Evolution — BIOLOGY STD 12 Science — Question

What is xenogamy. Explain in detail the various adaptations found in plants for xenogamy.

A burglar in a huff forgot to wipe off his blood-stains from the place of crime where he was involved in a theft and fight. Name the technique which can help in identifying the burglar from the blood-stains. Describe the technique.

1. Write your observations on the variations seen in the Darwin’s finches shown above.
2. How did Darwin explain the existence of different varieties of finches on Galapagos Islands?

Write a short note on Double fertilisation.

Distinguish between embryo and endosperm found in Angiosperms.

A dihybrid heterozygous round, yellow seeded garden pea was crossed with a double recessive plant.

1. What type of cross is this?
2. Work out the genotype and phenotype of the progeny.
3. What principle of Mendel is illustrated through the result of this cross?

Explain the pyramid of energy in ecosystem. ###What is meant by ecological pyramid? Describe an ideal pyramid of energy with diagram.

Rajesh was doing gel electrophoresis to purify DNA fragments. Given below is the sketch of the observations of the experiment performed by him.

1. At which end he would have loaded the samples and where?
2. Analyse the reason for different positions taken up by the DNA bands.
3. Elaborate the step he would have followed to visualise DNA bands.

Show with the help of diagram the stages in which a pollen mother celll transforms into a pollengrain.