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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