Ecology of Populations

Our Environment Humans are part of the Earth’s natural ecosystems. We depend on our planet for food, clean water, clean air to breath, and for living space. Humans need to be careful to preserve our ecosystems because our existence depends on it!!

Population Growth The Earth can sustain a certain number of humans on this planet and we need to find a way to slow population growth before the earth’s carrying capacity is reached. If we exceed the carrying capacity, future generations will suffer from famine, disease, high pollution levels, and wars over limited resources. Watch video!!

Age Distribution Horizontal axis = Number of individuals Age-Structure Diagram shows growth patterns of populations grouped into categories

Human Age Distribution Developed countries Less-developed countries

Humans are part of the Earth's ecosystem. Human activities can either deliberately or inadvertently alter the balance of an ecosystem. Once ecosystems are damaged, people may suffer from that damage just like any other species.

Most species in new environments will have a period of rapid population growth. Then the population growth will slow as the population number approaches the carrying capacity. The carrying capacity is the number of individuals the environment can support. Available resources such as food and water will decrease, while the pollutants and wastes of the population will rise as a population approaches the carrying capacity.

What do you Think??? How do human activities affect the environment?

Human Impacts on the Environment Global warming Use of machinery by humans seems to be increasing CO 2 levels in the air. CO 2 prevents heat from escaping, causes slight world wide temperature increases Rising water temperatures causes coral bleaching

Human impacts on the environment Deforestation Caused by demand for wood products, need for space, farmland, housing, roads Deforestation causes habitat fragmentation Animals and plants are forced into confined areas

Habitat Fragmentation

Pollution: Agricultural –DDT –Fertilizers –Animal wastes (nitrogen) Homes –Strong cleaning agents Industry –Toxic gases and wastes –Acid rain

Human impacts on the Environment Ozone depletion Caused by aerosol chemicals called chlorofluorocarbons (CFCs) CFC’s – Escape into atmosphere, reacts breaking down the ozone (O 3, a protective atmospheric layer) – UV rays penetrate the atmosphere and cause harm to many organisms

“HOLE” in the ozone (O3)

Human impacts on the Environment Fishing activities Demand for fish and shellfish Commercial Fishing be harmful to environment in many ways

Human impacts on the environment Invasive species (EXOTIC SPECIES) introduced by people accidentally or intentionally Can cause problems if no natural enemies are present Cane toad was introduced to Australia to control cane beetles, pest insects that destroy sugar cane crops

Human impacts on the Environment Exotic pet trade Capture and sell wild animals from exotic locations Wealthy buyers and collectors desire obscure animals Animals removed from their habitat causes an imbalance in the ecosystem

Importance of the Environment Biodiversity = Many different types of organisms Organisms depend upon one another Interfering with one Organism can have a Ripple effect to many w/in the habitat. What happens when a top predator is removed?

Importance of the environment Natural resources: Non-renewable- resources that we use that cannot be replaced. Includes fossil fuels (petroleum, coal),metals (aluminum, iron), minerals (silicon) Renewable- Resources that can be replaced in a relatively short amount of time. Includes animals, plants, water, wind, etc. –even renewable resources can run out

Importance of the Environment Natural resources Renewable energy sources include wind power, geothermal energy, ocean currents

Preserving our resources Increasing our use of renewable resources could mean that they become nonrenewable. For example, polluting a lake so that no one can drink the water or removing so many fish through commercial fishing that they are unable to find each other to reproduce to restore their numbers. Individuals can help maintain our supply of both renewable and nonrenewable resources by practicing the 3 R’s

Stewardship:

Natural Processes in Ecosystems Maintaining air quality- rainfall helps clean particles from the air and it keeps the air moist. The carbon- oxygen cycle of photosynthesis and respiration keep levels of oxygen and carbon dioxide at acceptable levels for life. Humans affect the air by polluting it with products of combustion (burning of fossil fuels) and other industrial gases.

Carbon – Oxygen Cycle

Soil Formation- soil forms when weathering breaks down rock and when dead and decaying material accumulates. Soil promotes the growth of many producer organisms and serves as a habitat for animals and decomposers too. Root systems hold the soil in place. Human or grazing animals remove vegetation and the soil is washed away by rain or blown away be wind. This is called erosion. We lose much fertile topsoil this way.

The Water Cycle- Through the water cycle fresh, clean water is made available for all organisms. Humans can pollute the water to the extent that the natural recycling methods do not clean up the water fast enough and the water becomes unusable.

Benefit of decomposers Waste removal and Recycling of Nutrients- Plants use the minerals in the soil as they grow. Animals eat the plants and the energy that the plants produced gets passed from organism to organism through the food chains and food web. When a body dies or creates wastes, decomposers break down the remains. The nutrients are returned to the soil, making the soil fertile again for the plants in the area. If an area had no decomposers, the nutrients would be “locked up” in the wastes of and remains of organisms. The soil would lose fertility and soon plants would not be able to grow there.

In the rain forest, the rates of decomposition and nutrient uptake by plants have to happen very rapidly or the rain will wash the nutrients away. When people cut down or burn the rain forest, the rain depletes what nutrients are in the soil rapidly and the land becomes useless. Humans can make compost, (a mix of decaying lawn and garden wastes) which is a natural fertilizer. We can make the soil around our home more fertile by spreading compost.