Bihar Board Class 10 · Science · Matric exam 2027
Chapter 15: Our Environment — notes
The chapter’s 6 parts in the book’s order — the first idea of each and the points Medha Ma’am writes on the board — and the summary at the end. The full lesson and a check question for each part are in the app.
1. Biodegradable and Non-biodegradable Waste
Okay, so — think about the waste you make every day.
- • Biodegradable = broken down by biological processes
- • Non-biodegradable = NOT broken down biologically
- • Enzymes are specific in action
- • Example: plastics persist, acted on only by heat/pressure
2. Ecosystem and its Components
Okay, so look around you — plants, animals, tiny microorganisms, even us.
- • Ecosystem = biotic + abiotic components
- • Biotic = living organisms
- • Abiotic = temperature, rainfall, wind, soil, minerals
- • Producers -> make food (photosynthesis)
- • Consumers -> herbivores, carnivores, omnivores, parasites
- • Decomposers -> bacteria, fungi break down dead matter
3. Food Chains, Trophic Levels and Food Webs
Okay, so, think about who eats whom, in order.
- • Food chain = series of organisms, each eating the one before
- • Trophic level = each step of a food chain
- • 1st: producers, 2nd: herbivores, 3rd: small carnivores, 4th: large carnivores
- • Green plants capture ~1% of sunlight as food energy
- • Only ~10% of food eaten passes to next level
4. Biological Magnification
Okay, so let's talk about something that happens without us even noticing.
- • Pesticides enter soil/water -> taken up by plants
- • Chemicals cannot be broken down
- • They build up MORE at each trophic level
- • Biological magnification = this progressive build-up
- • Humans, at the top, get the maximum concentration
5. The Ozone Layer and its Depletion
Okay, so let's talk about ozone.
- • Ozone = O3 (3 oxygen atoms); poisonous gas
- • O2 + UV -> O + O
- • O + O2 -> O3 (ozone)
- • Ozone layer shields earth from UV radiation
- • CFCs (refrigerants, fire extinguishers) deplete ozone
- • 1987: UNEP agreement to freeze CFC at 1986 levels
6. Managing the Garbage We Produce
Okay, so think about any town or city you've visited.
- • Improved lifestyle -> more waste generated
- • More disposable items used
- • Packaging changes -> more non-biodegradable waste
- • Plastic cups: hygienic but non-biodegradable
- • Clay kulhads: cause loss of fertile top-soil
- • Paper-cups now used as alternative
Summary
Okay, so let's go back over everything we covered today. We started with waste, and you learned there are two kinds. Biodegradable waste gets broken down by biological processes. Non-biodegradable waste doesn't — it just stays in the environment, because enzymes only act on specific substances. Then we looked at an ecosystem. It has biotic components, the living organisms, and abiotic components, the physical factors. You learned organisms are grouped as producers, consumers and decomposers. We saw how one organism feeding on another forms a food chain, with trophic levels. Only about 10% of energy moves from one level to the next — that's why chains stay short, and branch out into food webs. You also learned how harmful chemicals, like pesticides, build up as they move through the food chain. That's called biological magnification, and it reaches its highest level in human beings, right at the top. After that, we talked about the ozone layer. It's made of O3, and it shields the earth from harmful UV radiation. You learned CFCs have been depleting it since the 1980s. Finally, we saw how changing lifestyles and packaging have increased non-biodegradable waste, and how we've been searching for better options, like paper-cups, to manage our garbage. So — which of all these ideas felt the most new to you?
AskMedha · Medha Ma’am — Bihar Board Class 10 Science, Chapter 15. Written from the textbook, checked twice.
Questions parents and students ask
- How do I get the "Our Environment" notes as a PDF?
- Press "Save as PDF" — the phone’s print sheet opens; choose "Save as PDF" there. The PDF holds the notes only.
- Where are these notes written from?
- From the chapter’s own textbook text, part by part, in the book’s own terms; a second, independent model then checked every part against the book. The full lesson, a check question for each part and the practice are in the AskMedha app.
The same preparation, with Medha Ma’am — on your phone
Every question of every chapter with its model answer, practice questions in the board’s own shapes, 60 minutes of class a day, written answers marked, a test every Sunday and a WhatsApp report to parents.
Medha Ma’am is an AI teacher, not a live tutor. Every answer is checked twice; a person takes responsibility.