Assertion Reason Biology Chapter 13 Biodiversity and its Conservation
Questions of Assertion Reason Chapter 13 Biodiversity and its Conservation biology CBSE Class 12 are very simple to understand as this chapter deals with Biodiversity and its Conservation. To solve assertion reason type questions of biology, deeper understanding of concept about Biodiversity and its Conservation is required. In order to help the student in solving Assertion Reason type of questions, detailed process is explained.
How to solve Assertion Reason Type Questions?
In Assertion-Reason type of question, two statements are given, first is Assertion and second is called Reason. Student must have to think critically about both the statements in Assertion Reason Questions, since it combines multiple choice questions and true/false type of questions which requires a higher level of understanding.
How many types are there of Assertion Reason Type Questions?
Assertion-Reason type of questions can be asked either with four MCQ options or with five MCQ options. First four options are same in both the cases only one more options is being provided i.e. last one. One extra option increases the difficulty level of the questions.
In assertion reason type of questions, all 4 or 5 options are same for each question, which are as:
(a) Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A).
(b) Both assertion (A) and reason (R) are true but reason (R) is not the correct explanation of assertion (A).
(c) Assertion (A) is true but reason (R) is false.
(d) Assertion (A) is false but reason (R) is true.
(e) Both Assertion and Reason are false.
Then a question haunts in every student’s mind, which option is correct and when?
This can be understood clearly with the following table:
| Assertion (A) | Reason (R) | MCQ Options (Fixed for all questions) |
|---|---|---|
| If True | True | (a) Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A). |
| If True | True | (b) Both assertion (A) and reason (R) are true but reason (R) is not the correct explanation of assertion (A). |
| If True | False | (c) Assertion (A) is true but reason (R) is false. |
| If False | True | (d) Assertion (A) is false but reason (R) is true. |
| If False | False | (e) Both Assertion and Reason are false. |
Now, lets practice some Assertion Reason Questions of Biology : Chapter 13 Biodiversity and its Conservation.
Read instructions carefully before answering the questions.
For question given below, two statements are given- one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below:
(a) Both A and R are true and R is correct explanation of the assertion.
(b) Both A and R are true but R is not the correct explanation of the assertion.
(c) A is true but R is false.
(d) A is false but R is true.
Question.1.
Assertion: Alpha diversity is said· to be higher if the dissimilarity between communities is higher.
Reason: Alpha diversity is a measure of diversity between the communities.
Ans.1. (d)
Alpha diversity (within-community diversity) refers to the diversity of organisms sharing the same community/ habitat. A combination’ of species richness and equitability/evenness is used to represent diversity within a community or habitat. Generally, greater the species richness, greater is the species diversity. Species frequently change when habitat or community changes. The rate of replacement of species along a gradient of habitats or communities is called beta diversity between-community diversity. Higher the heterogeneity in the habitats in a region or greater the dissimilarity between communities, higher is the beta diversity. Diversity of the habitats over the total landscape or geographical area is called gamma diversity.
Question.2.
Assertion: The species diversity present in a given community or habitat is referred to as alpha diversity.
Reason: Alpha diversity is usually expressed by species richness and species evenness in that community habitat.
Ans.2. (a)
Alpha diversity within community diversity is species diversity in a given community or habitat. It is dependent upon species richness and species evenness / equitability. There is a lot of competition, adjustments and interrelationships amongst members of the same community. The number of species per unit area is called species richness. Number of individuals of different species represent species evenness or species equitability.
Question.3.
Assertion: Diversity observed in the entire geographical area, is called gamma diversity.
Reason: Bio-diversity decreases from high altitude to low altitude.
Ans.3. (c)
Biodiversity is not uniform on the earth. It varies with change in latitude or altitude. Biodiversity increase, when we move from high to low latitude (i.e. from the poles to the equator).
Question.4.
Assertion: A biosphere reserve is a specified area.
Reason: No restriction on human activities has been imposed in biosphere reserve.
Ans.4. (c)
Assertion is true but Reason is false.
Question.5.
Assertion: In tropical rain forests. O-horizon and A-Horizon of soil profile are shallow and nutrient-poor.
Reason: Excessive growth of micro-organisms in the soil depletes its organic content.
Ans.5. (c)
O-horizon occupies the topmost soil and is rich in mineral and decomposed organic matter (humus). A-horizon is dark coloured and has abundant minerals mixed with humus.
Question.6.
Assertion: Communities that comprise of more species tend to be more stable.
Reason: A higher number of species results in less animal variation in total biomass.
Ans.6. (a)
Communities with higher number of species are more stable as it can resist occasional disturbances. A stable community should show less variation in productivity from year to year and resistance towards alien species.
Question.7.
Assertion: Community with more species tends to be more stable than those with less species.
Reason: More will be the species, less will be year to year variation in total biomass.
Ans.7. (a)
Communities with more species tend to be more stable than those with less species. It is able to resist occasional disturbance . A stable community should not show too much variation in productivity from year to year; it must be resistant to invasions by alien species. David Tilman’s long term experiments showed the plots with more species, experience less year to year variation in total biomass.
Question.8.
Assertion: A stable community should not show too much variation in productivity from year to year.
Reason: A stable community must be resistant to invasions by the alien species.
Ans.8. (b)
A stable community should not show too much variation in productivity from year to year; it must be either resistant or resilient to occasional disturbances (natural or man-made), and it must also be resistant to invasions by alien species.
Question.9.
Assertion: Decrease in species diversity occurs as we ascend a high mountain.
Reason: Decrease in species diversity occurs with increase in altitude due to rise in
temperature.
Ans.9. (c)
Barring arid/semiarid and aquatic habitats, biodiversity shows a latitudinal and altitudinal gradient. A decrease in species is observed as we ascend a high mountain due to drop in temperature (lapse temperature being 6.5°C for 1 km or 1000 m) and greater seasonal variability.
Question.10.
Assertion: Most common forest type in India is tropical dry deciduous forests.
Reason: They are common in West Bengal.
Ans.10. (c)
The tropical monsoon deciduous forests are found in areas receiving an annual rainfall of 100 to 200cms in India, with a distinct dry and rainy season and minimum temperature. The south western ghats moist deciduous forests are a tropical moist broad leaf forest ecoregion of southern India. It covers the southern portion of the Western Ghats range and the Nilgiri Hills between 250 and 1000 meters elevation in Kerala, Karnataka and Tamil Nadu states.
Question.11.
Assertion: Tropical latitudes have greater biological diversity then temperate latitudes.
Reason: Tropical regions remain relatively undisturbed for millions of years.
Ans.11. (a)
Tropical latitudes have greater biological diversity. It is quite true. Ecologists and evolutionary biologists have proposed various hypothesis in support of this. Speciation is generally a function of time and unlike temperate regions, subjected to frequent glaciations. In the past, tropical latitudes remained undisturbed for millions of years, where species continued to flourish.
Question.12.
Assertion: If the species-area relationships are analyzed among very large areas like the entire continents, the value of Z i.e., slope of line lies in the range of 0.1 to 0.2.
Reason: The value of Z i.e., slope of line of species area relationships lies in the range of 0.6 to 1.2 when analysis is done among small areas.
Ans.12. (d)
Both Assertion and Reason are false.
Question.13.
Assertion: Speciation is a function of time and tropical regions had got a long evolutionary time for species diversification as compared to temperate regions.
Reason: Temperate regions have undergone frequent glaciations in the past whereas tropical regions have remained relatively undisturbed for millions of years.
Ans.13. (a)
Speciation is a function of time. Temperate regions have undergone frequent glaciations in the past, due to which many species had been killed. However, tropical latitudes have remained relatively undisturbed for millions of years and thus, had a long evolutionary time for species diversification.
Question.14.
Assertion: Taiga is also called North coniferous forest.
Reason: The ground flora is absent in Taiga.
Ans.14. (c)
Assertion is true but Reason is false.
Question.15.
Assertion: Temperate deciduous forest is two – storeyed forest.
Reason: Two stories are formed of soft wood and hard wood trees.
Ans.15. (d)
Both Assertion and Reason are false.
