Germany Jahrgangsstufe 9 Biology
Chapters: 6
1. Gaining, communicating and evaluating knowledge
Scientific inquiry in 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.
2. Microorganisms in biotechnology
Microorganisms in biotechnology
- Microorganisms: The Tiny Living Things All Around Us – Microorganisms (microbes) are living things too small to see without a microscope. The main groups are bacteria, fungi, protozoa and algae; viruses are also studied with them but are not cells. Bacteria have no nucleus (prokaryotes); the others have one (eukaryotes). Bacteria multiply by splitting in two, so their number doubles again and again. Most microbes are harmless or helpful: our gut microbiota helps digestion, microbes make curd and bread, recycle dead matter and fix nitrogen. A few are pathogens that cause disease. Antibiotics kill bacteria but not viruses, and misusing them breeds resistant bacteria.
3. Genetics and genetic engineering
From gene to trait · Chromosomes, DNA replication and mitosis · Meiosis, recombination and gene technology
- 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.
- 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.
4. Evolution
Evolution and origin of species
- 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.
5. Invertebrate biodiversity and adaptation
Movement in invertebrates · Invertebrate breathing, circulation and feeding · Invertebrate reproduction and metamorphosis · Invertebrate senses and communication
- Biodiversity and its Conservation – Biodiversity is the variety of life at three levels: genetic, species and ecological. It is highest near the equator and grows with area (log S = log C + Z log A). Every species matters, like rivets on a plane. We are losing species fast because of the 'evil quartet': habitat loss and fragmentation, over-exploitation, alien species invasions and co-extinction. The IUCN Red List (Red Data Book) ranks species from Least Concern to Extinct. We protect life in situ (hotspots, national parks, sanctuaries, biosphere reserves, sacred groves, Ramsar wetlands) and ex situ (zoos, botanical gardens, seed and gene banks).
- Diversity and Classification of Living Organisms – Earth has millions of kinds of living things, and India is one of the richest places. To study them, we sort them into groups by asking simple questions about their bodies: Is there a nucleus? One cell or many? Can it make its own food? This gives five kingdoms: Monera, Protista, Fungi, Plantae and Animalia. Animals split into invertebrates and vertebrates. Every species gets a two-part scientific name. Viruses are not cells, so they fit in no kingdom.
- 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).
- Animal Behaviour: Why Animals Do What They Do – Behaviour is everything an animal does in reply to a stimulus from outside (a predator, light, a sound) or inside (hunger, hormones). Some behaviour is innate (instinct, born with it); some is learned (habituation, conditioning, imprinting, insight). Behaviour has a function: it helps the animal survive and reproduce, often by living in groups. Many animals are sentient: they can feel pain, fear and pleasure.
6. Soil ecosystem
Soil as an ecosystem
- 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.