Ch 50

Ecology of Populations Ecology: the study of interactions of organisms with other organisms and with the physical environment

Population: members of the same species living in the same area

Community: all the different populations in an area

Population or Community?

Ecosystem: the community plus the nonliving factors

Biosphere: all the areas of the earth that supports life

Watch the Battle at Kruger. How many populations can you count?

Day Two: Population Characteristics

Ecologists ask questions about where species occur and why species occur where they do Figure 40.12-3 Chemical factors Why is species X absent from an area? Does dispersal limit its distribution? Area inaccessible or insufficient time Predation, parasitism, competition, disease Water, oxygen, salinity, pH, soil nutrients, etc. Do biotic factors (other species) Temperature, light, soil structure, fire, moisture, etc. Do abiotic factors Physical Yes No

Ch 52

Demography - the statistical study of a population; how they change over time (density, distribution, rate of growth) Population density: number of individuals per unit area

Factors that affect Density Figure 40.14 Births and immigration add individuals to a population. Deaths and emigration remove individuals from a population. Births Immigration Deaths Emigration

Why? Population distribution: pattern of dispersal of individuals: random, clumped, uniform Figure 40.15 (a) Clumped (c) Random (b) Uniform Why?

Life Table/Age Structure Diagrams age-specific summary of the survival pattern of a population It follows he fate of a cohort, a group of individuals of the same age, from birth to death

AGE STRUCTURE DIAGRAMS

Figure 46.16

Survivorship curve - probability of newborn individuals surviving to a particular age Late Loss (Type I) Constant loss (Type II) - death is often unrelated to age Early loss (Type III)

Figure 46.4c

Figure 46.4d

You can create a survivorship curve of a human population by studying cemetery data (Demography Lab)

Compare the two curves below: Which country is probably the better place to live? Defend your answer.

Per Capita Rate of Increase Change in population size can be defined by the equation − Change in population size Births Immigrants entering Deaths Emigrants leaving Population   Population growth = rN (r = growth rate, N = original population size)

The population growth rate can be expressed mathematically as  bN −mN where N is the change in population size, t is the time interval, B is the number of births, and D is the number of deaths Zero Population Growth - same number enters as leaves the population

Population Growth Models J-shaped curve showing exponential growth of a population Requires unlimited resources S-shaped curve shows how a population becomes limited by environmental factors Logistic Growth Carrying Capacity: the maximum size of a population that an area can support dN = rN dt dN = rN(K-N) dt K

the elephant population in Kruger National Park, South Africa, grew exponentially after hunting was banned Figure 40.18 6,000 Year Elephant population 2,000 8,000 4,000 1900 1930 1940 1950 1960 1970 1910 1920

Carrying capacity (K) is the maximum population size the environment can support

The Logistic Growth Model per capita rate of increase declines as carrying capacity is reached dN dt  rmaxN (K −N) K

1,000 Number of generations Population size (N)  1.0N 10 15 5 2,000 Figure 40.19 1,000 Number of generations Population size (N)  1.0N 10 15 5 2,000 1,500 500 dt dN Exponential growth Population growth begins slowing here. K  1,500 (1,500  N) Logistic growth

Number of Paramecium/mL Figure 40.20 1,000 Time (days) Number of Paramecium/mL 10 15 5 (a) A Paramecium population in the lab 800 200 400 600 140 160 30 (b) A Daphnia (water flea) population in the lab 40 60 20 100 120 80 Number of Daphnia/50 mL 180 150 90

Regulation of Population Size Density Independent Factors: weather and other natural disasters Density Dependent Factors: food, space, water, parasitism, competition

Figure 46.10 Density Independent Factor (Flash Flood) – it will have the same impact on a small pop as it does on a large pop. 60% loss for both - growth limited by the environment

Figure 46.11 Density Dependent Factor – as number increases, not all of them will have access to resources -the denser the population, the faster the resources get used up

Figure 46.12

Life History Patterns K-strategists - small numbers of offspring, usually parental care (Kangaroo) R-strategists - large numbers of offspring, no care, low survivability (Roaches)

Figure 46.14a

Figure 46.14b

Figure 46.13

HUMAN POPULATION GROWTH Current World Population: 7 billion (and growing) The human population is now in an exponential part of a J-shaped growth curve. World population increases the equivalent of one medium-sized city (216,000) per day and 79 million per year. The doubling time is the length of time for a population size to double, now 53 years. Zero population growth is when the birthrate equals the death rate and the population size remains steady. The world population may level off at 8, 10.5 or 14.2 billion, depending on the decline in net reproductive rate. http://www.census.gov/main/www/popclock.html

Biotic Potential: maximum rate at which a population could grow given optimal conditions (food, water, space) Factors that influence biotic potential: 1. age of reproduction 2. frequency of reproduction 3. number of offspring produced 4. reproductive life span 5. average death rate under ideal conditions

Penguins only hatch ONE offspring during a season, never twins Penguins only hatch ONE offspring during a season, never twins.  That offspring may not survive its first year.  Parents cannot start over if offspring dies. 

Don’t forget, a population can refer to plants, fungi and bacteria….. Algae bloom

How to calculate Population Size Mark and recapture http://www.biologycorner.com/flash/mark_recap.swf Random Sample