L19 - Life histories Flashcards
Why is age distribution important in understanding populations?
It reveals the population’s make-up and is sensitive to biotic and abiotic ecological influences
What do life tables describe, and what can be extracted from them?
Life tables describe population age structure and provide parameters like survivorship and age-specific mortality.
How is survivorship calculated?
Survivorship = number surviving this year / total number born
How is age-specific mortality calculated?
Age-specific mortality = number dying / number surviving
What can mortality data reveal about a population?
It can indicate factors like predation that affect population dynamics
What characterizes Type I survivorship curves?
Organisms with relatively few offspring that invest significant time and effort in them.
What characterizes Type III survivorship curves?
Organisms with many offspring but minimal time or effort invested in their care
How do environmental factors influence survivorship curves?
Factors like predation or herbivory can alter the shape of survivorship curves.
What does an organism’s life history describe?
The timing of key activities such as age at maturity, inter-birth intervals, generation time, and litter size
What is the simple population growth model for seasonal breeders?
Nt +1 = R0Nt, where R0 is the net reproductive rate
How does the continuous breeders’ growth model differ?
It uses 𝑑𝑁/𝑑𝑡=𝑟𝑁
, which generates exponential growth: Nt = N0ert
Why are simple growth models limited?
They assume unlimited resources and are only applicable in special cases, like new species in empty niches.
What does the logistic growth model account for?
Resource limitations, resulting in population stabilization near the carrying capacity:
dN/dt=rN(1−N/K)
What does the time-lag variation of the logistic model address?
Delayed density-dependent effects, such as disease or predation, modeled as
dN/dt=rN(1−(N
t−τ/K)).
What are r-selected species, and what is their growth strategy?
Species with high per capita growth rates, focusing on rapid reproduction
What are K-selected species, and what is their growth strategy?
Species with stable populations close to carrying capacity, emphasizing long-term survival
Why is age estimation important for savannah elephants?
It helps understand population dynamics, including reproductive and survival rates
How is age estimated in elephants using shoulder height?
Shoulder height is used with Von Bertalanffy growth functions, accurate up to 15 years for females and 36 years for males.
What does the Von Bertalanffy growth function represent?
Height at age
𝑖: ℎ𝑖 = ℎ𝑏 + (𝐻∞ − ℎ𝑏) (1−𝑒^−𝑘𝑡)
where
𝐻∞ is maximum adult height.
How does Darwin’s theory relate to population growth models?
Darwin’s theory requires animals to reproduce rapidly, yet populations remain constant due to limiting factors, modeled mathematically.
What are the two opposing life history strategies described by growth models?
- r-selection: High growth rates, opportunistic strategies.
- K-selection: Stable populations, competitive strategies near carrying capacity.
