https://teddyrookbook.com/biology/life-science/Recent content in Life Science on Teddy Rook Bookhttps://teddyrookbook.com/img/share.jpghttps://teddyrookbook.com/img/share.jpgHugoenhttps://teddyrookbook.com/biology/life-science/characteristics-of-life/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/characteristics-of-life/Living things are made of cells, use energy, grow and develop, respond to their surroundings, keep their insides steady, and produce offspring. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/fair-tests/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/fair-tests/In a fair test you change one thing (the independent variable), measure one thing (the dependent variable), and keep everything else the same, with a control group to compare against. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/microscope/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/microscope/A light microscope magnifies with two lenses: total magnification is the eyepiece power times the objective power, so 10× and 40× give 400×. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/field-of-view/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/field-of-view/Estimate a cell's size by how many fit across the field of view, and use micrometers: 1 millimeter = 1,000 micrometers (µm). Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/cell-theory/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/cell-theory/All living things are made of one or more cells, the cell is the basic unit of life, and every cell comes from a cell that already existed. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/one-or-many-cells/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/one-or-many-cells/Unicellular organisms, like bacteria and amoebas, live as a single cell that does every job. Multicellular organisms, like trees and people, are built of many specialized cells. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/cell-parts/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/cell-parts/Every cell has a cell membrane that controls what enters and leaves and cytoplasm inside. Cells of plants, animals and fungi also keep their DNA in a nucleus. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/organelles/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/organelles/Mitochondria release energy from food, ribosomes build proteins, the endoplasmic reticulum and Golgi apparatus make and ship materials, and vacuoles and lysosomes store and break things down. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/plant-animal-cells/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/plant-animal-cells/Plant cells have a cell wall, chloroplasts and a large central vacuole; animal cells have none of these. Both have a membrane, a nucleus and mitochondria. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/cell-size/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/cell-size/As a cell grows, its volume grows faster than its surface, so a big cell could not move food in and wastes out fast enough. Small cells have more surface for their size. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/diffusion-osmosis/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/diffusion-osmosis/Particles spread from where they are crowded to where they are less crowded (diffusion). Osmosis is the diffusion of water across a membrane, toward the side with more dissolved material. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/levels-of-organization/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/levels-of-organization/Similar cells form tissues, tissues form organs, organs work together in organ systems, and systems make up an organism. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/classification-ranks/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/classification-ranks/Scientists group living things in ranks: domain, kingdom, phylum, class, order, family, genus, species. Each rank holds fewer kinds of organisms that share more traits. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/scientific-names/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/scientific-names/Every species has a two-part scientific name, genus then species, like Canis lupus for the gray wolf. The genus starts with a capital, and the whole name is written in italics. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/dichotomous-keys/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/dichotomous-keys/A dichotomous key identifies an organism by a series of either-or choices about traits you can observe, leading step by step to its name. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/domains-kingdoms/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/domains-kingdoms/Life is grouped into three domains, Bacteria, Archaea and Eukarya. Eukarya includes protists, fungi, plants and animals. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/bacteria/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/bacteria/Bacteria are single cells with no nucleus. They live almost everywhere, and most are harmless or helpful: they break down dead matter, make yogurt and live in our gut. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/bacteria-growth/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/bacteria-growth/A bacterium splits into two, then those two split, and so on. With food and warmth the number doubles each generation: 1, 2, 4, 8, 16. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/viruses/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/viruses/A virus is genetic material in a protein coat. It is not a cell; it can make copies of itself only inside a living host cell. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/protists/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/protists/Protists are mostly single-celled organisms with a nucleus: animal-like amoebas and paramecia, plant-like algae that photosynthesize, and fungus-like water molds. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/fungi/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/fungi/Fungi, including yeasts, molds and mushrooms, absorb food from what they grow on. Many are decomposers, and yeast makes bread rise. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/helpful-harmful-microbes/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/helpful-harmful-microbes/Microbes make foods like cheese and bread, recycle nutrients and live in our bodies; a few cause disease. Antibiotics act on bacteria, not viruses, and washing hands with soap removes many germs. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/photosynthesis/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/photosynthesis/In chloroplasts, plants use light energy to turn carbon dioxide and water into sugar, giving off oxygen. The sugar stores the energy and builds the plant's body. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/cellular-respiration/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/cellular-respiration/Cells release the energy in sugar by combining it with oxygen, giving off carbon dioxide and water. Every living cell does it, plants included, day and night. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/photo-resp-together/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/photo-resp-together/The outputs of photosynthesis (sugar and oxygen) are the inputs of respiration, and the outputs of respiration (carbon dioxide and water) are the inputs of photosynthesis. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/plant-transport/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/plant-transport/Xylem carries water and minerals up from the roots; phloem carries sugar from the leaves to where it is used or stored. Water evaporates from leaves through tiny pores called stomata. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/plant-responses/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/plant-responses/Plants grow toward light (phototropism), roots grow down with gravity (gravitropism), and vines curl around what they touch (thigmotropism). Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/plant-groups/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/plant-groups/Mosses have no tubes for water and stay small; ferns have tubes but no seeds; conifers make seeds in cones; flowering plants make seeds inside fruits. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/flowers-seeds/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/flowers-seeds/A flower's stamens make pollen. Pollination carries pollen to the pistil, and then a seed forms; the part around the seeds grows into the fruit. Animals and wind help. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/plant-growth-factors/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/plant-growth-factors/A plant's growth depends on its genes and its surroundings: light, water, nutrients, temperature and space. The same seeds grow differently in different conditions. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/backbones/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/backbones/Vertebrates have a backbone; invertebrates do not. More than nine in ten known animal species are invertebrates. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/invertebrate-groups/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/invertebrate-groups/Sponges, cnidarians (jellyfish), worms, mollusks (snails, octopuses), arthropods (insects, spiders, crabs) and echinoderms (sea stars) are the major invertebrate groups. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/vertebrate-groups/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/vertebrate-groups/Fish, amphibians, reptiles, birds and mammals differ in coverings, how they breathe, and whether they keep a steady body temperature. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/structural-adaptations/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/structural-adaptations/Adaptations are inherited traits that help an organism survive where it lives, such as a duck's webbed feet, a hawk's hooked beak, or camouflage. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/behavioral-adaptations/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/behavioral-adaptations/Some behaviors are instincts, done right the first time without learning, like a spider spinning a web. Others are learned, like a crow learning which trash cans hold food. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/body-temperature/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/body-temperature/Birds and mammals are endotherms: they make heat inside and keep a fairly steady body temperature. Fish, amphibians and reptiles are ectotherms: their temperature follows their surroundings. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/biotic-abiotic/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/biotic-abiotic/An ecosystem is the living (biotic) parts, like plants, animals and microbes, together with the nonliving (abiotic) parts, like sunlight, water, soil, air and temperature. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/levels-ecology/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/levels-ecology/An organism is one living thing; a population is all of one species in an area; a community is all the populations together; an ecosystem adds the nonliving parts. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/ecosystem-roles/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/ecosystem-roles/Producers make their own food from sunlight; consumers eat other organisms; decomposers break down dead matter and wastes and return nutrients to the soil. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/food-webs/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/food-webs/A food web is many food chains linked together. Arrows point from the food to the eater, the direction energy and matter move. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/web-changes/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/web-changes/If one population in a food web grows or shrinks, others change too: lose the foxes, and rabbits may boom and then overeat the grass. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/energy-pyramids/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/energy-pyramids/Only about 10% of the energy at one level of a food chain is stored in the next level; the rest is used for living and lost as heat. That is why there are fewer top predators. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/species-interactions/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/species-interactions/Species compete for the same resources, predators eat prey, and in symbiosis two species live closely: both benefit (mutualism), one benefits without harm (commensalism), or one benefits at the other's cost (parasitism). Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/carbon-cycle/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/carbon-cycle/Carbon moves from the air into plants by photosynthesis, into animals by eating, and back to the air by respiration, decomposition and burning. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/nitrogen-cycle/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/nitrogen-cycle/Air is mostly nitrogen, but plants cannot use it directly. Bacteria in soil and in root nodules turn it into forms plants can absorb; decomposers and other bacteria return it to the soil and air. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/biomes/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/biomes/Biomes are large regions with a similar climate and similar kinds of life: tropical rainforest, desert, grassland, deciduous forest, taiga and tundra. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/succession/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/succession/After a disturbance, communities change in a series of stages. Primary succession starts on bare rock with no soil; secondary succession starts where soil remains, as after a fire. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/biodiversity/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/biodiversity/Biodiversity is the variety of life. Healthy ecosystems provide clean water, fertile soil, pollination and food, and more diverse ecosystems often recover better after disturbances. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/human-impact/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/human-impact/Habitat loss, invasive species, pollution and overharvesting can harm ecosystems, and solutions such as protected areas, cleanup and careful harvesting are weighed by what they cost and what they protect. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/population-growth/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/population-growth/A population grows when more individuals are added (by birth or arrival) than are lost (by death or leaving). With plenty of resources it can grow faster and faster. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/limiting-factors/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/limiting-factors/Food, water, space, shelter, disease and predators limit a population. The largest population an environment can support over time is its carrying capacity. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/predator-prey/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/predator-prey/When prey are plentiful, predators thrive and increase; then prey fall, and predators follow with a lag. The two populations rise and fall in turns. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/sampling-populations/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/sampling-populations/Ecologists estimate a population by counting in a few sample squares (quadrats) and scaling up: average count per square × number of squares in the whole area. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/skeletal-system/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/skeletal-system/The skeleton supports the body, protects organs (the skull guards the brain), works with muscles to move, and makes blood cells in the bone marrow. An adult has 206 bones. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/muscular-system/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/muscular-system/Skeletal muscles move bones, smooth muscle moves food and blood through organs, and cardiac muscle pumps the heart. Muscles can only pull, so they work in pairs. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/digestive-system/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/digestive-system/Food travels from the mouth through the esophagus, stomach, small intestine and large intestine. Teeth and stomach break it up; enzymes break it into small molecules the small intestine absorbs. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/circulatory-system/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/circulatory-system/The heart pumps blood through arteries (away from the heart), capillaries (where exchange happens) and veins (back to the heart). Blood carries oxygen, nutrients and wastes. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/respiratory-system/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/respiratory-system/The diaphragm pulls air into the lungs. In tiny air sacs (alveoli), oxygen moves into the blood and carbon dioxide moves out. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/nervous-system/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/nervous-system/Sense organs detect stimuli, nerves carry signals to the brain and spinal cord, and the brain sends signals out to muscles. A reflex is a fast response routed through the spinal cord. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/immune-basics/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/immune-basics/Skin and mucus keep most germs out. White blood cells attack germs that get in, and some remember a germ so the body can respond faster the next time. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/excretory-system/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/excretory-system/The kidneys filter wastes from the blood and make urine, the lungs remove carbon dioxide, and the skin releases some water and salt in sweat. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/systems-together/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/systems-together/During exercise, muscles need more oxygen and sugar, so breathing and heart rate rise, and the body sweats to shed heat. No system works alone. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/inherited-acquired/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/inherited-acquired/Inherited traits, like eye color, are passed from parents through genes. Acquired traits, like a scar, a skill or a language, come from experience and are not passed on. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/dna-genes/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/dna-genes/DNA carries the instructions for building an organism. A gene is a section of DNA with the instructions for one protein, and DNA is packed into chromosomes in the nucleus. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/genes-proteins-traits/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/genes-proteins-traits/A gene is a recipe for a protein, and proteins do the work of the cell: some make pigment, some build structures, some speed up reactions. That is how genes shape traits. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/one-or-two-parents/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/one-or-two-parents/Offspring of one parent, like a bacterium that splits, a yeast that buds or a plant grown from a cutting, get an exact copy of its genes. Offspring of two parents get half their genes from each, so they vary. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/alleles/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/alleles/Each gene comes in versions called alleles. You have two alleles for each gene, one from each parent. A dominant allele shows its trait even with one copy; a recessive one shows only with two copies. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/genotype-phenotype/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/genotype-phenotype/Your genotype is your pair of alleles (TT, Tt or tt); your phenotype is the trait that shows (tall or short). Two alleles alike is homozygous; two different is heterozygous. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/punnett-squares/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/punnett-squares/A Punnett square shows every way the parents' alleles can combine. Put one parent's alleles across the top and the other's down the side, then fill each box. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/punnett-probability/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/punnett-probability/Each box of a Punnett square is an equally likely outcome, so a box count gives a probability: 1 of 4 boxes is a 25% chance for each offspring. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/mutations/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/mutations/A mutation is a change in DNA. It can be harmful, helpful or neutral, depending on how it changes a protein and on the environment. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/breeding-engineering/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/breeding-engineering/People choose which plants and animals have offspring to shape traits over generations (selective breeding), and can move a gene into another organism (genetic engineering), as when bacteria make insulin. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/fossil-record/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/fossil-record/Fossils in rock layers, oldest at the bottom, show that life has changed over Earth's history: many species have gone extinct, and simpler forms appear before more complex ones. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/comparing-bodies/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/comparing-bodies/Homologous structures, like the arm of a person, the flipper of a whale and the wing of a bat, have the same bones arranged in the same way, a sign of a shared ancestor. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/natural-selection/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/natural-selection/Individuals vary; some variations are inherited; more young are born than can survive; those with helpful traits survive and reproduce more, so those traits become more common. Life Science · Biology Ladderhttps://teddyrookbook.com/biology/life-science/populations-change/Mon, 01 Jan 0001 00:00:00 +0000https://teddyrookbook.com/biology/life-science/populations-change/Data show natural selection at work: the dark form of the peppered moth rose and then fell as soot came and went, and bacteria exposed to antibiotics become resistant. Life Science · Biology Ladder