Comprehensive NYS Living Environment and Biology Regents Study Guide

Foundational Terms in the Science of the Living Environment

• Observation: Refers to what is seen or measured using the five senses or scientific tools.
• Inference: Describes a conclusion or deduction based upon observations or evidence provided.
• Hypothesis: An untested prediction regarding the outcome of a situation. A good hypothesis is typically structured as an "If-then" statement, which explicitly states both the cause and the effect.
• Theory: Defines a broad explanation of natural events that is supported by a large body of strong evidence.

Controlled Experiments and Scientific variables

• A controlled experiment compares the results of an experiment between two (or more) separate groups.
• Experimental Group: This is the group being tested or receiving a specific treatment, such as a new drug.
• Control Group: This is the "normal" group. It should be identical to the experimental group in every single way except for one factor: it does not receive the treatment. It may be given no drug, the original drug, or a placebo.
• Placebo: A fake treatment, such as a sugar pill, given to the control group so that the human subjects do not know which group they are in.
• Independent Variable: This is the variable that is being tested (e.g., the new drug). On a graph, the independent variable is always plotted on the X-axis.
• Dependent Variable: This is the variable that is measured at the end of the experiment to determine the results (e.g., whether the patient gets better). The dependent variable is always plotted on the Y-axis.

Characteristics of a Robust Scientific Experiment

• The experiment must be repeatable by anyone and yield the same results upon replication.
• It should have a large sample size and involve many test subjects to ensure reliability.
• It should be performed for longer periods of time to observe long-term effects.
• Only one variable should be tested at a time.
• Peer Review: The experiment must be examined by several other scientists to determine its accuracy and validity.
• Hypothesis Compatibility: The results do not have to agree with the hypothesis; a scientist's guess is allowed to be incorrect, which is often the case.
• Objectivity: The experiment and its conclusion must be fair and unbiased. Fact and opinion must not be mixed.

Characteristics of Living Things and Metabolism

• Homeostasis: All living things must maintain a stable internal environment. Failure to maintain homeostasis results in disease and death.
• Life Functions: To maintain homeostasis, organisms carry out basic life functions including nutrition, excretion, transport, respiration, growth, synthesis, and regulation.
• Metabolism: This term encompasses all the life processes that make up an organism’s total chemical activity.
• Nutrition:
  • Autotrophs: Organisms that make their own food.
  • Heterotrophs: Organisms that must eat other organisms for food.
  • Photosynthesis: Carried out by plants, alga, and blue-green bacteria. It captures the radiant energy of the sun and stores it in the chemical bonds of sugar molecules. This occurs primarily in the chloroplast of plant cells.
  • Stomates: Small holes in plant leaves that allow for the exchange of gases used in photosynthesis.
  • Guard Cells: Specialized cells that open and close the stomates to regulate gas exchange and water loss.

Cellular Respiration and Energy Production

• Organisms obtain energy by breaking the chemical bonds of sugar molecules.
• This released energy is used to produce ATP (Adenosine Triphosphate), the primary energy molecule for all organisms.
• Aerobic Respiration: Requires oxygen and yields more ATP per molecule of sugar than the alternative.
• Anaerobic Respiration: Does not require oxygen but yields significantly less ATP. In humans, anaerobic respiration produces lactic acid, which causes damage to muscles, often referred to as "the burn" felt during intense exercise.
• Relationship: Photosynthesis and Aerobic Respiration are opposite chemical reactions. They are vital for the cycling of oxygen, carbon, hydrogen, and water through the environment.

Transport and Cell Membrane Dynamics

• Diffusion: The movement of molecules from areas of high concentration to areas of low concentration. This is a form of passive transport and requires no energy.
• Active Transport: Requires the use of energy (ATP) to move molecules from a low concentration to a high concentration, which is against the flow of diffusion.
• Osmosis: The specific diffusion of water into or out of a cell.
  • If water diffuses into the cell, the cell swells and may burst.
  • If a cell loses water (for instance, when placed in salt water), it will shrivel up.
• Regulation: Coordination and control of other life functions.
  • Stimulus: A change in the environment to which an organism responds.
  • Neuron: A specialized nerve cell.
  • Impulse: The electrical signal carried by nerves.
  • Neurotransmitters: Chemicals that assist in carrying impulses between neurons.
  • Hormone: A chemical signal secreted by glands (e.g., insulin, adrenaline, testosterone, and estrogen).
  • Receptor Molecules: Proteins located on the surface of the cell membrane that receive signals from the nervous and endocrine systems. These are essential for cellular communication.

Biological Chemistry and Organic Molecules

• Common Elements: The most common elements in living things are Carbon, Hydrogen, Oxygen, and Nitrogen ($CHON$).
• Organic Compounds: Molecules that contain both Carbon AND Hydrogen (e.g., glucose, $C_6H_{12}O_6$). Organic molecules are generally larger than inorganic molecules (e.g., $H_2O$, $CO_2$, and $NO_3$ which are inorganic).
• Carbohydrates: Sugars and starches made from simple sugars like glucose. They are the primary supply of energy.
• Lipids: Fats, oils, and waxes used to store energy. They are composed of fatty acids and glycerol.
• Proteins: Made from amino acids. They form hormones and many body/cell structures. They are considered the most important organic molecules for body function.
  • Protein shape determines its specific function and how it fits with other molecules.
  • Four specific jobs of proteins: making enzymes, making receptor molecules on cell membranes, making antibodies, and making hormones.
• Enzymes: Biological catalysts that affect the rates of chemical reactions.
  • Lock and Key Model: One type of enzyme fits one specific type of molecule. If the shape changes, the enzyme fails to function.
  • Temperature Sensitivity: Very high temperatures cause proteins and enzymes to denature (lose their shape), which is why high fevers are dangerous.
• pH Scale: Measures the strength of acids and bases.
  • Low pH ($0$ to $6.9$) is an acid.
  • High pH ($7.1$ to $14$) is a base.
  • A pH of $7$ is neutral (e.g., water).

Cell Theory and Organelles

• Cells are the basic unit of life. All living things (excluding viruses) are composed of cells.
• Cell Theory states that all living things are made of cells.
• Essential Organelles: Cell membrane, cell wall, nucleus, chloroplast, cytoplasm, ribosome, vacuole, and mitochondria.
• Cell Membrane: Composed of lipids and proteins. It exhibits selective permeability, allowing small molecules like water and oxygen to pass while large molecules like starch or protein require active transport.
• Cell Membrane vs. Cell Wall: All cells have a cell membrane. Some cells (plants, fungi, bacteria, protists) also have a cell wall for protection. The animal kingdom is the only kingdom that completely lacks cell walls.

Classification and Taxonomy

• Classification is based primarily on evolutionary history. Organisms with common ancestors are grouped together.
• Kingdoms: Large groups of related organisms (Fungi, Bacteria, Protists, Animals, Plants).
• Species: A group of organisms able to successfully reproduce among its members.
• Scientific Name: Comprised of an organism's Genus and species names.

Organization and Specialization in the Human Body

• Hierarchy of Organization: Cells are organized into tissues, tissues into organs (e.g., heart, lungs, kidney), and organs into organ systems (e.g., digestive, nervous).
• Tissues: Groups of cells specialized to perform specific jobs (e.g., muscle tissue, nerve tissue).
• Differentiation/Specialization: Occurs because only specific genes in the nucleus are "turned on" or active. While almost every cell contains a complete set of genes ($46$ chromosomes in humans), only those needed for a cell’s specific job are active. For example, a red blood cell has the genes to make nerve cells, but those genes are turned off.

Human Body Systems

• Digestive System: A one-way passage (mouth, stomach, intestines) that breaks down food mechanically and chemically so it can enter tissues. Peristalsis describes the muscular contractions that move food. Undigested food is eliminated as solid waste (this is not technically excretion).
• Circulatory System: Moves materials (water, nutrients, hormones, wastes) throughout the body.
  • Red Blood Cells: Carry oxygen.
  • White Blood Cells: Fight disease.
  • Plasma: The fluid portion of blood that transports everything except oxygen.
  • Platelets: Facilitate blood clotting.
• Immune System: Protects the body against pathogens (viruses, bacteria, parasites).
  • Antigens: Substances that trigger an immune response.
  • Antibodies: Proteins made by white blood cells to attack specific antigens based on shape.
  • Vaccines: Injections of dead or weakened pathogens to trigger antibody production; they prevent disease but do not cure it.
  • Antibiotics: Drugs used to stop bacterial infections; they are ineffective against viruses.
  • Organ Rejection: The immune system may attack transplanted organs because they are recognized as foreign antigens.
  • Blood Types: Type O is the universal donor; type AB is the universal acceptor.
• Respiratory System: Breathing (physical respiration) provides oxygen for chemical respiration.
  • Diaphragm: The muscle that facilitates breathing.
  • Breathing Rate: Controlled by the buildup of $CO_2$ in the blood, not by the need for oxygen.
  • Alveoli: Microscopic sacs surrounded by capillaries where gas exchange occurs ($O_2$ enters blood, $CO_2$ leaves).
• Excretory System: Removes metabolic wastes ($CO_2$, salt, water, and urea).
  • Lungs: Excrete $CO_2$ and water.
  • Skin: Excretes sweat.
  • Kidneys: Filter waste from blood and reabsorb nutrients.
  • Liver: Filters toxins and dead red blood cells from the blood.
• Skeletal/Muscle System: Muscles only pull and must work in pairs. Bones, bone marrow, cartilage, tendons, and ligaments perform various support and mobility functions.
• Nervous System: Works with the endocrine system to regulate the body.
  • Brain Parts: Cerebrum, cerebellum, and medulla.
  • Spinal Cord: Controls reflexes and transmits impulses between the nerves and brain.
• Endocrine System: Regulates the body using hormones. It is slower than the nervous system but has longer-lasting effects.
  • Pancreas: Produces insulin and glucagon to control blood sugar levels.
  • Adrenal Glands: Produce adrenaline during stress.
  • Sex Hormones: Testosterone (male), Estrogen and Progesterone (female).
  • Negative Feedback: The mechanism that controls hormone levels to maintain balance.

Disease, Disorders, and Pathogens

• Diseases disrupt homeostasis. Common examples include heart attack, stroke, cancer, Down’s syndrome, diabetes, cystic fibrosis, sickle cell anemia, AIDS, and asthma.
• Pathogen Categories:
  • Viruses: AIDS, cold, flu, chicken pox.
  • Bacteria: Strep throat, food poisoning, syphilis.
  • Fungus: Athlete’s foot, ringworm.
  • Parasites: Tapeworm, leeches.
  • Genetic Disorders: Down’s Syndrome, sickle cell, cystic fibrosis.
  • Environmental Toxins: Lead poisoning, radiation.
  • Poor Nutrition: Scurvy, goiter.
  • Organ Malfunction: Heart attack, diabetes.
  • High-Risk Behavior: Smoking, drug use, sun exposure.

Reproduction and Development

• Asexual Reproduction: Faster and easier but provides no genetic variety; offspring are identical to the parent.
• Sexual Reproduction: Provides genetic variety but requires more time, effort, and risk.
• Mitosis: Used for asexual reproduction, growth, and healing. One division results in two identical diploid ($2n$) cells with the same chromosome number as the parent.
• Meiosis: Used for sexual reproduction to make gametes (sex cells). One cell divides twice to create four different haploid ($n$) cells, each with half the parent's chromosomes.
• Gamete Production: In humans, meiosis produces four sperm cells or one egg and three polar bodies.
• Fertilization: Occurs in the fallopian tube. The resulting fertilized egg is a zygote ($2n$).
• Development: The fetus develops in the uterus. Cleavage involves cell division without increasing in size. Differentiation follows, where cells begin to form specialized tissues. The embryo is highly vulnerable to alcohol and drugs during early organ developent.

Genetics and Heredity

• Chromosomes: Humans have $46$ chromosomes, or $23$ homologous pairs.
• Alleles: Different forms of a gene for the same trait. We have two alleles for each gene (one from each parent).
• Gene Expression: While genes determine traits, the environment can influence how those genes are expressed.
• DNA Structure: Made of four bases: Adenine ($A$), Thymine ($T$), Cytosine ($C$), and Guanine ($G$).
  • Base Pairing: $A-T$ and $C-G$.
  • A three-letter codon represents one specific amino acid.
• RNA: Uses Uracil ($U$) instead of Thymine ($A-U$). RNA carries the genetic code to ribosomes for protein synthesis.
• Mutations: Changes in DNA. They are only passed to offspring if they occur in reproductive cells (sperm or egg).
• Selective Breeding: Producing organisms with desired traits (e.g., disease resistance, larger fruit).
• Genetic Engineering (Gene Splicing): Inserting genes from one organism into another using enzymes. Bacteria are often used because they lack a nucleus and reproduce quickly.
  • Key Example: Human insulin genes inserted into bacteria to produce insulin for diabetics.
• Technology: Karyotyping and DNA fingerprinting help diagnose and treat genetic diseases, though cures are not yet available.

Evolution and Natural Selection

• Basic Theory: Modern species evolved from earlier, different species and share common ancestors.
• Natural Selection: Proposed by Charles Darwin as the mechanism for evolution involving overproduction of offspring, competition for limited resources, and survival of the "fit."
• Evolutionary Fitness: Refers to an organism's ability to adapt, survive, and reproduce in its environment. It is not necessarily equivalent to physical strength.
• Variation: For evolution to occur, variations must exist in a species BEFORE environmental changes. Variation results primarily from sexual reproduction and mutation.
• Theories of Change:
  • Gradualism: Evolution occurs slowly and steadily.
  • Punctuated Equilibrium: Evolution happens in quick spurts of change.
• Speciation: Usually requires geographic isolation, leading eventually to reproductive isolation.
• Evidence: Fossils (geology), radioactive dating, genetics, biochemistry, anatomy, and embryology.

Ecology and Human Impact

• Ecosystem Energy: Energy enters via the sun and is made usable by producers (autotrophs). As energy is passed up the food chain, most is lost for metabolic needs. High-level consumers have the least energy available and smaller populations.
• Carrying Capacity: The maximum size of a population that an ecosystem can support based on limiting factors (food, water, light, etc.).
• Niche: The role an organism plays in its environment. Competition usually limits a niche to one species at a time; species may divide resources (e.g., birds eating by day, bats by night).
• Succession: The process of ecological change over time.
• Biodiversity: The variety of life. High biodiversity increases ecosystem stability and provides resources for food and medicine.
• Human Negative Impacts: Resulting from population growth; includes pollution, deforestation, overhunting, and introduction of foreign species.
• Conservation Efforts: Recycling, using clean energy (solar), protecting habitats, biological controls (instead of pesticides), and planting trees.
• Ecological Terms:
  • Producer, Consumer, Omnivore, Herbivore, Carnivore, Predator, Parasite, Habitat, Niche, Population, Community, Ecosystem, Biosphere, Renewable Resource.
• Specific Ecological Problems: Acid rain, loss of habitat (deforestation), loss of diversity, global warming, ozone layer depletion, introduced species, and industrialization.