Human Reproduction — BIOLOGY STD 12 Science — Question

During the biology class on theories of evolution, the teacher was telling about Lamarckism. Katy was confused after listening to it and went to her teacher to clear her doubts. She asked if characters can be passed to generations, then why she does not have the tatoo that her mother has on her arm. The teacher smiled and told Katy that this is the reason why Lamarck's theory was rejected. The teacher explained her the other theories as well.

1. Name the book in which Lamarckism was explained.
2. What are the three factors of this theory?
3. What are the other theories of evolution?
4. What are the values shown by teacher?

Observe the representation of genes involved in the lac operon given below.

1. Identify the region where the repressor protein will attach normally.
2. Under certain conditions repressor is unable to attach at this site. Explain.
3. If repressor fails to attach to the said site what products will be formed by z, y and a?
4. Analyse why this kind of regulation is called negative regulation.

Jeremy went to a butcher's shop with his father and saw that the goats before slaughter were fed on grasses and was fascinated to see the sequence of organism through which the food passes. On seeing his fascination his father asked him the reason and he quickly explained him the concept of food chain.

1. Describe food chain.
2. Grass was eaten by goat which in turn is consumed by humans. Explain their relation.
3. Name different types of food chains.
4. What values are shown by Jeremy?

Which vectors can be used to clone a fragment of DNA with the following lengths?

1. 4Kb
2. 35Kb
3. 20Kb
4. 250Kb

(i) Define standing crop.
(ii) Explain important steps in the process of decomposition in a terrestrial ecosystem.

(i) Explain the significance of each of the following features present in plants given below:, (a) In rose-bay plant the stamens ripen before the stigma., (b) In certain species of primrose, the flowers have short stamen and long style., (c) The bisexual flower of mustard exhibits rejection of self-pollen grain., (ii) Explain how autogamy is prevented in castor and papaya plant respectively.

Had Darwin been aware of Mendel’s work, would he been able to explain the origin of variations. Discuss.

Fitness is the end result of the ability to adapt and get selected by nature. Explain with suitable example.

Answer the following questions:
Explain the menstrual phase in a human female. State the levels of ovarian and pituitary hormones during this phase.