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Biology-12 : 12 : Ecosystem - Flashcards

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What is an ecosystem?
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An ecosystem is a functional unit of nature where living organisms interact among themselves and with the surrounding physical environment.
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# Question Answer
1 What is an ecosystem? An ecosystem is a functional unit of nature where living organisms interact among themselves and with the surrounding physical environment.
2 How do ecosystems vary in size? Ecosystems vary from a small pond to a large forest or sea.
3 What do many ecologists regard as a global ecosystem? The entire biosphere is regarded as a global ecosystem composed of all local ecosystems on Earth.
4 Into which two basic categories are ecosystems divided? Ecosystems are divided into terrestrial and aquatic ecosystems.
5 Give examples of terrestrial ecosystems. Forest, grassland, and desert are examples of terrestrial ecosystems.
6 Give examples of aquatic ecosystems. Pond, lake, wetland, river, and estuary are aquatic ecosystems.
7 Name two man-made ecosystems. Crop fields and aquariums are man-made ecosystems.
8 What are the major topics studied in ecosystem structure and function? Productivity, energy transfer, food chain/web, nutrient cycling, degradation, and energy loss.
9 What is stratification in an ecosystem? Vertical distribution of different species occupying different levels is called stratification.
10 In a forest ecosystem, which plants occupy the top, second, and bottom layers? Trees occupy the top layer, shrubs the second, and herbs and grasses the bottom layers.
11 What are the four functional aspects of an ecosystem? Productivity, decomposition, energy flow, and nutrient cycling.
12 Why is a pond considered a good example of an ecosystem? A pond is fairly self-sustainable and exhibits all four basic components of an ecosystem.
13 What are the abiotic components of a pond ecosystem? Water with dissolved inorganic and organic substances and rich soil deposits at the bottom.
14 Which factors regulate the functioning of a pond ecosystem? Solar input, temperature cycle, day-length, and climatic conditions regulate the pond ecosystem.
15 What are the autotrophic components in a pond ecosystem? Phytoplankton, algae, and floating, submerged, and marginal plants.
16 Which organisms act as consumers in a pond ecosystem? Zooplankton, free-swimming forms, and bottom-dwelling forms.
17 Which organisms are decomposers in a pond ecosystem? Fungi, bacteria, and flagellates, especially abundant at the bottom of the pond.
18 What is the role of autotrophs in an ecosystem? Autotrophs convert inorganic material into organic material using solar energy.
19 What happens to dead matter in an ecosystem? Dead matter undergoes decomposition and mineralisation, releasing nutrients for reuse by autotrophs.
20 How does energy move in an ecosystem? Energy moves unidirectionally towards higher trophic levels and is lost as heat to the environment.
21 What is primary production? Primary production is the amount of biomass or organic matter produced per unit area over a time period by plants during photosynthesis.
22 What is productivity? The rate of biomass production is called productivity.
23 What are the two types of primary productivity? Gross Primary Productivity (GPP) and Net Primary Productivity (NPP).
24 Define Gross Primary Productivity (GPP). GPP is the rate of production of organic matter during photosynthesis.
25 Why is all GPP not available to consumers? A considerable amount of GPP is utilised by plants in respiration.
26 What is the formula for Net Primary Productivity (NPP)? GPP – R = NPP
27 What is Net Primary Productivity (NPP)? NPP is the available biomass for consumption by heterotrophs such as herbivores and decomposers.
28 What is secondary productivity? Secondary productivity is the rate of formation of new organic matter by consumers.
29 On what factors does primary productivity depend? It depends on plant species, environmental factors, nutrient availability, and photosynthetic capacity of plants.
30 What is the approximate annual net primary productivity of the biosphere? Approximately 170 billion tons (dry weight) of organic matter.
31 What is decomposition? Decomposition is the process by which decomposers break down complex organic matter into inorganic substances like carbon dioxide, water, and nutrients.
32 What is detritus? Dead plant remains, dead animal remains, and fecal matter constitute detritus.
33 What are the important steps of decomposition? Fragmentation, leaching, catabolism, humification, and mineralisation.
34 What is fragmentation in decomposition? Breakdown of detritus into smaller particles by detritivores is called fragmentation.
35 What happens during leaching? Water-soluble inorganic nutrients move down into the soil horizon and get precipitated as unavailable salts.
36 What is humus? Humus is a dark coloured amorphous substance highly resistant to microbial action and decomposes very slowly.
37 Why is humus important? Being colloidal in nature, humus serves as a reservoir of nutrients.
38 What is mineralisation? Release of inorganic nutrients from humus by microbes is called mineralisation.
39 Is decomposition an oxygen-requiring process? Yes, decomposition is largely an oxygen-requiring process.
40 Which type of detritus decomposes slowly? Detritus rich in lignin and chitin decomposes slowly.
41 Which type of detritus decomposes quickly? Detritus rich in nitrogen and water-soluble substances like sugars decomposes quickly.
42 Which climatic factors regulate decomposition? Temperature and soil moisture are the most important climatic factors regulating decomposition.
43 Which environmental condition favours decomposition? Warm and moist environment favours decomposition.
44 Which conditions inhibit decomposition? Low temperature and anaerobiosis inhibit decomposition.
45 What is the primary source of energy for almost all ecosystems on Earth? The sun is the primary source of energy for all ecosystems except deep sea hydro-thermal ecosystems.
46 What percentage of incident solar radiation is photosynthetically active radiation (PAR)? Less than 50% of incident solar radiation is PAR.
47 Which organisms fix solar energy into food? Plants and photosynthetic bacteria (autotrophs) fix solar energy into food.
48 What percentage of PAR is captured by plants? Plants capture only 2–10% of PAR.
49 How does energy flow in an ecosystem? Energy flows unidirectionally from the sun to producers and then to consumers.
50 Why do ecosystems require a constant supply of energy? Ecosystems require constant energy to synthesise molecules and counteract increasing disorderliness.
51 What are producers in an ecosystem? Green plants in an ecosystem are called producers.
52 What are the major producers in terrestrial ecosystems? Herbaceous and woody plants are the major producers in terrestrial ecosystems.
53 Name the producers in aquatic ecosystems. Phytoplankton, algae, and higher plants are producers in aquatic ecosystems.
54 Why are food chains and food webs formed? They are formed because organisms depend on one another for food.
55 What happens to the energy trapped by producers? The energy trapped by producers is either passed on to consumers or lost when the organism dies.
56 What marks the beginning of the detritus food chain? Death of organisms marks the beginning of the detritus food chain/web.
57 Why are animals called consumers and heterotrophs? Animals depend directly or indirectly on plants for food, so they are called consumers and heterotrophs.
58 Who are primary consumers? Organisms that feed directly on producers (plants) are primary consumers.
59 Who are secondary consumers? Animals that feed on plant-eating animals are secondary consumers.
60 What are primary consumers usually called? Primary consumers are herbivores.
61 Give examples of herbivores in terrestrial ecosystems. Insects, birds, and mammals are common herbivores in terrestrial ecosystems.
62 Which organisms are herbivores in aquatic ecosystems? Molluscs are herbivores in aquatic ecosystems.
63 What are carnivores that feed on herbivores called? They are called primary carnivores or secondary consumers.
64 What are secondary carnivores? Animals that depend on primary carnivores for food are called secondary carnivores.
65 Give an example of a grazing food chain (GFC). Grass → Goat → Man
66 How does the detritus food chain (DFC) begin? The DFC begins with dead organic matter.
67 Which organisms mainly make up decomposers in DFC? Fungi and bacteria mainly make up decomposers.
68 What are saprotrophs? Decomposers that obtain energy by degrading dead organic matter are called saprotrophs.
69 What do decomposers secrete to break down dead material? Decomposers secrete digestive enzymes.
70 Which food chain is the major conduit for energy flow in aquatic ecosystems? Grazing Food Chain (GFC) is the major conduit in aquatic ecosystems.
71 Which food chain dominates energy flow in terrestrial ecosystems? Detritus Food Chain (DFC) dominates energy flow in terrestrial ecosystems.
72 What is a food web? Natural interconnections among food chains form a food web.
73 What is a trophic level? The specific place occupied by an organism in a food chain based on its source of nutrition is called a trophic level.
74 Which trophic level do producers occupy? Producers occupy the first trophic level.
75 Which trophic level do herbivores occupy? Herbivores or primary consumers occupy the second trophic level.
76 Which trophic level do carnivores occupy? Carnivores or secondary consumers occupy the third trophic level.
77 What happens to energy at successive trophic levels? The amount of energy decreases at successive trophic levels.
78 What happens when an organism dies in an ecosystem? It is converted into detritus or dead biomass that serves as an energy source for decomposers.
79 On whom do organisms at each trophic level depend for energy? Organisms at each trophic level depend on organisms at the lower trophic level for energy.
80 What is standing crop? The mass of living material present at a trophic level at a particular time is called standing crop.
81 How is standing crop measured? Standing crop is measured as biomass or number of organisms in a unit area.
82 In what forms can biomass be expressed? Biomass can be expressed in terms of fresh weight or dry weight.
83 Why is dry weight preferred for biomass measurement? Measurement of biomass in terms of dry weight is more accurate.
84 Why is the number of trophic levels in a grazing food chain restricted? Because energy transfer follows the 10 percent law.
85 What is the 10 percent law? Only 10% of energy is transferred from one trophic level to the next higher trophic level.
86 Give the sequence of trophic levels in a grazing food chain. Producer → Herbivore → Primary Carnivore → Secondary Carnivore.
87 What is the shape of an ecological pyramid? It has a broad base and narrows towards the apex.
88 Ecological relationships can be expressed in terms of what three factors? Number, biomass, and energy.
89 What does the base of an ecological pyramid represent? The base represents producers or the first trophic level.
90 What does the apex of an ecological pyramid represent? The apex represents tertiary or top-level consumers.
91 What are the three types of ecological pyramids? Pyramid of numbers, pyramid of biomass, and pyramid of energy.
92 In a grassland ecosystem pyramid of numbers, which trophic level has the maximum number of organisms? Producers have the maximum number of organisms.
93 What does the pyramid of biomass generally show? It shows a sharp decrease in biomass at higher trophic levels.
94 Why is the pyramid of biomass inverted in aquatic ecosystems? A small standing crop of phytoplankton supports a large standing crop of zooplankton.
95 What must be included in calculations of energy content, biomass, or numbers at a trophic level? All organisms at that trophic level must be included.
96 Can a single organism occupy more than one trophic level? Yes, a given organism may occupy more than one trophic level simultaneously.
97 Why is trophic level considered a functional level and not a species level? Because the same species can occupy different trophic levels based on feeding habits.
98 When is a sparrow considered a primary consumer? When it eats seeds, fruits, and peas.
99 When is a sparrow considered a secondary consumer? When it eats insects and worms.
100 In most ecosystems, what is the nature of pyramids of number, biomass, and energy? They are upright.
101 Why are ecological pyramids usually upright? Producers are greater in number and biomass than herbivores, and herbivores exceed carnivores.
102 How does energy vary across trophic levels? Energy at a lower trophic level is always more than at a higher trophic level.
103 Why is the pyramid of energy always upright? Because some energy is always lost as heat at each trophic level during energy transfer.
104 Can the pyramid of energy ever be inverted? No, the pyramid of energy can never be inverted.
105 What does each bar in an energy pyramid represent? It represents the amount of energy present at each trophic level per unit area in a given time or annually.
106 Why can a species occupy more than one trophic level? Because trophic levels are functional levels based on feeding habits, not species identity.
107 Why is the pyramid of biomass in the sea generally inverted? Because the biomass of fishes far exceeds that of phytoplankton.
108 What are the abiotic components of an ecosystem? Air, water, and soil are the abiotic components of an ecosystem.
109 What are the biotic components of an ecosystem? Producers, consumers, and decomposers are the biotic components.
110 What gives an ecosystem its characteristic physical structure? Interaction among abiotic and biotic components gives an ecosystem its characteristic physical structure.
111 What are the two main structural features of an ecosystem? Species composition and stratification.
112 What determines the place occupied by an organism in an ecosystem? The source of nutrition determines the place occupied by an organism in an ecosystem.
113 Which are the four important functional components of an ecosystem? Productivity, decomposition, energy flow, and nutrient cycling.
114 What is primary productivity? Primary productivity is the rate of capture of solar energy or biomass production by producers.
115 Into which two types is primary productivity divided? Gross Primary Productivity (GPP) and Net Primary Productivity (NPP).
116 What is Gross Primary Productivity (GPP)? GPP is the rate of capture of solar energy or total production of organic matter.
117 What is Net Primary Productivity (NPP)? NPP is the remaining biomass or energy left after utilisation by producers.
118 What is secondary productivity? Secondary productivity is the rate of assimilation of food energy by consumers.
119 What happens during decomposition? Complex organic compounds of detritus are converted into carbon dioxide, water, and inorganic nutrients by decomposers.
120 What are the three processes involved in decomposition? Fragmentation, leaching, and catabolism.
121 Describe the direction of energy flow in an ecosystem. Energy flow is unidirectional, from plants to consumers and decomposers.
122 What forms a food chain in nature? Organisms of different trophic levels connected by food or energy relationships form a food chain.
123 What is nutrient cycling? Nutrient cycling is the storage and movement of nutrient elements through various components of the ecosystem.
124 Why are nutrients repeatedly used in ecosystems? Nutrients are repeatedly used through nutrient cycling.
125 What are the two types of nutrient cycles? Gaseous cycles and sedimentary cycles.
126 What is the reservoir for gaseous nutrient cycles? The atmosphere or hydrosphere is the reservoir for gaseous cycles such as carbon cycle.
127 What are ecosystem services? Products of ecosystem processes are called ecosystem services.
128 Give examples of ecosystem services mentioned in the text. Purification of air and water by forests.
129 What is one limitation of ecological pyramids? They do not account for the same species belonging to two or more trophic levels.
130 Why do ecological pyramids fail to represent natural ecosystems completely? They assume a simple food chain and do not accommodate food webs.
131 Why are saprophytes important despite not being included in ecological pyramids? Saprophytes play a vital role in the ecosystem.
132 In aquatic ecosystems, what is the limiting factor for productivity? Light is the limiting factor for productivity in aquatic ecosystems.
133 Name common detritivores in ecosystems. Earthworms are common detritivores.
134 What is the major reservoir of carbon on Earth? Oceans are the major reservoir of carbon on Earth.
135 Which trophic level has the largest population in a food chain? Producers have the largest population in a food chain.
136 What is the second trophic level in a lake ecosystem? Zooplankton forms the second trophic level in a lake ecosystem.
137 Who are secondary producers according to the exercise? Herbivores are secondary producers.
138 What percentage of incident solar radiation is PAR? About 50% of incident solar radiation is photosynthetically active radiation (PAR).
139 What are the two types of food chains mentioned in the exercises? Grazing food chain and detritus food chain.
140 Which two ecosystem processes are asked to be distinguished in the exercises? Production and decomposition.
141 Which two types of ecological pyramids are mentioned for comparison? Upright and inverted pyramids.
142 Which ecosystem concepts are asked to be differentiated together? Food chain and food web.
143 Which two terms related to decomposition are compared in the exercises? Litter and detritus.
144 Which two productivity terms are compared in the exercises? Primary productivity and secondary productivity.
145 Which ecological pyramids are specifically mentioned for description? Pyramids of number and biomass.