Essential Biology and Physics Concepts Summary

Biology Fundamentals

Genetics: DNA and RNA

• DNA: Double helix structure; carries genetic information. Bases pair A–T and C–G.
• RNA: Single strand; uses Uracil (U) instead of Thymine (T); assists in protein synthesis.

Cell Division

• Mitosis: Results in two identical daughter cells; essential for growth and repair.
• Meiosis: Results in four genetically different cells; produces gametes (sperm and egg).

Chromosomes

• Humans possess 23 pairs, totaling 46 chromosomes:
  • 22 pairs are autosomes.
  • 1 pair consists of sex chromosomes (X/Y).
• Sex determination: Males are XY; Females are XX.

Inheritance Principles

• Dominant Allele: Expressed even if only one copy is present.
• Recessive Allele: Expressed only when two copies are present.
• Use Punnett squares to predict trait outcomes in offspring.
• Pedigrees map genetic traits across family trees.

Mutations

• A change in the DNA sequence.
• Effects can be harmful, neutral, or beneficial.

Tip: Drawing simple diagrams for mitosis, meiosis, and Punnett squares aids memory retention!

Astronomy: The Universe

Stars

• Stars are massive spheres of gas, primarily fusing Hydrogen (H) into Helium (He) via nuclear fusion.
• Energy output includes light and heat.
• Color indicates temperature: Blue is hotter; Red is cooler.
• Spectra: Absorption spectra show dark lines; Emission spectra show bright lines.

Star Life Cycle

• Sequence: Nebula $\rightarrow$ Protostar $\rightarrow$ Main Sequence $\rightarrow$ Red Giant $\rightarrow$ End Stage (White Dwarf, Neutron Star, or Black Hole).

Galaxies

• Main types: Spiral, Elliptical, and Irregular.

Measuring Cosmic Distance

• Parallax: Measures apparent shift of a star against background objects to determine distance.
• 1 AU (Astronomical Unit): The average distance between the Earth and the Sun.
• 1 parsec: Approximately 3.26 light-years.

Universe Expansion

• Redshift: Indicates a galaxy is moving away from us, supporting the expanding universe theory.
• Hubble’s Law: Velocity ($v$) equals the Hubble constant ($H$) times distance ($d$): $v = H \times d$.
• Big Bang Theory: The universe originated from an extremely hot, dense state.
• Cosmic Microwave Background (CMB): Residual thermal radiation from the Big Bang.

Tip: Remember that blue stars have shorter, hotter lives; red stars burn slower and cooler.

Energy Concepts in Physics

Forms of Energy

• Kinetic (motion)
• Potential (stored due to position)
• Thermal (heat)
• Chemical (stored in molecular bonds)
• Nuclear (stored in atomic nuclei)
• Electrical (related to electric charge)
• Elastic (stored in stretched or compressed objects)

Key Equations

• Work: $W = F \times d$
• Kinetic Energy: $E_k = \frac{1}{2} m v^2$
• Gravitational Potential Energy: $E_p = m g h$
• Elastic Potential Energy: $E_e = \frac{1}{2} k x^2$
• Efficiency: $\eta = (\text{useful} \div \text{total}) \times 100\%$

Thermal Energy and Thermodynamics

• First Law of Thermodynamics: $\Delta U = Q - W$ (Change in internal energy equals heat added minus work done by the system).
• Energy is conserved: it cannot be created or destroyed.
• Heat transfer methods: conduction (direct contact), convection (fluid movement), and radiation (electromagnetic waves).

Definitions and Formulas

1. Work

Formula: $W = F \times d$

• W = Work (Joules, J)
• F = Force (Newtons, N)
• d = Distance moved in the direction of the force (meters, m)

2. Kinetic Energy

Formula: $E_k = \frac{1}{2} m v^2$

• Eₖ = Kinetic energy (J)
• m = Mass (kg)
• v = Velocity or speed (m/s)

3. Gravitational Potential Energy

Formula: $E_p = m g h$

• Eₚ = Gravitational potential energy (J)
• m = Mass (kg)
• g = Acceleration due to gravity ($\approx 9.8 \text{ m/s}^2$ on Earth)
• h = Height above a reference point (m)

4. Elastic Potential Energy

Formula: $E_e = \frac{1}{2} k x^2$

• Eₑ = Elastic potential energy (J)
• k = Spring constant (N/m)
• x = Extension or compression of the spring (m)

5. Efficiency

Formula: $\eta = \frac{\text{Useful energy output}}{\text{Total energy input}} \times 100\%$

• $\eta$ = Efficiency (expressed as a percentage)
• Useful energy is the desired output; Total energy is the input supplied.