • Occurs in all living cells (plants and animals).
    • Main organelle involved: mitochondria – energy powerhouses of the cell.
    • Process can occur with or without oxygen (aerobic vs anaerobic) depending on conditions.
    • Purpose: release energy from glucose to produce ATP for cellular work.
  • Relationship to photosynthesis
    • Photosynthesis stores energy in glucose; cellular respiration releases that energy to form ATP.
    • Overall equation (simplified):
    • C6H{12}O6 + 6O2
      ightarrow 6CO2 + 6H2O +
      \text{energy (ATP)}
  • Mitochondria
    • Contain circular DNA and can synthesize some of their own proteins.
    • Similar to chloroplasts in having their own DNA, supporting the endosymbiotic theory.
  • Endosymbiotic Theory
    • Hypothesis: ancestral free-living bacteria were taken up by a host cell via endocytosis and became integral organelles.
    • Mitochondria and chloroplasts originated from engulfed bacteria, explaining their own DNA and double-membrane structure.

Notes on plant transport tissues (brief reference)

  • Xylem – transports water and dissolved minerals from roots to leaves.
  • Phloem – conducts sugars from leaves to all parts of the plant.
  • Both tissues contain their own DNA in organelles and contribute to cellular energy and function.