connells elegant field experiment explains competitive release

Connell’s elegant field experiments on rocky sea coasts of Scotland is the evidence of

Habitat diversification

Prudent predators

Competitive release

Competitive exclusion

The correct option is D Competitive exclusion Competitive exclusion i.e. removal of inferior by a superior. Here Connell's Elegant field experiment showed that on rocky sea coasts of Scotland, the larger and superior barnacle Balanus dominates the intertidal area, and excludes the smaller barnacle Chathalamus from that zone.

Connell’s elegant field experiments on rocky sea coasts of Scotland is the evidence of

The steep rocky coasts rising almost vertically above the sea level are called

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Connell's field experiment illustrates

Competitive release

Competitive exclusion

Interference of competition

Commensalism

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The correct Answer is: A

Step-by-step solution: 1. understanding connell's field experiment : the experiment was conducted by ecologist joseph connell on the rocky coast of scotland. it focused on two species of barnacles: balanus (the larger, superior species) and chthamalus (the smaller, inferior species). 2. observations made : connell observed that balanus barnacles occupied the lower intertidal zone, while chthamalus barnacles were found in the upper intertidal zone. when both species were present, balanus outcompeted chthamalus for space in the lower zone. 3. conclusion drawn : the experiment demonstrated that the presence of the larger balanus barnacles led to the exclusion of the smaller chthamalus barnacles from the lower intertidal zone. this phenomenon is known as competitive exclusion, where one species outcompetes another for limited resources, leading to the latter's local extinction or displacement. 4. identifying the correct option : given the observations and conclusions from connell's experiment, the correct answer to the question "connell's field experiment illustrates" is competitive exclusion. 5. final answer : therefore, the correct option is b: competitive exclusion. ---, topper's solved these questions, similar questions.

Choose the correct match from the following. i. Co-evolution -Endoparasite and host ii. Mutualism - Relation of plants and BGA iii. Sexual deceit - shown by Opuntia plant iv. Connell's elegant field experiment - Competition

Use the below pair of names of fill the gaps in the given statement. ''Connell's elegant field experiments showed that on rock sea coasts of Scotland , the larger and competitively superior barnacle ………dominates the intertidal area, and exclude smaller barnacle ........... from that zone''

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AAKASH SERIES - ORGANISMS AND POPULATIONS - EXERCISE-I (POPULATION INTERACTIONS)

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Evidence for competition from nature Connells barnacles

The classic experimental demonstration of competition in the field was done by Joseph Connell (1961a, 1961b) on the barnacle species Chthamalus stellatus and Balanus balanoides. These two species are found growing in the rocky intertidal zone off the coast of Scotland. Intertidal zones frequently show vertical zonation of species based on their abilities to survive periods of exposure to the air during low tides, and wave action followed by submersion during high tides. Balanus is consistently found on lower rock surfaces, usually near mean tide level or slightly above. Chthamalus, however, is found on the upper rocks, between mean high neap tide and mean high spring tide. While the adults of these two barnacle species have non-overlapping distributions, the larvae of both species settle over a wide variety of rock surfaces, showing a great deal of overlap. The question Connell posed was, is the distribution of adults the result of competition, or is there a difference in the fundamental niches of the two species? Connell performed a variety of experiments in which he moved the barnacles to different levels of the intertidal zone. He also experimentally removed one species or the other where the two were growing together, and observed the results of putting the two species together. He found that whenever he removed Balanus, Chthamalus was able to survive in the lower regions of the intertidal zone. However, in the presence of Balanus, Chthamalus was overgrown and eventually displaced. In the upper regions of the intertidal zone, however, Balanus was unable to survive the long exposures to air during low tides. Since Chthamalus was able to survive this exposure, it survives in the upper intertidal zone. Thus the two species occupy mutually exclusive microhabitats due to a combination of competition and differences in their fundamental niches.

Direct observations of competition in ants

Because both worker and soldier ants are numerous, easy to observe, and usually diurnal, aggressive interactions among ant species, demonstrating interference competition, can be documented throughout the world (Holldobler and Wilson 1990). Placing a food bait of tuna or sugar water will provoke competitive interactions in a matter of minutes to hours. Once bait is put out in the West Indies, where there are few ant species, there is a kind of predictable sequence, reminiscent of ecological succession (a kind of "ant succession"). As described by Holldobler and Wilson (1990), first to arrive are workers of Paratrechina longicornis, known locally as "hormigas locas" (crazy ants). These workers are very adept at locating food and often are the first to arrive at newly placed baits. They fill their crops rapidly and hurry to recruit nestmates with odor trails laid from the rectal sac of the hindgut. But they are also very timid in the presence of competitors. As soon as more aggressive species begin to arrive in force, the Paratrechina withdraw and search for new, unoccupied baits. Paratrechina is an example of an "opportunist" species. They are poor competitors, but excellent dispersers. Next to arrive are species known as "extirpators." These species recruit other workers by odor trails and fight it out with competitor species. Examples include species in the genera Pheidole and Crematogaster, the fire ant (Solenopsis geminata), and the "little fire ant" (Wasmannia auropunctata). Some of these species have well-developed soldier castes that play a key role in the aggressive interactions. Injury and death are commonplace, and one species eventually dominates the bait. Pre-emption is usually the deciding factor. The colony whose foragers arrive first typically wins; foragers recruit nestmates, who surround the bait. When worker scouts encounter a large number of workers from another colony, they are easily repulsed (Holldobler and Wilson 1990). Species with a third strategy, called "insinuators," also arrive at the baits. These are small colonies with small-sized worker ants such as Tetramorium simillimum and species of Cardiocondyla. A scout who discovers the bait will recruit only one nestmate at a time. Small size and stealthy behavior allow these individuals to take some of the bait without provoking a response from the extirpator species, - a situation reminiscent of small animals sneaking in and removing bits of food at a lion kill.

Holldobler and Wilson also emphasize that territorial fighting and "ant wars" are common, especially among species with large colonies. Numerous cases have been documented in which introduced ant species have eliminated other species over a few years' time. For example, on Bermuda Iridomyrmex humilis has been replacing Pheidole megacephala since the former was introduced in 1953, although the two species may be reaching equilibrium short of extinction of Pheidole (Lieberburg et al. 1975). As a final example, the red imported fire ant (Solenopsis invicta) has virtually eliminated the native fire ant (S. xyloni) from most of its range in the United States (Holldobler and Wilson 1990).

Literature reviews of field studies on competition

In the 1980s the importance of interspecific competition in nature was questioned by a number of biologists. Strong et al. (1983), among others, challenged much of the evidence usually cited for the prominent role assigned to competitive interactions in structuring natural communities. They asserted that the data were often indistinguishable from random models. Others charged that there were few experimental studies of competition from nature, and that predation was a much more significant ecological interaction. Still others, such as Wiens (1977), asserted that competition is a temporally sporadic, often impotent, interaction. Schoener (1982, 1983) decided to review the literature to determine if competition had been affirmed as an important interaction in nature. He found, to his surprise, over 150 experimental field studies of competition in natural ("field" settings), many of which had been conducted in the previous five years. Schoener carefully defined an interspecific competition experiment as a manipulation of the abundance of one or more hypothetically competing species. All such experiments had to have proper controls. Prior to these experimental studies, there had been a dependence on "natural experiments," which will be discussed below (Diamond 1983).

The "field" was defined as a study in which some major natural factors extrinsic to the organism remain uncontrolled. Schoener did not allow laboratory or greenhouse setups, but did count experiments involving fenced exclosures or caged portions of shorelines to fit the definition of a field study.

Through 1982 Schoener found that 164 published studies fitted the criteria. Of those 164, 90% (148) of the studies and 76% of the species involved did show positive evidence of interspecific competition. In a separate analysis and using different criteria, Connell (1983) found evidence of competition in 40% of the experiments and 50% of the species. There were, however, few studies involving herbivorous insects that demonstrated interspecific competition. Schoener suggested, as had Hairston et al. (1960), that herbivores, which occupy an intermediate position in the food web, are controlled by predators and therefore competition is a less important interaction for this trophic position. Schoener's literature review found little evidence to support Wiens' idea that there is a great deal of temporal variability in competition. Competitive variability is especially rare in marine ecosystems. Variability was mostly found in dry, continental habitats. This is interesting in that Wiens developed his ideas after carrying out research on bird communities in North American arid or semi-arid shrub habitats.

A decade after the analyses of Schoener and Connell, Gurevitch et al. (1992) analyzed competition studies carried out from 1980 to 1989, using a statistical approach. They found "medium" effects of competition on primary producers, carnivores, and herbivorous marine mollusks. Larger effects of competition were detected on some herbivores and stream arthropods. As found by Schoener, however, studies on herbivorous terrestrial insects usually failed to show significant effects of competition.

One can conclude from these literature reviews that competition is a common event in nature that contributes to the organization of ecological communities. It is, however, not the only important interspecific interaction.

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Readers' Questions

What do you predict would happen if chthamalus were experimentally removed?

Why dont barnacle species overlap?

There are several reasons why barnacle species do not overlap: Competition for resources: Each barnacle species has specific requirements for survival, such as food availability, water temperature and salinity, substrate type, and wave exposure. If two barnacle species have similar ecological niches and requirements, they will compete for limited resources, leading to decreased fitness and population decline. Therefore, barnacle species tend to occupy different habitats where their specific needs are met, minimizing competition. Differential colonization abilities: Barnacles have limited dispersal abilities and rely on larval stages to settle and colonize new areas. Different barnacle species have varying abilities to colonize and establish populations in different habitats. Some species may have adaptations that make them more successful in intertidal zones, while others may be more successful in subtidal or offshore environments. This differential colonization ability contributes to the spatial separation of barnacle species. Biogeographical factors: Barnacle species distributions are also influenced by biogeographical factors such as ocean currents, geographical barriers, and historical events. These factors can restrict species dispersal and gene flow, leading to the formation of distinct populations and limiting the overlap of different species. For example, species on separate sides of a continental landmass or isolated islands may have little or no chance of overlap due to physical barriers. Ecological interactions: Barnacles interact with other organisms in their environment, including predators, competitors, and symbiotic species. These interactions can influence barnacle species distributions and overlap. For instance, if a particular predator species preys on one barnacle species, it may limit its population and restrict its overlap with other species that are not preyed upon. Similarly, if a barnacle species has a mutualistic relationship with a specific partner, they may be limited to areas where their partner species is present. Overall, the lack of overlap in barnacle species can be attributed to a combination of competition, differential colonization abilities, biogeographical factors, and ecological interactions.

How is the process of experimenting of connells barnacles with one?

The process of experimenting with Connell's barnacles involves several steps. Here is a general outline of the process: Selection of barnacles: Identify a population of barnacles to study. This could be done by collecting barnacles from a natural habitat or obtaining them from a supplier. Set up experimental tanks: Prepare tanks or containers filled with seawater to mimic the barnacles' natural environment. Ensure the tanks have appropriate lighting, temperature, and water quality. Acclimatize the barnacles: Gradually introduce the barnacles to the experimental tanks, allowing them to acclimate to the new conditions. This helps to reduce stress and ensure their survival during the experiment. Manipulate variables: Determine the specific variables you want to test. These could include factors like temperature, salinity, food availability, or water flow. Manipulate these variables in the experimental tanks to observe their effects on the barnacles. Control group: In a controlled experiment, it is essential to have a control group that is not subjected to the manipulated variable. This allows for comparison and helps determine the actual impact of the variable being tested. Observation and data collection: Regularly observe the barnacles and record relevant data. This may include growth rates, survival rates, reproductive success, or other measurable parameters. Use tools such as microscopes, calipers, or cameras to facilitate accurate measurements and observations. Replication: Repeat the experiment multiple times to ensure the results are consistent and reliable. This helps account for any variation or errors in the initial experiment. Analysis: Analyze the collected data using statistical methods to identify patterns, correlations, or significant differences between the experimental groups. Compare the results of the manipulated group(s) with the control group. Draw conclusions: Based on the analyzed data, draw conclusions about the effects of the manipulated variables on the barnacles. Determine if there were any observed trends, relationships, or impacts. Communication of results: It is crucial to communicate the findings of the experiment through scientific reports, presentations, or publications. This allows other researchers or interested parties to learn from the study and build upon it. Remember, specific protocols and equipment may vary depending on the complexity of the experiment and the research goals.

When was connell's barnacles and exclusion principle?

published Connell's barnacles and exclusion principle was published in 1955.

Why are controls not needed in the arthropods experiment described in the study guide?

Controls are not needed in the arthropods experiment because the study is focusing on the interactions between different species of arthropods and their environment. Since there is no manipulation of the environment or of the arthropods, there is no need to use a control group.

Can crazy ants conduct electricity?

No, crazy ants cannot conduct electricity.

Are barnacles herbivores?

No, barnacles are not herbivores; they are filter-feeding omnivores.

Which of the following compete for space on intertidal rocks?

• Mussels • Barnacles • Anemones • Seaweeds • Sea stars • Algae

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  Competition: Interspecific competition is a potent force in organic evolution. Competition generally occurs when closely related species compete for the same resources that are limiting, but this not entirely true: Firstly: totally unrelated species could also compete for the same resources. American lakes visiting flamingoes and resident fishes have their common food, zooplanktons. Secondly: resources need not be limiting for competition to occur. Abingdon tortoise in Galapagos Islands became extinct within a decade after goats were introduced on the island, due to greater browsing ability. Competitive release : A species, whose distribution is restricted to a small geographical area because of the presence of a competitively superior species, is found to expand its distributional range dramatically when the competing species is experimentally removed. Connell’s elegant field experiment showed that superior barnacle Balanus dominates the intertidal area and excludes the smaller barnacle Chathamalus from that zone. Gause’s ‘ competitive Exclusion Principle’ : two closely related species competing for the same resources cannot co-exist indefinitely and the competitively inferior will be eliminated eventually. Resource partitioning : If two species compete for the same resource, they could avoid competition by choosing, for instance, different times for feeding or different foraging pattern. MacArthur showed five closely related species of warblers living on the same tree were able to avoid competition and co-exist due to behavioral differences in their foraging activities. Parasitism: Parasitic mode of life ensures free lodging and meals. Some parasites are host-specific (one parasite has a single host) in such a way that both host and parasite tend to co-evolve. Parasitic adaptation Loss of unnecessary sense organs. Presence of adhesive organs or suckers to cling on to the host. Loss of digestive system. High reproductive capacity Parasites having one or more intermediate host or vectors to facilitate parasitisation of its primary host. Liver fluke has two intermediate hosts (snail and a fish) to complete its live cycle.   Effects on the host: Parasite always harms the host. They reduce the survival, growth and reproduction of the host. Reduce its population density. They make the host more vulnerable to the predators, by making it physically weak.   Ectoparasite: feeds on the external surface of the host. Lice on human Ticks on dog Marine fish infested with copepods Cuscuta a parasitic plant grow on hedge plants. Endoparasites: are those that live inside the host body at different sites. Life cycle is more complex. Morphological and anatomical features are greatly simplified. Highly developed reproductive system. Brood parasitism: Special type of parasitism found in birds. The parasitic birds lay its eggs in the nest of its host and let the host incubate them. The egg of the host is very similar with the egg of the host. Cuckoo lays eggs in the nest of the crow. Commensalism: This is the interaction in which one species benefits and the other is neither benefited nor harmed. Orchids growing as an epiphyte on a mango branch. Clown fish living among tentacles of sea anemone. Barnacles on back of whales. Cattle Egret and grazing cattle. Mutualism: interaction between two living organism, both are equally benefited, no one is harmed. Lichen: a mycobiont and a Phycobiont. Mycorrhiza: relationship between fungi and root of higher plant. Pollinating insects and flowering plants. Fig trees and its pollinating agent wasp. Sexual deceit Mediterranean orchid Ophrys employs ‘sexual deceit’ . Petal of the flower resembles the female bee. The male bee attracted to what it perceives as a female, ‘pseudocopulates’ with the flower but does not get any benefits.  

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Connel’s field experiment on the rocky seacoast of Scotland, where larger Barnacle balanus dominates the intertidal area and removes the smaller Barnacle chthamalus. This happened due to (a) Predation (b) Competition (c) Parasitism (d) Mutualism

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Organisms and Populations - Notes | Class 12 | Part 5: Population Interactions

13. organisms and populations.

• Predators control prey populations.

When certain exotic species are introduced into a geographical area, they spread fast due to the absence its natural predators. E.g. Prickly pear cactus introduced into Australia (1920’s) caused havoc by spreading. Later, it was controlled by introducing a cactus-feeding predator moth.

• Predators are used in Biological control methods.
• Predators maintain species diversity in a community by reducing competition among prey species.

E.g. the predator starfish Pisaster in the rocky intertidal communities of American Pacific Coast. In an experiment, all these starfishes were removed from an enclosed intertidal area. It caused extinction of over 10 invertebrate species within a year, due to interspecific competition.

• Camouflage (cryptic colouration) of some insects & frogs.
• Some are poisonous and so avoided by the predators.
• Monarch butterfly is highly distasteful to its predator bird. It is due to a special chemical in its body. It is acquired during its caterpillar stage by feeding on a poisonous weed.
• Thorns (Acacia, Cactus etc.) are the most common morphological means of defense of plants.
• Many plants produce chemicals that make the herbivore sick, inhibit feeding or digestion, disrupt its reproduction or kill it. E.g. Calotropis produce highly poisonous cardiac glycosides. Therefore cattle or goats do not eat it. Nicotine, caffeine, quinine, strychnine, opium, etc. are defenses against grazers and browsers.
• The Abingdon tortoise in Galapagos Islands became extinct within a decade after goats were introduced on the island, due to greater browsing efficiency of the goats.
• Competitive release: It is the expansion of distributional range of a species when the competing species is removed.
• Connell’s field experiments: On the rocky sea coasts of Scotland, there are 2 barnacle species: Balanus (larger & competitively superior) & Chthamalus (smaller). Balanus dominates intertidal area and excludes Chthamalus.

When Connell experimentally removed Balanus, Chthamalus colonized the intertidal zone.

• Human liver fluke depends on 2 intermediate hosts (a snail & a fish) to complete its life cycle.
• Malarial parasite needs mosquito to spread to other hosts.
• Lice on humans.
• Ticks on dogs.
• Ectoparasitic Copepods on many marine fishes.
• Cuscuta plant on hedge plants.
• Orchid (+) growing as epiphyte on a mango branch (0).
• Barnacles (+) growing on the back of a whale (0).
• Cattle egret (+) & grazing cattle (0). The egrets forage close to where the cattle are grazing. As the cattle move, the vegetation insects come out. Otherwise it is difficult for the egrets to find and catch the insects.
• Sea anemone (0) & clown fish (+). Stinging tentacles of sea anemone gives protection to fish from predators.
• Lichen: It is a mutualistic relationship between a fungus & photosynthesizing algae or cyanobacteria.
• Mycorrhizae: Associations between fungi & the roots of higher plants. The fungi help the plant in the absorption of essential nutrients from the soil while the plant provides the fungi with carbohydrates.
• Mutualism b/w plant & animal through pollination and seed dispersion: 

Fig trees & wasps. The fig species is pollinated only by its ‘partner’ wasp species. Female wasp pollinates the fig inflorescence while searching for suitable egg-laying sites in fruits. The fig offers the wasp some developing seeds, as food for the wasp larvae. Orchids show diversity of floral patterns. They can attract the right pollinator insect (bees & bumblebees) to ensure pollination. Not all orchids offer rewards. ‘Sexual deceit’ of Ophrys (Mediterranean orchid). One petal of its flower resembles female bee in size, colour & markings. So male bee ‘pseudocopulates’ with the flower and is dusted with pollen. When this bee ‘pseudocopulates’ with another flower, it transfers pollen to it.

If the female bee’s colour patterns change slightly during evolution, pollination success will be reduced unless the orchid flower co-evolves to maintain the resemblance of its petal to the female bee.

• Topic 1: Organisms and its Environment
• Topic 2: Responses to Abiotic Factors
• Topic 3: Populations
• Topic 4: Population Growth
• Topic 5: Population Interactions