chapter 19 Flashcards
what are some population characteristics
gene pool–> all genes of all the individuals in the population
density–>the number of individuals per unit area or volume
pattern of distribution-> random, clumped, or regular
age structure- percent of individuals in the three ecologically significant age groups [prereproductive, reproductive & postreproductive]
what are the two opposing forces that operate in the growth and development of populations
biotic potential—>ability to reproduce and survive at a given rate
environmental–> opposition to growth from biological, chemical and physical forces in nature
what is exponential growth
exponential growth–> J-shaped curve—rate of growth of a population under ideal conditions, unregulated growth, cannot continue indefinitely because food supplies and space become limited and waste products build
what is logistic growth
logistic growth–> S shaped curve—population growth that is slowed by limiting factors—growth may start off exponential but it levels off at the carrying capacity of the environment
what is carrying capacity
number of individuals that an environment can support for prolonged period of time
what are 3 ways an individual’s contribution to population growth can be increased
- -producing a larger number of offspring at a time
- -having a longer reproductive life
- -reproducing earlier in life
which of these 3 is the most important
producing a larger number of offspring at a time
what are the 2 types of reproductive strategies
r-selection & K-selection
what are the characteristics of an r-selection strategy
- -typically reproduce once
- -have many young
- -young are small
- -young mature rapidly
- -young have little or no parental care
[many insects, weeds that invade new habitats]]
what are the characteristics of a K-selection strategy
- -typically reproduce more than one
- -have few young at a time
- -young are larger
- -young mature more slowly
- -young have parental care, often intensive care
[humans, plants that have fewer but larger seeds[stored food=parental care]
what is a survivorship curve
the length of time an individual of a particular age can expect to survive—
r-selected typemost individuals die at an early age, many as eggs K-selected typemost individuals live for a long time and die as a result of the diseases of old age
how do density dependent factors regulate population size,
as population density increases these factors intensify and affect a large proportion of individuals—these factors reduce the population growth by decreasing reproduction or by increasing mortality
what are some examples of density dependent factors
resource limitations—>food, space
predation—>predator more likely to encounter crowded prey population
intrinsic factors—>high density leads to stress syndrome which can delay maturation or inhibit reproduction or suppress immunity
how do density independent factors regulate population size,
these factors affect the same percent of the population without regard to its density
what are some examples of density independent factors
seasonal weather changes—> freezing in winter, heat in summer
catastrophic weather events –> floods, earthquakes, forest fires—severe enough to kill 50% of the population—large or small population
