exam III-supplement 11

Question 1

what is MVP

Answer 1

• It stands for “minimum viable population”, it was developed to define the number of individuals necessary to ensure the long-term survival of a species.
• It is stated that “a minimum viable population for any given species in any given habitat is the smallest isolated population having a 99% chance of remaining extant for 1000 years despite the foreseeable effects of demographic, environmental, and genetic stochasticity, and natural catastrophes”
• In other words, this is the smallest number of a species predicted to have a very high chance of persisting for the foreseeable future
• A key point: this allows a quantitative estimate to be made of how a large population must be to ensure long-term survival

Question 2

figure 11.1 related to MVP

Answer 2

o Evaluates how larger MVP is needed to ensure a greater number of years for survival
o Bighorn sheep: all populations of more than 100 individuals persisted beyond 50 years
o All populations less than 50 individuals died out in less than 50 years
o Small populations that were managed are not included in this analysis

Question 3

what is MDA? and how is it determined?

Answer 3

• This term was developed once a species has been established (MVP), stands for “minimum dynamic area” (MDA)
• This is the area of suitable habitat necessary for maintaining the minimum viable population
• It has been estimated that reserves in Africa of 100-200 km2 are needed to maintain many small mammal populations
• The smaller populations are subject to rapid decline in numbers and local extinction
• This can be estimated by studying the home range size of individuals and colonies of endangered species

Question 4

what three main reasons result in small populations having a high extinction risk?

Answer 4

• Loss of genetic variability and related problems of inbreeding depression and genetic drift
• Demographic fluctuations due to random variations in birth and death rates
• Environmental fluctuations due to variation in predation, competition, disease, and food supply and due to natural catastrophes, that occur at irregular intervals, such as fires, floods, storms, or droughts

Question 5

figure 11.2 related to the three main risks in regard to small population extinction

Answer 5

o Yes, because those populations with fewer than 10 breeding pairs had overall 39% probability of extinction over 80 years.
o As the population size increased the probability of extinction lowered.

Question 6

what is effective population size?

Answer 6

the size of the population as estimated by numbers of its breeding individuals

Question 7

what are the factors that influence effective population size?

Answer 7

• species size
• sex ratios
• age
• gestation period
• fertility

Question 8

why is heterozygosity important?

Answer 8

• Heterozygosity is the proportion of individuals with 2 different allele forms of the gene, and it is important to allow more gene varieties and mutations with in a population as it increases, allowing more adaptability to diseases and such.

Question 9

what factors influence heterozygosity?

Answer 9

small populations leading to inbreeding, leading to a loss of evolutionary flexibility, lack of mates, unequal ratios.

Question 10

what is demographic stochasticity?

Answer 10

variation in birth and death rates among individuals and across years within a given population – measure birth and death rates, major factor in measuring population is sample size (avg male height = 5’9”, sample sizes will affect whether classes at Wesleyan would match this), time of year is another important variable of when to measure. Survey population and study actual population (for breeding etc.) set boundaries based on these.

Question 11

what is environmental stochasticity?

Answer 11

random variations within the biological and physical environment affects the entire population – food, weather, temperature, natural catastrophes, rain fall, vegetation, other species

Question 12

what is allee effect?

Answer 12

• Allee effect: Interactions between population size, population density, population growth rate and behavior – most significant affect would be social interactions in reproductive behavior
• Preferred definition - Pos relationship between any component of physical fitness and numbers of conspecific (same species); Heterospecific – different species
• Smaller population size Allee effect kicks in
• Paper – How hives collapse: honey bees, everyone dies, diseases affect it, population gets too small
• Lower the population, lower the recruitment (birth rate)

Question 13

what is extinction vortex?

Answer 13

tendency of a small population to spiral faster and faster towards extinction

Question 14

how are the previous questions related to extinction vortex?

Answer 14

• Slowly linear downward, then dramatic down sweep towards extinction
• Smaller breeding population, smaller growth rates, leading to more and more unbreedable animals, young animals die often from accidents, so breeding population takes further hits. Tied to how many individuals there are within a population