LE Regents Review

1. Scientific Method and Laboratory Skills

1. Experimental Design

   • Control Group: The group that does not receive the experimental treatment; used as a baseline for comparison.

   • Independent Variable: The factor that the scientist deliberately changes (plotted on the $x$-axis).

   • Dependent Variable: The factor that is measured or changes in response (plotted on the $y$-axis).

   • Hypothesis: A predictive statement (often "If… then…") that can be tested.

2. Lab Tools and Indicators

   • Total Magnification: Calculated as $\text{eyepiece (10x)} \times \text{objective (4x, 10x, or 40x)}$.

   • Starch Indicator (Iodine): Turns from amber to blue-black in the presence of starch.

   • Glucose Indicator (Benedict’s): Turns from blue to orange/red when heated in the presence of glucose.

2. The Cell and Homeostasis

1. Biological Organization

   • Organelles $\rightarrow$ Cells $\rightarrow$ Tissues $\rightarrow$ Organs $\rightarrow$ Organ Systems $\rightarrow$ Organism.

2. Key Organelles

   • Nucleus: Contains genetic information ($DNA$) and controls cell activities.

   • Ribosomes: The site of protein synthesis.

   • Mitochondria: The site of cellular respiration; produces $ATP$ (energy).

   • Chloroplasts: Found in plant cells; site of photosynthesis.

   • Cell Membrane: Regulates the movement of materials into and out of the cell to maintain homeostasis.

3. Cell Transport

   • Passive Transport (Diffusion): Movement of molecules from high to low concentration without energy.

   • Active Transport: Movement from low to high concentration requiring energy ($ATP$).

3. Energy and Metabolism

1. Photosynthesis

   • Performed by autotrophs (plants).

   • Equation: $6CO<em>{2} + 6H</em>{2}O + \text{light} \rightarrow C<em>{6}H</em>{12}O<em>{6} + 6O</em>{2}$.

2. Cellular Respiration

   • Performed by all organisms (autotrophs and heterotrophs) to extract energy from food.

   • Equation: $C<em>{6}H</em>{12}O<em>{6} + 6O</em>{2} \rightarrow 6CO<em>{2} + 6H</em>{2}O + 36 \text{ ATP}$.

4. Genetics and Biotechnology

1. DNA Structure

   • A double helix made of four nitrogenous bases: Adenine ($A$), Thymine ($T$), Guanine ($G$), and Cytosine ($C$).

   • Base pairing rules: $A$ pairs with $T$, and $G$ pairs with $C$.

2. Protein Synthesis

   • DNA sequence $\rightarrow$ RNA sequence $\rightarrow$ Amino Acid sequence $\rightarrow$ Protein Shape $\rightarrow$ Protein Function.

3. Modern Technology

   • Genetic Engineering: Using restriction enzymes to cut and paste genes from one organism into another (e.g., bacteria making human insulin).

   • Gel Electrophoresis: A technique used to separate DNA fragments by size to determine evolutionary relationships or for forensics.

5. Evolution and Reproduction

1. Natural Selection

   • Individuals with favorable adaptations are more likely to survive and pass on their genes to the next generation.

2. Reproduction

   • Asexual: One parent; offspring are genetically identical (mitosis).

   • Sexual: Two parents; offspring have genetic variation (meiosis and fertilization).

3. Development

   • Zygote (fertilized egg) undergoes cleavage (mitosis) and differentiation to become an embryo with specialized cells.

6. Ecology and Human Impact

1. Energy Pyramids

   • Producers are at the bottom; only about $10\%$ of energy is transferred to the next level (the rest is lost as heat).

2. Biodiversity

   • The variety of species in an ecosystem. High biodiversity increases the stability of an ecosystem.

3. Human Problems

   • Global Warming: Caused by the burning of fossil fuels releasing $CO_{2}$, which traps heat.

   • Deforestation: Leads to habitat loss and decreased biodiversity.

   • Industrialization: Can lead to acid rain and water pollution.