Population of Ecology

1. Population of Ecology

2. Ecology • Study of the interactions of organisms in their biotic and abiotic environments • Organism  population community  Ecosystem  biophsere

3. Demographics of populations • Demography – statistical study of a population (density, distribution, growth rate) • Population density - # of individuals per unit area (can be misleading) • Population distribution – pattern of dispersal across an area (controlled by resources and limiting factors) clumped, random, uniform

4. Population growth • Rate of natural growth (r) based on birth and death rate. • Biotic potential – highest possible growth rate with unlimited resources.

5. Survivorship curves • Probability that newborn will survive to certain ages. • Curve I – characteristic of a population in which most individuals survive well past midpoint of lifespan. Ex. Large mammals, humans

6. Curve II – survivorship decreases at a constant rate throughout the life span. Ex. Songbird, small mammals (death is usually unrelated to age) • Curve III – most individuals die young. Ex. Insects, fish, humans in less developing countries.

7. Survivorship Curves

8. Age distribution • Age structure diagrams • Increasing population • Prereproductive ages is largest, birth rate is higher than death rate. • Stable population (bell shape) • Reproductive ages equal prereproductive ages • Decreasing population (urn shape) • reproductive ages is larger than prereproductive ages, postreproductive age is largest

10. U.S. Population

11. Population Growth Models • 2 patterns of population growth: • Discrete breeding – single reproductive event • Continuous breeding – many reproductive events • Research: not always have to be one or the other.

12. Exponential Growth • Number of individuals added each generation increases as the total # of females increases. • Lag phase – growth is slow to start • Exponential growth phase – accelerated growth • J shaped curve

15. Logistic growth • S-shaped curve • Lag phase, exponential growth phase • Deceleration phase – growth slows • Stable equilibrium phase – little to no growth, BR = DR

16. Logistic Growth

17. Carrying capacity • Maximum # of individuals of a species an environment can support. • Exponential growth can not continue due to carrying capacity • Resources become scarce • Competition and predation • Exponential growth occurs when population size is much lower than carrying capacity. • Population stabilizes when carrying capacity is reached.

18. Regulation of population size • Density independent factors – those that are not dependent on numbers • Weather, natural disasters • Density dependent factors – occur because of population of species • Competition, predation, parasitism • Intrinsic factors? – anatomy, behavior have an affect on population?

19. Life History Patterns - Opportunistic • r – strategists • Small individuals, short life span, fast to mature, many offspring, little/no care for offspring, early reproductive age • Bacteria, fungi, insects, rodents, annuals

21. Life History Pattern - Equilibrium • K-strategists • Large individuals, long life span, slow to mature, few and large offspring, care for offspring, most live to reproductive age • Large mammals, birds of prey, long-lived plants

23. Human population growth • MDC’s – North America, Europe, Japan, Australia, growth is slow • LDC’s – Latin America, Africa, Asia, population rising rapidly • Ways to reduce projected population increase: • Strengthen family planning • Education, raising status of women, reduce child mortality • Delay onset of childbearing, wider spacing of births

24. Population Growth and Environmental Impact • LCD = population growth in numbers • MCD = consume larger proportion of Earth’s resources • Average family in North America consumes the amount of resources and produces wastes of 30 people from India.