Biology Chapter 28 Ecosystems Objectives Trace the passage

Biology Chapter 28 Ecosystems

Objectives • Trace the passage of energy from producers to consumers in an ecosystem. • Relate the flow of energy through an ecosystem to the pyramid of energy. • Analyze the importance of recycling in an ecosystem and describe how such recycling occurs. • Distinguish among parasitism, commensalism, and mutualism.

Trophic Levels • Biotic factors – relationships among different organisms. • Bio = living, so living factors are referred to as biotic. • Interaction of a community with its environment is an ecological system, or ecosystem.

Trophic Levels • Interactions between organisms and environment is a give and take relationship. • Usually a delicate balance between organisms and environment. • As organisms take things from the environment to obtain energy, other organisms are transferring things back to the environment.

Trophic Levels • Only photosynthetic organisms can transfer the sun’s energy into a form they can use. • Other organisms feed on these autotrophs. • Still more organisms feed on these organisms. • Each feeding step represents a trophic level in the passage of energy and materials.

Trophic Levels • All organisms within an ecosystem have functions in that ecosystem. • An organism’s niche describes how an organism fits into an ecosystem, or its role in the ecosystem. ▫ Where an organisms lives, what it eats, what eats it, and how it interacts with the biotic and abiotic parts of an ecosystem describe its niche. ▫ NO TWO ORGANISMS CAN OCCUPY THE SAME NICHE IN THE SAME ECOSYSTEM.

Trophic Levels • In order for an ecosystem to function, organisms depend on each other. • Example: Energy needs to pass from the sun, to producers, to consumers.

Producers Herbivores Carnivores Omnivores We can see here the beginnings of the development of a food chain, or a food web. 3 rd order consumers 2 nd order consumers 1 st order consumers

Food Chains and Webs

Pyramid of Energy • As we move up a level, only about 10% can be transferred to a higher level. • Remember, energy is not gained or lost, it is only transferred to a different form (Law of Conservation of Energy).

Other Pyramids Used by Ecologists • Loss of energy in a food chain explains several ecological principles. • Explains things like: ▫ Why there is usually only 3 or 4 levels. ▫ Also helps us see why there are usually fewer organisms the higher up the chain we move.

Pyramids of Numbers and Biomass

Materials are cycled • Things like oxygen, carbon, sulfur, nitrogen, water, are recycled throughout ecosystems. • Organisms such as decomposers help with this, as do many plants in the environment.

Carbon cycle

Nitrogen Cycle

Availability • The amount of these types of materials found in an environment is often crucial. ▫ Can limit the distribution of organisms ▫ Can limit the size of populations ▫ Can affect other populations of organisms within the system

Other Biotic Relationships • Most obvious interactions among organisms involve feeding, but others exist. • Commensalism – one organism benefits without aiding or harming the host. Example: Orchids growing on trees in the rainforest. • Mutualism – both organisms benefit. Ex: bees pollinate plants at the same time they feed. • Parasitism – one is harmed, one benefits. Tapeworms

Abiotic Factors - Water • Water – all organisms need water. • How can the availability of water impact an ecosystem? • Water cycles throughout the Earth. ▫ Determines what types of plants live there. ▫ Determines what types of animals live there.

Abiotic Factors - Soil • Soil also plays a big part in determining which organisms live where. • Organisms are integral in the development and formation of soil, as well. • They help break down rocks and minerals and when dead add to the organic content.

Abiotic Factors - Light • Light is required as an energy source in most ecosystems. • It also provides for better vision. • Used to make vitamin D in humans.

Abiotic Factors - Temperature • Organisms do best in a certain range of temperatures that vary from species to species. • Temperatures warming allow peach trees to bloom after they have been exposed to a cold period.

Disrupting the Balance • Some ecosystems more balanced than others. • Some more fragile than others. • When disruption occurs, it affects all organisms in the ecosystem in some way. • Algal blooms are a good example. Caused by increases in phosphates into a water system.