Definition of predator and prey relationship

Predator–Prey Relationships |

definition of predator and prey relationship

Predation is a biological interaction where one organism, the predator, kills and includes a wide variety of feeding methods; and some relationships that result in the prey's death are not generally called predation. There are literally hundreds of examples of predator-prey relations. information on Predator–Prey Relationships: Environmental Science: In Context dictionary. American Heritage® Dictionary of the English Language, Fifth Edition. Predator -prey relationship quantified: power law for animal abundances matches '3/4.

There are literally hundreds of examples of predator-prey relations.

definition of predator and prey relationship

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.

Predator-prey relationship - Biology-Online Dictionary | Biology-Online Dictionary

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.

  • Predation & herbivory
  • Predator-Prey Relationships
  • Predators and prey

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.

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.

definition of predator and prey relationship

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.

definition of predator and prey relationship

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.

BBC - GCSE Bitesize: Predators and prey

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.

Population dynamics of predators and prey Populations of predators and prey in a community are not always constant over time.

definition of predator and prey relationship

Instead, in many cases, they vary in cycles that appear to be related. The most frequently cited example of predator-prey dynamics is seen in the cycling of the lynx, a predator, and the snowshoe hare, its prey. Strikingly, this cycling can be seen in nearly year-old data based on the number of animal pelts recovered by trappers in North American forests. The number of hares fluctuates between 10, at the low points and 75, toat the high points.

Predator–Prey Relationships

There are typically fewer lynxes than hares, but the trend in number of lynxes follows the number of hares. The classic explanation is this: As hare numbers increase, there is more food available for the lynx, allowing the lynx population to increase as well. When the lynx population grows to a threshold level, however, it kills so many hares that the hare population begins to decline.

This is followed by a decline in the lynx population due to scarcity of food. When the lynx population is low, the hare population begins to increase—due, at least in part, to low predation pressure—starting the cycle anew.

Today, ecologists no longer think that the cycling of the two populations is entirely controlled by predation.

definition of predator and prey relationship

For instance, it appears that availability of plant foods eaten by the hares—which decreases when hares become too abundant, due to competition—may also be a factor in the cycle. Defense mechanisms against predation When we study a community, we must consider the evolutionary forces that have acted—and continue to act!

Species are not static but, rather, change over generations and can adapt to their environment through natural selection. Predator and prey species both have adaptations—beneficial features arising by natural selection—that help them perform better in their role. For instance, prey species have defense adaptations that help them escape predation. These defenses may be mechanical, chemical, physical, or behavioral. Mechanical defenses, such as the presence of thorns on plants or the hard shell on turtles, discourage animal predation and herbivory by causing physical pain to the predator or by physically preventing the predator from being able to eat the prey.

Chemical defenses are produced by many animals as well as plants, such as the foxglove, which is extremely toxic when eaten.

An important thing to realize is that as both organisms become faster to adapt to their environments, their relationship remains the same: This is true in all predator-prey relationships. Another example of predator-prey evolution is that of the Galapagos tortoise. Galapagos tortoises eat the branches of the cactus plants that grow on the Galapagos islands.

On one of the islands, where long-necked tortoises live, the branches are higher off the ground. On another island, where short-necked tortoises live, the branches are lower down.