https://teddyrookbook.com/biology/high-school-biology/Recent content in High School Biology on Teddy Rook Bookhttps://teddyrookbook.com/img/share.jpghttps://teddyrookbook.com/img/share.jpgHugoenhttps://teddyrookbook.com/biology/high-school-biology/hypotheses-experiments/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/hypotheses-experiments/A hypothesis is a testable explanation that makes a prediction. A controlled experiment changes one independent variable, measures a dependent variable, holds the rest constant, and repeats trials. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/reading-data/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/reading-data/Read a graph by its axes and units first, then the trend; compare groups by their means and spread, and tell correlation from cause. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/scientific-theories/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/scientific-theories/In science, a theory is a well-tested explanation that ties together many facts and observations, like the cell theory and the theory of evolution. A law describes a pattern; a theory explains it. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/elements-bonds/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/elements-bonds/Living things are built mostly of carbon, hydrogen, oxygen and nitrogen, with phosphorus and sulfur. Atoms share electrons in covalent bonds; ionic bonds and weak hydrogen bonds hold molecules to each other. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/water-properties/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/water-properties/Water is polar, so its molecules form hydrogen bonds. That gives cohesion, adhesion, surface tension, a high specific heat, its power as a solvent, and ice that floats. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/ph/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/ph/pH measures how acidic a solution is: 7 is neutral, lower is acidic, higher is basic. Each step of 1 is a tenfold change, and buffers keep the pH of living things steady. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/monomers-polymers/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/monomers-polymers/Large biological molecules are chains of small units. Dehydration synthesis joins monomers and releases water; hydrolysis splits polymers by adding water. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/carbohydrates/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/carbohydrates/Sugars (monosaccharides like glucose) are quick energy; polysaccharides store energy (starch in plants, glycogen in animals) or build structure (cellulose in plant cell walls). High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/lipids/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/lipids/Fats, oils, phospholipids and steroids do not mix with water. Fats store energy compactly, phospholipids build membranes, and steroids include cholesterol and some hormones. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/proteins/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/proteins/Proteins are chains of amino acids (20 kinds) folded into precise shapes. The shape decides the job: enzymes, structure, transport, signals and defense. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/nucleic-acids/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/nucleic-acids/DNA and RNA are chains of nucleotides, each a sugar, a phosphate and a base. DNA stores genetic information; RNA helps use it to build proteins. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/enzymes/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/enzymes/Enzymes are proteins that speed up reactions by lowering the activation energy. The substrate fits the active site; the enzyme is not used up and can work again and again. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/enzyme-conditions/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/enzyme-conditions/Each enzyme works best at an optimal temperature and pH. Too far away, the enzyme's shape changes (it denatures) and it stops working. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/prokaryotes-eukaryotes/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/prokaryotes-eukaryotes/Prokaryotic cells (bacteria and archaea) have no nucleus or membrane-bound organelles; eukaryotic cells have both. All cells have a membrane, cytoplasm, ribosomes and DNA. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/endomembrane/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/endomembrane/A protein made for export follows a path: ribosomes on the rough ER, then a vesicle to the Golgi apparatus, then a vesicle to the cell membrane, where it is released. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/endosymbiosis/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/endosymbiosis/Mitochondria and chloroplasts descend from bacteria taken in by an ancient cell. Evidence: they have their own circular DNA and ribosomes, two membranes, and divide like bacteria. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/membrane-structure/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/membrane-structure/The membrane is a double layer of phospholipids (water-loving heads out, water-fearing tails in) with proteins floating in it: the fluid mosaic model. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/diffusion/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/diffusion/Particles spread from higher to lower concentration until evenly mixed. Small nonpolar molecules like oxygen and carbon dioxide diffuse straight through the membrane. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/osmosis-tonicity/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/osmosis-tonicity/Water moves across a membrane toward the side with more solute. In a hypotonic solution a cell gains water; in a hypertonic one it loses water; in an isotonic one there is no net change. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/channels-pumps/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/channels-pumps/Ions and polar molecules cross through proteins. Facilitated diffusion goes down the gradient with no energy; active transport, like the sodium-potassium pump, uses ATP to move against it. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/bulk-transport/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/bulk-transport/Cells take in large particles by wrapping them in membrane (endocytosis) and release large molecules by fusing vesicles with the membrane (exocytosis). Both use energy. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/atp/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/atp/ATP releases energy when its last phosphate is removed, becoming ADP. Cells couple that release to work, and recharge ADP back to ATP with energy from food. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/photosynthesis/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/photosynthesis/6CO₂ + 6H₂O + light → C₆H₁₂O₆ + 6O₂. In the chloroplast, the light-dependent reactions split water and make ATP and NADPH; the Calvin cycle uses them to build sugar from CO₂. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/photosynthesis-factors/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/photosynthesis-factors/The rate of photosynthesis rises with light, carbon dioxide and temperature until something else becomes the limiting factor, and falls at high temperature as enzymes denature. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/cellular-respiration/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/cellular-respiration/C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP. Glycolysis (cytoplasm) splits glucose; the Krebs cycle and the electron transport chain (mitochondria) release the rest, about 30 ATP per glucose in all. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/fermentation/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/fermentation/Without oxygen, cells keep glycolysis running by fermentation: muscle cells make lactic acid; yeast make ethanol and carbon dioxide, which makes bread rise. Only 2 ATP per glucose. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/photo-resp-carbon/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/photo-resp-carbon/Photosynthesis pulls CO₂ from the air into sugars; respiration by plants, animals and decomposers returns it. Their balance, along with burning and the ocean, sets the carbon dioxide in the air. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/chromosomes/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/chromosomes/A body cell of a species has a set number of chromosomes in matching (homologous) pairs: 46 in humans, so the diploid number is 2n = 46 and the haploid number n = 23. A copied chromosome is two sister chromatids joined at a centromere. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/cell-cycle/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/cell-cycle/A cell spends most of its life in interphase (G1 growth, S DNA copying, G2 preparation), then divides in the mitotic phase. Checkpoints decide whether it goes on. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/mitosis/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/mitosis/In prophase chromosomes condense; in metaphase they line up in the middle; in anaphase sister chromatids pull apart; in telophase two nuclei form. Cytokinesis splits the cell into two identical cells. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/cell-cycle-control/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/cell-cycle-control/Proteins at checkpoints let the cycle continue only when the cell is ready and its DNA is intact. When those controls fail, cells can divide without limit, which is what happens in cancer. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/meiosis/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/meiosis/Meiosis is two divisions that turn one diploid cell into four haploid cells. Meiosis I separates homologous pairs; meiosis II separates sister chromatids. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/meiosis-variation/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/meiosis-variation/Crossing over swaps pieces between homologs, and independent assortment lines each pair up on its own: with n pairs there are 2ⁿ ways to sort the chromosomes, so every cell made is unique. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/mitosis-vs-meiosis/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/mitosis-vs-meiosis/Mitosis: one division, two identical diploid cells, for growth and repair. Meiosis: two divisions, four different haploid cells, with crossing over and independent assortment. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/mendel/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/mendel/Mendel crossed true-breeding pea plants: the F1 all showed one trait, and the F2 showed both in about a 3:1 ratio. He explained it with paired factors, now called genes, that separate (segregate). High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/monohybrid/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/monohybrid/For one gene, write each parent's gametes, fill the Punnett square, and read the genotype ratio (1:2:1 for Aa × Aa) and the phenotype ratio (3:1). High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/test-cross/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/test-cross/To learn whether a dominant-looking organism is AA or Aa, cross it with a recessive (aa) one: any recessive offspring show it was Aa. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/probability-rules/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/probability-rules/For independent events, multiply (the product rule): the chance of aa and bb is ¼ × ¼. For outcomes that can happen in different ways, add (the sum rule). High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/dihybrid/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/dihybrid/For two genes on different chromosomes, AaBb × AaBb gives four gamete types each and a 16-box square with a 9:3:3:1 phenotype ratio. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/incomplete-codominance/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/incomplete-codominance/In incomplete dominance the heterozygote is in between (red × white snapdragons give pink); in codominance both alleles show fully (red and white hairs in a roan coat). High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/multiple-alleles/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/multiple-alleles/The ABO blood type gene has three alleles: Iᴬ and Iᴮ are codominant and both dominant to i. Six genotypes give four blood types: A, B, AB and O. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/polygenic/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/polygenic/Traits like human height and the color of wheat kernels are shaped by many genes and the environment, giving a smooth range (a bell-shaped curve) instead of a few clear types. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/x-linked/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/x-linked/Genes on the X chromosome show a special pattern: XY individuals have one X, so a single recessive allele shows. Red-green color blindness is a common example. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/pedigrees/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/pedigrees/A pedigree traces a trait through a family. Two unaffected parents with an affected child show a recessive trait; a dominant trait does not skip generations. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/dna-structure/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/dna-structure/DNA is a double helix of two antiparallel strands. Sugars and phosphates form the backbone; bases pair in the middle, A with T and G with C, by hydrogen bonds. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/dna-replication/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/dna-replication/Helicase unzips the helix; DNA polymerase adds matching nucleotides to each old strand. Each new DNA molecule has one old strand and one new (semiconservative). High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/transcription/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/transcription/In the nucleus, RNA polymerase reads a gene's template strand and builds a matching mRNA: A in DNA pairs with U in RNA, T with A, G with C, C with G. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/translation/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/translation/At the ribosome, each three-base codon of mRNA is matched by a tRNA anticodon carrying an amino acid. The ribosome links the amino acids into a protein until it reaches a stop codon. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/genetic-code/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/genetic-code/Use a codon table to translate mRNA: start at AUG (methionine), read three bases at a time, and stop at UAA, UAG or UGA. 64 codons code for 20 amino acids. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/mutations/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/mutations/A substitution can be silent (same amino acid), missense (a different one) or nonsense (a stop). An insertion or deletion shifts the reading frame, changing every codon after it. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/gene-regulation/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/gene-regulation/Every cell has the same DNA, but each cell type uses different genes. Proteins that bind DNA switch genes on and off, as when bacteria make lactose-digesting enzymes only when lactose is present. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/pcr/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/pcr/The polymerase chain reaction copies a chosen piece of DNA by cycles of heating (separate strands), cooling (primers bind) and warming (polymerase builds). Each cycle doubles it: 2ⁿ copies after n cycles. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/gel-electrophoresis/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/gel-electrophoresis/DNA is negatively charged, so in a gel it moves toward the positive end. Shorter pieces move farther; comparing bands with a ladder of known sizes gives each piece's length. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/recombinant-dna/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/recombinant-dna/Restriction enzymes cut DNA at specific sequences; ligase joins pieces, so a gene can be put into a plasmid and taken up by bacteria, which then make the protein, such as human insulin. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/natural-selection/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/natural-selection/Evolution by natural selection follows from variation, heritability, more offspring than can survive, and differences in survival and reproduction. Over generations, helpful heritable traits become more common. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/selection-patterns/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/selection-patterns/Directional selection shifts the average one way; stabilizing selection favors the middle; disruptive selection favors both extremes. Read each from how a trait's graph changes. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/adaptation-in-action/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/adaptation-in-action/Antibiotic and pesticide resistance and the changing beaks of Galápagos finches after a drought show natural selection measured within a few generations. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/evidence-fossils-anatomy/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/evidence-fossils-anatomy/Transitional fossils (early whales with legs, Tiktaalik), homologous structures, and vestigial structures such as a whale's hip bones point to common ancestry. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/molecular-evidence/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/molecular-evidence/Species that share a more recent common ancestor have more similar DNA and protein sequences. Counting differences in a sequence lets us compare relatedness. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/phylogenetic-trees/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/phylogenetic-trees/A phylogenetic tree shows common ancestry: each branch point is a common ancestor. Relatedness is read from the most recent shared branch point, not from how close the tips are on the page. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/cladograms/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/cladograms/Group organisms by shared derived traits: the trait shared by all but one marks the first branch, and each newer trait marks a smaller group nested inside. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/hardy-weinberg/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/hardy-weinberg/In a population that is not evolving, allele frequencies p + q = 1 stay constant and genotype frequencies are p² + 2pq + q² = 1. Find q from the share of recessive individuals: q = √(q²). High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/mechanisms-evolution/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/mechanisms-evolution/Allele frequencies change through mutation, genetic drift (chance, strongest in small populations, as in bottlenecks and founder effects), gene flow (migration) and natural selection. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/speciation/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/speciation/A species splits when populations stop exchanging genes: a barrier divides them (geographic isolation), or they come to live in different habitats or flower or reproduce at different seasons. In plants, a doubled chromosome set can make a new species in one generation. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/population-models/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/population-models/With unlimited resources a population grows exponentially (a J-curve); as resources run short, growth slows toward the carrying capacity K (an S-curve, logistic growth). High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/density-factors/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/density-factors/Density-dependent factors like food, disease and predation hit harder as a population grows crowded; density-independent factors like floods, fires and frosts hit regardless of size. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/community-interactions/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/community-interactions/Each species has a niche, its role and needs. Two species cannot share exactly the same niche for long (competitive exclusion); predation, mutualism and parasitism shape communities too. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/energy-flow/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/energy-flow/Energy enters as sunlight captured by producers and flows up the trophic levels, with roughly 10% passed on at each step. Biomass and numbers usually shrink up the pyramid too. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/matter-cycles/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/matter-cycles/Carbon cycles through photosynthesis, respiration, the ocean and fossil fuels; nitrogen through fixation, nitrification and denitrification by bacteria; phosphorus slowly through rock, soil and water, with no gas phase. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/aerobic-anaerobic/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/aerobic-anaerobic/Where oxygen runs short, as in waterlogged soil or deep mud, some microbes use fermentation or other pathways, which changes how carbon and nitrogen cycle there. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/stability-change/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/stability-change/Ecosystems hold fairly steady when conditions are steady, and recover from small disturbances. Large changes, like a new predator or a changed climate, can shift them to a new state. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/keystone-species/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/keystone-species/A keystone species has a much larger effect than its numbers suggest: removing sea otters let sea urchins boom and strip kelp forests, a trophic cascade. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/group-behavior/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/group-behavior/Herding, flocking, schooling and cooperative hunting can improve survival: more eyes watch for predators, and individuals cut their own risk. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/biodiversity-impact/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/biodiversity-impact/Biodiversity is measured by richness (how many species) and evenness (how balanced). Habitat loss, invasive species, pollution and overharvesting reduce it; conservation solutions are judged by evidence and trade-offs. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/feedback-loops/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/feedback-loops/Homeostasis keeps the internal environment within a narrow range. In negative feedback a sensor detects a change and effectors push it back; positive feedback amplifies a change until an event ends it, as when blood clots. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/temperature-control/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/temperature-control/When the body is too warm, the brain triggers sweating and wider skin blood vessels; when too cold, shivering and narrower skin vessels. Each is negative feedback. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/blood-sugar/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/blood-sugar/After a meal, the pancreas releases insulin, which helps cells take up glucose and the liver store it, lowering blood sugar. Between meals, glucagon tells the liver to release glucose. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/body-systems-hierarchy/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/body-systems-hierarchy/Cells form tissues, organs and organ systems that work together: oxygen taken in by the respiratory system is carried by the circulatory system to cells, controlled by the nervous and endocrine systems. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/circulation/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/circulation/Blood takes two loops: right side of the heart → lungs → left side → body → back to the right side. Valves keep it moving one way. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/gas-exchange/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/gas-exchange/In the alveoli, oxygen diffuses from air into the blood and carbon dioxide diffuses out. Huge surface area, thin walls and steady blood flow keep the gradients steep. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/digestion-absorption/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/digestion-absorption/Enzymes break food into absorbable units: amylase splits starch, proteases split proteins, lipase splits fats. Villi in the small intestine absorb them into the blood and lymph. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/neurons/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/neurons/A neuron receives signals at its dendrites and sends an electrical impulse along its axon. At a synapse, chemical messengers (neurotransmitters) carry the signal to the next cell. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/immune-system/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/immune-system/Innate defenses (skin, inflammation, cells that engulf germs) act fast against anything foreign. Adaptive defenses (B cells making antibodies, T cells) target one invader and leave memory cells; vaccines work by producing that memory without the illness. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/kidneys/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/kidneys/Nephrons filter blood, reabsorb what the body needs (water, glucose, salts) and leave the wastes in urine. A hormone, ADH, makes the kidneys keep more water when the body is short of it. High School Biology · Biology Ladderhttps://teddyrookbook.com/biology/high-school-biology/plant-homeostasis/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/high-school-biology/plant-homeostasis/Guard cells swell and open stomata when water is plentiful and shrink to close them when it is short, balancing carbon dioxide intake against water loss. High School Biology · Biology Ladder