Chapter 14: Population Ecology Flashcards
Ecology
The study of the interactions between organisms and their environments
Individuals
Individual organisms
Populations
Groups of individual organisms that interbreed with each other
Communities
Populations of different species that interact with each other within a location
Ecosystems
All living organisms as well as non living elements that interact in a particular area
Population Ecology
A sub field of ecology that focuses on populations of organisms of a species and how they interact with the environment
Growth Rate
The change in the number of individuals in the population in some unit of time
Calculating Growth Rate
The growth of the population in a year is the growth rate times the number of individuals present to start with
r
Birth rate minus the death rate
N
Number of individuals in the population now
Exponential Growth
The bigger the population the faster it grows
As population increases
Food supplies are reduced, less places to live, increased disease, and increased predation risk
Population Density
The number of individuals in a given area
Density Dependent Factors
Any factor limiting the size of a population whose effect is dependent on the number of individuals in the population. Ex. Disease
Carrying Capacity
The ceiling of growth. Death rate increases, emigration rate increases, and usually a reduction in birth rate, reduction in fertility
Slowing Down Exponential Population Growth
(r x N) x [(K - N)/K].
Logistic Growth
When a population grows exponentially at first but then slows down as the population size approaches the carrying capacity
Density Independent Factors
Forces like floods, earthquakes, and fires that disrupt growth. Takes time before Growth goes back to logistic Growth
Maximum Sustainable Yield
The size of a natural population at which it produces a maximum rate of increase, usually about half of the carrying capacity
Life History
Tells us as much about a species as possible in a small amount of information. Includes vital statistics, age at first reproduction, litter size, frequency, and longevity
Reproductive Investment
All of the material and energetic contribution that an individual will make to its offspring
Big Bang Reproduction
Reaches sexual maturity at one year, mates intensely over a 3 week period, males die shortly after mating period, and females usually die after weaning their first litter
Fast, Intensive Reproductive Investment
Reaches sexual maturity at one month and produces litters of six to ten offspring every month
Slow, Gradual Reproductive Investment
Reaches sexual maturity at one year and produces about one offspring per year
What is the cost of the reproductive Investment during any reproductive episode?
Chance of predation and the wear and tear of reproduction on an individuals body takes its toll. Smaller litters are usually preferred because of the possibility of additional litters
What is an individuals likelihood of surviving to have future reproductive episodes?
Small organisms like mice need to produce multiple offspring per litter while humans only need to produce one offspring per litter
Tradeoffs: Reproduction and Survival
In Big Bang reproducers investment in reproduction is high. If individuals are physically prevented from reproducing they can live many more years
Tradeoffs: Reproduction and Growth
Growth can sometimes be stunted when organisms spend time reproducing
Tradeoffs: Number and Size of Offspring
Some lizards can lay more eggs if they are smaller but a higher proportion of the offspring survive if the eggs are larger
Life Table
Tallies the number of people in a population within a certain age and the number of individuals within that age range that die
Survivorship Curves
Graphs showing the proportion of individuals of a particular age that are now alive in a population
Type I Survivorship Curve
High survivorship until old age, then rapidly decreasing survivorship
Type II Survivorship Curve
Survivorship decreases at a steady pace
Type III Survivorship Curve
High mortality early in life but those that survive the early years live long lives
Aging
Emerges as a definitive and measurable feature. It is an increased risk of dying with increasing age after reaching the age of maturity
Hazard Factor
Includes the risk of death from all types of external forces
Demographic Transition
Refers to the transition from high birth and death rates to lower birth and death rates as a country develops into an industrialized economic system
