Ecology March 2013 Pre AP biology

What is an ecosystem? Ecology is the study of organisms and their interactions with their living and nonliving environment. Where we start this study is with an ecosystem which is an area of study that includes living and non living parts.

What makes up an ecosystem? An Ecosystem has two parts: 1.Biotic factors – all the living organisms 2.Abiotic factors – physical, nonliving aspects

Use the picture below to list all the biotic factors you see or can assume are there

Use the picture below to list all the abiotic factors you see or can assume are there

Habitat, Population, Community A habitat is the place where a particular population lives. A population is all the individuals in a particular species living in one place A community is all the populations living in one habitat

Biomes A large region composed of similar ecosytems; biomes have a specific climate and animal and plant communties.

Where does an ecosystem fit in? Individual organisms make up  populations which make up  communities which make up  ecosystems which make up  biomes

Ecosystems can change When a new habitat is formed by volcanoes, or receding glaciers new species inhabit. The first thing to grow in a new habitat is called a pioneer species. It is usually a plant or fungus that does not need a lot of nutrients to live. The pioneer species breaks down the rock into soil that will support larger plant life. Over time the pioneer species is replaced by shrubs and then trees

Succession The progression of species replacement is called succession There are two kinds of succession: 1.Primary succession – occurs where life has not existed before (vocanoes, glaciers, etc) 2.Secondary succession – occurs where there has been previous growth (abandoned fields, forest clearings)

Energy Flow in Ecosystems Everything that organisms do in an ecosystem requires energy. How much energy is available directly influences biodiversity Our ultimate source of energy is the SUN.

Primary productivity The rate at which organic material is produced is called primary productivity. All other organisms depend on the primary productivity to directly or indirectly provide them with food. Photosynthetic organisms use sunlight to produce organic materials (what we call food)

Producers and Consumers Producers are organisms that first capture energy They include: some bacteria, all plants, and algae. Producers make energy-storing molecules Consumers are organisms that consume producers or other organisms in order to obtain the energy they need.

Trophic Levels Sun Producer Consumer Organisms are assigned to a trophic level (feeding level) based on the organism’s source of energy. Energy moves from one trophic level to the next.

Trophic Levels Sun Producer 1 st Trophic Level Consumer Producers are always on the 1 st trophic level. They receive the sun’s energy and, through photosynthesis, convert it to organic molecules.

Trophic Levels Sun Producer 1 st Trophic Level Consumer 2 nd trophic level Consumer Consumers are on all levels except the first. Anything that eats a producer is on the 2 nd trophic level. All herbivores are on the 2 nd trophic level. Herbivores are also called primary consumers

Trophic Levels Sun Producer 1 st Trophic Level Consumer 2 nd trophic level Consumer 3 rd trophic level Any consumer that eats herbivores is on the 3 rd trophic level and is called a secondary consumer.

Trophic Levels Sun Producer 1 st Trophic Level Consumer 2 nd trophic level Consumer 3 rd trophic level Consumers either eat both producers and consumers (called an omnivore), or they eat only organisms in the 2 nd trophic level and above (called carnivore).

Above the 3 rd trophic level Some organisms like humans, sharks and hawks are carnivores that eat other carnivores and can be placed on the 4 th trophic level. They are called tertiary consumers. It is very rare for an ecosystem to have more than four trophic levels

Food chain The path of energy through the trophic levels of an ecosystem is called a food chain In a food chain the arrows always point to the organism doing the eating. (Imagine an arrow pointing into the eater’s mouth)

Detritivores Detritivores are organisms that obtain their energy from the organic wastes and dead bodies that are produced at all trophic levels. They include worms, fungus and bacteria Bacteria and fungus are known as decomposers because they cause decay. They are important because they recycle nutrients back into the environment

Food Web Most ecosystems do not follow simple straight paths because individual animals often feed at several trophic levels. This creates a series of interconnected chains called a food web.

Loss of energy A plant stores only a small amount of the energy it absorbs. The rest is given off as heat or used by the plant to support its daily processes. The same is true for a primary consumer. It will take in energy stored in the plant, but will either use the energy immediately or it will be given off as heat. It will only store 10% of the energy it took in. During every transfer of energy in an ecosystem, energy is lost as heat or used by the organism and only about 10% is stored at each step.

The 10% Rule You can calculate the amount of energy available to each trophic level by remembering the 10% rule. Sun – 100,000 kcal (kilocalories) Grass 10,000 kcal is available to the next trophic level Zebra 1,000 kcal is available to the next trophic level Lion 100 kcal is available to the next trophic level Humans 10 kcal is available to the next trophic level

Energy Pyramid The flow of energy in an ecosystem can be illustrated using an energy pyramid It is a diagram in which each trophic level is represented by a block that represents the amount of available energy.

Energy Pyramid If you ate a snake, how much energy would be available in you? If a falcon ate the snake and then a wolf ate the falcon, how much energy would be available in the wolf?

Limitations of Trophic Levels Read page 349 and explain why we can’t depend on the beef industry as the solution to feeding the world. Why do they always ship grain to countries experiencing famine? Should we give them calves so they can have ranches? Why not?

Cycling of Materials in Ecosystems Certain nutrients cycle through the environment and get reused over and over. The most important nutrients to cycle are water, carbon, nitrogen and phosphorus. Biogeochemical cycle – the cycling of these materials from the living to nonliving aspects of an environment This DOES NOT apply to energy