Life history adaptations:  r-selected and k-selected species

AIPMT-NEET Aspirants, read out the next AIPMT-NEET Biology Study material/ Notes of r-selected and k-selected species, important for AIPMT-NEET Biology. Free online notes for AIPMT-NEET.

Life history adaptations depend on availability of resources. Species vary in their capacity to reproduce due to adaptation to different habitat conditions. r-selected species use wide variety of resources and  tolerate wide range of conditions while k-selected species are adapted to predictable environment, use resources in specialized way and are less tolerant to variations.

These are also called as life history strategies, i.e. r-strategies and k-strategies.

r-selected species achieve the maximum possible rate of population increase in favorable environment while k-selected species population increase is checked by carrying capacity (K) of the environment.

NOTE: Carrying capacity is the maximum number of individuals in a population that can be supported by resources present in that environment.

Following is the table indicating the difference between r-selected species and k-selected species.

Division on the basis of r-selected species k-selected species
Life span  Short Long
Body size Small Large
Maturation time Short Long
Mortality rate High Low
Reproductive age Early Late
Mating type Random mating Mate choice
Number of reproductions in life Reproduce once (called as Semelparity) Reproduce many times (called as Iteroparity)
Number of offspring produced per reproduction Many Few
Parental care No parental care Extensive care
Size of offspring/eggs Small Large
Habitat Broad range of habitat Specific habitat
Example House flies, cockroaches, mice, dandelions etc. Coconut palms, whales, human, oak trees etc.


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