Changes Over Time Ecological Succession – natural changes and species replacements in communities of an ecosystem Occurs in stages as different species create conditions suitable for some species and unsuitable for others Often difficult to observe – can take decades

In the beginning… New land can be created or exposed where no life existed before Lava destroying all life in its path and forms new land An avalanche exposes new areas and ledges A city street has never before had life growing from it. New communities of organisms colonizing these areas is called Primary Succession The first species in the area are called Pioneer Species Example: Lichens (can grow without soil on rocks and other surfaces)

And then… Pioneer organisms die and become the first patches of soil The presence of soil allows weedy plants to emerge, and over time vines, shrubs, and trees appear When this primary succession slows down and the community becomes stable This mature community undergoing little or no change is called the Climax Community.

From Pioneer Species to Climax Community

Disaster Strikes… When natural disaster or human actions disrupt or destroy a community, the following community changes are called Secondary Succession Like Primary Succession, the communities of organisms gradually change Unlike Primary Succession, this occurs where there was once life and on land that contains soil

Secondary Succession Because there is soil Pioneer Species will be different from the Primary Succession Example: Lichens were pioneers in Primary where wildflowers may be pioneers in Secondary Secondary Succession will take less time to reach Climax Community Though Pioneer Species may be different, the Climax Community will most likely be similar if the climate it the same.

Secondary Succession

Population Growth What is Population Growth? An increase in the size of a population over time Some things exhibit Linear Growth As time goes by, growth occurs at a steady rate when graphed, it is a straight line

How do Populations Grow? Populations show a J-shaped curve Initial increases are slow, but as the population gets larger, it grows faster Why? There are more organisms available to reproduce This pattern is called Exponential Growth

Can it go on Forever? Eventually, population growth will be affected by limiting factors Such as: availability of food and space The number of organisms an environment can support is called the Carrying Capacity In time, the population growth will level off making an s-shaped curve

Environmental Limitations Two main types of Limitation Factors Density-Dependent Density-Independent Density-Dependent Factors have an increased effect as population increases (more organisms, more risk) Disease Competition Parasites Predation

Environmental Limitations Density-Independent Factors affect all populations regardless of their density (more organisms, same risk) Temperature Storms Natural Disasters (floods, hurricanes, etc) Drought Habitat Destruction Pollution Most are abiotic factors

Organism Interactions: Predation The number of predators affects the prey population More predators, more risk to prey The number of prey affects the predator population More prey, more food for predators

Organism Interactions: Competition Competition – a density-dependant factor Organisms within a population must compete for resources If population numbers are low, resources are plentiful When populations grow, resources are in higher demand If demand is greater than supply……population must decrease Fight and kill each other Reproduce less

Human Activities vs. Earth’s Processes Human populations have a carrying capacity as well. To have a sustainable population, there needs to be a balance between the Earth’s resources, the needs of humans, and the needs of other species on Earth. Factors that affect human population sustainability are: Population growth Technology Agricultural Industrial Alternative Energy Resource Consumption

Population Population growth world-wide has grown exponentially and is expected to continue to do so. Population growth will naturally slow down as it nears its carrying capacity due to an increase in the death rate and a decrease in the birth rate as a result of: Food and water shortages Pollution of the environment Spread of diseases An increasing population can have an effect on: the amount of available clean water the amount of waste that is produced the amount of available fertile soil for agriculture (food resources). When these resources become scarce, many natural processes (such as the water cycle, the carbon cycle, the nitrogen cycle, and the physical process of soil regeneration) are affected.

Technology Technology applies scientific knowledge to help meet the needs of humans. These technological advances in agriculture, industry, and energy can have a positive or negative impact on Earth. Agricultural technology Advances in agricultural methods, tools, and biotechnology have improved the ability to grow crops to sustain a growing world population. Sustainable agricultural practices can help conserve fertile soil and reduce soil erosion. Farm machinery (such as tractors and combines) consumes nonrenewable resources and can contribute to erosion and air pollution. The addition of substances (such as fertilizers, pesticides, fungicides, livestock waste) to the environment can alter the composition of soil and can have a positive or negative effect on the water, carbon or nitrogen cycles.

Industrial Technology Advances in industrial technology have changed the world and have lead to developments in communication, transportation, and industry. The development of certain chemicals have contributed to the depletion of the ozone layer, which results in increased ultraviolet rays reaching Earth. Technological advances have revolutionized the communication industry; however, the disposal of outdated or damaged equipment is becoming an increasing concern. The burning of fossil fuels for industry and transportation increases sustainability of the growing human population; however, it also: increases the greenhouse gases released in the atmosphere (mainly carbon dioxide), which increases global temperatures (global warming) that affect sea levels, climate and atmospheric composition produces acid rain (pollutants in the air combining with water to cause the normal water pH to be lowered)

Technology Alternative energy technology Using natural renewable energy sources (such as wind, water, geothermal, or solar energy) decreases the burning of fossil fuels, which increases the quality of the atmosphere and the cycles involved. Using nuclear energy technology provides an alternative energy source that does not impact the atmosphere. However, the waste produced from nuclear energy use is becoming an increasing concern.

Resource Consumption As the population increases and technology expands, the demand for Earth’s limited supply of resources also increases. Some resources (such as food, clean water, and timber) are considered renewable resources, those that can be produced at roughly the same rate that they are consumed. Renewable resources have factors that limit their production, for example the amount of grain that can be produced is limited by the amount of land available for farming, fertility of the land, productivity of the grain, or availability of clean water.

Resource Consumption Other resources, such as fossil fuels, are nonrenewable resources, those that cannot be produced at the same rate that they are consumed. For example, The demand for minerals, metals, and ores increases because these strategic materials are vital to industry but are decreasing in availability. Minerals are regarded as nonrenewable because mineral deposits that can be extracted economically are formed so slowly by geological processes that their formation as a means of replacing what we are using is of no practical use to us. Sustainable use of resources can be accomplished by reducing consumption, reusing products rather than disposing of them, or recycling waste to protect the environment.