Reproductive Patterns 10/28/08

Types of Reproduction

Sexual reproduction involves two parents involves sex cells that contain half of the genetic information (sperm and egg) offspring receive genes from both parents

Asexual Reproduction involves only one parent offspring are genetically identical to parent ex) strawberries, bacteria, mushrooms

Disadvantages of sexual reproduction Males do not give birth Females need to have twice as many young as an asexual organism to maintain the same number of young in the next generation Increased change of genetic errors and defects Courtship or mating rituals consume time and energy, can transmit disease, and can inflict injury on males of some species if they compete

Advantages of sexual reproduction Provides greater genetic diversity Greater chance of reproducing and evolving if environmental conditions change Males of some species can gather food for the female and young and protect them

Reproductive patterns Opportunists have large numbers of small offspring and competitors have fewer, better developed offspring Carrying Capacity (K) time Number of individuals K-species r-species Population growth (r)

R-selected vs. K-selected R-selected species have a capacity for a high rate of population increase Have many small offspring Little to no parental care or protection Overcome the massive loss of offspring by producing so many that a few will survive Algae, bacteria, rodents, annual plants (dandelions), and most insects

R-selected vs. K-selected R-selected species are opportunists Reproduce and disperse rapidly when conditions are favorable or when a disturbance opens up a new habitat or niche for invasion Adapted to unstable climate and environmental conditions Generalists Population fluctuates wildly above and below carrying capacity

R-selected vs. K-selected K-selected species have a lower population growth rate Have fewer, larger offspring with long life spans Later reproductive age Offspring are born fairly large, mature slowly, and have high parental care Most large mammals, birds of prey, large and long-lived plants

R-selected vs. K-selected K-selected species do well in competitive conditions when their population size is near the carrying capacity of their environment Specialists Competitors Adapted to stable climate and environmental conditions

R vs. K selected species

Most organisms have reproductive patterns between the extremes of r-selected and K-selected species The reproductive strategy of a species may give it a temporary advantage, but the availability of a suitable habitat for individuals of a population in a particular area determines its ultimate population size

Thinking about the future If the earth experiences significant warming during this century as projected, is this likely to favor r-selected or K-selected species? Explain your answer.