Sunday, January 3, 2021

Organisms and Populations | Class 12 Botany| Previous Years Questions and Answers (2018 to 2020)

6. ORGANISMS AND POPULATIONS

2020 SAY

1.   Choose the correct answer: (1)

An organism that has the ability to concentrate its urine is:

(a) Desert Lizard               (b)  Seal

(c)  Flamingo                    (d)  Kangaroo rat

ü Answer:

(d) Kangaroo rat

2.   Analyse the following table showing population interaction: (3)

Species A

Species B

Name of interaction

+

(i)

Commensalism

+

+

(ii)

(a)    Identify (i) and (ii).

(b)   Define (ii).

(c)    Give an example of commensalism.

ü Answer:

(a) i. 0           ii. Mutualism.

(b) Mutualism is the interaction that confers benefits for both interacting species.

(c) Orchid and Mango tree / Grazing cattle and egret etc.

2020 MARCH

1.   Fill up the blank suitably. (1)

Mortality: No. of deaths in the population during a given period.

..........................: No. of births in the population during a given period.

ü Answer:

Natality.

2.   Identify the types of population growth noted in the graph as 'A' and 'B'. (2)

ü Answer:

A= Exponential growth / J- shaped growth curve.

B= Logistic growth / S- shaped growth curve.

3.   Given below are examples for some ecological/population interactions. Place them under suitable columns provided below. (3)

a.  Abingdon tortoise and goat.

b.  Cuscuta and host tree.

c.  Fig tree and wasp.

d.  Algae and fungi in Lichens

e.  Belanus and Chathamalus bemacles

f.  Lice on humans.

Competition

Parasitism

Mutualism

·        

·        

·        

·        

·        

·        

ü Answer:

Competition

Parasitism

Mutualism

·  Abingdon tortoise and goat

·  Belanus and Chathamalus bemacles

·  Cuscuta and host tree

·  Lice on humans

·     Fig tree and wasp

·     Algae and fungi in Lichens

 

2019 SAY June

1.   Differentiate natality and mortality. Write the alphabets used to indicate natality and mortality. (2)

ü Answer:

Natality: It is the number of births in a population during a given period.

Mortality: It is the number of deaths in a population during a given period.

Natality is indicated by the letter B.

Mortality is indicated by the letter D.  

2.   Name the interaction between sea anemone and clown fish. Justify your answer with suitable explanation. (2)

ü Answer:

Name of the interaction: Commensalism.

Clown fish protection from predators because predators stay away from the stinging tentacles of sea anemone. But sea anemone does not get any benefit from clown fish.

2019 MARCH


1.   Match the columns (A) and (B): (2)


(A)

(B)

(i) Mutualism

(ii) Predation

(iii) Commensalism

(iv) Competition

(a)    An orchid growing on a tree trunk

(b)   Gauss's Exclusion Principle

(c)    Biological control

(d)   Derives nutrition from the host organism

(e)    Mycorrhizae

ü Answer:

(A)

(B)

(i) Mutualism

(ii) Predation

(iii) Commensalism

(iv) Competition

(e) Mycorrhizae

(c) Biological control

(a) An orchid growing on a tree trunk

(b) Gauss's Exclusion Principle


2.   Observe the flow chart given below: (2)



a.   Name the processes represented as A and B.

b.   If 'Nt' is the population density at time t, then write down the population density equation at time t + 1.

ü Answer:

(a) A= Mortality (D)      B= Emigration (E)

(b) Nt + 1 = Nt + [(B + I) – (D + E)].


2018 SAY June

1.   A population has certain attributes that an individual organism does not. What are they? (2)

ü Answer:

Natality, mortality, sex ratio, age distribution, population density.

2.   Parasites evolved special adaptations to live on host. What are they? (2)

ü Answer:

Ÿ High reproductive capacity.

Ÿ Presence of suckers.

Ÿ Digestive system absent.


2018 MARCH

1.   Under unfavourable conditions many zooplanktons species in lakes and Ponds are known to enter a stage of suspended development. Name that stage. (1)

ü Answer:

Diapause.

2.   The following graph shows two types of pollution growth curves. (3)


a.  Name the growth curves.

b.  What does K stand for?

ü Answer:

(a) Exponential (Geometric) growth curve and Logistic (Sigmoid) growth curve.

(b) Carrying capacity.


 

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