HOW POPULATIONS GROW Chapter 5-1

I. Characteristics of Populations =Area inhabited by a population =The # of individuals per unit area =Rate at which a population changes size =Different ages of the organisms in a population A. Geographic Distribution B. Density C. Growth rate D. Age structure

II. Population Density The number of individuals per unit area

A. Cactus: small #’s Low density B. Shrubs: higher #’s High density II. Population Density A. Cactus: small #’s Low density B. Shrubs: higher #’s High density

III. Population Growth Factors that affect population size: =the amount of births =the amount of deaths =moving into an area =moving out of an area A. Birth Rate B. Death Rate C. Immigration D. Emigration

IV. How is the Population Affected? Increase or Decrease A.  birth rate &  death rate B.  birth rate &  death rate C.  immigrants &  emigrants D.  immigrants &  emigrants Decrease Increase

V. Exponential Growth B. Produces a J – shaped Curve when graphed A. Will occur under IDEAL conditions 1. unlimited resources 2. no predators 3. no disease 4. plenty of space B. Produces a J – shaped Curve when graphed

VI. Logistic Curve S- Curve A. In ecosystems: 1. Resources are limited 2. Predators 3. Disease B. The growth of populations slows or stops (actually averages out to a steady size) When: 1. Birth rate = death rate 2. Immigration = emigration C. Leveled-off population reached its carrying capacity

Logistic Curve S-Curve

1. Carrying Capacity (K) The largest number of organisms that a given ecosystem can support

K selected species The letter K represents the carrying capacity of a habitat for members of a given sort of organism.

K selected species Organisms that are K-strategists occupy more stable environments. Are larger in size and have longer life expectancies. stronger or are better protected generally are more energy efficient. They produce, during their life spans, fewer progeny, but place a greater investment in each Examples: elephants, and humans

K selected species Their reproductive strategy is to grow slowly, live close to the carrying capacity of their habitat and produce a few progeny each with a high probability of survival.

R- selected species r represents the slope of the line representing exponential growth.

R selected species Organisms that are r-strategists typically live in unstable, unpredictable environments. reproduce rapidly (exponentially). They have little investment in any one progeny individual they are typically weak and subject to predation They have short life spans, are generally small, quick to mature and waste a lot of energy. Typical examples of r-strategists are salmon corals insects bacteria

R-selected species The “strategic intent” is to flood the habitat with progeny so that, regardless of predation or mortality, at least some of the progeny will survive to reproduce.

R and K selected organisms Characteristics of r- and K-selected organisms r-organisms K-organisms short-lived long-lived small large weak strong or well-protected waste a lot of enrgey energy efficient less intelligent more intelligent have large litters have small litters reproduce at an early age reproduce at a late age little care for offspring much care for offspring