National Year 11 Biology
Chapters: 3
1. 4.5 Homeostasis and response
4.5.1 Homeostasis · 4.5.2 The human nervous system · 4.5.3 Hormonal coordination in humans · 4.5.4 Plant hormones (Biology only)
- 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.
- Nervous System, Reflex Action and the Human Brain – Nerve cells (neurons) carry messages as electric impulses and pass them to the next cell with chemicals across a gap called a synapse. Quick safety responses (reflexes) are handled by the spinal cord; thinking and control come from the brain, which is guarded by the skull and a fluid cushion.
- Hormones in Animals: Endocrine Glands and Feedback – Endocrine glands release chemical messengers called hormones straight into the blood. The blood carries them all over the body, but they act only on target cells. Hormones control growth, metabolism, emergency response, blood sugar and puberty, and their amount is kept right by feedback.
- Coordination in Plants: Tropic Movements and Plant Hormones – Plants have no nerves or muscles, yet they respond. Some responses are quick and do not involve growth (touch-me-not leaves fold by moving water). Others are slow, directional growth movements called tropisms, controlled by plant hormones such as auxin, gibberellin, cytokinin and abscisic acid.
2. 4.6 Inheritance, variation and evolution
4.6.1 Reproduction · 4.6.2 Variation and evolution · 4.6.3 The development of understanding of genetics and evolution · 4.6.4 Classification of living organisms
- 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.
- 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.
- 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.
3. 4.7 Ecology
4.7.1 Adaptations, interdependence and competition · 4.7.2 Organisation of an ecosystem · 4.7.3 Biodiversity and the effect of human interaction on ecosystems · 4.7.4 Trophic levels in an ecosystem (Biology only) · 4.7.5 Food production (Biology only)
- 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.
- Biodiversity and the Effect of Human Activity on Ecosystems – Biodiversity is the variety of all the different species of organisms on Earth or in one ecosystem. High biodiversity makes an ecosystem stable, because species depend on each other for food, shelter and a steady physical environment, and it gives people food, medicines and clean air and water. A growing human population uses more resources and makes more waste. Pollution of water, land and air, land use for building, farming, quarrying and landfill, peat removal, deforestation and global warming all reduce biodiversity. We can protect it with breeding programmes, restoring habitats, hedgerows and field margins, reducing deforestation and carbon dioxide emissions, and recycling instead of dumping waste.
- Food Production – Food production is how humans grow, raise and catch enough food. Food security means everyone always has enough safe, healthy food. It is threatened by a growing population, changing diets, new pests, climate change, war and cost. We raise output with farming techniques (fertiliser, pest control, irrigation, intensive animal farming), keep fish stocks alive with net-size rules and quotas, and use biotechnology such as mycoprotein and GM crops.