Russia 10 класс Biology (advanced)

Chapters: 12

1. Biology as a science

Modern biology

The Scientific Method – The scientific method is the careful way scientists find out how the world works. Observe something, ask a testable question, make a hypothesis (a clear, testable guess), test it with a fair experiment (change one variable, measure one, keep the rest the same), repeat and record data, analyse it, draw a conclusion and share it so others can check. Results that fail the test are useful too: they send you back to a new hypothesis.

Properties and levels of life

The Living World – Earth has millions of kinds of living things; this variety is biodiversity. To study them we sort them into groups. Taxonomy is naming, describing and classifying; systematics also asks how groups are related. All life falls in three domains: Bacteria, Archaea and Eukarya. Organisms are placed in 7 main ranks, from kingdom down to species, and each species gets a two-part Latin name like Mangifera indica.

Cell theory

Cell: The Unit of Life – Every living thing is made of cells, and every new cell comes from an old cell. Prokaryotic cells (bacteria) have no nuclear envelope and no membrane-bound organelles; eukaryotic cells have a true nucleus and many organelles. The membrane is a fluid mosaic of lipids and proteins; plants add a cellulose wall. ER, Golgi, lysosomes and vacuoles form the endomembrane system. Mitochondria and plastids make energy and food, ribosomes make proteins, the cytoskeleton, cilia, flagella and centrioles give shape and movement, and the nucleus holds the DNA.

Biomolecules

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.

Cell structure

Cell: The Unit of Life – Every living thing is made of cells, and every new cell comes from an old cell. Prokaryotic cells (bacteria) have no nuclear envelope and no membrane-bound organelles; eukaryotic cells have a true nucleus and many organelles. The membrane is a fluid mosaic of lipids and proteins; plants add a cellulose wall. ER, Golgi, lysosomes and vacuoles form the endomembrane system. Mitochondria and plastids make energy and food, ribosomes make proteins, the cytoskeleton, cilia, flagella and centrioles give shape and movement, and the nucleus holds the DNA.

Energy and plastic metabolism

Respiration in Plants – Respiration breaks food like glucose to release energy stored as ATP. Plants take in O₂ through stomata and lenticels. Glycolysis in the cytoplasm splits glucose into two pyruvates. Without O₂, pyruvate is fermented to ethanol or lactic acid. With O₂, pyruvate enters the mitochondrion, runs the Krebs cycle, and the electron transport system uses O₂ to make most of the ATP: up to 38 per glucose. The same path also builds molecules (amphibolic). RQ = CO₂ given out ÷ O₂ taken in.

Matrix synthesis

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.

Cell cycle

Cell Cycle and Cell Division – A cell grows, copies its DNA and splits in a fixed order called the cell cycle: interphase (G1, S, G2) and M phase. In S phase the DNA doubles (2C → 4C) but the chromosome number stays the same. Mitosis (prophase, metaphase, anaphase, telophase) and cytokinesis give two cells identical to the parent – it is an equational division used for growth and repair. Meiosis has two divisions; in meiosis I homologous chromosomes pair, cross over and separate, halving the chromosome number (2n → n). It makes four haploid cells for gametes and creates variation.

Organism systems

Coming soon

Reproduction and ontogenesis

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.

History and methods of genetics · Laws of heredity · Laws of variation · Human genetics

Principles of Inheritance and Variation – Genes come in pairs (alleles). Each parent passes one allele of each pair to the child. Mendel showed dominance (3 : 1), segregation and independent assortment (9 : 3 : 3 : 1). Real life has twists: incomplete dominance (1 : 2 : 1), co-dominance (AB blood), multiple alleles, pleiotropy (one gene, many effects) and polygenic traits (many genes, one trait). Genes sit on chromosomes, so genes on the same chromosome are linked and are separated only by crossing over. Sex chromosomes decide sex (XX-XY in humans, ZW in birds, haplo-diploid in honeybees) and carry sex-linked genes (haemophilia, colour blindness). Mistakes in genes cause Mendelian disorders (thalassemia, sickle-cell) and mistakes in chromosome number cause Down, Turner and Klinefelter syndromes.

Breeding · Biotechnology and synthetic biology

Biotechnology: Principles and Processes (Recombinant DNA Technology) – Genetic engineering means changing the genes of a living thing on purpose. We cut the gene we want with restriction enzymes (molecular scissors), paste it into a carrier DNA called a vector using DNA ligase (molecular glue), put it into a host cell, pick out the cells that took it, and grow them in big tanks (bioreactors) to collect the product. PCR makes millions of copies of a gene, and gel electrophoresis sorts DNA pieces by size.