During adverse season, therophytes survive by
Therophytes are those plants which survive the adverse season like winter as a seed and complete their life cycle between spring and autumn.
The rate at which light energy is converted to the chemical energy of organic molecules is the ecosystem’s
The rate at which organic molecules are formed in a green plant is called gross productivity.
Approximately how much of the solar energy that falls on the leaves of a plant is converted to chemical energy by photosynthesis?
50% of the solar energy incident over earth is present in PAR (photosynthetically active reaction). About 1-5% of total incident solar energy or 2-10% of PAR is captured by the photosynthetic organisms for photosynthesis.
Upper part of sea / aquaticeco system contains
Plankton → Organisms passively floating in upper water.
Nekton → Actively swimming Benthos → Lead sedentary life upon the sea bottom
What is true of ecosystem?
In an ecosystem producers (green plants) are always more than consumers (herbivores, carnivores etc.)
In an ecosystem, which one shows one-way passage
Energy f low takes place only in one direction i.e., producers → herbivores → carnivores whereas, nutrients use carbon, nitrogen and potassium shows cyclic flow.
Sudden mass killing of fishes is likely in
Organic pollutants provide nutrients for stimulating growth of algae and other plants. Algal bloom reduces availability of light to submerged plants which get killed. The dead submerged plants consume more oxygen in decomposition. This reduces availability of oxygen to other life forms leading to death of organisms. This is known as eutrophication.
Pneumatophores are characteristic of plants growing in
Some plants growing in salty marshes develop special roots for respiration, called pneumatophores. They are (–) vely geotropic.
The greatest biomass of autotrophs in the oceans is that of
The greatest biomass of autotrophs in the oceans is that of free floating microalgae, cyanobacteria and nanoplankton.
Bamboo plant is growing in a fir forest then what will be the trophic level of it?
First trophic level is occupied by producers. Second trophic level is occupied by primary consumers. Third trophic level is occupied by the secondary consumers.
Which of the following is expected to have the highest value (gm/m2/yr) in a grassland ecosystem?
Grasslands will have highest value of gross production. Net production is obtained after subtracting the respiratory utilization from gross production. Secondary and tertiary production is related with secondary and tertiary consumers respectively.
If by radiation all nitrogenase enzymes are inactivated, then there will be no
Nitrogenase is an enzyme involved in biological nitrogen fixation. Enzyme nitrate reductase is involved in conversion of nitrate to nitrite. Conversion of ammonia to nitrate is carried out by Nitrosomonas and Nitrobacter.
An ecosystem which can be easily damaged but can recover after some time if damaging effect stops will be having
An ecosystem having low stability can be easily damaged. An ecosystem having high resilience will take less time to recover.
Barophiles are bacteria which live in high pressure environments. They are generally found on ocean floors, where pressure generally exceeds 380 atm (38 MPa). Some have been found at the bottom of the Pacific Ocean where the maximum pressure is roughly 117 MPa.
More than 70% of world’s freshwater is contained in:
Three fourth surface of earth is covered by oceans which contain 97.5% of total water. It is marine water with about 3.5% salt content only 2.5% is fresh water which occurs on land. Most of this water (1.97%) occurs as frozen ice caps and glaciers, 0.5% fresh water occurs as ground water. Rivers and lakes contain 0.02%, soil 0.01% while atmosphere possesses 0.001% of water as vapours.
Which one of the following is not used for construction of ecological pyramids?
Fresh weight is not used for the construction of ecological pyramids because the total fresh weight does not change into energy. Hence we can say that fresh weight is not continuous in the tropic levels.
Which one of the following ecosystem types has the highest annual net primary productivity?
They are found in the equatorial regions rainfall exceeds 140 cm. The warm humid climate supports broad leaved evergreen plants. Productivity is very high (12000 k. cal/m2/ year). The vegetation show stratification into two or more well defined layers.
About 70% of total global carbon is found in
About 70% oftotal global carbon is found in oceans. This oceanic reservoir regulates the amount of carbon dioxide in the atmosphere. Atmosphere contains only about one percent of total global carbon.
The slow rate of decomposition of fallen logs in nature is due to their
The microorganisms breakdown the complex compounds of dead protoplasm of producers and consumers absorb some of the decomposition products and release simple substances. The slow rate of decomposition of fallen logs in nature is due to their low moisture content The cellulose is in high amount in fallen logs.
Consider the following statements concerning food chains
(a) removal of 80% tigers from an area resulted in greatly increased growth of vegetation
(b) removal of most of the carnivores resulted in an increased population of deers
(c) the length of food chains is generally limited to 3-4 trophic levels due to energy loss
(d) the length of food chains may vary from 2 to 8 trophic levels
Which two of the above statements are correct?
Food chain is the transfer of energy from green plants (Primary producers), through a sequence of organisms occupies in a food chain is known as its trophic level. Therefore, statements b and c are correct.
The correct sequence of plants in a hydrosere is:
The cor rect sequence of plants in a hydrosere is Volvox, Hydrilla, Pistia, Scirpus, Lanatana and Oak. A hydrosere is a plant succession which occurs in a fresh water lake. In time, an area of open fresh water such as a lake will naturally dry out, ultimately becoming woodland. During this change, a range of different landtypes such as swamp and marsh will succeed each other. The succession from open water to climax woodland is likely to take at least two hundred years.
Which one of the following types of organisms occupy more than one trophic level in a pond ecosystem?
A pond ecosystem is a delicate balance of fish, plants and other animals. Fish occupy more than one tropic level in pond ecosystem. Small fishes act as secondary consumer. They feed on primary consumer. Large fishes act as tertiary consumer. They feed on smaller fish.
Study the four statements (a–d) given below and select the two correct ones out of them:
(i) A lion eating a deer and a spar row feeding on grain are ecologically similar in being consumers
(ii) Predator star fish Pisaster helps in maintaining species diversity of some invertebrates
(iii) Predators ultimately lead to the extinction of prey species
(iv) Production of chemicals such as nicotine, strychnine by the plants are metabolic disorders The two correct statements are:
The statement (i) and (ii) are correct. The statement (iii) is incorrect because predators cannot lead to the extinction of prey species. Predator and prey evolve together. The statement (iv) is incorrect because chemical such as nicotine and strychnine produced by the plants are not metabolic disorders but are metabolic wastes.
The biomass available for consumption by the herbivores and the decomposers is called:
The biomass available for consumption by the herbivores and the decomposers is called net primary productivity. It is equal to the rate of organic matter created by photosynthesis minus the rate of respiration and other losses.
Mass of living matter at a trophic level in an area at any time is called
A standing crop is the quantity or total weight or energy content of the organism, which are in a particular location at a particular time.