Balance within ecosystems

How do populations change in size? Ecologists are scientists who study biotic (living) and abiotic (nonliving) factors of an ecosystem and the interactions between them. Some ecologists study populations and monitor the sizes of populations over time. Populations can change in size when new members join the population or when members leave the population.

Births and Deaths The most common way in which new individuals join a population is by being born into it. When the birth rate (the number of births per 1000 individuals for a given period of time) is greater than the death rate (the number of deaths per 1000 individuals for a given period of time), the population may increase. When the death rate is higher than the birth rate, the population may decrease. When the birth and death rates are the same, the population stays the same.

Immigration and emigration Immigration – means moving into a population Emigration – means leaving a population What are some reasons that animals would immigrate to a population? What are some reasons that animals would emigrate a population?

Population density The population density is the number of individuals in an area of a specific size. Population Density = Number of Individuals Unit Area In the pond on the top, there are 10 flamingos in 8 square meters. The population density is 1.25 flamingos per square meter. What is the population density of the flamingos in the pond on the bottom? If 14 more flamingos landed in the pond on the bottom, what would the population density be then? What do you think would happen if the population density of flamingos in the pond on the bottom became too great?

What factors limit population growth? Limiting factor – an environmental factor that causes a population to stop growing or decrease in size. Some limiting factors for populations are weather conditions, space, food, and water. The largest population that an area can support is called its carrying capacity.

Adaptations Adaptations are behavioral and physical characteristics that allow an organism to live successfully in its environment. Every organism has a variety of adaptations that are suited to its specific environment and help it survive.

Behavioral adaptations A behavioral adaptation is a behavior that helps an organism to survive and reproduce. An instinct is a behavioral adaptation that an organism is born with, such as a spider’s ability to weave a web. Other behavioral adaptations are learned, such as a wolf pups ability to hunt.

Structural adaptations A structural adaptation is a physical characteristic that allows an organism to survive and reproduce. Some structures, such as beaks and poisonous tentacles, help predators find and capture prey. Other structures such as sharp teach, help predators eat their prey.

Variations within species Members of a species generally share the same characteristics. However, individual members have differences, or variations. The process by which individuals with variations most suited to their environments survive and are most likely to reproduce is called natural selection.

Two types of succession: Changing ecosystems The series of predictable changes that occur in a community over time is called succession. Two types of succession: Primary succession – the series of changes that occurs in an area where no soil or organisms exist. Secondary succession – series of changes that occurs in an area where the ecosystem has been disturbed, but where soil and organisms still exist.

Primary succession Primary succession occurs after events such as a volcanic eruption or when a slab of rock is uncovered under a sheet of ice. No organisms are present at that time. Pioneer species are the first species to populate an area. They often travel by wind or water. Typical pioneer species are moss and lichens. Lichens are fungi and algae. As they grow, they help break up rock and form soil. When organisms die, they provide nutrients and enrich the soil forming on the rocks. As the soil becomes more plentiful, saplings begin to grow.

Secondary succession Secondary succession happens after natural disturbances such as fires, hurricanes, and tornadoes. Human activities, such as farming, logging, and mining, may also disturb an ecosystem and cause secondary succession to begin. Unlike primary succession, secondary succession occurs in a place where an ecosystem already exists. Secondary succession usually occurs more rapidly than primary succession because soil already exists and seeds from some plants remain in the soil.

Humans and the environment The resources that humans obtain from ecosystem include abiotic and biotic resources. Abiotic Resources Non-living resources in our ecosystem; water, air, soil, sunlight, oxygen, and minerals. Biotic Resources Living resources in our ecosystem provide us with food, materials to build shelter, and fuels. Decomposers are also biotic resources.

How do human activities affect ecosystems? Obtaining resources can cause changes in ecosystems. Human activities may affect the balance in an ecosystem and thereby change the ecosystem. Nonnative Species Humans can harm ecosystems by introducing new species. The introduction of Nutria into Louisiana caused a decrease in a native plant whose roots are important in holding the soil together. (This causes erosion) Overuse of Resources When humans overuse resources the plants and animals are affected. In the mid-west they use grassy plains to feed their cattle. If the cattle eat the grass too quickly, the plain may become bare and desert-like. This causes the soil to lose nutrients and not support plant growth.

How does technology affect the environment? Some technology used in energy production, agriculture, human habitation, and transportation impact the environment.

Energy production Technologies have been developed to obtain and process energy resources such as coal and oil. One mining method involves stripping the rock and soil off mountain tops. During this process the materials may be deposited in nearby streams or forest destroying the ecosystem. When burning fossil fuels, carbon dioxide is released into the atmosphere, too much carbon dioxide can affect temperatures.

agriculture Technologies have been produced to increase the production of food to meet demands. Farmers may use different types of chemicals to increase their crop yields as well as keeping pest away. The run off of these chemicals causes damage to other ecosystems.

Human habitation and transportation Building homes, towns, and transportation requires resources. To obtain these different resources we may need to cut down trees or burn fossil fuels. Traveling in cars, planes, and trains releases carbon dioxide into the air, having too much causes a greenhouse effect. The greenhouse effect is the process of which certain gases are trapped in the atmosphere trapping heat.