branch ANIMALS

=Parental Care Strategies= There are essentially two basic strategies when it comes to reproduction. Organisms tend to either invest their energy into producing many offspring or into ensuring that their few offspring survive (parental care). [image:] Species such as barnacles can produce 500 million fertilised eggs per year. They invest energy into producing many offspring, but provide no parental care. As a result only a very small proportion survive. Species such as gorillas only give birth approximately once every 5 years, however, they invest significant time and energy into ensuring the survival of their offspring. ==r and k selected species== [image:] '''R selected species''' exhibit very rapid growth into new, uncolonised areas. They reproduce and spread quickly but are less competitive and are dependant on invading new areas to survive. When conditions are right they produce huge numbers of offspring ("population boom"), often more than the environment can sustain (carrying capacity) and so this is often followed by a sharp decline in numbers ("population bust"). These species tend to spend most of their time in a reproductive 'r' phase. '''K selected species''' exhibit slower growth but are more competitive in their environment. They tend to reproduce until the population reaches the environmental carrying capacity. Their numbers tend to fluctuate very little around the carrying capacity and are therefore fairly constant ('k' phase). ==Survivorship== [image:] Because of their reproductive strategy and parental care most k-selected species tend to survive for the majority of their maximum possible lifespan. Most r-selected species only tend to live for a very short time, the vast majority dying after a short period of time. However, those few who do survive to a reproductive age can live for very long periods of time. For instance trees may produce many thousands of seeds that develop into tiny seedlings. Only a very few of these will survive and grow into an adult tree, but those that do can live for a very long time.