France Seconde Life and Earth Sciences
Chapters: 3
1. Earth, life and organisation of the living world
Organisation of life: cells, metabolism, DNA · Biodiversity as result and stage of evolution
- The Cell: Basic Unit of Life – Every living thing is made of cells. Robert Hooke first saw cells in cork in 1665. Cells are prokaryotic (no true nucleus, like bacteria) or eukaryotic (true nucleus). Plant cells have a cell wall, chloroplasts and a big vacuole; animal cells do not. Each organelle has a job. Water enters and leaves cells by osmosis. Cells make new cells by mitosis (growth) and meiosis (sex cells).
- 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.
2. Contemporary planetary issues
Geoscience: erosion and sedimentation · Agrosystems, soils and sustainability
- Geomorphic Processes: How Forces Build and Wear the Land – The Earth's surface is shaped by two sets of forces. Endogenic forces come from inside, powered by the Earth's heat: diastrophism (folding, faulting, uplift, sinking) and volcanism build up the land. Exogenic forces come from outside, powered by the Sun and gravity: weathering breaks rock where it stands, mass movements move it down slopes, and running water, wind, glaciers and waves erode and deposit it, slowly lowering high land. Weathered rock plus plants and tiny organisms over a long time becomes soil. Parent rock, climate, relief, living things and time decide what kind of soil forms.
3. Human body and health
Reproduction and sexuality · Microbes, microbiota and health
- 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.
- 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.