Class 12th Biology 2017 Set1 Delhi Board Paper Solution
Name three representative kinds of age pyramids for human population and list the characteristics for each one of them.
For human population age pyramids generally show age distribution of males and females. The shape of pyramids reflects the growth status of the population.
i. whether it is growing
ii. stable
iii declining
Population having large number of young members grow rapidly, while, the population bearing more number of post-reproductive members tends to be declining. There are basically three types of age pyramids found to be present in human population. These are as follows:
(i) Expanding or Triangular Age Pyramid : In this, number of pre-reproductive individuals is very lar ge, number of age reproductive individuals is moderate, while post-repr oductive individuals are fewer. This type of age pyramid shows that population is growing. The rate of growth depends upon the size of pre-reproductive population. This type of population growth is observed in developing cou ntries like India, Brazil.
(ii) Stable or Bell-shaped Age Pyramid : In this, the number of pre-reproductive and reproductive in dividuals is almost equal. Post-reproductive individuals are comparat ively fewer. The population size remains stable, neither growing nor diminishing. This type of population growth is o bserved in countries like USA, Denmark.
(iii) Declining or Urn-shaped Pyramid : The proportion of reproductive age group is higher than the i ndividuals in pre-reproductive age group. The number of post-reproducti ve individuals in also sizeable. It is declining or diminishing population with negative growth. This type of p opulation growth is observed in countries like Japan.
Popular Questions of Class 12th biology
- Q:- What is spermatogenesis? Briefly describe the process of spermatogenesis.
- Q:- Why is reproduction essential for organisms? Answer
- Q:- Write a short note on
(a) Adaptations of desert plants and animals
(b) Adaptations of plants to water scarcity
(c) Behavioural adaptations in animals
(d) Importance of light to plants
(e) Effect of temperature or water scarcity and the adaptations of animals. - Q:- With a neat diagram explain the 7-celled, 8-nucleate nature of the female gametophyte.
- Q:- What is DNA fingerprinting? Mention its application.
- Q:- What is oogenesis? Give a brief account of oogenesis.
- Q:- Describe the structure of a seminiferous tubule.
- Q:- What is triple fusion? Where and how does it take place? Name the nuclei involved in triple fusion.
- Q:- With a neat, labelled diagram, describe the parts of a typical angiosperm ovule.
- Q:- Explain the Law of Dominance using a monohybrid cross.
Recently Viewed Questions of Class 12th biology
- Q:- What are the major components of seminal plasma?
- Q:- List 10 modern-day animals and using the internet resources link it to a corresponding ancient fossil. Name both.
- Q:- Briefly describe various steps involved in plant breeding.
- Q:- Find out through internet and popular science articles whether animals other than man have self-consciousness.
- Q:- Name important defence mechanisms in plants against herbivory.
- Q:- Define phenotypic adaptation. Give one example.
- Q:- In our society the women are often blamed for giving birth to daughters.
Can you explain why this is not correct? - Q:- Why are offspring of oviparous animals at a greater risk as compared to offspring of viviparous animals?
- Q:- What are the major causes of species losses in a geographical region?
- Q:-
What is menstrual cycle? Which hormones regulate menstrual cycle?