biodiversity ch. 11 part 1

Minimum viable population (MVP)

the number of individuals necessary to ensure the long-term survival of a species in average and harsh years. The smallest isolated population having a 99% chance of remaining extant for 1000 years despite the foreseeable effects of demographic, environmental, genetic stochasticity (random variation), and natural catastrophes

Genetic drift

the random process of allele frequency change in a population. It is separate from allele changes due to natural selection (adaptive advantage). It causes small populations to lose genetic variation more rapidly compared to large populations.

Effective population size

the size of the population as estimated by the number of its breeding individuals.

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Effective population size

50/500 rule

isolated populations need to have at least 50 individuals, and preferably 500 individuals, to maintain genetic variability

Inbreeding

mating among close relatives in a natural population

Outbreeding

tendency to mate with unrelated individuals of the same species

Outbreeding depression

species that have a condition that results in weakness, sterility and lack of adaptability to the environment that occurs when individual of different species or different populations mate. This rarely occurs if the species is abundant or the habitat is not damaged.

ex: donkey is mainly sterile and is a mating of domestic horses and donkeys

Loss of evolutionary flexibility

if genetic variability is lost then natural selection in the right environmental conditions will not occur as rapidly. Species will not adapt to changes in climate, pollution, diseases, etc

Monogamy

one male, one female with examples of geese, penquins

Polygyny

one male mating with many females, elephant seals

Polyandry

one female mating with many males, crickets, honeybee, pipefish

Population bottleneck

a population is greatly reduced in size and loses rare alleles if no individuals possessing those alleles survive and reproduce.

Environmental stochasticity

random variation in the biological and physical environment . This can increase the risk the of extinction in small populations. This can be changes in resources, changes in predators, changes in climate bringing floods, earthquakes, etc.

Demographic stochasticity

random variation in birth, death, and reproductive rates in small populations sometimes causing further decline in population size. Also called demographic variation.

Allee effect

social interactions (especially mating) become unstable once a population density falls below a certain size. The interaction among population size, population density, population growth rates, and behavior.

Extinction vortex

The tendency of a small population to decline toward extinction has been linked to a vortex, a whirling mass of liquid or gas spiraling inward – the closer the object gets to the center, the faster it moves. At the center of the vortex is oblivion: the local extinction of the species. Once in the vortex it’s difficult for the species to resist the pull toward extinction.

What are some reasons why some individuals in a population may not reproduce?

•Inability to find a mate

•Too old or too young to mate

•Poor health

•Sterility

•Malnutrition

•Small body size

•Social structure (polygamy)