What is BOD?
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Solution and Explanation
Step 1: Understanding BOD.
BOD stands for **Biochemical Oxygen Demand**. It is a measure of the amount of oxygen required by microorganisms to break down organic material in water. A higher BOD indicates a higher level of pollution in water, as more oxygen is needed for microbial activity.
Step 2: Conclusion.
BOD is an important parameter for assessing the quality of water and its level of contamination.
Top Questions on Ecology and Environment
Study the figure given below and answer the questions that follow.
- Identify the figure and state its importance.
- Why is air diffused into the aerator tank? Explain.
-
- [(i)] What changes take place in the settling tank?
OR - [(ii)] How is BOD related to organic matter present in the water?
- [(i)] What changes take place in the settling tank?
- CBSE CLASS XII - 2025
- Biology
- Ecology and Environment
- Name the type of food chains responsible for the flow of larger fraction of energy in an aquatic ecosystem and a terrestrial ecosystem, respectively. Mention any two differences between the two food chains.
- CBSE CLASS XII - 2025
- Biology
- Ecology and Environment
- (a) What do you mean by activated sludge in an STP?
(b) Explain the biological treatment of the major part of the sludge transferred from the large aeration tank into the anaerobic sludge digesters before its final release into the natural water bodies.- CBSE CLASS XII - 2025
- Biology
- Ecology and Environment
- Correctly depict (also indicate the trophic level) and describe the ecological pyramid of biomass in sea with 40 standing crop of phytoplankton supporting 90 standing crop of zooplankton which further supports 120 small fishes.
- CBSE CLASS XII - 2025
- Biology
- Ecology and Environment
Highly conserved proteins such as Haemoglobin and Cytochrome-C provide the best biochemical evidence to trace evolutionary relationships between different groups. Cytochrome-C is formed of 104 amino acids. Cytochrome-C is the respiratory pigment present in all eukaryotic cells. It has evolved at a constant rate during evolution. In chimpanzees and humans, Cytochrome-C genes are identical. The given data shows the evolution of the Cytochrome-C gene in different mammals from kangaroos, cows, rodents to humans:
Groups Nucleotide substitution in the gene of Cytochrome-C Millions of years ago Human/Kangaroo 100 125 mya Human/Cow 75 120 mya Human/Rodent 60 75 mya (a) Select the correct option for the time of separation of two groups and the number of nucleotide substitutions in the gene of Cytochrome-C:
Options Time of separation of two groups during evolution Number of nucleotide substitutions (i) Lesser Greater (ii) Greater Lesser (iii) Greater Greater (b) What do you infer about the type of evolution (convergent or divergent) for the given pair of groups and why?
(i) Human and Kangaroo
(ii) Human and Rodent
(c)
(i) Define convergent evolution.
OR
(ii) Define divergent evolution.- CBSE CLASS XII - 2025
- Biology
- Ecology and Environment
Questions Asked in MPBSE Class XII Board exam
निम्नलिखित में से किसी एक विषय पर निबंध लिखिए:
(i) पर्यावरण की सुरक्षा
(ii) दुखों की उपयोगिता
(iii) विद्यार्थी और अनुशासन
(iv) राष्ट्रीय एकता और अखंडता
(v) इंटरनेट का दैनिक जीवन में अनुपयोगपरीक्षा की तैयारी की जानकारी देते हुए पिता को पत्र लिखिए।
द्वनि विस्तारक यंत्रों पर प्रतिबंध लगाने हेतु जिला सचिव महोदय को प्रार्थना पत्र लिखिए।
निम्नलिखित गद्यांश की संदर्भ-प्रसंग सहित व्याख्या कीजिए: गद्यांश: पैसा पावर है। पर उसके स्वभाव में आस-पास सालों तक जमा न जमा हो तो क्या वह ताकत पावर है! पैसे को देखने के लिए बैंक-हिसाब सीट, पर माल-असबाब, मकान-कोठी तो अनदेखे भी दीखते हैं। पैसे के उस 'पेसींग पावर' के प्रयोग में ही पावर का खेल है।
निम्नलिखित गद्यांश की संदर्भ-प्रसंग सहित व्याख्या कीजिए: गद्यांश: एक बार वह 'डांग' देखने श्यामनगर शेला गया। पहलवानों की कुस्ती और डांव-पेच देखकर उससे नहीं रहा गया। जवानी की मस्ती और होल की ललकारती हुई आवाज़ ने उसकी नसों में बिजली उत्पन्न कर दी। उसने बिना कुछ सोचे-समझे दंगल में 'शेर के बच्चों' को चुनौति दे दी।