Human Reproduction — BIOLOGY STD 12 Science — Question

Differentiate between oviparous and viviparous animals with an example of each.

Questions 1-3 are based on the following diagram. Read the questions and fill the blank spaces:

1. Each level of a pyramid represents a trophic level. With reference to the grazing food web, name an organism at the first trophic level. ______ (a) ______. Two organisms at the second trophic level ______(b)______ Two organisms at the third trophic level ______ (c) ______.
2. With reference to a pyramid of energy, why is each trophic level reduced in size?
3. Why is there a limited number of trophic levels?

During his studies on genes in Drosophila that were sex-linked T.H. Morgan found F2 -population phenotypic ratios deviated from expected 9:3:3:1. Explain the conclusion he arrived at.

Define a climax community. How does a sere differ from a seral community?

Plant breeding technique has helped sugar industry in North India. Explain how.

Where is acrosome present in humans? Write its function.

Study the given flow chart and answer:

1. Name the defence mechanism used.
2. In which plant it has been done?
3. Name the pathogen.
4. Name the vector used in this technique.

Prabha has seen huge garbage dumps outside your school which are not being regularly disposed of by MCD. Prabha discusses the problems with school mates and decide to organize rally to spread awareness among local people about public hygiene.
→ Prepare two slogans for rally
→ Name any two infectious diseases which may spread due to such unhygienic conditions at public place

How did Hershey and Chase differentiate between DNA and protein in their experiment while proving that DNA is the genetic material?

Spermatids possess haploid chromosome number. Explain.