*Unit 3 Flashcards
Why do specialists tend to have an advantage in habitats that remain constant? Why do generalists tend to have an advantage in habitats that are changing?
When there is a disturbance to a habitat, specialists cannot adapt to use other food sources or habitats as quickly as generalists can. These species reproduce much quicker and adapt easily to disturbances. In contrast, specialists have the advantage in stable environments because “they do what they do well”, and easily outcompete other species for resources.
What is the difference between generalists and specialists?
Generalists don’t have any specific food, resource, or habitat requirements while specialists do. Generalists also have greater ecological tolerance than specialists do.
What are K-selected species?
K-selected species tend to be large, have few offspring, mature after many years of parental care, have long life spans, reproduce more than once in their lifetime, and live in stable environments. Competition for resources in these species’ habitats tends to be high.
What are r-selected species?
r-selected species tend to be small, have many offspring, mature early, have short life spans, reproduce once in their lifetime, and are able to thrive in disturbed environments. Competition for resources in these species’ habitats tends to be low.
What is biotic potential?
Biotic potential is the maximum reproductive rate of a population in ideal conditions.
Why are most invasive species r-selected species?
Invasive species are typically r-selected because of their reproductive potential. They grow and mature quickly, and as a result, are able to out compete native specialist species.
Why are K-selected species more adversely affected by invasive species than r-selected species?
K-selected species tend to be specialists that have low population growth rates. This allows generalists like invasive species to quickly take over a habitat. r-selected species are minimally affected by this because they can easily switch to a different resource to avoid competition.
Are all species distinctly K or r selected species?
No, more often then not, a species will fall on a spectrum from K to r, having some K-selected qualities and some r- selected qualities.
What are survivorship curves and how do you interpret them?
A survivorship curve represents the percent survival rate for different age groups in a population from birth to maximum age for that species. These curves give insight into K and r selected species, and allow ecologists to calculate a variety of statistics regarding population size. There’s 3 types of curves that are typically represented: Type I, II, or III.
Type I: A large % of the population survives from birth to death (dies of old age rather than another factor) occurs because of great infant care
Type II: Death rate is constant from birth to death (equal amount of population dying throughout a species’ life span)
Type III: A large % of the population dies early in life (most die right after birth) *occurs due to a lack in infant care
What is the impact of carrying capacity on ecosystems?
If an organism exceeds its carrying capacity, it can experience die back, possibly even bringing the population below the carrying capacity (ex. Reindeer of St. Matthew Island).
What is carrying capacity (K)?
Carrying capacity is the amount of organisms an environment can support without the degradation of resources. K-selected species tend to maintain their population around their carrying capacity, and the population of r-selected species tends to fluctuate.
What is environmental resistance?
Environmental resistance inhibits a species’ ability to continue growing at its biotic potential, creating a carrying capacity.
Density-dependent resistance factors:
- Tend to be biotic
- Have a strong influence when the number of organisms per unit area reaches a certain level
- Competition for resources
- Predation
- Parasitism/Disease
Density-independent resistance factors:
- Tend to be abiotic
- Have an affect on all populations regardless of density
- Natural disasters/severe weather events
- Drought
When do populations experience exponential growth? Logistic growth?
ALL populations, regardless of K or r selected species, experience exponential growth when small because competition (a density dependent factor) doesn’t come into play. However, once a population reaches its carrying capacity, population growth shifts to a logistic model because of an increase in competition.
What factors might cause a less developed country (LDC) to have a significant increase in life expectancy?
- Increased access to health care
- Improved food quality or quantity
- Increased access to clean water
- Fewer pregnancies
- Increased health-related education
What factors might cause a less developed country (LDC) to have a significant decrease in fertility rate?
- Increased education of women
- More economic opportunities for women
- Later marriage age for women
- Cultural acceptance of family/planning strategies/increased access to family planning
- Increased women’s rights/gender equality/empowerment of women
- Increased industrialization/economic development
- More social programs to support elderly citizens
