Populations Ch 5 Essential Standard: 2.1.4

Objectives SWBAT define evology as the study of interactions between organisms and their environment SWBAT identifty ecological levels of organization SWBAT describe the properties of a population and interpret population curves SWBAT identify the carrying capacity of an environment SWBAT compare and contrast exponential and logistic population growth. WBAT compare and contrast habitat and a niche SWBAT define a limiting factor and provide examples WBAT define the competitive exclusion principle and compare/contrast interspecifc and intraspecific competition SWBAT define and provide examples of 3 forms of symbiosis: mutualism, commensalisms, and parasitism SWBAT create and interpret food chains and webs SWBAT describe flow of matter and energy in an ecosystem SWBAT interpret the pyramids of energy and matter SWBAT define and describe the laws of conservation of matter and energy SWBAT describe the process of succession and provide examples of primary and secondary sucession as a climax community SWBAT describe the various cycles in nature SWBAT describe terrestrial and aquatic biomes SWBAT explain natural systems such as climate change, ozone production, erosion, deposition

CHARACTERISTICS OF POPULATIONS OBJ describe the properties of a population and interpret population curves

Characteristics of Populations Geographic distribution (range) – the area inhabited by a population Density – the number of individuals per unit of area (varies depending on species and ecosystem); example = cactus Growth Rate

Population Growth Number of births – growth if more births than deaths Number of deaths – shrinks if more deaths than births Number of individuals entering/leaving a population Immigration – movement of individuals into an area Emigration - movement of individuals out of an area

Exponential Growth Individuals in a population reproduce at a constant rate (unchecked) ideal conditions /unlimited resources “J curve”

Logistic Growth As resources become less available, the growth of a population slows or stops Due to the carrying capacity (the largest number of individuals that an environment can support) “S curve”

LIMITING FACTORS OBJ define a limiting factor and provide examples

Limiting factors – anything that causes a population growth to decrease Density dependent factors = limiting factor that depends on the population size (only becomes an issue when the density reaches a certain level) – competition, predation, parasitism, and disease Limits to Growth

Limits to Growth Cont’d Density independent factors- Affect all populations in similar ways; not dependent on the population size – Unusual weather, natural disasters, seasonal cycles and human activities (damming rivers, clear-cutting forests In response to these factors, species show a crash in population size

Human Population Growth Human population increases with time Growth started out slow (Disease, lack of food, caused high death rates) – Higher death rates created situations where families were larger (had more children) to ensure that some children would survive The human population began to rapidly grow 500 years ago (agriculture and industry made life easier and safer: More reliable food supply, shipping essentials around the world, improved sanitation, medicine, and health care) – Birth rates remained high, and thus the world human population grew

Human Population Growth

Patterns of Population Growth Demography characteristics of human populations and how the populations change over time Birth rates, death rates, and the age structure of a population help predict why some countries have high growth rates while others grow more slowly

Demographic Transition Demographic transition (a dramatic change in birth and death rates) – Over the past century, the U.S., Japan, and most of Europe have slowed population growth – Hypotheses about this decrease

Demographic Transition Most societies = high death rates/ have high birth rates Advanced in nutrition, sanitation, and medicine enable more children to survive into adulthood, and more adults live to older ages Lower death rates and the demographic transition begins (this happened in the U.S. from 1790 to 1910) When societies modernize, raise education level and standard of living, families have fewer children causing the population growth to slow The worldwide population is still growing exponentially

Age Structure Population depends on how many people of different ages make up the population Age-structure diagrams (population profiles) graph the numbers of people in different age groups in the population

Age Structure

Future Population Growth Demographers must consider the age structure of the country and the prevalence of life- threatening diseases (AIDS, malaria, cholera) A lower growth rate means that the human population will grow more slowly over the next 50 years Since the growth rate is larger than 0, the population will continue to grow