Ecology Unit

Chapter 16: Ecosystems

What is ecology?Ecology is the study of interactions

- these interactions can be among organisms or between organisms and their environment.

A community is a collection of populations living in the same habitat. Communities are comprised of multiple species.

An ecosystem is a combination of the community and the environment around it.- the organisms comprise the community (biotic factors)- the soil, water, climate, etc. comprise the environment (abiotic factors)

BiodiversityBecause the world has

such an array of not only organisms, but many ways in which they congregate and where they live, it is said to be very biodiverse

We as humans experience diversity just among our own populations in many ways: ecologically, culturally, etc.

Ecosystems contain a variety of lifeWhen we look at

ecosystems, we can’t just look at the “large” inhabitants (such as top predators)

Believe it or not, the largest population in an ecosystem might be a bacterial population!

Change is always occurringAs we discussed in

evolution, change is always occurring.

Over time, some land is being lost, but there is also land being made due to forces such as volcanism.

New land forming causes species to inhabit it.- pioneer species are small, fast growing plants that form on new land in the presence of soil.

Change is always occurringAlong with

inhabiting new land, there is a cycling process among the species that live on previously inhabited lands

This cycling, or “species replacement” is called succession

There are two types of succession- primary succession is replacement that happens where life has not existed before- secondary succession is replacement that happens in areas that have experienced growth before (the growth may have been cut down, caught fire, etc.)

succession

How does energy flow?Energy flows up in an ecosystemThe primary source of energy is the sunThe sun provides this energy for plants (as well

as algae and some bacteria), which are called primary producers.-primary producers are important because they create organic material through photosynthesis

Those that consume plants (herbivores), make up the first level of consumers called primary consumers-a consumer eats plants, animals, or both to get the energy necessary for them to live. The levels of consumers can go from primary to tertiary

How does energy flow?The levels just mentioned (primary producer,

primary consumer, etc.) are called trophic levels.

The trophic level an organism belongs to determines where they get their energy from

So, if we were looking at a food chain, or the path the energy takes up the trophic levels, this is how the energy would move.

Sungrassgazellelion The primary energy comes from the sun, which is absorbed by the grass that the gazelle eats. That gazelle gets eaten by the lion.

Energy movementWhen going up a food

chain, the amount of energy that each subsequent level receives is about 10% of the previous level’s.

This is shown in an energy pyramid-going up each level, there is less energy moving up-each level also has fewer organisms in it

QuestionsIf only 10% of energy flows up the trophic

levels, what happens to the other 90%?

Food chains show energy flow

Food chains show energy flowA food chain shows the path of energy through

the trophic levels of an ecosystemThe first level is the producers (plants, algae,

photosynthetic bacteria)The second level is the first level of consumers,

which are herbivores (those that eat the producers)

The third level begins the chain of animals eating other animals-in these levels, the animals can be carnivores (meat eaters) or omnivores (meat and plant eaters)

Food chains show energy flowFungi and non-photosynthetic bacteria are not

left out of the equation, even though their presence may not be written out in a food web or a food chain

Fungi and bacteria are decomposers, which means they cause material to decay- bacteria and fungi get their energy from this dead material or organic wastes that are produced at all trophic levels- they are in a group of consumers called detritovores- they are very helpful in recycling nutrients back to the Earth for reuse.

What is a top predator?If a food chain were to go up to higher

levels, such as tertiary or quaternary consumers, then those would be carnivores eating other carnivores

These higher level carnivores are said to be apex, or top predators- these predators generally don’t have any natural predators

Examples of top predators: owls, hawks, sharks

Top predators

QuestionDoes all energy flow in one straight line, as

shown by looking at a food chain?

Energy doesn’t just flow in one straight lineNo, energy does not flow just how one food

chain suggestsWe have to combine many food chains

together in order to see a more accurate energy flow- this is because many organisms may be located in different trophic levels depending on which food chain we are looking at.

This combination of food chains is called a food web

Food web

QuestionWhy is there a limit on how many trophic

levels there can be?

Only so much energy is availableThere can only be so many trophic levels because

there is only so much energy availableBecause so little energy gets transferred from one

level to the next, it doesn’t take long for there to be too little energy left to sustain life

Also, different organisms are different sizes and/or need different amounts of energy to survive compared to others, so it’s hard to see just how much energy there is to go around at any one level-finding the biomass (the dry weight of tissue and other organic matter in a specific ecosystem) is a way we can see just how much energy is available in the ecosystem

Self Check Quiz1. Why aren’t plants examples of abiotic factors?2. When finding the biomass of an ecosystem,

what must we eliminate?3. Why doesn’t energy flow down the trophic

levels?4. Why can we only have so many trophic

levels?5. What happens to the 90% of energy that

doesn’t get absorbed and used in an ecosystem?

6. Draw the pyramid of ecology

Biogeochemical cyclesWater, carbon, phosphorous, and nitrogen

cyclesIn a biogeochemical cycle, a pathway forms

when a substance enters living organisms, stays in that organism for some time, and then returns to the non-living environment

Water cycle

Carbon cycle

Phosphorous and Nitrogen cyclesComplex process with

four steps1. assimilation-the absorption and incorporation of nitrogen into organic compounds by plants2. ammonification-the production of ammonia by bacteria during the decay of organic matter

3. Nitrification- the production of nitrate from ammonia4. denitrification- the conversion of nitrate to nitrogen gas

KNOW- Phosphorous and Nitrogen are both essential in protein/nucleic acid building in organisms

Phosphorous and Nitrogen cycles

Animations http://www.epa.gov/ogwdw000/kids/flash/fl

ash_watercycle.html for water cycle

http://www.teachersdomain.org/resource/lsps07.sci.life.eco.nitrogen/ for nitrogen cycle