France Première Biology-Ecology
Chapters: 2
1. Contemporary environmental issues
Acquiring resources: photosynthesis · Food webs and consumers · Reproduction modes and environment · The ecological niche · Biodiversity surveys and community structure
- Life Processes and Photosynthesis – Life processes are the jobs every living body must keep doing to stay alive: nutrition, respiration, transport and excretion. Green plants do nutrition by photosynthesis: using sunlight and chlorophyll, they turn carbon dioxide and water into glucose and give out oxygen.
- 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.
- 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.
- The Ecological Niche – Every organism lives in a habitat (its address) and has a niche (its role: what it eats, where and when it is active, and how it affects others). Its life is shaped by abiotic factors (temperature, light, water, pH) and biotic factors (food, predators, competitors). For each factor it has a range of tolerance with an optimum in the middle. The potential (fundamental) niche is everything it could use; the realised niche is the smaller part it actually uses when competitors and predators are present. When two species' niches overlap fully, one pushes the other out (competitive exclusion); partly overlapping species can coexist by sharing resources. Species with narrow tolerance can act as bioindicators.
- 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.
2. Contemporary health issues
Balanced diet, digestion and absorption · Malnutrition; diabetes and blood sugar · Locomotor system, injuries, doping, muscle metabolism · Single-gene disorders and genetic engineering
- 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.
- 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.
- Muscle Physiology: How Muscles Contract – A skeletal muscle is made of long cells called fibres. Each fibre holds chains of tiny units called sarcomeres. In a sarcomere, thin actin filaments and thick myosin filaments overlap. A nerve signal releases calcium, myosin heads grab actin and pull it to the middle, and the muscle shortens. Every pull uses ATP. ATP comes from creatine phosphate (seconds), fermentation that makes lactate (up to about two minutes) and aerobic respiration (long exercise). When ATP runs low the muscle tires.
- Genetic Disorders – A genetic disorder is a health problem caused by a change in a gene or in the number or shape of chromosomes. Single-gene disorders can be recessive (cystic fibrosis, sickle cell anaemia: you need two faulty copies), dominant (Huntington disease: one faulty copy is enough) or X-linked (haemophilia, colour blindness: mostly boys). Chromosome disorders such as Down syndrome (an extra chromosome 21) come from a mistake when egg or sperm cells form. Punnett squares predict the chance of each outcome, and genetic testing, counselling and gene therapy help families.