Ukraine 9 клас Biology
Chapters: 8
1. Introduction
Biology as a science
- Nature of Science: How Scientific Knowledge Is Built and Changed – Science is a way of knowing that rests on evidence anyone can check. Scientists observe, infer, test ideas that could be proved wrong, and let other experts check their work. Laws describe what happens; theories explain why. Scientific knowledge is reliable but always open to change, and sometimes a whole way of seeing (a paradigm) is replaced.
2. Chemical composition of the cell
Inorganic compounds · Organic compounds · Non-cellular life forms
- Biomolecules – A cell is mostly water, plus four big families of carbon compounds: proteins, carbohydrates, lipids and nucleic acids. Grinding tissue in acid separates small molecules (acid-soluble pool) from big ones – proteins, polysaccharides and nucleic acids (acid-insoluble pool). Proteins are chains of amino acids folded into four levels of structure. Polysaccharides are chains of sugars; lipids are fatty acids on glycerol; nucleic acids are chains of nucleotides. Enzymes are protein catalysts that bind a substrate at the active site, lower the activation energy, and are affected by temperature, pH, substrate level and inhibitors.
3. The cell
Cell structure · Cell metabolism · Cell cycle and cell theory
- The Cell: Basic Unit of Life – Every living thing is made of cells. Robert Hooke first saw cells in cork in 1665. Cells are prokaryotic (no true nucleus, like bacteria) or eukaryotic (true nucleus). Plant cells have a cell wall, chloroplasts and a big vacuole; animal cells do not. Each organelle has a job. Water enters and leaves cells by osmosis. Cells make new cells by mitosis (growth) and meiosis (sex cells).
- Cell Division: How One Cell Becomes Two (or Four) – All living things grow because their cells divide. Every cell comes from another cell (cell theory). Before dividing, a cell copies its chromosomes. Mitosis gives 2 identical cells with the same chromosome number, used for growth and repair. Meiosis divides twice and gives 4 cells with half the chromosomes, used to make sex cells.
4. Heredity and variation
Genes and gene expression · Laws of inheritance · Variation · Human genetics
- Molecular Basis of Inheritance – DNA is the genetic material in most living things (some viruses use RNA). It is a double helix: two antiparallel strands of nucleotides, A pairs with T by 2 hydrogen bonds and G with C by 3. Long DNA is packed on histones into nucleosomes and then chromatin. DNA copies itself semi-conservatively (Meselson–Stahl). The central dogma says DNA → RNA → protein. Transcription makes RNA from one strand; in eukaryotes the hnRNA is capped, tailed and spliced. The genetic code is a triplet, has 64 codons (61 for amino acids, 3 stops), starts with AUG, is nearly universal and degenerate. Ribosomes translate mRNA into protein with tRNA adaptors. Genes are switched on and off; the lac operon is the classic example. The Human and Rice Genome Projects read whole genomes, and DNA fingerprinting uses repeat DNA (VNTRs) to identify people.
- 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.
- 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.
5. Reproduction and development of organisms
Reproduction · Ontogenesis
- 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.
- Development: From One Cell to a Whole Body – Development (ontogenesis) is the life story of one organism. The zygote divides by cleavage into a ball of cells, the blastula. In gastrulation cells move inwards and make three germ layers: ectoderm, mesoderm and endoderm. Cells then differentiate: every cell has the same genes, but each type switches on a different set. Signals between cells (induction) and master genes such as Hox genes decide where each part forms. After birth or hatching the organism grows, develops directly or by metamorphosis, ages and can sometimes regenerate.
6. Biology for breeding, biotechnology and medicine
Breeding · Biotechnology
- Plant Breeding: Making Better Crops – Plant breeding is the purposeful change of crop genes to create better varieties: higher yield, better quality, disease and pest resistance, and tolerance of drought, salt, heat or cold. The oldest method is artificial selection: keep seeds only from the best plants, generation after generation. Hybridisation crosses two parents so the offspring gets good traits from both. Inbreeding (crossing close relatives or selfing) makes pure lines; too much causes inbreeding depression. Outbreeding crosses unrelated lines; the F1 hybrid of two pure lines is often stronger than both parents (heterosis). Interspecific crosses (wheat × rye = triticale) need chromosome doubling. Modern tools: mutation breeding, polyploidy, tissue culture, DNA markers and gene editing. Vavilov showed crops have centres of origin rich in wild relatives, and related species vary in similar (homologous) series.
7. Humans and the biosphere
Ecosystems · Human impact and sustainability
- 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.
- 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.
8. Evolution of the living world
Evolutionary theory · Origin and history of life
- 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.
- 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.