There are four relationships
Predator - Prey
Predator - Prey relationships mean an organism (the predator) eats another organism (the prey).
An example of this is the lion and the zebra where the lion (the predator) eats the zebra (the prey).
Over generations predators and prey develop special skills to help them catch prey or escape from predators. Predators may need to develop strong leg muscles for speed and prey may need to be able to change their skin colour for camouflage to hide from the predator for example the chameleon.
Developing special skills over generations happens because of nature’s basic law, survival of the fittest. The faster lions are successful at catching the prey and the slower lions die of hunger. The faster lions then live to have babies while the slower lions die out. This means that the next generation of lions will be faster than the previous generation for example by having stronger leg muscles.
The same law of survival of the fittest happens with prey as well.
The predator- prey relationship must be balanced. If you reduce the population of lions for example by hunters killing them, the zebras will increase in numbers and their food source, the grass, will become scarce and then the zebras would die out. If the number of zebras decreased then there wouldn’t be enough food for the lions and the lions would die.
Parasitic relationships are when an organism (the parasite) lives off another organism (the host). The parasite needs the host’s body to live. The parasite benefits but harms the host or sometimes even causes the host to die.
An example of this relationship is a flatworm called a tapeworm and humans, where the tapeworm is the parasite and enters the human host.
Tapeworms enter the human body when the person eats under -cooked meat like beef and pork. The tapeworms then attach themselves to the host’s intestines (guts). The tapeworm eats the partly digested food in the host’s intestines, stopping the person from getting the nutrients they need. This causes the person to lose weight and sometimes die.
Tapeworms can grow up to fifteen metres in length!
Competitive relationships mean two organisms competing over the same resources. The resources are usually limited food or shelter.
Competition for resources can be between two animals of the same species, for example two bears fighting over a fish.
Competition for resources can also be between animals of different species for example cheetahs and lions which are different species but compete for the same prey
Mutually Beneficial Relationships
Mutually beneficial relationships mean two organisms work together and there is a benefit for both of them.
An example of this is
the rhinoceros and birds. The birds perch on the rhino’s back and eat ticks and
fleas off it. This benefits the birds as this is an easy way for them to get food and the rhino benefits as
the fleas and ticks are removed stopping it getting itchy from flea bites or
sick from the ticks.