Evolutionary Biology Terms Starting With K
Evolutionary Biology Glossary: K
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K-Selected Species
/ KAY sih-LEK-ted SPEE-sheez / · K comes from carrying capacity in population ecology
K-selected species are organisms whose life history is characterized by low reproductive rates, high parental investment per offspring, slow maturation, and populations that tend to stabilize near the carrying capacity of their environment.
The concept of K-selection emerged from r/K selection theory developed by ecologists Robert MacArthur and Edward O. Wilson in the 1960s, contrasting species that maximize reproductive rate with those that maximize competitive ability in resource-limited environments. K-selected organisms typically produce few offspring per reproductive event, extend substantial energy toward offspring survival through behaviors such as nursing, guarding, and teaching, and reach sexual maturity late relative to their lifespan.
African elephants (Loxodonta africana) exemplify this strategy, carrying a single calf through a 22-month gestation, nursing for up to 4 years, and not reaching reproductive maturity until age 10 to 12. Because each offspring represents a large energetic investment, losing one offspring carries a much steeper fitness cost than it would for a species producing thousands of young.
Great white sharks (Carcharodon carcharias) carry pups internally for an estimated 12 to 18 months, one of the longest gestation periods among fish, and give birth to litters of only 2 to 10 pups. Despite being apex predators with few natural enemies, great white populations recover extremely slowly from overfishing precisely because their K-selected life history produces so few offspring per female per decade.
K-selected species are inherently better adapted than species with high reproductive rates. Each strategy succeeds under different ecological conditions; r-selected species outperform K-selected ones in unpredictable or disturbed environments where rapid population growth matters more than competitive efficiency.
Wandering albatrosses (Diomedea exulans) lay a single egg every two years and invest roughly 12 months in raising each chick to fledging. Adults live up to 50 years and do not breed successfully until age 10 or older, concentrating lifetime reproductive effort into a small number of well-provisioned offspring rather than many low-investment young.
Elephant →Kin Recognition
/ KIN rek-ug-NISH-un / · From Old English cynn meaning family and Latin recognitio meaning knowing again
Kin recognition is the ability of an organism to distinguish genetic relatives from non-relatives using sensory cues, allowing it to direct social behaviors preferentially toward individuals that share genes by common descent.
Kin recognition mechanisms range from simple spatial rules, where organisms treat nearby individuals as kin, to precise chemical discrimination based on major histocompatibility complex (MHC) molecules or other genetically encoded odor signatures. Phenotype matching is a widely documented mechanism in which an individual compares the sensory characteristics of others against a learned template derived from familiar relatives such as parents or littermates, then treats similar individuals as kin. Colonial tunicates (Botryllus schlosseri) use recognition alleles at a single highly polymorphic locus to decide whether to fuse with or reject neighboring colonies, fusing only when they share at least one allele at that locus.
Belding’s ground squirrels (Urocitellus beldingi) raised in the laboratory without contact with sisters can still recognize them by scent when reunited as adults, demonstrating that some kin recognition is genetically encoded rather than learned. Selection pressure from social parasites, such as cuckoos that mimic host nestlings, drives the evolution of increasingly precise recognition systems in host species.
Tadpoles of the American toad (Anaxyrus americanus) preferentially school with full siblings over half-siblings, and with half-siblings over unrelated individuals, even when raised in isolation from birth. This graded preference, demonstrated in controlled laboratory experiments, shows that kin recognition can operate through chemical cues alone without any prior social experience with relatives.
Animals consciously understand genetic relationships the way humans conceptualize family trees. Kin recognition operates through evolved sensory rules that reliably correlate with genetic relatedness, producing appropriate social behavior without any awareness of the underlying genetics.
Paper wasps (Polistes fuscatus) recognize individual nestmates through unique patterns of yellow and black facial markings, and wasps with more variable faces are recognized more accurately than those with uniform coloration. Experiments painting over facial patterns caused nestmates to treat familiar individuals as strangers and increased aggressive interactions, confirming that visual pattern matching drives nestmate recognition in this species.