Ukraine 10 клас Biology and Ecology (profile level)
Chapters: 6
1. Introduction
Life and the scientific method
- 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.
2. Biodiversity
Systematics and phylogeny · Levels of biodiversity · Domains of life · Ecosystem biodiversity
- 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.
- Biological Classification – Whittaker (1969) sorted living things into five kingdoms, Monera, Protista, Fungi, Plantae and Animalia, using cell type, cell wall, body plan, mode of nutrition, reproduction and relationships. Monera are prokaryotes (bacteria, archaebacteria, cyanobacteria, mycoplasma). Protista are one-celled eukaryotes in five groups. Fungi are heterotrophs with chitin walls in four classes. Lichens are an alga and a fungus living together. Viruses, viroids and prions are not placed in any kingdom.
3. Metabolism and energy
Nutrition and transport · Digestion · Enzymes and respiration · Protein synthesis · Photosynthesis and chemosynthesis · Excretion and osmoregulation
- Human Digestive System and Heterotrophic Nutrition – Heterotrophs take ready-made food from other living things. Humans are holozoic: we eat whole food and break it down in a long tube, the alimentary canal. Teeth, saliva, stomach acid, enzymes, bile and pancreatic juice cut big food molecules into small ones that villi in the small intestine absorb into blood.
- 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.
- Protein Synthesis: From Gene to Protein – A gene is a stretch of DNA that holds the recipe for one protein. In transcription, the cell copies the gene into messenger RNA (mRNA) inside the nucleus; U replaces T. The mRNA goes to a ribosome in the cytoplasm. In translation, the ribosome reads the mRNA three bases at a time (a codon). Each codon matches one amino acid, carried in by a transfer RNA (tRNA). The amino acids join into a chain that folds into a protein. A change in the DNA (a mutation) can change the protein.
- Photosynthesis in Higher Plants – Green plants make sugar from carbon dioxide and water using light. It happens in chloroplasts. The light reaction in the thylakoids splits water, gives out oxygen and makes ATP and NADPH. The Calvin cycle in the stroma uses that ATP and NADPH to fix CO₂ into sugar. C₄ plants add a CO₂ pump that stops the wasteful photorespiration. The slowest factor, such as light, CO₂ or temperature, sets the rate.
- Excretory Products and their Elimination – Animals must remove nitrogen waste. Ammonia is most toxic and needs lots of water; urea is less toxic; uric acid needs least water. Humans are ureotelic. Each kidney has about a million nephrons. Urine forms in three steps: glomerular filtration (about 125 mL/min, 180 L/day), reabsorption (about 99% taken back) and secretion. The loop of Henle and vasa recta make the medulla salty by a counter-current mechanism, so urine can be concentrated. ADH, the renin-angiotensin-aldosterone system and ANF control water and salt. Lungs, liver, skin and sweat also help. Failed kidneys need dialysis or a transplant.
4. Heredity and variation
Gene structure and genome · Inheritance · Variation
- Gene Structure: What Is Inside a Gene? – A gene is a stretch of DNA that carries the instructions to make a functional product, usually a protein (sometimes an RNA). A typical gene has a promoter (where RNA polymerase binds and transcription starts), a coding region (the message) and a terminator (where transcription stops). The template strand is read; the coding strand has the same sequence as the mRNA (with T instead of U). In prokaryotes, genes are continuous (no introns) and related genes are often grouped in an operon under one promoter, making one polycistronic mRNA. In eukaryotes, genes are split: coding exons are separated by non-coding introns. The whole gene is copied into pre-mRNA; then introns are removed and exons joined (splicing), a cap and a poly-A tail are added, and the mature mRNA leaves the nucleus. Alternative splicing lets one gene make several proteins. The genome is all the DNA of an organism; in humans only about 1–2% codes for protein.
- 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.
- Mutations – A mutation is a sudden, lasting change in the DNA. Gene (point) mutations change one or a few bases: substitution, insertion or deletion. Insertions and deletions shift the reading frame. Chromosome mutations change big pieces or the number of chromosomes. Mutations happen by chance or because of mutagens such as UV light, X-rays and some chemicals. They can be harmful, neutral or useful, and they are the first source of all genetic variation.
5. Reproduction
DNA replication and viruses · Cell division · Reproduction of organisms
- DNA Replication: How a Cell Copies Its DNA – Before a cell divides, it makes an exact copy of its DNA so each new cell gets a full set of instructions. Helicase unzips the double helix. Each old strand is a template. DNA polymerase adds matching bases (A with T, G with C). The result is two DNA molecules, each with one old and one new strand (semi-conservative). Polymerase checks its work, so mistakes are very rare; a mistake that stays is a mutation.
- 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.
- 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.
6. Development
Embryonic development · Post-embryonic development and growth
- 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.