Overview
This lecture reviews core concepts of the New York State Life Science Biology Regents Exam, covering cell function, genetics, ecology, evolution, and human impact on the environment.
Homeostasis and Feedback
- Homeostasis is the maintenance of stable internal conditions in organisms.
- Feedback loops regulate vital functions like blood pressure and water balance.
- Disruptions in feedback can cause disease or death.
- Stomata in plants regulate water loss and gas exchange via feedback.
Cell Structure and Transport
- Three main types of cell transport: diffusion (high to low concentration, no energy), facilitated diffusion (uses proteins), and active transport (low to high, uses ATP).
- All living things have DNA; in eukaryotes it’s in the nucleus, in prokaryotes in the nucleoid.
- Cell organelles include nucleus, vacuole, lysosome, Golgi apparatus, endoplasmic reticulum (ER), ribosome, cell wall, chloroplast, and mitochondrion.
DNA, Proteins, and Cell Division
- DNA is made of nucleotides: phosphate, deoxyribose sugar, and base.
- The central dogma: DNA → mRNA (transcription) → protein (translation).
- DNA condenses into chromosomes before cell division; chromatin is uncondensed DNA.
- Cell cycle includes interphase (G1, S, G2) and M phase (mitosis and cytokinesis).
- Mitosis produces identical cells; meiosis produces haploid gametes with genetic variation.
Photosynthesis and Cellular Respiration
- Photosynthesis converts light energy, CO₂, and water into glucose and O₂ in chloroplasts.
- Cellular respiration uses glucose and O₂ to make ATP in mitochondria, releasing CO₂ and water.
- Anaerobic respiration occurs without oxygen and is less efficient.
Cycles and Energy Flow in Ecosystems
- The carbon cycle involves photosynthesis, respiration, decomposition, combustion, and ocean absorption.
- The nitrogen cycle relies on bacteria to make nitrogen usable for plants and animals.
- Energy decreases up trophic levels; most energy is lost as heat.
- Carrying capacity limits population size in ecosystems.
Human Impact and Environmental Issues
- Renewable resources regenerate quickly; non-renewable resources like fossil fuels do not.
- Human activities cause global warming, species introduction, habitat destruction, and pollution.
- Conservation and sustainable practices can reduce negative impacts.
Genetics and Inheritance
- Chromosomal disorders result from errors in meiosis (e.g., Down syndrome).
- Genetic variation arises from independent assortment, crossing over, and mutations.
- Genotype is genetic makeup; phenotype is physical expression.
- Punnett squares predict inheritance probabilities.
- Inheritance patterns include dominance, codominance (AB blood type), incomplete dominance (blending), and polygenic traits (height).
- Environment can affect gene expression and traits.
Evolution and Natural Selection
- Evolution is genetic change in populations over time.
- Natural selection favors traits increasing reproductive success in current environments.
- Evidence for evolution includes fossils, biochemical similarities, embryology, and biogeography.
- Adaptations are traits favorable in a particular environment; diversity increases resilience.
Domains of Life and Phylogeny
- Three domains: Bacteria, Archaea (extremophiles), and Eukarya (plants, animals, fungi, protists).
- Phylogenetic trees (cladograms) show evolutionary relationships based on common ancestry and shared traits.
Key Terms & Definitions
- Homeostasis — maintaining stable internal conditions.
- Diffusion — movement from high to low concentration without energy.
- Active Transport — movement from low to high concentration using energy.
- Chromosome — condensed DNA structure for cell division.
- Mitosis — process producing identical cells.
- Meiosis — process producing gametes with half the chromosomes.
- Photosynthesis — process using light to create glucose and oxygen.
- Cellular Respiration — process using glucose and oxygen to create ATP.
- Carrying Capacity — maximum population an environment can support.
- Genotype — an organism’s genetic makeup.
- Phenotype — physical expression of genotype.
- Adaptation — inherited trait increasing survival or reproduction.
- Cladogram/Phylogenetic Tree — diagram of evolutionary relationships.
Action Items / Next Steps
- Review major vocabulary and cell organelles.
- Practice drawing and interpreting Punnett squares and cladograms.
- Study cycles (carbon, nitrogen) and energy flow in ecosystems.
- Complete any assigned reading or practice questions on homeostasis, genetics, and evolution.