Human Health and Disease — BIOLOGY STD 12 Science — Question

Give the term/ reason:
Sperm cannot reach ovum without seminal plasma.

In a biology class, teacher was telling the students that the structures/components and their functions in a watch can be compared with various levels of organisation we find in nature. Radhika was surprised and asked teacher to explain it. Teacher got impressed with Radhika's interest and explained that there is a systematic arrangement of smaller and simpler components into larger one in a hierarchy or pyramid having different levels where each level is formed of components of lower level and itself becomes part of higher level for achieving a common goal.
(i) What are the four levels of biological organisation found in nature?
(ii) What is the basic unit of ecological organisation?
(iii) Define community.
(iv) What values are shown by Radhika?

What do you understand by conservation? Describe the methods how biological resources are conserved?

Write short notes on the followings : (a) Predation (b) Competition

Describe the different methods of treatment of cancer.

What are recombinant DNA vaccines? Give two examples of such vaccines. Discuss their advantages.

Study the following flow chart. Name the hormones involved at each stage. Explain their functions.
Hypothalamus → Pituitary → Testes → Sperms.

a. Draw the embryo sac of a flowering plant and label the following:
i. Central cell
ii. Chalazal end
iii. Synergids
b. Name the cell and explain the process it undergoes to develop into an embryo sac.
c. Explain the development of endosperm in coconut.

Describe about gastrulation and formation of germinal cartex with the help of a diagram.