Predator-prey cycles (video) | Ecology | Khan Academy
When the predator population becomes too large, however, the prey population This canonical view of predator-prey relationships was first. Predation is a biological interaction where one organism, the predator, kills and eats another . There is a positive correlation between the size of a predator and its prey. .. Increases or decreases in the prey population can also lead to increases or .. in a Solitary Predator Is Independent of Body Size and Growth Rate". Population Growth Models. • Exponential (J-shaped): Unlimited growth (such as bacteria, shown at the bottom left). • Logistic (S-shaped): Growth is limited;.
Predators are often highly specialized in their diet and hunting behaviour; for example, the Eurasian lynx only hunts small ungulates. When prey have a clumped uneven distribution, the optimal strategy for the predator is predicted to be more specialized as the prey are more conspicuous and can be found more quickly;  this appears to be correct for predators of immobile prey, but is doubtful with mobile prey.
This has led to a correlation between the size of predators and their prey. Size may also act as a refuge for large prey. For example, adult elephants are relatively safe from predation by lions, but juveniles are vulnerable. Members of the cat family such as the snow leopard treeless highlandstiger grassy plains, reed swampsocelot forestfishing cat waterside thicketsand lion open plains are camouflaged with coloration and disruptive patterns suiting their habitats.
Female Photuris firefliesfor example, copy the light signals of other species, thereby attracting male fireflies, which they capture and eat. Venom and Evolution of snake venom Many smaller predators such as the box jellyfish use venom to subdue their prey,  and venom can also aid in digestion as is the case for rattlesnakes and some spiders.
These changes are explained by the fact that its prey does not need to be subdued. Antipredator adaptation To counter predation, prey have a great variety of defences. They can try to avoid detection. They can detect predators and warn others of their presence.
If detected, they can try to avoid being the target of an attack, for example, by signalling that a chase would be unprofitable or by forming groups. If they become a target, they can try to fend off the attack with defences such as armour, quills, unpalatability or mobbing; and they can escape an attack in progress by startling the predator, shedding body parts such as tails, or simply fleeing.
They can also adopt behaviour that avoids predators by, for example, avoiding the times and places where predators forage. Camouflage and Mimicry Dead leaf mantis 's camouflage makes it less visible to both predators and prey. Syrphid hoverfly misdirects predators by mimicking a waspbut has no sting.
Prey animals make use of a variety of mechanisms including camouflage and mimicry to misdirect the visual sensory mechanisms of predators, enabling the prey to remain unrecognized for long enough to give it an opportunity to escape.
Camouflage delays recognition through coloration, shape, and pattern. In mimicry, an organism has a similar appearance to another species, as in the drone flywhich resembles a bee yet has no sting. It is lowest for those such as woodpeckers that excavate their own nests and progressively higher for those on the ground, in canopies and in shrubs.
Birds also choose appropriate habitat e. Similarly, some mammals raise their young in dens. However, there are exceptions: For example, Belding's ground squirrel can distinguish several aerial and ground predators from each other and from harmless species. Prey also distinguish between the calls of predators and non-predators.
There are literally hundreds of examples of predator-prey relations. A few of them are the lion-zebra, bear-salmon, and fox-rabbit. A plant can also be prey. Bears, for example, feed on berries, a rabbit feeds on lettuce, and a grasshopper feeds on leaves. Predators and prey exist among even the simplest life forms on Earth, single-celled organisms called bacteria.
The bacteria Bdellovibrio feed on other bacteria that are bioluminescent they produce internal light due to a chemical reaction. Indeed, the study of Bdellovibrio predation has revealed a great deal of the mechanics of predation and how the predator and prey populations fluctuate in number over time in a related fashion.
Predator and prey populations respond dynamically to one another. When the numbers of a prey such as rabbits explode, the abundance at this level of the food chain supports higher numbers of predator populations such as foxes.
If the rabbit population is over-exploited or drops due to disease or some other calamity, the predator population will soon decline. Over time, the two populations cycle up and down in number. In many higher organisms, the prey can be killed by the predator prior to feeding. For example, a cheetah will stalk, run down, and kill its prey examples include the gazelle, wildebeest, springbok, impala, and zebra.
In contrast, fish and seals that are the prey of some species of shark are examples of prey that is fed on while still alive. The key aspect of a predator-prey relationship is the direct effect that the predation has on numbers of their prey. Historical Background and Scientific Foundations Predators and prey have evolved together, and their relationship is ancient.
For example, fossils dating back nearly million years have revealed evidence that extinct animals known as Hederellids were the prey of an as yet unknown creature that killed them by drilling holes through their tubular shells.
As species developed and flourished, other species exploited them as their food. A species that has become a successful predator and has survived has developed a few or a number of strategies to acquire the prey. The predator may use speed; stealth the ability to approach unnoticed by being quiet and deliberate in its movements, or by approaching from upwind ; camouflage; a highly developed sense of smell, sight, or hearing; tolerance to poison produced by the prey; production of its own prey-killing poison; or an anatomy that permits the prey to be eaten or digested.
Likewise, the prey has strategies to help it avoid being killed by a predator. A prey species can also use the aforementioned attributes listed for the predator to avoid being caught and killed.
The fitness of the prey population—the number of individuals in the population, chance of being able to reproduce, and chance of survival—is controlled by the predator population. The ways in which predators stalk, kill, and feed on their prey can be used in a classification scheme.
A so-called true predator kills the prey and then feeds on it.
Predation - Wikipedia
True predation usually does not involve harm to the prey prior to death. For example, prior to being chased down and killed by a cheetah, a gazelle is healthy. Cattle that graze on grass are not considered a predator-prey relationship, as only a portion of the grass is eaten, with the intact roots permitting re-growth of the grassy stalk to occur.
A predator and its prey can both be microscopic, as is the case with the bacterium Bdellovibrio and other Gram-negative bacteria.
But, the size difference between predator and its prey can be immense. Predator-prey relationships can be more complex than a simple one-to-one relationship, because a species that is the predator or the prey in one circumstance can be the opposite in a relationship with different species. For example, birds such as the blue jay that prey on insects can become the prey for snakes, and the predatory snakes can be the prey of birds such as hawks.
This pattern is known as a hierarchy or a food chain. The hierarchy does not go on indefinitely, and ends at what is described as the top of the food chain. For example, in some ocean ecosystems, sharks are at the pinnacle of the food chain.
Other than humans, such so-called apex predators are not prey to any other species. This relationship applies only to the particular ecosystem that the apex predator is in.
If transferred to a different ecosystem, an apex predator could become prey. For example, the wolf, which is at the top of the food chain in northern forests and tundra environments, could become the prey of lions and crocodiles if it were present in an African ecosystem. Predator-prey relationships involve detection of the prey, pursuit and capture of the prey, and feeding.
Adaptations such as camouflage can make a prey species better able to avoid detection. By blending into the background foliage or landscape and remaining motionless, an insect or animal offers no visual cue to a predator since it mimics its surroundings. There are many examples of mimicry in predator-prey relationships. Some moths have markings on their outer wings that resemble the eyes of an owl or that make the creature look larger in size.
Insects popularly known as walking sticks appear similar to the twigs of the plants they inhabit. Another insect species called the praying mantis appears leaflike. The vertical stripes cause individual zebras in a herd to blend together when viewed for a distance. To a predator like a lion, the huge shape is not recognized as a potential source of food. Camouflage can also be a strategy used by a predator to avoid detection by prey. An example is the polar bearwhose white color blends in with snow, reducing the likelihood that the bear will be detected as it approaches its prey.
In this case, the same strategy and color can be utilized by young seals, since their color allows them to be invisible as they lie on the snowy surface. The community of individuals and the physical components of the environment in a certain area.
A sequence of organisms, each of which uses the next lower member of the sequence as a food source. An interconnected set of all the food chains in the same ecosystem. The natural location of an organism or a population.
Factors that influence the evolution of an organism. An example is the overuse of antibiotics, which provides a selection pressure for the development of antibiotic resistance in bacteria.
The opposite of camouflage can occur.