CBSE Questions for Class 12 Medical Biology Ecosystem Quiz 7 - MCQExams.com

An ecosystem which can be easily ruined/damaged but can recover after some time if damaging effect stops. The ecosystem is characterised by having
  • Low and poor stability with low resilience
  • High stability and low resilience
  • Low stability and high resilience
  • High stability and high resilience
Which one of the following class of animals constitutes the largest biomass on earth?
  • Insects
  • Fish
  • Mammals
  • Reptilians
Select the correct match :
III
i) Competitiona) Tapeworm and man
ii) Commensalismb) Lichen
iii) Mutualismc) Cattle egret and cattle
iv) Parasitismd) Lions and Leopards
  • i - d, ii - c, iii - b, iv - a
  • i - d, ii - b, iii - c, iv - a
  • i - c, ii - b, iii - d, iv - a
  • i - a, ii - b, iii - d, iv - c
Last stable community is succession which depends on climate is 
  • Seral community
  • Climax community
  • Poineer community
  • None of the above
Keystone species are 
  • Species belonging to same period
  • Species that determine structure of biotic community
  • Species reproducing sexually
  • Species recorded only in the fossil state
Instead of excreting, these can store urea in the tissues
  • Birds
  • Fish
  • Elephants
  • Camels
Keystone species deserve protection because these
  • Are capable of surviving in harsh environmental conditions
  • Indicates presence of certain minerals in the soil
  • Have become rare due to the over-exploitation
  • Play an important role in supporting other species
Given below is one of the types of ecological pyramids

This type represents
  • Pyramid of numbers in a grassland
  • Pyramid of biomass in a fallow land
  • Pyramid of biomass in a lake
  • Energy pyramid in a spring
In a lake ecosystem, pyramid of biomass is
  • Upright
  • Inverted
  • Anything is possible
  • None of the above
Succession is
  • Orderly process of community change till stability
  • Gradual, directional and continuous process
  • Series of biotic communities that appear gradually in a barren area
  • All of the above
Water requirement of Kangaroo/Desert rat is largely met by
  • Hydration of food
  • Metabolic water
  • Hygroscopic skin
  • Moist soil
Formation of organic matter takes place by
  • Chemical weathering
  • Soil micro-organisms
  • Herbivores
  • Soil water
Climax community is 
  • First stable community
  • Unstable
  • Unstable that develops in the beginning of succession
  • The last stable community
Series of changes on  previously barren area is 
  • Sere
  • Climatic climax
  • Primary succession
  • Secondary seccession
As compared to seral communities, the number of niches in climax communities would be 
  • Same
  • Fewer and generalised
  • More and specialised
  • None of the above
A community, which starts succession in a habitat is 
  • Pioneer community
  • Seral community
  • Biotic community
  • Ecosere
What does the following sequence represent ?

Blue-Green Algae $$\rightarrow$$ Crustose Lichens $$\rightarrow$$ Foliose Lichens $$\rightarrow$$ Mosses $$\rightarrow$$ Shrubs $$\rightarrow$$ Dicotyledonous trees 
  • A food pyramid
  • Ecological succession
  • Genetic drift
  • Phylogenetic trend
In ecological succession from pioneer to climax community, the biomass shall
  • Decrease
  • Increase and then decrease
  • No relation
  • Increase continuously
Keystone species is of 
  • Always dominant
  • Useful in maintaining structure and function of biotic community
  • With maximum biomass
  • All the above
Succession in a 6 metre deep pond exhibits a sequence of :
  • Submerged Plants $$\rightarrow $$Reeds $$\rightarrow$$Herbs $$\rightarrow$$Floating Plants $$\rightarrow$$ Shrubs $$\rightarrow$$Trees
  • Floating Plants $$\rightarrow$$Submerged Plants $$\rightarrow$$ Reeds $$\rightarrow$$Herbs$$\rightarrow$$ Shrubs $$\rightarrow$$Trees
  • Shrubs$$\rightarrow$$Trees$$\rightarrow$$submerged Plants $$\rightarrow$$ Floating Plants $$\rightarrow$$ Reeds $$\rightarrow$$ Herbs
  • Submerged Plants $$ \rightarrow$$Floating Plants $$\rightarrow$$Reeds$$\rightarrow$$ Herbs$$\rightarrow$$Shrubs$$\rightarrow$$Trees.
Primary succession is development of communities on
  • Newly exposed habitat
  • Cleared forest area
  • Freshly harvested crop field
  • Pond filled after a dry season
Plant succession occurring in a sandy area is 
  • Psammosere
  • Halosere
  • Xerosere
  • Hydrosere
Last stabilised community in a plant succession is known as
  • Seral Community
  • Pioneer Community
  • Ecosere
  • Climax Community
In pond ecosystem, the shape of pyramid of number is?
  • Linear
  • Irregular
  • Upright
  • Inverted
Keystone species should be protected as they 
  • Are capable of certain minerals in the soil.
  • Indicate presence of certain minerals in the soil.
  • Have become rare due to over-exploitation.
  • Play an important role in supporting other species.
In succession, the structural complexity
  • Drastically increases
  • Remains constant
  • Slowly increases
  • Does not increases
Term used to describe non-dominant species that dictates community structure is
  • Pioneer species
  • Keystone species
  • Transitional species
  • All of the above
Nature of climax community depends upon
  • Water
  • Temperature
  • Soil fertility
  • Climate
Deserts can be converted into green land by 
  • Tropical trees
  • Oxylophytes
  • Halophytes
  • Psammophytes
Which of the following is not a primary coloniser?
  • Viruses
  • Lichens
  • Blue-green algae
  • Mosses
A keystone species is the one which has
  • A small proportion of total biomass but has a huge impact on the community's organisation and survival.
  • A plenty of biomass but low impact on community's organisation.
  • A rare species with little impact on biomass and other species in the community.
  • A dominant species which has a large proportion of biomass and which affects many other species.
In autogenic succession,
  • The community itself modifies its own environment thus causing its own replacement by a new community.
  • Early dominance of heterotrophs.
  • Replacement of existing communities due to external conditions.
  • Early and continued dominance of autotrophic organisms.
  • There is previously built substratum with already existing matter.
In grassland ecosystem, the pyramid of biomass is
  • Linear
  • Upright
  • Inverted
  • Inverted upright
Succession is 
  • Orderly process of community change till stability.
  • Gradual convergent, directional and continuous process.
  • Series of biotic communities that appear generally in barren area.
  • All of the above.
The correct order of succession in xerarch is 
  • Annual herb stage, perennial herb stage , lichen moss stage , scrub stage forest
  • Perennial herb stage , annual herb stage, lichen moss stage , scrub stage forest
  • Lichen moss stage , annual herb stage , perennial herb stage , scrub stage forest
  • Forest , scrub stage , annual herb stage perennial herb stage , lichen moss stage.
In ecological succession, the climax community is best recognised by the following state 
  • P = R
  • P > R
  • P < R
  • P $$\neq$$ R
Correct sequence of plants in a hydrosere is 
  • Pistia $$\rightarrow$$ Volvox $$\rightarrow$$ Scirpus $$\rightarrow$$Hydrilla $$\rightarrow$$ Oak $$\rightarrow$$ Lantana
  • Oak $$\rightarrow$$ Lantana $$\rightarrow$$ Volvox $$\rightarrow$$ Hydrilla $$\rightarrow$$ Pistia $$\rightarrow$$ Scirpus
  • Oak $$\rightarrow$$ Lantana $$\rightarrow$$ Scirpus $$\rightarrow$$ Pistia $$\rightarrow$$ Hydrilla $$\rightarrow$$ Volvox
  • Volvox $$\rightarrow$$ Hydrilla $$\rightarrow$$ Pistia $$\rightarrow$$ Scirpus $$\rightarrow$$ Lantana $$\rightarrow$$ Oak
The species though insignificant in number determines the existence of many other species in a given ecosystem
  • Extinct species
  • Endemic species
  • keystone species
  • Sacred secies
Stage of hydrarch are :

(a) Marsh meadow stage (b) Reed swamp stage (c) submerged plant stage (d) Phytoplankton stage 
(e) Submerged free-floating stage. 

Identify the correct sequence :
  • d , c, e , b , a
  • c , e , a , b , d
  • b , d , c , a , e
  • d , e , c , b , a
  • e , c , b, a , d
Select the correct matches :

(a) Sedimentary nutrient cycle - Nitrogen cycle (b) Pioneer species - Lichens (c) Secondary succession - Burnt forest (d) Pyramid of biomass in sea - upright
  • a, b, and d only
  • b, and c only
  • a, and c only
  • b, and d only
Figs belong to 
  • Keystone species as they show animal dependent pollination.
  • Keystone species as they produce food and provide protection to animals during the lean period.
  • Critical link species as they form connecting link between trees and herbs.
  • Critical link species as they establish essential links for absorbing nutrients from the soil and organic residues.
Which one is first colonizer of bare rock/pioneer community in xerarch?
  • Annual herb
  • Perennial herb
  • Lichen/Moss
  • Scrub
  • Forest
Different communities appearing and replacing one another are called 
  • Climax communities
  • Seral communities
  • Serial communities
  • Successive communities
The pyramid which cannot be inverted in a stable ecosystem is that of
  • Biomass
  • Number
  • Energy
  • All the above
Pyramid of numbers deals with number of
  • Species in an area
  • Individuals in a community
  • Individuals in a trophic level
  • Subspecies in a community
Sedimentary cycle having a small gaseous component is found in
  • Phosphorus
  • Nitrogen
  • Carbon
  • Sulphur
Lithosphere is reservoir of
  • Carbon
  • Oxygen
  • Phosphorus
  • Nitrogen
Pyramid of energy (in a forest/pond ecosystem) is
  • Always inverted
  • Always upright
  • Spindle - shaped
  • Both upright and inverted depending upon ecosystem
Crystalline rocks are natural source of
  • Calcium
  • Phosphorus
  • Magnesium
  • Sulphur
Both hydrarch and xerarch successions lead to
  • Medium water conditions
  • Excessive wet conditions
  • Xeric conditions
  • Highly dry conditions
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