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2 ends of reproductive strategy continuum

r-selection and k-selection


R- selection

Selection for high population growth rates
- an advantage in newly disturbed habitats and uncrowded condition.
- r is the intrinsic rate of increase of a population.
(“live fast, die young”):
- Short life spans, rapid development, early maturation, low parental investment, high reproduction rates
- Most insects, small vertebrates such as mice, weedy plant species



Selection for lower growth rates in populations that are at or near K, the carrying capacity for a population.
- This is an advantage in crowded conditions; efficient reproduction is favoured.
(“slow and steady”):
- Long-lived, develop slowly, late maturation, invest heavily in each offspring, low reproduction rates
- Large mammals, reptiles such as tortoises and crocodiles, and long-lived plants such as oak and maple trees


trade offs

Organisms allocate limited energy or resources to one function at the expense of another.
- The larger the investment in each individual offspring, the fewer offspring can be produced.
- Investments: Energy, resources, time and loss of chances for other activities such as foraging.