Honors & Lvl 1 Biology 2025 Final Exam Review Checklist Notes
Basics, Nature of Science, Definition of Science, and Life
Define biology: Biology is the scientific study of life. It encompasses the structure, function, growth, origin, evolution, and distribution of living organisms.
Compare and contrast a scientific theory and a hypothesis:
Hypothesis: A hypothesis is a testable explanation for a specific phenomenon or a narrow set of observations. It is a tentative statement that can be supported or refuted through experimentation or observation.
Scientific Theory: A scientific theory is a well-substantiated explanation of some aspect of the natural world that can incorporate facts, laws, inferences, and tested hypotheses. It is broader in scope than a hypothesis and is supported by a large body of evidence. Theories are not mere guesses; they are robust explanations that have withstood repeated testing.
Homeostasis, Osmosis, Cell Transport
Compare osmosis & diffusion:
Diffusion: Diffusion is the movement of molecules from an area of higher concentration to an area of lower concentration. This movement occurs due to the random motion of molecules and does not require energy.
Osmosis: Osmosis is a specific type of diffusion involving the movement of water molecules across a semi-permeable membrane from an area of higher water concentration (lower solute concentration) to an area of lower water concentration (higher solute concentration). Water moves to equalize solute concentrations on both sides of the membrane.
Understand how concentration gradients help predict flow of water in or out of a cell:
A concentration gradient is the difference in the concentration of a substance across a space. Water moves from areas of high water concentration (low solute concentration) to areas of low water concentration (high solute concentration) to reduce the concentration gradient. If the solute concentration is higher outside the cell, water will flow out, and vice versa.When can a cell use passive transport to move solutes? When must it use active transport?
Passive Transport: A cell can use passive transport when moving solutes down their concentration gradient (from high to low concentration). Passive transport does not require energy input from the cell. Examples include simple diffusion, facilitated diffusion, and osmosis.
Active Transport: A cell must use active transport when moving solutes against their concentration gradient (from low to high concentration). Active transport requires energy, usually in the form of ATP, to pump solutes across the membrane.
Solute vs. solvent. Which is water?
Solute: A solute is a substance that is dissolved in a solvent.
Solvent: A solvent is a substance that dissolves a solute. In biological systems, water is the primary solvent.
Understand drawings of solutes and make predictions. Can you explain why the dots spread out? Can you identify a high concentration? Solutes? What if there was a semi-permeable membrane?
Dots spread out due to the natural tendency of molecules to move from areas of high concentration to areas of low concentration (diffusion), driven by the kinetic energy of the molecules.
High concentration is identified by a large number of dots (solute molecules) in a given area.
Solutes are the dissolved particles represented by the dots.
With a semi-permeable membrane, only certain molecules (typically water) can pass through. If there's a concentration difference of solutes, water will move via osmosis to equalize the concentration, if possible.
Cell division and Chromosomes
Define mitosis. What is the purpose of mitosis? How do the daughter cells compare to the parent cells in this process?
Mitosis: Mitosis is a type of cell division that results in two daughter cells each having the same number and kind of chromosomes as the parent nucleus, typical of ordinary tissue growth.
Purpose of Mitosis: The purpose of mitosis is for asexual reproduction (in some organisms), growth, and repair of tissues. It ensures that each new cell receives a complete and identical set of chromosomes.
Daughter Cells: Daughter cells are genetically identical to the parent cell. They have the same number of chromosomes and the same genetic information.
Define meiosis. What is the purpose of meiosis? How do the daughter cells compare to the parent cells in this process?
Meiosis: Meiosis is a type of cell division that results in four daughter cells each with half the number of chromosomes of the parent cell, as in the production of gametes and plant spores.
Purpose of Meiosis: The purpose of meiosis is to produce gametes (sperm and egg cells) for sexual reproduction. It reduces the chromosome number by half to prevent doubling upon fertilization.
Daughter Cells: Daughter cells are genetically different from the parent cell and from each other. They have half the number of chromosomes as the parent cell (haploid).
Define crossing over. Why is it important? Can you draw a picture?
Crossing Over: Crossing over is the exchange of genetic material between homologous chromosomes during prophase I of meiosis. It results in new combinations of genes on each chromosome.
Importance: Crossing over increases genetic variation within a population by creating new combinations of genes.
In what phase of cell division is DNA replicated? Why does DNA need to be replicated?
DNA Replication: DNA is replicated during the S phase (synthesis phase) of interphase, which precedes both mitosis and meiosis.
Why DNA needs to be replicated: DNA needs to be replicated so that each daughter cell receives a complete and identical copy of the genetic material. This ensures that the new cells can function properly.
Compare and contrast diploid vs. haploid
Diploid: Diploid refers to cells that contain two sets of chromosomes (2n), one from each parent. Somatic cells (body cells) are typically diploid.
Haploid: Haploid refers to cells that contain one set of chromosomes (n). Gametes (sperm and egg cells) are haploid.
How many chromosomes do humans have? How many do human sperm and eggs have?
Humans have 46 chromosomes in their diploid cells (2n = 46).
Human sperm and eggs have 23 chromosomes (haploid, n = 23).
What is fertilization?
Fertilization: Fertilization is the process by which a haploid sperm cell fuses with a haploid egg cell to form a diploid zygote.
What does fertilization have to do with the terms diploid and haploid?
During fertilization, two haploid (n) gametes (sperm and egg) fuse to form a diploid (2n) zygote. This restores the diploid number of chromosomes in the offspring, maintaining the correct chromosome number from one generation to the next. The zygote then divides by mitosis to develop into a new organism.