This Class 12 Biology Practical focuses on studying different types of symbiotic associations found in nature. Students observe root nodules in leguminous plants to understand nitrogen-fixing bacteria like Rhizobium. The practical also includes examining Cuscuta (dodder), a parasitic plant that derives nutrition from its host, and studying lichens as a perfect example of mutualism between algae and fungi. This activity helps learners identify the structure, function, and ecological importance of these associations. It strengthens practical knowledge, supports exam preparation, and builds clear concepts for board exams and competitive exams. Ideal for CBSE and other boards.
Aim
To study symbiotic association in root nodules of leguminous plants, Cuscuta on host, lichens.
Observation
1) Symbiotic association in root nodules of leguminous plants
- Root nodules are commonly found in the roots of leguminous plants
- They are formed due to association with a nitrogen fixing bacteria,Rhizobium
- Rhizobium is gram - ve bacteria
- Root nodules contains pink oolour leghaemoglobin pigment
- It also contains enzyme nitrogenase which helps in the formation of Ammonia
2) Cuscuta on host
- Cuscuta commonly called dodder /amberal live as stem ectoparasite on other plants.
- Stem of Cuscuta is thin and slender shaped without cholorophyll.
- It winds around the stem of host plant.
- Stem of cuscuta fixes with the host plant by the special structure called Haustoria.
- Haustoria direct connection with host plant and withdraw water ,carbohydrates and other solutes.
- Cuscuta can weaken or kill host plant and reduce crop yield.
3. Lichens
- Lichens are composite organisms representing a symbiotic association between fungus and algae
- The algal component is phycobiont and the fungal component is myoobiont
- They grow on land, rocks, tree trunks and walls of houses.
- Algae prepares food for fungi and Fungi provides shelter and absorbs minerals nutrients and water to algae.
- Main three different types are crustose, foliose, fructicose
Class 12 Biology Lab Manual – Final Practicals | Complete Lab Experiment File
A. List of Experiments
1. Prepare a temporary mount to observe pollen germination.
2. Study the plant population density by quadrat method.
3. Study the plant population frequency by quadrat method.
4. Prepare a temporary mount of onion root tip to study mitosis.
5. Isolate DNA from available plant material such as spinach, green
pea seeds, papaya, banana etc.
B. Study and observe the following (Spotting):
1. Flowers adapted to pollination by different agencies (wind, insects, birds).
2. Pollen germination on stigma through a permanent slide or scanning electron
3. Identification of stages of gamete development, i.e., T.S. of testis and T.S. of
ovary through permanent slides (from grasshopper/mice).
4. Meiosis in onion bud cell or grasshopper testis through permanent slides.
5. T.S. of blastula through permanent slides (Mammalian).
6. Mendelian inheritance using seeds of different colour/sizes of any plant.
7. Prepared pedigree charts of any one of the genetic traits such as rolling of tongue,
blood groups, ear lobes, widow's peak and colour blindness.
8. Controlled pollination - emasculation, tagging and bagging.
9. Common disease causing organisms like Ascaris, Entamoeba, Plasmodium, any
fungus causing ringworm through permanent slides, models or virtual images or
specimens. Comment on symptoms of diseases that they cause.
10. Models specimens showing symbiotic association in lichens, root nodules of
leguminous plants, and parasitic mode of nutrition shown by Cuscuta on host.
11. Flash cards / models showing examples of homologous and analogous organs.
Class
Biology
AssignmentNCERT Solutions
MCQ
Handwritten Notes
Important Questions
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