Chapters 56 (Population Ecology) and 59 (Human Population Growth) Flashcards
Chapter 56
Define population
A group of individuals of the same species that occupy the same geographical location.
What does population ecology study?
Factors that affect population size.
Describe the following dispersion (distribution) patterns?
- Clumped
- Random
- Uniform
- Clumped: individuals are clustered together. It is the most common distribution pattern and occurs due to resources being clustered (e.g., water is not evenly distributed in the environment), social interactions (e.g., many species form herds and flocks), and protection from predators.
- Uniform: organisms keep an even distance from each other. This could be due to competition for resources or due to social behaviors (each individual prefers a certain amount of territory).
- Random: the pattern of distribution is random because resources are not limited.
In a dense forest where there is a lot of competition for resources (e.g. light, soil nutrients) trees maintain a relatively even distance from one another so that each organism can obtain sufficient resources. What type of distribution pattern is displayed by these trees?
Uniform dispersion. Organisms will become evenly spaced because each organism requires a certain amount of territory.
Geese form flocks and their populations are clustered around watery habitats, such as lakes. What type of distribution pattern is displayed by geese?
Clumped. Individuals are clumped together.
When do populations show exponential growth, and what shape is an exponential growth curve?
Populations show exponential growth when resources are essentially unlimited (i.e., there is no competition for resources), and there are no other factors limiting to population growth (such as a predator). An exponential growth curve has a characteristic J shape.
When do populations show logistic growth and what shape is a logistic growth curve?
Populations show logistic growth when there is an upper boundary to population size called the carrying capacity. The environment does not have enough resources to support a population size
above the carrying capacity. A logistic growth curve has a characteristic S shaped curve. As the population size increases, the growth rate decreases as the population size approaches carrying capacity and then stops growing when carrying capacity is reached.
Life survival strategies describe the traits of a species that are related to survival and
reproduction. At one end of the spectrum are r-selected species, and the other end of the spectrum are k-selected species. Put the following descriptions in the correct column for whether they describe r-selected or k-selected species.
i) Small size
ii) Large size
iii) Short lifespan
iv) Long lifespan
v) Reach sexual maturity later in life
vi) Reach sexual maturity at an early age
vii) Have few offspring, but offspring receive good quality parental care, and there is low
offspring mortality
viii) Have many offspring, but offspring receive limited parental care, and there is high offspring mortality
ix) Tend to live in unstable environments (e.g. they have a high probability of being
killed by a predator or being outcompeted for available resources).
x) Tend to live in stable environments (e.g., low probability of being killed by a predator
and they have good competitive ability for resources).
r-selected k-selected
r-selected:
- small size
- short lifespan
- reach sexual maturity at an early age
- have many offspring, but offspring receive limited parental care, and there is high offspring mortality
- tend to live in unstable environments (they have a high probability of being killed by a predator or being outcompeted for available resources)
k-selected:
- large size
- long lifespan
- reach sexual maturity later in life
- have few offspring, but offspring receive good quality parental care, and there is low offspring mortality
- tend to live in stable environments (low probability of being killed by a predator and they have good competitive ability for resources)
The lifespan of a gorilla is approximately 35 – 40 years. Gorillas reach sexual maturity by 10 years old, and typically have 2 – 6 offspring in a lifetime. Each offspring receives intensive parental care with offspring fed milk from their mother for 3 years. Are gorillas more k-selected or r-selected species?
k-selected
The lifespan of a mouse is typically less than 2 years in the wild. Mice reach sexual maturity by about 8 weeks old and have between 5 – 10 litters of offspring per year with 6 – 8 young each litter. Are mice more r-selected or k-selected?
r-selected
Describe the characteristics of i) a type I survivorship curve, ii) a type II survivorship curve, iii) a type III survivorship curve?
i) Type I: young organisms have a high rate of survival, and most individuals die late in
life. Organisms tend to have few offspring, but most offspring survive to reproduce.
ii) Type II: there is a uniform decline in survival over time.
iii) Type III: there is very low survival of young organisms with few organisms surviving to old age. However, the rate of decline levels off for the organisms that do reach it to adulthood. Organisms tend to have many offspring, but few of them survive to reproduce.
Describe the characteristics the following reproductive strategies?
- Semelparity
- Seasonal iteroparity
- Continuous iteroparity
- Semelparity: organisms produce all of their offspring in a single reproductive event.
- Seasonal iteroparity: organisms reproduce repeatedly, but only during distinct breeding
seasons. - Continuous iteroparity: organisms reproduce continuously at any time of the year.
Which reproductive strategy would be shown by a songbird that reproduces every spring?
Seasonal iteroparity
Chapter 59
