Population Ecology Chapter 53

Population Groups of individual of the same species that live in the same place Characteristics of populations 1. Population range Area where it occurs 2. Spacing patterns Spacing of individuals 3. Size

Population range No population is in all habitats No population is static 1. Changing environment (receding glaciers) 2. Expansion to new areas

Cattle egret Current 1970 1966 1965 1960 1961 1958 1943 1937 1951 1956 Figure 52.7 Dispersal of the cattle egret in the Americas 1970

Population Density Dispersion Pattern of spacing

Spacing 1. Randomly spaced 2. Uniformly spaced 3. Clumped spacing Little interaction 2. Uniformly spaced Competition for resources 3. Clumped spacing Uneven distribution of resources Social interactions (herd, flock, pride)

Demography Statistical study of populations Grows: births outweigh deaths Shrinks: deaths outweigh births Sex ratios (females > males) Generation time (birth to reproduce) Reproduction Survivorship curves

Age structure Cohort Group of individuals that are of the same age Fecundity: Birth rate Mortality: Death rate Age structure # of individuals in a given cohort

Number of survivors (log scale) Survivorship curve 1,000 I 100 II Number of survivors (log scale) 10 Figure 53.6 Idealized survivorship curves: Types I, II, and III III 1 50 100 Percentage of maximum life span

Factors regulate populations Cost of reproduction Age at first birth Semelparity: Single birth event Annuals/insects Iteroparity: Several births over several years

Factors regulate populations Carrying capacity K: Maximum population an environment can sustain Density-dependent effects Increase density decreased birth rates Light, water, space, food, disease Density-independent effects: Fire, volcano, cold

Number of hares (thousands) Number of lynx (thousands) Carrying capacity Snowshoe hare 160 120 9 Figure 53.20 Population cycles in the snowshoe hare and lynx Lynx Number of hares (thousands) Number of lynx (thousands) 80 6 40 3 1850 1875 1900 1925 Year

Factors regulate populations K-selection: Density dependent selection r-selection: Density independent selection

Human growth

Population pyramids

Life expectancy (years) Infant mortality (deaths per 1,000 births) Fig. 53-26 60 80 50 60 40 Life expectancy (years) Infant mortality (deaths per 1,000 births) 30 40 20 20 Figure 53.26 Infant mortality and life expectancy at birth in industrialized and less industrialized countries (data as of 2005) 10 Indus- trialized countries Less indus- trialized countries Indus- trialized countries Less indus- trialized countries

13.4 9.8 5.8 Not analyzed Log (g carbon/year) Ecological footprint Figure 53.27 The amount of photosynthetic products that humans use around the world 5.8 Not analyzed

2,000 = 1.0N 1,500 = 0.5N Population size (N) 1,000 500 5 10 15 Fig. 53-10 2,000 dN = 1.0N dt 1,500 dN = 0.5N dt Population size (N) 1,000 500 5 10 15 Number of generations

Fig. 53-11 8,000 6,000 Elephant population 4,000 2,000 1900 1920 1940 1960 1980 Year

Table 53-3

Exponential growth 2,000 = 1.0N 1,500 K = 1,500 Population size (N) Fig. 53-12 Exponential growth 2,000 dN = 1.0N dt 1,500 K = 1,500 Population size (N) Logistic growth 1,000 dN 1,500 – N = 1.0N dt 1,500 500 5 10 15 Number of generations

Number of Paramecium/mL Fig. 53-13 1,000 180 150 800 120 Number of Paramecium/mL 600 Number of Daphnia/50 mL 90 400 60 200 30 5 10 15 20 40 60 80 100 120 140 160 Time (days) Time (days) (a) A Paramecium population in the lab (b) A Daphnia population in the lab