NYS Living Environment Regents Comprehensive Notes

UNIT ONE: Science and the Living Environment

A. Terms

  • Observation: What is seen or measured.
  • Inference: A conclusion based on observation or evidence.
  • Hypothesis: A prediction based on available evidence. A good hypothesis states both cause and effect.
    • A correct hypothesis can be tested and falsified (proven incorrect) using an experiment.
    • The easiest way to write a correct hypothesis is as an “if-then” statement. (example: If I give patients this pill, then they will not get sick.)
  • Theory: An explanation of natural events that is supported by strong evidence.
    • Theories tie together many scientific facts, hypotheses and laws.
    • Misconception: “Theories are things that are opinions, or are not proven.” This is an incorrect use of the word “theory” in a scientific context. A scientific theory is not a simple guess or conjecture, and is strongly supported by evidence.

B. Controlled Experiment

  • Compares the results of an experiment between two (or more) groups.
  • Experimental group: Group being tested or receiving treatment.
  • Control group: “Normal” group. Should be identical to experimental group in every way except one: it does not receive the new treatment.
  • Placebo: A sugar pill or other “fake” treatment given to the control group.
  • Independent Variable: Variable that is being tested (e.g., new drug, new fertilizer).
    • The “If” part of an “If-then” hypothesis.
    • The independent variable is always plotted on the X axis.
  • Dependent Variable: Variable that is measured at the end of an experiment; the results.
    • The “then” part of an “If-then” hypothesis.
    • The dependent variable is always plotted on the Y axis.

C. Graphs and Data Tables

  • Data tables are used to organize data which will be plotted in a graph.
    • First column in the table is for the independent variable.
    • Second column is for the dependent variable.
    • Each column should be titled, and include units of measurement.
    • Data in the table must be arranged in ascending or descending order.
  • Both the x and y axis of the graph must be labeled or titled, typically the same as in the data table, with units.
  • The independent variable is always plotted on the x-axis.
  • The dependent variable is always plotted on the y-axis.
  • The x and y axis must be numbered with a uniform increment (e.g., 1, 2, 5, 10, etc.).
  • Your numerical scales should take up most of the axes; avoid cramping data into a small corner.
  • You do not need to start numbering your axis with 0.
  • To date, all graphs drawn on the LE Regents have been line graphs. Bar graphs are not allowed for this part of the test.
  • All points plotted on your graph must be surrounded by a circle (or square/triangle depending on directions).

D. Characteristics of a good experiment

  • Can be repeated the same way and yield the same results.
  • Have large sample size/many test subjects.
  • Are performed for longer periods of time.
  • Test only one independent variable; all other tested group characteristics are kept the same.
  • Are peer reviewed – examined by several scientists to determine accuracy.
  • Must test the hypothesis and show whether it is wrong or right.
  • Are objective – the experiment and conclusion are fair and unbiased; fact and opinion are not mixed.
  • Follow established ethical and legal standards.

UNIT TWO: Characteristics of Living Things

A. Chemistry

  • The most common elements in living things (in order): Carbon, Hydrogen, Oxygen and Nitrogen (CHON).
  • Organic Compounds:
    • Have Carbon AND Hydrogen. Example: C6H{12}O6 is organic; H2O is not.
    • Organic molecules are larger than inorganic molecules.
  • Carbohydrates: sugars and starches.
    • All carbohydrates are made from simple sugars (like glucose) and they supply energy.
    • Enzymes may break down starches and complex sugars into simple sugars.
  • Lipids: store energy and include fats, oils and waxes.
  • Proteins: made from amino acids.
    • Proteins build and run an organism; they are the most important among the three major organic molecules for body function.
    • The SHAPE of proteins and how they fit with other molecules determines what proteins can do.
    • Four specific jobs of proteins:
      1) Enzymes
      2) Receptor molecules on the cell membrane (receive chemical messages like hormones)
      3) Antibodies (proteins which fight infection)
      4) Hormones (chemical messengers)
    • A starch (A) can be broken down by an enzyme (B) into two simple sugars (C, D) – a demonstration of the lock-and-key model.

B. Homeostasis, metabolism, and life processes

  • All living things must maintain homeostasis: a balanced state.
  • Dynamic equilibrium means the body stays balanced by taking action when balance is disturbed (e.g., sweating when hot).
  • Basic life functions to maintain homeostasis: transport, nutrition, excretion, respiration, growth, synthesis, regulation, and synthesis. (Know these terms!)
  • Metabolism: the sum of all life processes.
  • Failure to maintain homeostasis results in disease or death.

C. Transport

  • Diffusion: movement of molecules from high to low concentration; requires no energy (passive transport).
  • Active Transport: requires energy, moving molecules from low concentration to high concentration (against diffusion).
  • Osmosis: diffusion of water into or out of the cell; water movement can cause swelling or shrinking.
  • Lock-and-key model note: in this context, an enzyme (C) can control a synthesis reaction.

D. Nutrition

  • Autotrophs make their own food; heterotrophs eat other organisms.
  • Photosynthesis is carried out by plants, algae, and blue-green bacteria (autotrophs).
    • It takes radiant energy from the sun and stores it in the bonds of sugar molecules.
    • Occurs mostly in the chloroplasts of plant cells.
    • Plants have stomates (holes) in leaves to exchange gases; guard cells regulate stomata opening to prevent dehydration.
    • Xylem and phloem transport water and food in plants.
    • Common mistakes:
    • “Photosynthesis gives us energy.” Photosynthesis stores energy in glucose; respiration releases energy for use.
    • “Guard cells protect plants from diseases.” Guard cells primarily prevent water loss.

E. Respiration

  • Respiration: process that releases energy from sugar by producing ATP (the energy currency).
  • Aerobic respiration requires oxygen and yields more ATP per sugar than anaerobic respiration.
  • When energy is produced anaerobically, lactic acid is produced, which can damage muscles (the “burn”).
  • Photosynthesis and aerobic respiration are opposite reactions and cycle oxygen, carbon, hydrogen, and water through the environment.
  • Common mistakes:
    • “Plants use photosynthesis, not respiration.” All organisms respire.
    • “Respiration is breathing.” Breathing moves air; respiration is cellular energy production.
    • “Oxygen is used to breathe.” Breathing brings in oxygen; oxygen is used in respiration to produce ATP.
    • “All living things need oxygen to breathe.” Anaerobic organisms do not need oxygen.

F. Regulation

  • Regulation/coordination of life functions through nervous and endocrine systems.
  • A stimulus is a change in the environment that elicits a response.
  • A neuron is a nerve cell.
  • An impulse is the electrical signal carried by nerves.
  • Neurotransmitters help carry impulses.
  • A hormone is a chemical signal secreted by glands (e.g., insulin, adrenaline, testosterone, estrogen).
  • Receptor molecules on the cell membrane receive signals from nervous and endocrine systems; their function depends on shape (Lock-and-key model).
  • Receptor molecules can accept signals only if the signals have the correct shape.
  • Example of neural–muscular signaling: two neurons carry an impulse to a muscle cell.

G. Cells

  • Cells are the basic unit of life; all living things (except viruses) are made of cells.
  • Cell theory:
    • All living things are made of one or more cells.
    • Cells carry out all life functions.
    • All cells come from other cells.
  • Organelles and their functions to know: cell membrane, cell wall, nucleus, chloroplast, cytoplasm, ribosome, vacuole, mitochondria.
  • Plant vs. animal cells:
    • Plant cells have cell walls and chloroplasts; animal cells do not.
    • Animal cells have centrioles; plant cells do not.
    • Animal cells typically have many small vacuoles; plant cells usually have fewer, larger vacuoles.
  • The cell membrane is made of lipids and proteins and shows selective permeability.
    • Small molecules (O2, H2O, CO2, sugars) pass by diffusion.
    • Large molecules (proteins, starches) require transport proteins.
    • If energy is needed to move a molecule, it’s stored energy and the process is active transport.
  • Basic types of proteins in the cell membrane:
    1) Receptor proteins
    2) Transport proteins
    3) Antigens
  • Note on common mistakes (in this section): the statement that plant cells have cell walls and animal cells have membranes; in fact, ALL cells have a cell membrane; cell walls are an additional protective feature in some organisms.

UNIT THREE: Homeostasis and the Human Body

A. Organization

  • Cells are specialized into tissues.
    • Tissues are groups of cells specialized to perform particular jobs (e.g., muscle tissue, nerve tissue).
    • Differentiation is the process by which stem cells become specialized tissues.
    • Almost every cell has a complete set of genes, but only the needed genes for the cell’s job are turned on.
    • Stem cells are undifferentiated cells.
  • Tissues form organs; organs form organ systems (e.g., digestive, nervous, endocrine).

B. The Nervous System

  • Regulates the body with electrochemical impulses.
  • The spinal cord controls reflexes and relays impulses between brain and body.

C. Endocrine System

  • Uses hormones to regulate the body; slower than nervous system but longer lasting effects.
  • The pancreas makes insulin and glucagon, which control blood sugar. Common mistake: insulin lowers blood pressure. Insulin and glucagon control blood sugar, not blood pressure.
  • Adrenal glands make adrenaline under stress.
  • Sex hormones: Testosterone (males); Estrogen and Progesterone (females) produced in gonads (testes/ovaries).
  • Hormone levels are controlled by feedback mechanisms involving the brain and some endocrine glands.

D. Transport/Circulatory System

  • Moves materials (water, nutrients, hormones, wastes) through the body to cells.
  • The heart acts as the pump of the circulatory system.
  • Red blood cells carry oxygen; white blood cells fight disease.
  • Plasma: fluid of the blood; transports all components except oxygen.
  • Platelets clot blood.
  • Common mistakes:
    • The heart controls the body; in reality, brain, nerves, and endocrine glands regulate the body. The heart is a pump.
    • The heart pumps oxygen to the brain; actually the heart pumps blood carrying oxygen to all tissues.
    • Oxygen diffuses into and out of the heart; diffusion occurs in capillaries, not inside the heart.

E. Respiratory System

  • Breathing provides oxygen for cellular respiration and excretes CO2.
  • The diaphragm enables breathing.
  • You breathe faster when CO2 builds up in the blood, not because you need more oxygen.
  • Alveoli are tiny sacs where oxygen enters the blood and CO2 leaves; alveoli are surrounded by capillaries.

F. Immune System

  • Protects the body against pathogens (viruses, bacteria, parasites).
  • White blood cells (WBCs) are the main components; roles include:
    1) Identify pathogens
    2) Tag pathogens for destruction by other WBCs
    3) Consume/digest pathogens
    4) Destroy pathogens using chemicals
    5) Produce antibodies
  • Antigens are protein tags on cells or viruses; immune response targets cells/viruses with different antigens.
  • Antibodies are proteins made by WBCs to attack antigens; each antibody targets a specific antigen (shape-specific).
    • Explain why organ transplants are rejected by immune response.
    • Blood type O is the universal donor; AB is the universal recipient.
  • Vaccines: injection of dead or weakened pathogen; stimulate antibody production; prevent disease (not a cure).
  • Antibiotics: drugs that stop bacterial infections; do not work against viruses; unlike vaccines, they can cure bacterial infections.

G. Excretory System

  • Removes metabolic waste: salt, water, urea, CO2.
  • Lungs excrete CO2 and water; skin excretes sweat.
  • Kidneys filter wastes from blood and reabsorb nutrients.
  • Liver filters toxins and dead red blood cells from blood.

H. Digestive System

  • Breaks down food so nutrients can enter body tissues/cells.
  • Digestive system is a one-way passage: mouth → stomach → intestines.
  • Movement through digestive system by peristalsis (muscular contractions).
  • Food is broken down mechanically and chemically.
  • Undigested food is eliminated as feces.
  • Common mistakes:
    • Feces are excreted from cells; they are not.
    • The digestive system excretes waste; excretion and elimination are different.
    • The digestive system gives you energy; it provides nutrients, energy comes from cellular respiration.

I. Interaction Between Systems

  • Explain how systems work together to maintain homeostasis:
    • Nutrients from digestion are transported to cells by the circulatory system.
    • Wastes from respiration are removed by the excretory system.
    • Nervous and endocrine systems coordinate body activities.
    • Immune system protects the nervous system from disease.
    • Digestive system provides nutrients to the endocrine system.

J. Diseases and Disorders

  • Be familiar with causes and how they disrupt homeostasis; focus on understanding mechanisms rather than memorizing every disease.
  • Key diseases to know:
    • AIDS: caused by HIV; weakens immune system; spread via bodily fluids; not curable; prevention methods listed.
    • Cancer: uncontrolled cell division; tumors; resources diverted from healthy tissue; causes include radiation, chemicals, viruses; treatments include surgery, radiation, chemotherapy.
    • Diabetes: disorder of blood sugar control; insulin injections from engineered bacteria as a treatment in some cases.
    • Allergies: immune system overreacts to harmless substances (e.g., pollen); Asthma is a form of allergy.

UNIT FOUR: Reproduction

A. Asexual reproduction

  • Advantages: faster, easier.
  • Disadvantage: no genetic variety; offspring identical to parent.

B. Sexual reproduction

  • Advantage: genetic variety due to recombination of genes.
  • Disadvantage: more time, effort, and risk.

C. Mitosis

  • Used in all forms of asexual reproduction.
  • Chromosome number and types in daughter cells are the same as in the parent.
  • Growth and healing in larger organisms; reproduction in simpler organisms.
  • One division of a cell yields two identical, diploid (2n) cells.

D. Meiosis

  • Produces gametes for sexual reproduction.
  • One cell divides twice to form four DIFFERENT haploid (1n) cells.
    • Separates homologous chromosomes so offspring get one chromosome from each parent.
    • Each gamete gets only one half of the chromosomes of the parent.

E. Male Reproductive System

  • Testes produce and store sperm.
  • Testosterone is the male sex hormone produced in the testes.

F. Female Reproductive System

  • Ovaries produce eggs.
  • The menstrual cycle averages 28 days; key events:
    • Ovulation: release of an egg (typically one per cycle).
    • Menstruation: shedding of the uterine lining.
    • Pregnancy pauses the menstrual cycle.
  • Fallopian tube transports the egg to the uterus.
  • The uterus (womb) is where the baby develops.
  • The vagina (birth canal) is the passage for birth.
  • Mitosis vs Meiosis: note that chromosome number stays the same in mitosis, but is halved in meiosis.

G. Fertilization

  • Occurs in the fallopian tube (oviduct).
  • A fertilized egg is a zygote.
  • Fertilization restores the complete set of chromosomes; the zygote is diploid (2n).

H. Development

  • A zygote develops into an embryo and then a fetus.
  • The placenta transfers nutrients and oxygen from mother to fetus by diffusion; maternal and fetal blood do not mix.
  • The fetus is attached to the placenta by the umbilical cord; wastes diffuse from fetus to mother via placenta.
  • The fetus does not eat solid food; waste management differs.

I. Embryo and fetus development in the uterus

  • Early development includes cleavage (cell division without growth) followed by differentiation into various tissues.
  • The embryo is vulnerable to alcohol and drugs during organ development.
  • Common mistake: “The fetus develops in the placenta (or vagina, stomach, etc).” The correct location is the uterus.

J. Early vs Late Development (visual references)

  • Overview of development stages and postnatal development visuals.

UNIT FIVE: Genetics

A. Humans have 46 chromosomes, or 23 homologous pairs.

  • Common mistake: confusing numbers; memorize correctly. (
    • 46 chromosomes total; 23 pairs; 22 autosomal pairs + 1 pair of sex chromosomes)
      )

B. Chromosome pairs carry alleles for the same trait; we have two alleles for each gene, one on each member of the homologous pair.

C. Sex chromosomes

  • Females: XX; Males: XY.
  • The Y chromosome is smaller; males may carry one copy of some traits (sex-linked traits).

D. Environment can influence gene expression.

E. Each chromosome has hundreds to thousands of genes.

F. Each gene codes for a particular protein.

  • Common mistake: “Genes/DNA are made from protein.” Genes are made of nucleic acids; they code for proteins.

G. DNA structure

  • Bases: A, T, C, G.
  • A three-letter codon represents a specific amino acid; amino acids are assembled into proteins.

H. Base pairing

  • DNA: A-T, C-G; RNA: A-U, C-G.

I. RNA carries the genetic code to ribosomes, where ribosomes synthesize proteins.

J. Mutations

  • Changes to DNA are called mutations; can be passed on only if they occur in reproductive cells.
  • Mutagens include radiation, chemicals, and viruses.
  • Mutations may alter protein structure and function.

K. All cells contain the same genes; only some genes are turned on.

L. Genetic technology examples

  1. Selective breeding (artificial selection) to produce desired traits (disease resistance, larger fruit, more meat/milk, colors).
  2. Genetic engineering (gene splicing) inserts genes from one organism into another; enzymes cut/copy DNA; bacteria used due to lack of nucleus and rapid reproduction to produce medicines (insulin).
    • Important example: Inserting a human insulin gene into bacteria so bacteria produce human insulin, which is safer for diabetics.
  3. New technologies (karyotyping, DNA fingerprinting) aid diagnosis and treatment of genetic diseases.
  • Note: Cannot yet cure all genetic diseases.

M. Ethical considerations in genetic research

  • Genetic research raises many ethical questions that science alone cannot answer.
  • A karyotype shows all 23 pairs of human chromosomes; last pair indicates sex (male/female).

UNIT SIX: Evolution

A. Evolutionary relationships

  • Modern species evolved from earlier species and share a common ancestor.

B. Natural selection (Darwin)

  • Basic steps:
    1) Overproduction of offspring; offspring have variation.
    2) Competition for limited resources; variations affect success.
    3) Survival and reproduction, or death with no reproduction.
    4) Beneficial variations become more common; harmful variations diminish.

C. Fitness

  • “Fit” organisms are those better adapted to survive and reproduce in their environment.
  • Evolutionary fitness is not equivalent to physical strength; it’s about reproductive success in a given environment.
  • Common misconception: “Stronger organisms are more fit.” Not necessarily; fitness is environmental-adaptation dependent.

D. Evolution and the environment

  • Evolution is driven by environmental changes and/or changes in living populations.
  • Species that cannot adapt become extinct.
  • Individual organisms do not become extinct; species do.

E. Pre-adaptation and variation

  • Variations must exist prior to environmental change (pre-adaptation).
  • Variation arises largely from sexual reproduction and mutation.
  • Species with more variation adapt better to environmental changes.

F. Rates of evolution

  • Gradualism: slow, gradual changes.
  • Punctuated equilibrium: evolutionary changes occur in rapid bursts.

G. Speciation

  • Geographic isolation often leads to reproductive isolation and the creation of new species.

H. Evidence for evolution

  • Geology (fossil record, radioactive dating); genetics; biochemistry; anatomy; embryology (and more).

I. Classification

  • Organisms are classified based on evolutionary relationships.
  • Kingdoms: fungi, bacteria, protists, animals, plants.
  • A species is able to reproduce successfully among its members.
  • Cladograms (branching trees) illustrate evolutionary relationships.
  • Gradualism (Model I) vs Punctuated Equilibrium (Model II).

J. Homologous structures and transitional forms

  • Homologous structures show related structures adapted for different functions.
  • Transitional forms in fossils illustrate evolution from common ancestors to modern species.
  • Evolutionary trees show relationships between living and extinct species; deeper fossils are typically older.

UNIT SEVEN: Ecology

A. Core concept

  • This is the most important part of the test: understand interactions of organisms with their environment (food webs, nutrient cycles).

B. Energy flow

  • Energy comes from the sun and is made usable by producers (plants and other autotrophs).
  • Energy is transferred through food chains/webs; much is lost at each transfer; energy pyramids illustrate this loss.
  • High-level consumers have less energy available and typically smaller populations due to energy loss at each trophic step.

C. Carrying capacity and environment

  • Environmental factors (air, water, light, temperature, pH, food, predators) determine who can live in an ecosystem and how large populations can be.
  • Carrying capacity: maximum population size that an environment can sustain indefinitely.

D. Ecological roles and competition

  • Niche: role or position of a species within its ecosystem.
  • Competition between species can lead to one species occupying a niche at a time; often resources are divided to reduce competition (resource partitioning).

E. Ecological processes

  • Know basics of ecological succession (sequence of community change over time leading to a stable climax).
  • Understand a complex food web and energy flow via an energy pyramid.

F. Human impact and biodiversity

  • Negative environmental effects largely due to increasing human population and activities (development, pollution, hunting, etc.).
  • Biodiversity refers to the variety of life on Earth; loss of biodiversity reduces ecosystem stability and resilience and may remove valuable human resources (food, medicines).

G. Human actions to reduce damage and restore ecosystems

  • Recycling and conservation of resources.
  • Use cleaner energy sources (e.g., solar instead of fossil fuels).
  • Protect habitats and endangered species.
  • Use biocontrols instead of pesticides/herbicides.
  • Plant native species; restore habitats; rotate crops; use cover crops to reduce soil loss.
  • Legislation to control pollution, land management, hunting, fishing, etc.

H. Common ecological problems and causes

  • acid rain, deforestation (loss of habitat), loss of biodiversity, global warming, ozone depletion, introduced species, industrialization.
  • For each problem, identify cause, negative effects, and human mitigation strategies.

I. Ecological concepts recap

  • Ecological succession – series of steps where new communities replace older ones until a stable climax is established.
  • A complex food web shows who is consuming whom.
  • An energy pyramid shows energy transfer and losses at each trophic level.

APPENDIX: State Labs

A. Making Connections (Clothespin Lab)

  • Part A1: Measured how exercise affects pulse rate; learning: exercise increases pulse rate.
  • Part A2: Clothespin squeezing test:
    • If you squeeze more in the second round, it may be because finger muscles warmed up from increased circulation.
    • If you squeeze less, it may be due to fatigue.
  • Part B: Designed an experiment to test how exercise affects squeezing a clothespin; learning: design an experiment (see pages 3-5).

B. Relationships and Biodiversity (Botana curus lab)

  • What you did: Compared 4 plant species using structural and molecular traits.
  • Learnings:
    • Related species share similar traits.
    • Different techniques (gel electrophoresis, paper chromatography) determine relationships.
    • Endangered species should be protected because they may offer human benefits.

C. Beaks of Finches

  • What you did: Observed finch species competition for food.
  • Learnings: Different environmental conditions (food availability) favored different finch species; some survived and reproduced, others did not.

D. Gel Electrophoresis

  • Used to show how species are related. DNA fragments cut by restriction enzymes are separated by size in an electric field; similar banding patterns indicate related organisms.

E. Diffusion Through a Membrane

  • Part A: Model cell with dialysis tubing containing glucose and starch; outside solution contained starch indicator (iodine).
    • Inside of cell turned black (iodine diffused in); starch did not diffuse into the cell.
    • Glucose diffused out, as shown by Benedict’s test.
    • Learnings: Small molecules diffuse through a membrane; large molecules do not; indicators can identify presence of specific substances.
  • Part B: Observed onion cells under microscope with salt water and distilled water.
    • Salt water caused cells to shrivel (water diffused out).
    • Distilled water caused cells to swell again (water diffused in).
    • Learnings: Water diffusion follows osmosis; osmosis explains cell volume changes in different environments.