Human Reproduction — BIOLOGY STD 12 Science — Question

Why is predation required in a community of different organisms?

When do you describe the relationship between two organisms as mutualistic, competitive and parasitic? Give one example of each type.

Explain Gause's Competitive Exclusion Principle with the help of a suitable example.

In a Polymerase Chain Reaction (PCR), give the temperature required for the steps:

1. Denaturation.
2. Annealing.
3. Extension, respectively.

Bio-fertilisers are organisms that enrich the nutrient quality in the soil. Explain the role of three main sources of bio-fertilisers.

Differentiate between benign tumor and malignant tumor.

Rearrange the following in the correct sequence to accomplish an important biotechnological reaction:

1. In vitro synthesis of copies of DNA of interest.
2. Chemically synthesised oligonucleotides.
3. Enzyme DNA-polymerase.
4. Complementary region of DNA.
5. Genomic DNA template.
6. Nucleotides provided.
7. Primers.
8. Thermostable DNA-polymerase (from Thermus aquatics).
9. Denaturation of ds-DNA.

Where does triple fusion take place in a flowering plant? Why is it so called? Mention its significance.

Fill in the missing stages in the given primary hydrarch succession.
Phytoplankton → (a) → (b) → (c) → Submerged free-floating → (d) → Forest plant stage.
What is common between hydrarch and xerarch succession?

With the help of a schematic diagram, explain the location and role of the following in a transcription unit.
Promoter, structural gene, terminator.