China 八年级（初二） Biology
Chapters: 8
1. U4 Ch.6 Regulation of human life activities
Sensing the environment (eye, ear) · Nervous regulation; reflex arc · Movement under nervous control (muscles, bones, joints) · Hormonal regulation (thyroid, insulin, sex hormones)
- Sense Organs – Sense organs let us pick up changes around us (stimuli). The eye senses light, the ear sound and balance, the nose smell, the tongue taste, and the skin touch, pressure, heat, cold and pain. Each has receptor cells that turn the stimulus into nerve signals. The signal goes along a sensory nerve to the brain or spinal cord, which sends an order to a muscle: the response.
- Nervous System, Reflex Action and the Human Brain – Nerve cells (neurons) carry messages as electric impulses and pass them to the next cell with chemicals across a gap called a synapse. Quick safety responses (reflexes) are handled by the spinal cord; thinking and control come from the brain, which is guarded by the skull and a fluid cushion.
- The Skeletal System – The skeleton is the body's frame of 206 bones (adult). It has five main jobs: support and shape, protection, movement (with muscles), making blood cells in red marrow, and storing minerals like calcium. Bones meet at joints; hinge joints (elbow, knee) bend one way, ball-and-socket joints (shoulder, hip) move in all directions. Ligaments join bone to bone, tendons join muscle to bone, cartilage cushions the ends. Muscles only pull, so they work in antagonistic pairs such as biceps and triceps.
- Hormones in Animals: Endocrine Glands and Feedback – Endocrine glands release chemical messengers called hormones straight into the blood. The blood carries them all over the body, but they act only on target cells. Hormones control growth, metabolism, emergency response, blood sugar and puberty, and their amount is kept right by feedback.
2. U4 Ch.7 Healthy living
Infectious diseases and prevention · Immunity and vaccination programme · Medicines and first aid (CPR, bleeding) · Healthy lifestyle (tobacco, alcohol, drugs, chronic disease) · Project: health promotion show
- Infectious Diseases: How Germs Spread and How We Stop Them – An infectious (communicable) disease is caused by a tiny living thing called a pathogen: a bacterium, virus, fungus or protist. It passes from one person to another through air, water and food, touch, or a vector such as a mosquito. The body fights back with skin, mucus, stomach acid and white blood cells. Vaccines train the immune system in advance. Hand washing, clean water, cooking food well, mosquito nets and staying home when sick all cut the spread.
- The Immune System: How Your Body Fights Germs – Germs (pathogens) cause infectious disease. The body has three lines of defence: barriers (skin, mucus, acid), a fast general (innate) response (inflammation, fever, phagocytes) and a slow, specific (adaptive) response (B cells make antibodies, T cells kill infected cells). Memory cells make the second attack fast. Vaccines create memory safely. Immunity can go wrong: allergy, autoimmune disease, immunodeficiency (e.g. HIV).
- First Aid: What to Do in an Emergency – First aid is the help you give an injured or ill person until trained help arrives. Its aims: preserve life, stop things getting worse, help recovery. Follow DRABC: Danger, Response, Airway, Breathing, CPR/Call. Breathing but unresponsive → recovery position. Not breathing normally → CPR 30:2 at 100-120 pushes a minute, 5-6 cm deep, and an AED. Bleeding → direct pressure. Burns → cool running water 20 minutes. Choking → back blows and abdominal thrusts. Sprains → RICE.
- Healthy Lifestyle: Daily Habits That Keep You Well – A healthy lifestyle is a set of daily habits: a balanced diet from five food groups, enough water, 9–11 hours of sleep for school-age children and about 8–10 for teenagers, at least 60 minutes of activity a day, good posture, safe food handling and avoiding tobacco, alcohol and drugs. These habits lower the risk of lifestyle (non-communicable) diseases such as type 2 diabetes, heart disease and some cancers.
3. U5 Ch.1 Ecosystems
Organisms and environment interact · Ecosystem structure and function; food chains and webs · The biosphere · Project: sealed ecosphere bottle
- Ecosystem, Food Chains and Energy Flow – An ecosystem is all the living things in a place plus the non-living things around them, working together. Energy enters as sunlight, passes one way up a food chain, and only about 10% moves to each next level.
- The Biosphere – The biosphere is the part of Earth where life exists. It is a thin layer where the geosphere (rock and soil), hydrosphere (water) and atmosphere (air) meet, from about 10 km above sea level to about 11 km below it. It is one huge system made of all ecosystems together. Energy flows through it in one direction, from the Sun to plants to animals and out as heat, while matter such as carbon, water and nitrogen goes round in cycles. Living things also change the other spheres: they make oxygen, build soil and store carbon. Humans now change the biosphere strongly, so we must protect it.
4. U5 Ch.2 Ecological security
Human impact on the environment · Protecting ecological security (invasive species etc.)
- Environmental Issues: Causes, Effects and Solutions – Environmental issues are harmful changes to air, water, land, climate and living things, mostly caused by human activity. The big ones are air pollution, water pollution, land pollution and waste, climate change, deforestation and loss of biodiversity, and overuse of resources. They grow with the number of people and how much each person uses (the ecological footprint). We can reduce them with clean energy, saving and recycling, treating waste water, protecting forests and good laws, at home, in the city, in the country and across the world.
- Ecological Security: Invasive Species and Protecting Nature – Ecological security means keeping ecosystems healthy so they keep giving us clean water, food and air. Invasive species, which arrive from another place and spread fast because they have no natural enemies, are a big threat. We protect nature in its home (reserves, parks: in-situ), away from home (seed banks, zoos: ex-situ) and by laws against hunting and trade in wild species.
5. U6 Ch.1 Reproduction
Asexual reproduction · Project: cuttings or grafting · Sexual reproduction (plants, insects, amphibians, birds) · Project: build a device to raise an animal
- Reproduction in Human Beings and Reproductive Health – At puberty, hormones from the brain make the testes and ovaries start working. The male system makes and carries sperm; the female system makes eggs and provides a place (uterus) where a baby develops. Fertilisation happens in the oviduct, and the embryo is fed through the placenta. Reproductive health includes safe choices, contraception, avoiding female foeticide, and preventing sexually transmitted diseases such as HIV/AIDS.
- How Do Organisms Reproduce? DNA Copying and Asexual Reproduction – Reproduction makes new individuals by copying DNA. The copies are never perfect, and these small changes (variations) help a species survive when its surroundings change. In asexual reproduction a single parent makes offspring by fission, fragmentation, regeneration, budding, vegetative propagation or spores.
- Sexual Reproduction in Flowering Plants – Sexual reproduction joins a male and a female gamete, mixing DNA from two parents and creating more variation. In a flower, pollen from the anther reaches the stigma (pollination), grows a pollen tube to the ovule, and the male gamete fuses with the egg (fertilisation). The zygote becomes the embryo, the ovule becomes the seed and the ovary becomes the fruit.
- Reproduction in Animals – Animals make young in two ways. In asexual reproduction one parent makes copies of itself (budding in hydra, splitting, regrowing from a piece, or eggs that need no male). In sexual reproduction a male gamete (sperm) joins a female gamete (egg) to make a zygote; this mixes genes and gives variation. Fertilisation can happen outside the body in water (frogs, most fish) or inside the body (insects, reptiles, birds, mammals). Land animals lay shelled eggs with membranes, or keep the young inside. After hatching, many animals change shape: complete metamorphosis (egg, larva, pupa, adult) or incomplete metamorphosis (egg, nymph, adult).
6. U6 Ch.2 Heredity and variation
Genes and traits · Passing genes to offspring (DNA, chromosomes) · Dominant and recessive genes · Human sex determination · Variation; breeding and GM
- Chromosomes, Genes, Alleles and Polygenic Inheritance – Each cell nucleus holds chromosomes made of DNA. All the DNA of an organism is its genome. A gene is a stretch of DNA at a fixed place on a chromosome; its different forms are alleles. Chromosomes come in pairs, one from each parent. Meiosis puts one chromosome of each pair into each gamete, and fertilisation restores the pairs. Some traits, like height, depend on many genes together (polygenic) and so show a smooth range. All living things use the same four-letter DNA code.
- Chromosomes: Where Your Genes Live – A chromosome is a thread-like packet of DNA inside the nucleus. Genes are short pieces of that DNA, lined up one after another. A human body cell has 46 chromosomes in 23 pairs: one chromosome of each pair from the mother and one from the father. Egg and sperm carry only 23 each, so a baby gets 46 again. Sutton saw that chromosomes behave like Mendel's factors, and Morgan showed that genes sit on them in a line.
- Heredity and Mendel's Laws – Heredity is the passing of traits from parents to children through genes. Each parent gives one copy of every gene. A dominant copy hides a recessive one, which is why Mendel saw 3:1 in a monohybrid cross and 9:3:3:1 in a dihybrid cross. Genes are pieces of DNA that make proteins, and proteins build the trait.
- Sex Determination in Humans – Human body cells have 23 pairs of chromosomes: 22 pairs of autosomes and 1 pair of sex chromosomes. Women are XX and men are XY. Every egg carries X; half the sperm carry X and half carry Y. X + X gives a girl, X + Y gives a boy, so the chance is 50:50 and the father's sperm decides.
- Variation in Living Things – Variation means the differences between living things of the same species. Continuous variation has every value in a range (height, mass); discontinuous variation falls into clear groups (blood group, flower colour). Variation is caused by genes, by the environment, or by both. Only changes in genes are heritable. People use variation in selective (and hybrid) breeding, and genetic modification adds a useful gene directly.
7. U6 Ch.3 Evolution
Origin of life · History of evolution; fossils · Causes of evolution; natural selection · Human origins
- Evolution: Origin of Life, Mechanisms and Human Evolution – Life began on the early Earth from simple chemicals: Oparin and Haldane proposed it and Miller made amino acids in a flask. Evidence of evolution comes from fossils, homologous and analogous organs, embryos, molecules and changes we can watch (industrial melanism, drug resistance). Darwin explained it by natural selection acting on variation in populations; the modern synthetic theory adds genes: mutation, recombination, gene flow, genetic drift and natural selection change allele frequencies. If none of these act, frequencies stay constant: Hardy–Weinberg, p² + 2pq + q² = 1. Selection can be stabilising, directional or disruptive. One ancestor spreading into many habitats gives adaptive radiation (Darwin’s finches, Australian marsupials). Humans evolved from Dryopithecus-like apes through Australopithecus, Homo habilis, Homo erectus and Neanderthals to Homo sapiens.
- Evolution: How New Kinds of Living Things Arise – Variations arise during reproduction. Nature selects those that help survival, so over many generations populations change: this is evolution. Only inherited (DNA) changes pass on; acquired changes do not. Separated populations can become new species. Homologous organs, analogous organs and fossils help us trace who is related to whom, and complex organs evolved step by step.
8. U6 Ch.4 Biodiversity
Evolution and biodiversity · Living in harmony with nature
- Biodiversity and Evolution – Biodiversity is the variety of life. It has three levels: species diversity (many kinds of living things), genetic diversity (differences inside one species) and ecosystem diversity (many kinds of habitats). Evolution made this variety: living things change over many generations, and natural selection keeps the changes that help survival, so one ancestor can split into many species.