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Why are small populations more vulnerable to extinction?
They face increased risks from genetic drift, inbreeding, demographic stochasticity, and environmental catastrophes.
What is the difference between deterministic and stochastic extinction factors?
Deterministic: predictable factors like habitat loss or predation. Stochastic: random events like storms or disease outbreaks.
What is a Minimum Viable Population (MVP)?
The smallest population with a 99% chance of surviving for 1000 years despite random environmental and demographic events.
What is effective population size (Ne)?
The number of individuals in a population that contribute genes to the next generation (i.e., the breeding population).
Why is Ne often lower than the census population size?
Not all individuals reproduce due to age, health, social status, or other factors.
Why is genetic diversity critical for populations?
It enables adaptability to changing environments and protects against inbreeding depression.
What is heterozygosity?
The proportion of individuals with two different alleles at a gene locus; an indicator of genetic variability.
How does genetic drift affect small populations?
It causes random loss of alleles over generations, reducing genetic variability.
What is a population bottleneck?
A sharp reduction in population size that limits genetic diversity and increases extinction risk.
Can mutation alone counteract genetic drift in small populations?
No, mutation rates are typically too low to offset the rapid loss of alleles due to drift.
What is inbreeding depression?
Reduced fitness due to increased expression of harmful recessive alleles in homozygous individuals.
How did inbreeding affect the Florida Panther?
Fewer than 30 individuals led to high rates of deformities, heart defects, and poor sperm quality.
What is outbreeding depression?
Reduced fitness resulting from mating between genetically distant individuals or subspecies, disrupting local adaptations.
Give an example of outbreeding depression.
Crossbreeding Capra ibex with other ibex species led to mistimed births and juvenile mortality in cold winters.
What is the extinction vortex?
A self-reinforcing cycle where small population size leads to inbreeding, genetic drift, and reduced viability, accelerating extinction.