Biology Concepts Recap

Overview

This lecture provides a recap of major biology concepts, focusing on the characteristics of life, cell biology, genetics, classification, ecology, and human body systems.

Characteristics of Life and Levels of Organization

• Life is difficult to define and exceptions exist; common characteristics include organization, metabolism, homeostasis, growth, reproduction, and response to stimuli.
• Levels of organization: cell → tissue → organ → organ system → organism → population → community → ecosystem → biome → biosphere.
• Cell theory: all living things are made of cells, cells are the smallest living unit, and all cells come from pre-existing cells.

Biomolecules and Enzymes

• Four main biomolecules: carbohydrates (monosaccharides), lipids (fatty acids & glycerol), proteins (amino acids), nucleic acids (nucleotides).
• Enzymes are proteins with an active site for substrates, speeding up reactions; affected by temperature and pH (denaturing can occur).

Cells and Membranes

• Prokaryotes: no nucleus or membrane-bound organelles (bacteria, archaea); eukaryotes: have nucleus and organelles (plants, animals, fungi, protists).
• All cells have DNA, cytoplasm, ribosomes, and a cell membrane; eukaryotes have additional organelles.
• The cell membrane controls homeostasis via selective permeability; passive and active transport regulate molecule movement; osmosis moves water.

Energy in Cells: Respiration and Photosynthesis

• Mitochondria perform cellular respiration (glucose → ATP); chloroplasts perform photosynthesis (light + CO₂ → glucose).
• Some organisms use anaerobic respiration or fermentation in absence of oxygen.

DNA, Cell Division, and Protein Synthesis

• DNA is made of nucleotides: phosphate, sugar, nitrogenous base (A-T, C-G pairs).
• DNA replicates before cell division; enzymes involved: helicase, primase, DNA polymerase, ligase.
• Cell cycle: G1 (growth), S (DNA synthesis), G2 (prep), M (mitosis/cytokinesis); checkpoints regulate cycle.
• Mitosis produces identical body cells; meiosis produces four genetically different gametes (haploid).
• Crossing over in prophase I increases genetic diversity; gametes combine to restore diploid number in fertilization.
• Genes have alleles (dominant, recessive); Punnett squares predict inheritance patterns.
• Protein synthesis: transcription (DNA to mRNA in nucleus), translation (mRNA to protein in ribosome).

Genetics and Inheritance Patterns

• Mendelian inheritance: dominant and recessive alleles, genotypes, phenotypes.
• Non-Mendelian inheritance includes sex-linked traits, multiple alleles, incomplete dominance, and codominance.
• Pedigrees track traits through families; symbols: circles (female), squares (male), shading (trait presence).
• Mutations: gene (substitution, deletion, insertion) and chromosomal (duplication, inversion, translocation); frameshift mutations change reading frame.

Evolution, Natural Selection, and Biodiversity

• Natural selection: traits increasing fitness become more common; fitness measured by offspring produced.
• Genetic drift: random changes in allele frequency (bottleneck, founder effect).
• Biodiversity and ecological succession (primary and secondary) shape communities and ecosystems.

Bacteria, Viruses, and Classification

• Bacteria: unicellular prokaryotes, beneficial (digestion, decomposition, nitrogen fixation) or harmful (pathogens); treated with antibiotics.
• Viruses: non-cellular, need a host to reproduce; affected by lytic and lysogenic cycles; not living.
• Three domains: Bacteria, Archaea, Eukarya; classification levels: Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.
• Scientific names are more reliable than common names.

Plants and Ecosystems

• Plants: autotrophs, perform photosynthesis, have structures like stomata, xylem, and phloem.
• Angiosperms (flowering plants) reproduce sexually; parts: stamen (male), pistil (female); double fertilization produces seeds and fruit.
• Food chains/webs: energy flows from producers to various consumer levels, with only ~10% energy transfer per level.
• Energy pyramids and the importance of biodiversity in ecosystems.

Ecological Cycles and Relationships

• Carbon cycle: photosynthesis and respiration circulate carbon; burning fossil fuels increases CO₂.
• Nitrogen cycle: bacteria fix nitrogen; nitrifying, ammonifying, and denitrifying bacteria maintain the cycle.
• Ecological relationships: predation, competition, symbiosis (mutualism, commensalism, parasitism).

Human Body Systems

• Eleven systems: circulatory, digestive, endocrine, excretory, immune/lymphatic, integumentary, muscular, nervous, reproductive, respiratory, skeletal.
• Systems work together to maintain body function (e.g., response to adrenaline involves several systems).

Key Terms & Definitions

• Cell Theory — All living things are made of cells; cells arise from other cells.
• Enzyme — Protein that speeds up chemical reactions.
• Osmosis — Movement of water across a semi-permeable membrane.
• Chromosome — Condensed DNA and protein, carries genetic information.
• Allele — Different form of a gene.
• Mutation — A change in DNA sequence.
• Natural Selection — Process where traits increasing reproductive fitness become more common.
• Symbiosis — Close relationship between different species (mutualism, commensalism, parasitism).

Action Items / Next Steps

• Review videos on complex genetics (Punnett squares, inheritance patterns, pedigrees).
• Study the differences between cell types, division processes, and biomolecule functions.
• Revisit videos for topics needing more clarification or detail.
• Check out the study strategies video and related learning materials.