Netherlands HAVO 5 (eindexamenjaar) Biology
Chapters: 4
1. Self-regulation (part 2)
Self-regulation of the organism · Defence of the organism · Regulation of ecosystems
- Homeostasis – Homeostasis is how the body keeps its internal environment (blood and tissue fluid) steady even when the outside world changes. It controls body temperature (about 37 °C), blood glucose (about 4–6 mmol/L), water and salt, and blood pH (about 7.4). It mostly uses negative feedback: a receptor senses a change, a control centre decides, and an effector brings the level back to its set point.
- 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).
2. Self-organisation of cells
Self-organisation of cells
- 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.
3. Interaction
Molecular interaction · Behaviour and interaction · Sexuality · Interaction in ecosystems
- Gene Regulation: How Cells Switch Genes On and Off – Every cell carries the same DNA but uses only some genes. Cells control mostly at transcription. In bacteria, the lac operon is a set of genes under one promoter and one operator: a repressor blocks it when there is no lactose; lactose removes the repressor and the genes are read (an inducible operon). In eukaryotes, transcription factors, enhancers and silencers control each gene, and epigenetic marks (DNA methylation, histone packing) can keep genes off without changing the DNA code. Different on/off patterns make different cell types (differentiation).
- 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.
- 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.
4. Evolution
Selection · Speciation · Biodiversity
- 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.
- 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).