Ecology

ECOLOGY ● What is Ecology? ○ The scientific study of interactions between organisms and the environment ○ Study of interactions between different groups of organisms ○ Study of interactions between the living and nonliving components of the environment ○ These interactions occur on many levels, ranging from the organismal level to a global level ● Levels of Ecological Organization ○ Scientists recognize a hierarchy of organization in the environment; each level with unique properties that result from the interactions among its components. From broadest to most specific, these levels are: ■ The biosphere ■ Ecosystems ■ Communities ■ Populations ■ Organisms ● The Biosphere ○ The Broadest level of ecological organization and includes ALL OTHER LEVELS. ○ Contains the combined portions of the planet in which all life exists, including land, water, and air. ■ All organisms are found within the biosphere. ■ The biosphere extends 5-6 miles above the Earth’s surface to the deepest parts of the ocean. ● Ecosystems ○ The biosphere is composed of smaller units called ecosystems. ■ An ecosystem is a collection of all the organisms that live in a particular place, together with their nonliving, or physical environment. ○ EXAMPLE: Consider a pond ecosystem. ■ What living organisms might live in this ecosystem? Fish, insects, turtles, plants, algae, bacteria, protists, amphibians, birds, and more. ■ What are some nonliving components of this ecosystem? The level of oxygen and carbon dioxide dissolved in the water, the supply of nitrogen and phosphorous, the pH of the water, the amount of sunlight received by the pond ● Communities ○ A community is all of the living organisms found in a particular area ■ A community may contain thousands of species. A scientist who studies communities studies the interactions between these living organisms. ■ In the pond ecosystem examples used above, the fish, insects, turtles, plants, etc. all make up a community. ● Populations ○ A population includes all the members of a single species that live in an area. ○ Communities are composed of many different populations. ● Organisms ○ This is the simplest level of organization in ecology. ○ An organismal scientist would concentrate on the adaptations that allow organisms to overcome the challenges of their environment. ● The Theme of Ecology ○ No organism is isolated ○ All organisms interact with other organisms in their surroundings and with the nonliving portion of their environment ■ The survival of the organism depends on these interactions. ○ There is interdependence; the members of an ecosystem are dependent on one another for their survival. ■ Example: Plants depend on animals to give off carbon dioxide so they can use it in photosynthesis. Animals depend on plants as a source of food as well as a source of oxygen for cellular respiration. ● Biotic and Abiotic Factors ○ Biotic Factors ■ Living components of the environment, includes all of the living things that affect the organism. ■ These include every living thing an organism might interact with. ○ Abiotic Factors ■ Nonliving factors that influence or affect the ecosystem. ○ Both of these factors are dependent upon one another ■ For example, the growth of a plant is dependent on getting nitrogen from the soil. The amount of nitrogen in the soil is affected by the plants that are absorbing the nitrogen. ■ Biotic and abiotic factors determine the survival and growth of the organisms and the productivity of the ecosystem. ● Producers and Consumers ○ Autotrophs ■ These are organisms that are capable of using energy from the environment to make their own food in the form of molecules of glucose ■ Also referred to as “producers” ● Convert carbon dioxide and water into carbohydrates (glucose) photosynthesis ■ Plants, algae, some protists, a few species of bacteria ○ Heterotrophs ■ Organisms that are not capable of harnessing energy directly from the environment ● Not capable of producing molecules of glucose ■ Include all animals, fungi, many bacteria - referred to as “consumers” ● Must consume other living organisms for their food supply and energy ■ Types of heterotrophs: ● Herbivores: Obtain their energy by eating only plants ● Carnivores: Obtain their energy by eating other animals ● Omnivores: Obtain their energy by eating both plants and animals ● Detritivores: Feed on plant and animal wastes, and other dead matter ○ Examples: Vultures, mites, earthworms, snails, crabs ● Decomposers: Cause decay by breaking down organic compounds ○ Include bacteria and fungi ○ Some of the molecules released during decay are consumed by the decomposer, and some are returned to the soil or water. ○ The action of these decomposers makes the nutrients contained in dead bodies and wastes available to autotrophs ■ Process of decomposition recycles chemical nutrients ● Food Chains ○ The energy in a food chain flows in a one-way path through the ecosystem. ■ Energy enters the ecosystem in the form of sunlight ■ Photosynthetic organisms convert the sun’s energy into molecules of glucose. ■ This energy is then passed on to the animals that eat the plants and the animals that eat other animals. ■ SUN → AUTOTROPHS → HETEROTROPHS ○ A food chain is a series of steps in which organisms transfer energy from one organism to another by being consumed. All food chains begin with the SUN, and the first organism is an AUTOTROPH. A basic food chain. Note how it starts with the sun and how the energy flows. Image via CK-12 Foundation. ● Food Webs ○ In an ecosystem, the feeding relationships between organisms are much too complex to be shown in a single food chain ■ Many consumers eat more than one type of food, more than one species may feed on the same organism. ○ A food web is a network of complex interactions formed by the feeding relationships among the various organisms in an ecosystem. ■ A food web links all the food chains in an ecosystem together. A basic food web. Note how the autotrophs are at the bottom. Image via BrainPOP. ● Trophic Levels ○ Each step in a food chain is called a trophic level ■ The trophic level indicates the organism’s position in the sequence of energy transfers ○ The first trophic level in a food chain is always made up of producers. These organisms are referred to as primary producers. ○ The second trophic level is occupied by the herbivores that feed on the producers. These organisms are called primary consumers. ○ Predators of herbivores belong to a third level; these organisms are called secondary consumers. ■ Each consumer depends on the trophic level below it for energy. ■ Most ecosystems only contain three or four trophic levels ● As the trophic levels increase, the amount of energy in the trophic levels decrease - this makes it more difficult for predators to survive; this is why they are adapted to hunt well. ■ 10% Rule: Only about 10 percent of energy stored as biomass in a trophic level is passed from one level to the next A trophic level pyramid. Image via Texas Gateway. ● Invasive Species ○ An invasive species is any organism that causes damage to an environment that it didn’t originate in. ■ Invasive species ALWAYS have a negative impact on the environments they have invaded - Remember… they don’t belong there. ○ In nature, only the strong survive. ○ Invasive species are able to take over the habitats they invade by devouring the majority of the food, and destroying the habitat for the native species. ■ They compete for resources and often win.