Biodiversity and Conservation — BIOLOGY STD 12 Science — Question

Write a short note on hormones secreted during pregnancy.

List the different types of pollination depending upon the source of pollen grain.

Name the type of curve that characterises most population growing in favourable environment. Also define carrying capacity.

Justify with the help of an example where a deliberate attempt by humans has led to the extinction of a particular species.

What is natural ecosystem? Explain with the help of suitable example.

A heavily bleeding and bruised road accident victim was brought to a nursing home. The doctor immediately gave him an injection to protect him against a deadly disease.

1. What did the doctor inject into the patient's body?
2. How do you think this injection would protect the patient against the disease?
3. Name the disease against which this injection was given and the kind of immunity it provides.

Explain why the term ‘homozygous’ and ‘heterozygous’ with respect to an X–linked trait are applicable to human females but not to human males?

Describe briefly the following:
Origin of replication

In angiosperms, zygote is diploid while primary endosperm cell is triploid. Explain.

Name the group of organisms which constitute 'flocs'. Write their influence in the level of BOD during biological treatment of sewage.

OR

Explain the role of flocs in sewage treatment.