CSEC Biology Essentials: Organisms, Environment, and Life Processes

This cheat sheet covers fundamental CSEC Biology concepts, from the characteristics of living organisms and ecosystems to cellular processes, human systems, and genetic principles. It emphasizes key definitions, classifications, and biological mechanisms essential for understanding life.

Core Principles

• Living organisms share characteristics: Growth, Respiration, Irritability, Movement, Nutrition, Excretion, Reproduction (GRINMER).
• Organisms are classified hierarchically based on shared characteristics, moving from broad kingdoms to specific species.
• Ecosystems involve interactions between biotic (living) and abiotic (non-living) factors.
• Energy flows unidirectionally through trophic levels in food chains, with significant loss at each stage.
• Cellular processes like photosynthesis and respiration are vital for energy production and nutrient synthesis.
• Transport systems in plants (xylem, phloem) and animals (circulatory system) move essential substances.
• Homeostasis maintains a stable internal environment despite external changes.
• Genetics explains heredity through DNA, genes, alleles, and their expression (genotype/phenotype).
• Variation within a species is crucial for adaptation and survival.
• Reproduction ensures the continuity of species, either asexually or sexually.

Action Steps

• Identify the seven characteristics of living organisms (GRINMER).
• Distinguish between unicellular and multicellular organisms.
• Understand the hierarchical structure of biological classification (Kingdom to Species).
• Define ecosystem components: biotic, abiotic, population, community, niche, habitat.
• Trace energy flow through trophic levels, noting the 10% rule.
• Explain the processes of photosynthesis and cellular respiration.
• Describe the functions of xylem and phloem in plants.
• Outline the components and functions of the human circulatory system.
• Explain homeostasis and its mechanisms (e.g., temperature regulation, blood glucose).
• Differentiate between genotype and phenotype, dominant and recessive alleles.
• Understand the principles of natural and artificial selection.
• Describe the processes of mitosis and meiosis.
• Identify the structures and functions of the human reproductive systems.
• Explain the mechanisms of disease transmission and prevention.

Formulas

• Photosynthesis: $6CO_2 + 6H_2O \xrightarrow{Light \text{ energy}} C_6H_{12}O_6 + 6O_2$
• Aerobic Respiration: $C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + ATP$
• Anaerobic Respiration (animals): $C_6H_{12}O_6 \rightarrow 2C_3H_6O_3 + ATP$
• Anaerobic Respiration (plants/yeast): $C_6H_{12}O_6 \rightarrow 2CO_2 + 2C_2H_5OH + ATP$

Key Terms

• Unicellular: An organism composed of only one cell.
• Multicellular: An organism composed of many cells, often specialized.
• Metabolism: The sum of all chemical processes that occur in the body.
• Locomotion: The ability of an organism to move from one place to another.
• Species: A group of organisms that can interbreed and produce fertile offspring.
• Taxon: A level in the hierarchical classification system of organisms.
• Binomial Name: A two-part scientific name for a species (Genus species).
• Ecosystem: A system of living (biotic) and non-living (abiotic) factors interacting with each other.
• Niche: An organism's role and position in its environment.
• Habitat: The specific place where an organism lives.
• Autotroph: An organism that produces its own food (producer).
• Heterotroph: An organism that obtains nutrition by consuming other organisms (consumer).
• Decomposer: An organism that breaks down dead organic matter.
• Trophic Level: Each stage in a food chain, representing energy transfer.
• Food Web: A network of interconnected food chains within an ecosystem.
• Predator: An animal that hunts and kills other animals for food.
• Prey: An animal that is hunted and killed by another animal for food.
• Symbiosis: A close, long-term interaction between two different biological species.
• Parasitism: One organism benefits, the other is harmed.
• Commensalism: One organism benefits, the other is unaffected.
• Mutualism: Both organisms benefit from the relationship.
• Natural Selection: The process whereby organisms better adapted to their environment tend to survive and produce more offspring.
• Competition: An interaction where organisms strive for the same limited resources.
• Quadrat: A square frame used for sampling organisms in ecological studies.
• Transect: A line or path along which quadrats are placed to study changes in species distribution.
• Photosynthesis: The process by which light energy is converted into chemical energy in the form of glucose.
• Respiration: The process of releasing energy from glucose, typically involving oxygen (aerobic) or not (anaerobic).
• ATP: Adenosine triphosphate, the main energy currency of the cell.
• Diffusion: Movement of molecules from high to low concentration.
• Active Transport: Movement of molecules from low to high concentration, requiring energy (ATP).
• Osmosis: Movement of water molecules across a partially permeable membrane from high to low water concentration.
• Enzyme: A biological catalyst that speeds up chemical reactions.
• Substrate: The molecule upon which an enzyme acts.
• Denaturation: The loss of an enzyme's specific three-dimensional shape, rendering it inactive.
• Balanced Diet: A diet containing all necessary nutrients in the correct proportions.
• Malnutrition: A condition resulting from an unbalanced diet (deficiency or excess).
• Alimentary Canal: The pathway through the digestive system, from mouth to anus.
• Villi: Finger-like projections in the small intestine that increase surface area for absorption.
• Ventilation: The process of breathing air into and out of the lungs.
• Gaseous Exchange: The diffusion of gases (O2 and CO2) between an organism and its environment.
• Alveoli: Tiny air sacs in the lungs where gaseous exchange occurs.
• Oxygen Debt: The extra oxygen needed after strenuous exercise to metabolize accumulated lactic acid.
• Gills: Respiratory organs in fish used for extracting dissolved oxygen from water.
• Circulatory System: The system responsible for transporting blood, nutrients, and gases throughout the body.
• Double Circulation: A circulatory system where blood passes through the heart twice in one complete circuit.
• Arteries: Blood vessels that carry blood away from the heart.
• Veins: Blood vessels that carry blood towards the heart.
• Capillaries: Tiny blood vessels connecting arteries and veins, facilitating exchange with tissues.
• Blood Plasma: The liquid component of blood, carrying cells, nutrients, and waste.
• Phagocytes: White blood cells that engulf and digest foreign particles and pathogens.
• Lymphocytes: White blood cells that produce antibodies to fight infection.
• Antibodies: Proteins produced by lymphocytes that target specific antigens.
• Blood Clotting: The process of forming a clot to stop bleeding from a wound.
• Lymphatic System: A network of vessels and nodes that transports lymph and fights infection.
• Xylem: Plant tissue that transports water and dissolved minerals upwards.
• Phloem: Plant tissue that transports sugars (organic nutrients) throughout the plant.
• Transpiration: The evaporation of water from plant surfaces, mainly through stomata.
• Xerophytes: Plants adapted to survive in dry environments.
• Skeleton: The framework of bones that supports and protects the body.
• Joints: The points where two or more bones meet.
• Cartilage: A flexible connective tissue found in joints and other parts of the body.
• Ligaments: Tough, fibrous bands that connect bones to other bones.
• Tendons: Tough, fibrous bands that connect muscles to bones.
• Antagonistic Muscles: Muscles that work in pairs, one contracting while the other relaxes to produce movement.
• Germination: The process by which a seed sprouts and begins to grow.
• Dispersal: The movement of seeds or spores away from the parent plant.
• Phototropism: Growth of a plant in response to light.
• Gravitropism: Growth of a plant in response to gravity.
• Auxin: A plant hormone that promotes cell elongation and influences growth responses.
• Excretion: The elimination of metabolic waste products from the body.
• Egestion: The removal of undigested food material (feces) from the body.
• Nephron: The functional unit of the kidney, responsible for filtering blood and producing urine.
• Ultrafiltration: The process in the kidney where small molecules are filtered from the blood into Bowman's capsule.
• Selective Reabsorption: The process in the kidney where useful substances are reabsorbed from the filtrate back into the blood.
• Homeostasis: The regulation of the body's internal environment to maintain a stable state.
• Stimulus: A detectable change in the external or internal environment that elicits a response.
• Receptor: A cell or group of cells that detect stimuli.
• Effector: A muscle or gland that responds to a stimulus.
• Nervous System: The system that transmits signals between different parts of the body using electrical impulses.
• Endocrine System: The system that regulates body functions using hormones secreted by glands.
• Neuron: A nerve cell that transmits electrical and chemical signals.
• Synapse: The gap between two neurons where information is transmitted chemically.
• Neurotransmitter: A chemical messenger that transmits signals across a synapse.
• Reflex Arc: The pathway of nerve impulses during a reflex action, bypassing conscious brain processing.
• Hormone: A chemical messenger produced by endocrine glands that travels in the blood to target organs.
• Pupil: The opening in the center of the iris that allows light to enter the eye.
• Iris: The colored part of the eye that controls the size of the pupil.
• Retina: The light-sensitive layer at the back of the eye containing rods and cones.
• Rods: Photoreceptor cells in the retina sensitive to dim light and peripheral vision.
• Cones: Photoreceptor cells in the retina sensitive to bright light and color vision.
• Accommodation: The eye's ability to change the shape of the lens to focus on objects at different distances.
• Pathogen: A microorganism that causes disease.
• Vector: An organism that transmits a pathogen from one host to another.
• Vaccination: The administration of a vaccine to stimulate an immune response and provide immunity to a disease.
• Antibiotics: Drugs used to treat bacterial infections.
• Drug Abuse: The excessive or non-prescribed use of drugs.
• Tolerance: Reduced response to a drug after repeated use, requiring higher doses.
• Addiction: A compulsive craving for a drug, leading to dependence and withdrawal symptoms.
• Immunity: An organism's ability to resist infection by a particular disease.
• Immunization: The process of making an individual resistant to a disease, usually through vaccination.
• Memory Cells: Specialized lymphocytes that provide long-term immunity after exposure to a pathogen.
• DNA: Deoxyribonucleic acid, the molecule carrying genetic information.
• Gene: A segment of DNA that codes for a specific trait or protein.
• Chromosome: A structure made of DNA and proteins, carrying genetic information.
• Allele: An alternative form of a gene.
• Genotype: The genetic makeup of an organism, represented by letters (e.g., BB, Bb, bb).
• Phenotype: The observable physical characteristics of an organism, determined by its genotype.
• Homozygous: Having two identical alleles for a particular gene (e.g., BB or bb).
• Heterozygous: Having two different alleles for a particular gene (e.g., Bb).
• Dominant: An allele whose trait is expressed even when only one copy is present.
• Recessive: An allele whose trait is only expressed when two copies are present.
• Gamete: A reproductive sex cell (sperm or egg).
• Zygote: A fertilized egg cell formed by the fusion of gametes.
• Diploid: Having two sets of chromosomes (2n).
• Haploid: Having one set of chromosomes (n).
• Mitosis: Cell division producing two identical daughter cells for growth and asexual reproduction.
• Meiosis: Cell division producing four genetically varied haploid gametes.
• Asexual Reproduction: Reproduction involving one parent, producing genetically identical offspring.
• Sexual Reproduction: Reproduction involving two parents, producing genetically varied offspring.
• Fertilization: The fusion of male and female gametes to form a zygote.
• Contraception: Methods used to prevent pregnancy.
• Pollination: The transfer of pollen from an anther to a stigma.
• Monohybrid Inheritance: The inheritance of a single genetic characteristic.
• Sex-Linked: A trait or disease carried on a sex chromosome (usually X).
• Multiple Alleles: A gene that exists in more than two allelic forms within a population.
• Variation: Differences among individuals within a species.
• Mutation: A random change in the DNA sequence.
• Genetic Engineering: The direct manipulation of an organism's genome.

Pro Tips

• Remember the 10% energy transfer rule between trophic levels.
• Distinguish between excretion (metabolic waste) and egestion (undigested food).
• Note that viruses are not considered living organisms.
• Understand that ADH regulates water reabsorption in the kidneys.
• Recognize the difference between mitosis (growth, asexual reproduction) and meiosis (gamete formation).
• Pay attention to the specific roles of hormones like insulin, glucagon, and adrenaline.
• Differentiate between natural and artificial selection: environment vs. human intervention.
• Understand that mutations are random but mutagens increase their risk.

Pitfalls to Avoid

• Confusing breathing (ventilation) with respiration (energy release).
• Mistaking egestion (removal of undigested food) for excretion (removal of metabolic waste).
• Assuming all organisms fit the five-kingdom model without considering later revisions.
• Forgetting that decomposers are distinct from carrion feeders and detritivores.
• Overlooking the role of ATP in active transport and cellular processes.
• Confusing symbiotic relationships: parasitism, commensalism, mutualism.
• Not understanding that only gametes are haploid; somatic cells are diploid.
• Assuming antibiotics work against viruses.
• Confusing artificial selection with genetic engineering.

Myth vs Reality

• Breathing is the same as respiration.: Breathing (ventilation) is the mechanical process of moving air in and out of the lungs. Respiration is the chemical process of releasing energy from glucose, often using oxygen.
• Viruses are living organisms.: Viruses are not classified under any kingdom because they are not considered living organisms; they require a host cell to replicate.
• All organisms have a bony skeleton.: Invertebrates like earthworms and jellyfish have hydrostatic skeletons, which use fluid pressure for support and movement.
• Antibiotics can cure viral infections.: Antibiotics are effective against bacteria, not viruses. Viral infections require antiviral medications.

Real World Examples

• Peppered moths changing color during the Industrial Revolution.: Demonstrates natural selection based on environmental changes (pollution).
• Using antibiotics to treat bacterial infections.: Pharmaceutical application of drugs to combat pathogens.
• Selective breeding of dogs for specific traits.: Example of artificial selection to enhance desirable characteristics.
• Insulin production using recombinant DNA technology.: Genetic engineering application in medicine for treating diabetes.
• The role of xylem and phloem in transporting water and nutrients to plant leaves.: Essential plant transport systems for photosynthesis and growth.
• The human circulatory system delivering oxygen to muscles during exercise.: Demonstrates the function of arteries, capillaries, and the heart in transport.
• Kidneys filtering waste products from the blood.: Illustrates the excretory function and homeostasis in maintaining blood composition.
• The iris adjusting pupil size in response to light.: Demonstrates a reflex response to environmental stimuli for vision.

Statistics

• Energy Transfer Efficiency (Trophic Level): Approximately 10%
• Human Chromosome Number (Diploid): 46 (2n)
• Human Gamete Chromosome Number (Haploid): 23 (n)
• Typical Human Blood Pressure: 120/80 mmHg

Timeline

• 19th Century: Gregor Mendel conducts experiments on pea plants, laying the foundation for modern genetics.
• Early 20th Century: Discovery of antibiotics (e.g., Penicillin by Alexander Fleming).
• Mid-20th Century: Discovery of DNA structure by Watson and Crick, revolutionizing molecular biology.
• Late 20th Century: Development of genetic engineering techniques, including recombinant DNA technology.
• Late 20th - Early 21st Century: Advancements in understanding and treating diseases like HIV/AIDS, and development of vaccines.
• 21st Century: Completion of the Human Genome Project, providing a comprehensive map of human genes.

People

• Gregor Mendel: Monk and biologist, considered the father of modern genetics for his work on heredity.
• Charles Darwin: Naturalist who proposed the theory of evolution by natural selection, notably studying finches.
• Robert Whittaker: Ecologist who proposed the five-kingdom system for classifying organisms.
• Alexander Fleming: Scientist credited with the discovery of penicillin, the first mass-produced antibiotic.
• James Watson and Francis Crick: Scientists who discovered the double-helix structure of DNA.