Speciation is the evolutionary process by which biological populations evolve to become distinct species. The biologist Orator F. Cook coined the term speciation in 1906 for the splitting of lineages or cladogenesis, Charles Darwin was the first to describe the role of natural selection in speciation in his 1859 book The Origin of Species. He identified sexual selection as a mechanism, but found it problematic. There are four modes of speciation in nature, based on the extent to which speciating populations are isolated from one another, peripatric, parapatric. Speciation may be induced artificially, through animal husbandry, whether genetic drift is a minor or major contributor to speciation is the subject matter of much ongoing discussion. All forms of speciation have taken place over the course of evolution, however. During allopatric speciation, a population splits into two isolated populations. When the populations come back into contact, they have evolved such that they are isolated and are no longer capable of exchanging genes.
Island genetics is the associated with the tendency of small. Examples include insular dwarfism and the changes among certain famous island chains. The Galápagos Islands are particularly famous for their influence on Charles Darwin, though the finches were less important for Darwin, more recent research has shown the birds now known as Darwins finches to be a classic case of adaptive evolutionary radiation. In peripatric speciation, a subform of allopatric speciation, new species are formed in isolated and it is related to the concept of a founder effect, since small populations often undergo bottlenecks. Genetic drift is often proposed to play a significant role in peripatric speciation, parapatric speciation may be associated with differential landscape-dependent selection. Even if there is a gene flow between two populations, strong differential selection may impede assimilation and different species may eventually develop, habitat differences may be more important in the development of reproductive isolation than the isolation time.
Ecologists refer to parapatric and peripatric speciation in terms of ecological niches, a niche must be available in order for a new species to be successful. Ring species such as Larus gulls have been claimed to illustrate speciation in progress, the grass Anthoxanthum odoratum may be starting parapatric speciation in areas of mine contamination. Sympatric speciation refers to the formation of two or more descendant species from an ancestral species all occupying the same geographic location. Often-cited examples of sympatric speciation are found in insects that become dependent on different host plants in the same area, the existence of sympatric speciation as a mechanism of speciation remains highly debated
The trophic level of an organism is the position it occupies in a food chain. The word trophic derives from the Greek τροφή referring to food or feeding, a food chain represents a succession of organisms that eat another organism and are, in turn, eaten themselves. The number of steps an organism is from the start of the chain is a measure of its trophic level. Food chains start at trophic level 1 with primary producers such as plants, move to herbivores at level 2, predators at level 3, the path along the chain can form either a one-way flow or a food web. Ecological communities with higher biodiversity form more complex trophic paths, the three basic ways in which organisms get food are as producers and decomposers. Producers are typically plants or algae and algae do not usually eat other organisms, but pull nutrients from the soil or the ocean and manufacture their own food using photosynthesis. For this reason, they are called primary producers, in this way, it is energy from the sun that usually powers the base of the food chain.
An exception occurs in deep-sea hydrothermal ecosystems, where there is no sunlight, here primary producers manufacture food through a process called chemosynthesis. Consumers are species that cannot manufacture their own food and need to other organisms. Animals that eat primary producers are called herbivores, animals that eat other animals are called carnivores, and animals that eat both plant and other animals are called omnivores. Decomposers break down plant and animal material and wastes and release it again as energy. Decomposers, such as bacteria and fungi, feed on waste and dead matter, Trophic levels can be represented by numbers, starting at level 1 with plants. Further trophic levels are numbered according to how far the organism is along the food chain. Level 1, Plants and algae make their own food and are called primary producers, level 2, Herbivores eat plants and are called primary consumers. Level 3, Carnivores that eat herbivores are called secondary consumers, level 4, Carnivores that eat other carnivores are called tertiary consumers.
Level 5, Apex predators that have no predators are at the top of the food chain. In real world ecosystems, there is more than one chain for most organisms. A diagram that sets out the network of intersecting and overlapping food chains for an ecosystem is called its food web
In biology/ecology, parasitism is a non-mutual relationship between species, where one species, the parasite, benefits at the expense of the other, the host. Traditionally parasite referred primarily to organisms visible to the naked eye, Parasites can be microparasites, which are typically smaller, such as protozoa and bacteria. Examples of parasites include the plants mistletoe and cuscuta, and animals such as hookworms, unlike predators, parasites typically do not kill their host, are generally much smaller than their host, and will often live in or on their host for an extended period. Both are special cases of consumer-resource interactions, Parasites show a high degree of specialization, and reproduce at a faster rate than their hosts. Classic examples of parasitism include interactions between vertebrate hosts and tapeworms, the Plasmodium species, and fleas, parasitism differs from the parasitoid relationship in that parasitoids generally kill their hosts. Parasites reduce host biological fitness by general or specialized pathology, such as parasitic castration and impairment of secondary sex characteristics, Parasites increase their own fitness by exploiting hosts for resources necessary for their survival, e. g. food, heat and transmission.
Although parasitism applies unambiguously to many cases, it is part of a continuum of types of interactions between species, rather than an exclusive category, in many cases, it is difficult to demonstrate harm to the host. In others, there may be no apparent specialization on the part of the parasite, coined in English in 1611, the word parasitism comes from the Greek παρά + σιτισμός feeding, fattening. Parasites are classified based on their interactions with their hosts and on their life cycles, an obligate parasite is totally dependent on the host to complete its life cycle, while a facultative parasite is not. A direct parasite has one host while an indirect parasite has multiple hosts. For indirect parasites, there always be a definitive host. Parasites that live on the outside of the host, either on the skin or the outgrowths of the skin, are called ectoparasites and those that live inside the host are called endoparasites. Endoparasites can exist in one of two forms, intercellular parasites or intracellular parasites, intracellular parasites, such as protozoa, bacteria or viruses, tend to rely on a third organism, which is generally known as the carrier or vector.
The vector does the job of transmitting them to the host, an example of this interaction is the transmission of malaria, caused by a protozoan of the genus Plasmodium, to humans by the bite of an anopheline mosquito. Those parasites living in a position, being half-ectoparasites and half-endoparasites, are called mesoparasites. An epiparasite is one that feeds on another parasite and this relationship is sometimes referred to as hyperparasitism, exemplified by a protozoan living in the digestive tract of a flea living on a dog. Social parasites take advantage of interactions between members of social organisms such as ants and bumblebees, an extreme example of social parasitism is the ant species of Tetramorium inquilinum of the Alps, which spend their whole lives on the back of Tetramorium host ants. With tiny and deprecated bodies they have evolved for one single task, if they fall off, they most likely would not have the strength to climb back on top of another ant, and eventually they will die
Omnivore /ˈɒmnivɔər/ is a consumption classification for animals that have the capability to obtain chemical energy and nutrients from materials originating from plant and animal origin. Often, omnivores have the ability to incorporate food sources such as algae, omnivores come from diverse backgrounds that often independently evolved sophisticated consumption capabilities. For instance, dogs evolved from primarily carnivorous organisms while pigs evolved from primarily herbivorous organisms, what this means is that physical characteristics are often not reliable indicators of whether an animal has the ability to obtain energy and nutrients from both plant and animal matter. The variety of different animals that are classified as omnivores can be placed into categories depending on their feeding behaviors. Frugivores include maned wolves and orangutans, insectivores include swallows and pink fairy armadillos, granivores include large ground finches, all of these animals are omnivores, yet still fall into special niches in terms of feeding behaviors and preferred foods.
Being omnivores gives these animals more food security in times or makes possible living in less consistent environments. The word omnivore derives from the Latin omnis, and vora, from vorare, having been coined by the French, traditionally the definition for omnivory was entirely behavioral by means of simply including both animal and vegetable tissue in the diet. This has subsequently conditioned two context specific definitions, This definition is used to specify if a species or individual is actively consuming both plant and animal materials. Physiological, This definition is used in academia to specify species that have the capability to obtain energy. Though Carnivora is a taxon for species classification, no equivalent exists for omnivores. The Carnivora order does not include all species, and not all species within the Carnivora taxon are carnivorous. It is common to find physiological carnivores consuming materials from plants or physiological herbivores consuming material from animals, e. g. felines eating grass, from a behavioral aspect, this would make them omnivores, but from the physiological standpoint, this may be due to zoopharmacognosy.
Physiologically, animals must be able to both energy and nutrients from plant and animal materials to be considered omnivorous. For instance, it is documented that animals such as giraffes, camels. Felines, which are regarded as obligate carnivores, occasionally eat grass to regurgitate indigestibles, aid with hemoglobin production. Occasionally, it is found that animals historically classified as carnivorous may deliberately eat plant material, for example, in 2013 it was considered that American alligators may be physiologically omnivorous once investigations had been conducted on why they occasionally eat fruits. It was suggested that alligators probably ate fruits both accidentally but deliberately, life-history omnivores is a specialized classification given to organisms that change their eating habits during their life cycle. Some species, such as grazing waterfowl like geese, are known to eat animal tissue at one stage of their lives
Competition is an interaction between organisms or species in which both the organisms or species are harmed. Limited supply of at least one used by both can be a factor. Competition both within and between species is an important topic in ecology, especially community ecology, competition is one of many interacting biotic and abiotic factors that affect community structure. Competition among members of the species is known as intraspecific competition. Competition is not always straightforward, and can occur in both a direct and indirect fashion, according to the competitive exclusion principle, species less suited to compete for resources should either adapt or die out, although competitive exclusion is rarely found in natural ecosystems. Competition occurs by various mechanisms, which can generally be divided into direct and indirect and these apply equally to intraspecific and interspecific competition. Biologists typically recognize two types of competition and exploitative competition, during interference competition, organisms interact directly by fighting for scarce resources.
For example, large aphids defend feeding sites on cottonwood leaves by ejecting smaller aphids from better sites, in contrast, during exploitative competition, organisms interact indirectly by consuming scarce resources. For example, plants consume nitrogen by absorbing it into their roots, plants that produce many roots typically reduce soil nitrogen to very low levels, eventually killing neighboring plants. Exploitation competition occurs indirectly through a limiting resource which acts as an intermediate. For example, use of resources depletes the amount available to others, apparent competition occurs indirectly between two species which are both preyed upon by the same predator. For example, species A and species B are both prey of predator C, competition vary from complete symmetric to perfectly size symmetric to absolutely size-asymmetric. Competition can occur between individuals of the species, called intraspecific competition, or between different species, called interspecific competition.
Studies show that intraspecific competition can regulate population dynamics and this occurs because individuals become crowded as a population grows. Since individuals within a population require the resources, crowding causes resources to become more limited. Some individuals eventually do not acquire enough resources and die or do not reproduce and this reduces population size and slows population growth. Species interact with other species that require the same resources, interspecific competition can alter the sizes of many species populations at the same time. Experiments demonstrate that when species compete for a resource, one species eventually drives the populations of other species extinct
A cactus is a member of the plant family Cactaceae, a family comprising about 127 genera with some 1750 known species of the order Caryophyllales. The word cactus derives, through Latin, from the Ancient Greek κάκτος, Cacti occur in a wide range of shapes and sizes. Most cacti live in habitats subject to at least some drought, many live in extremely dry environments, even being found in the Atacama Desert, one of the driest places on earth. Cacti show many adaptations to conserve water, almost all cacti are succulents, meaning they have thickened, fleshy parts adapted to store water. Unlike many other succulents, the stem is the part of most cacti where this vital process takes place. Most species of cacti have lost true leaves, retaining only spines, as well as defending against herbivores, spines help prevent water loss by reducing air flow close to the cactus and providing some shade. In the absence of leaves, enlarged stems carry out photosynthesis, Cacti are native to the Americas, ranging from Patagonia in the south to parts of western Canada in the north—except for Rhipsalis baccifera, which grows in Africa and Sri Lanka.
Cactus spines are produced from specialized structures called areoles, a kind of highly reduced branch, areoles are an identifying feature of cacti. As well as spines, areoles give rise to flowers, which are usually tubular, Cactus stems are often ribbed or fluted, which allows them to expand and contract easily for quick water absorption after rain, followed by long drought periods. Like other succulent plants, most cacti employ a mechanism called crassulacean acid metabolism as part of photosynthesis. Transpiration, during which carbon enters the plant and water escapes, does not take place during the day at the same time as photosynthesis. The plant stores the carbon dioxide it takes in as malic acid, retaining it until daylight returns, because transpiration takes place during the cooler, more humid night hours, water loss is significantly reduced. Many smaller cacti have globe-shaped stems, combining the highest possible volume for water storage, the tallest free-standing cactus is Pachycereus pringlei, with a maximum recorded height of 19.2 m, and the smallest is Blossfeldia liliputiana, only about 1 cm in diameter at maturity. A fully grown saguaro is said to be able to absorb as much as 200 U. S. gallons of water during a rainstorm, a few species differ significantly in appearance from most of the family.
At least superficially, plants of the genus Pereskia resemble other trees and they have persistent leaves, and when older, bark-covered stems. Their areoles identify them as cacti, and in spite of their appearance, Pereskia is considered close to the ancestral species from which all cacti evolved. In tropical regions, other cacti grow as forest climbers and epiphytes and their stems are typically flattened, almost leaf-like in appearance, with fewer or even no spines, such as the well-known Christmas cactus or Thanksgiving cactus. Cacti have a variety of uses, many species are used as ornamental plants, others are grown for fodder or forage, cochineal is the product of an insect that lives on some cacti
Black-and-white colobuses are Old World monkeys of the genus Colobus, native to Africa. They are closely related to the brown colobus monkeys of genus Piliocolobus, the word colobus comes from Greek κολοβός kolobós, and is so named because in this genus, the thumb is a stump. Colobuses are herbivorous, eating leaves, fruit and their habitats include primary and secondary forests, riverine forests, and wooded grasslands, they are found more in higher-density logged forests than in other primary forests. Their ruminant-like digestive systems have enabled these leaf-eaters to occupy niches that are inaccessible to other primates, colobuses live in territorial groups of about nine individuals, based upon a single male with a number of females and their offspring. Cases of allomothering are documented, which members of the troop other than the infants biological mother care for it. Colobuses are important for seed dispersal through their sloppy eating habits and they are prey for many forest predators, and are threatened by hunting for the bushmeat trade and habitat destruction
A frugivore /fruːdʒᵻvɔːr/ is a fruit eater. It can be any type of herbivore or omnivore where fruit is a preferred food type, because approximately 20% of all mammalian herbivores eat fruit, frugivory is common among mammals. Since frugivores eat a lot of fruit, they are dependent on the abundance. Frugivores can either benefit fruit-producing plants by dispersing seeds, or they can hinder plants by digesting seeds along with the fruits, when both the fruit-producing plant and the frugivore species benefit by fruit-eating behavior, their interaction is called mutualism. Seed dispersal is important for plants because it allows their progeny to move away from their parents over time, the advantages of seed dispersal may have led to the evolution of fleshy fruits, which entice animals to eat the fruits and move the plants seeds from place to place. While many fruit-producing plant species would not disperse far without frugivores, many types of animals are seed dispersers. Mammal and bird species represent the majority of seed-dispersing species, frugivorous tortoises, lizards and even fish disperse seeds.
For example, cassowaries are a species because they spread fruit through digestion. While frugivores and fruit-producing plant species are present worldwide, there is evidence that tropical forests have more frugivore seed dispersers than the temperate zone. Frugivore seed dispersal is a phenomenon in many ecosystems. However, it is not a specific type of plant–animal interaction. For example, a species of frugivorous bird may disperse fruits from several species of plants. This lack of specialization could be because fruit availability varies by season and year, different seed dispersers tend to disperse seeds to different habitats, at different abundances, and distances, depending on their behavior and numbers. There are a number of characteristics that seem to be adaptive characteristics to attract frugivores. Many animal-dispersed fruits advertise their palatability to animals with bright colors, Fruit pulp is generally rich in water and carbohydrates and low in protein and lipids. However, the nutritional composition of fruits varies widely.
The seeds of animal-dispersed fruits are often adapted to survive digestion by frugivores, for example, seeds can become more permeable to water after passage through an animals gut. This leads to higher germination rates, some mistletoe seeds even germinate inside the dispersers intestine
In biology, coevolution occurs when two or more species reciprocally affect each others evolution. Charles Darwin mentioned evolutionary interactions between flowering plants and insects in On the Origin of Species, the term coevolution was coined by Paul R. Ehrlich and Peter H. Raven in 1964. Each party in a coevolutionary relationship exerts selective pressures on the other, Coevolution includes many forms of mutualism, host-parasite, and predator-prey relationships between species, as well as competition within or between species. In many cases, the selective pressures drive an evolutionary arms race between the species involved, Coevolution is primarily a biological concept, but researchers have applied it by analogy to fields such as computer science and astronomy. Coevolution is evident in the development of relationships between many pairs of organisms, and serving a wide variety of types of mutual benefit. Each fig species has its own fig wasp which pollinates the fig, some ant species can exploit trees without reciprocating, and hence have been given various names such as cheaters, exploiters and freeloaders.
Although cheater ants do important damage to the organs of trees, their net effect on host fitness is difficult to forecast. He first mentioned coevolution as a possibility in On the Origin of Species, modern insect-pollinated flowers are conspicuously coadapted with insects to ensure pollination and in return to reward the pollinators with nectar and pollen. The two groups have coevolved for over 100 million years, creating a network of interactions. Either they evolved together, or at some stages they came together, likely with pre-adaptations, the term coevolution was coined by Paul R. Ehrlich and Peter H. Raven in 1964, to describe the evolutionary interactions of plants and butterflies. Several highly successful insect groups—especially the Hymenoptera and Lepidoptera as well as types of Diptera and Coleoptera —evolved in conjunction with flowering plants during the Cretaceous. However, a group of wasps sister to the bees evolved at the time as flowering plants. At least three aspects of flowers appear to have coevolved between flowering plants and insects, because they involve communication between these organisms.
Firstly, flowers communicate with their pollinators by scent, insects use this scent to determine how far away a flower is, to approach it, flowers such as some orchids mimic females of particular insects, deceiving males into pseudocopulation. The yucca, Yucca whipplei, is pollinated exclusively by Tegeticula maculata, the moth eats the seeds of the plant, while gathering pollen. The pollen has evolved to become sticky, and remains on the mouth parts when the moth moves to the next flower. The yucca provides a place for the moth to lay its eggs and ornithophilous flowers have evolved a mutualistic relationship. The flowers have nectar suited to the diet, their color suits the birds vision
A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthparts adapted to rasping or grinding and other herbivores have wide flat teeth that are adapted to grinding grass, tree bark, and other tough plant material. A large percentage of herbivores have mutualistic gut flora that help them digest plant matter and this gut flora is made up of cellulose-digesting protozoans or bacteria living in the herbivores intestines. Herbivore is the form of a modern Latin coinage, herbivora. Richard Owen employed the term in an 1854 work on fossil teeth. Herbivora is derived from the Latin herba meaning a small plant or herb, Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants and photosynthesizing bacteria. More generally, organisms feed on autotrophs in general are known as primary consumers. Herbivory usually refers to eating plants, fungi and protists that feed on living plants are usually termed plant pathogens.
Flowering plants that obtain nutrition from other living plants are usually termed parasitic plants, there is however no single exclusive and definitive ecological classification of consumption patterns, each textbook has its own variations on the theme. Insects fed on the spores of early Devonian plants, and the Rhynie chert provides evidence that organisms fed on plants using a pierce, during the next 75 million years, plants evolved a range of more complex organs, such as roots and seeds. There is no evidence of any organism being fed upon until the middle-late Mississippian,330.9 million years ago, further than their arthropod status, the identity of these early herbivores is uncertain. Hole feeding and skeletonisation are recorded in the early Permian, with surface fluid feeding evolving by the end of that period, Herbivory among four-limbed terrestrial vertebrates, the tetrapods developed in the Late Carboniferous. Early tetrapods were large amphibious piscivores, while amphibians continued to feed on fish and insects, some reptiles began exploring two new food types and plants.
The entire dinosaur order ornithischia was composed with herbivores dinosaurs, carnivory was a natural transition from insectivory for medium and large tetrapods, requiring minimal adaptation. In contrast, a set of adaptations was necessary for feeding on highly fibrous plant materials. Arthropods evolved herbivory in four phases, changing their approach to it in response to changing plant communities, tetrapod herbivores made their first appearance in the fossil record of their jaws near the Permio-Carboniferous boundary, approximately 300 million years ago. The earliest evidence of their herbivory has been attributed to dental occlusion, the evolution of dental occlusion led to a drastic increase in plant food processing and provides evidence about feeding strategies based on tooth wear patterns. Examination of phylogenetic frameworks of tooth and jaw morphologes has revealed that dental occlusion developed independently in several lineages tetrapod herbivores and this suggests that evolution and spread occurred simultaneously within various lineages
Biomass, is the mass of living biological organisms in a given area or ecosystem at a given time. Biomass can refer to species biomass, which is the mass of one or more species, or to community biomass and it can include microorganisms, plants or animals. The mass can be expressed as the mass per unit area. How biomass is measured depends on why it is being measured, the biomass is regarded as the natural mass of organisms in situ, just as they are. For example, in a fishery, the salmon biomass might be regarded as the total wet weight the salmon would have if they were taken out of the water. In other contexts, biomass can be measured in terms of the organic mass, so perhaps only 30% of the actual weight might count. For other purposes, only biological tissues count, and teeth, bones, in some applications, biomass is measured as the mass of organically bound carbon that is present. Apart from bacteria, the total biomass on Earth is about 560 billion tonnes C. The total live biomass of bacteria may be as much as that of plants, the total amount of DNA base pairs on Earth, as a possible approximation of global biodiversity, is estimated at 5.0 x 1037, and weighs 50 billion tonnes.
In comparison, the mass of the biosphere has been estimated to be as much as 4 TtC. An ecological pyramid is a representation that shows, for a given ecosystem. A biomass pyramid shows the amount of biomass at each trophic level, a productivity pyramid shows the production or turn-over in biomass at each trophic level. An ecological pyramid provides a snapshot in time of an ecological community, the bottom of the pyramid represents the primary producers. The primary producers take energy from the environment in the form of sunlight or inorganic chemicals and this mechanism is called primary production. The pyramid proceeds through the trophic levels to the apex predators at the top. When energy is transferred from one level to the next. The remaining ninety percent goes to metabolic processes or is dissipated as heat and this energy loss means that productivity pyramids are never inverted, and generally limits food chains to about six levels. However, in oceans, biomass pyramids can be wholly or partially inverted, terrestrial biomass generally decreases markedly at each higher trophic level
Behavioral ecology, spelled behavioural ecology, is the study of the evolutionary basis for animal behavior due to ecological pressures. If an organism has a trait which provides them with an advantage in its environment. Adaptive significance therefore refers to the qualities, any given modified trait conveys. e. Individuals are always in competition with others for limited resources, including food, conflict will occur between predators and prey, between rivals for mates, between siblings and even between parents and their offspring. The value of a social behavior depends in part on the behavior of an animals neighbors. For example, the more likely a male is to back down from a threat. The more likely, that a rival will attack if threatened, when a population exhibits a number of interacting social behaviors such as this, it can evolve a stable pattern of behaviors known as an evolutionarily stable strategy. In other words, at equilibrium every player should play the best strategic response to each other, when the game is two player and symmetric each player should play the strategy which is the best response to itself.
Therefore, the ESS is considered to be the end point subsequent to the interactions. Behavioral evolution is therefore influenced by both the environment and interactions between other individuals. An example of how changes in geography can make a strategy susceptible to alternative strategies is the parasitization of the African honey bee, the term economic defendability was first introduced by Jerram Brown in 1964. Economic defendability states that defense of a resource have costs, such as energy expenditure or risk of injury, territorial behavior arises when benefits are greater than the costs. Studies of the golden-winged sunbird have validated the concept of economic defendability, when resources are at low density, the gains from excluding others may not be sufficient to pay for the cost of territorial defense. In contrast, when availability is high, there may be so many intruders that the defender would have no time to make use of the resources made available by defense. Sometimes the economics of resource competition favors shared defense, an example is the feeding territories of the white wagtail.
The white wagtails feed on insects washed up by the river onto the bank, if any intruders harvested their territory the prey would quickly become depleted, but sometimes territory owners tolerate a second bird, known as a satellite. The two sharers would move out of phase with one another, resulting in decreased feeding rate but increased defense, one of the major models used to predict the distribution of competing individuals amongst resource patches is the ideal free distribution model. Within this model, resource patches can be of variable quality, an experiment by Manfred Malinski in 1979 demonstrated that feeding behavior in three-spined sticklebacks follows an ideal free distribution