Cycles in the EcosystemCycles in the Ecosystem

PA 4.6PA 4.6

I. Matter CyclesI. Matter CyclesA.A. Unlike the continuous flow of energy from Unlike the continuous flow of energy from

the sun, the matter that is found on the Earth the sun, the matter that is found on the Earth is in a closed system.is in a closed system.1.1. That means that the amount we have now is the That means that the amount we have now is the

same amount we had a million years ago.same amount we had a million years ago.

2.2. Matter continuously cycles through out the parts Matter continuously cycles through out the parts of an ecosystem, going from the environment to of an ecosystem, going from the environment to living organisms and back to the environment.living organisms and back to the environment.

B.B. There are several major There are several major cycles that are at work in cycles that are at work in an ecosystem but we are an ecosystem but we are going to focus on three:going to focus on three:

1.1. The water cycleThe water cycle

2.2. The carbon cycleThe carbon cycle

3.3. The nitrogen cycleThe nitrogen cycle

Let’s start with the water Let’s start with the water cycle…cycle…

C.C. Earth is considered the water Earth is considered the water planet with over 70% of surface planet with over 70% of surface covered with water.covered with water.1.1. More importantly, most More importantly, most

living things are dependent living things are dependent on water and cannot exist on water and cannot exist without it. without it.

2.2. Do you know how much of Do you know how much of the human body is water?the human body is water?a. 65%a. 65%

3.3. How long can we survive How long can we survive without water?without water?a. 3-5 days depending on a. 3-5 days depending on

conditions.conditions.

4.4. So the water you are drinking today, is the same So the water you are drinking today, is the same water the dinosaurs bathed in 65 million years water the dinosaurs bathed in 65 million years ago.ago.Sounds gross…but isn’t because of the water Sounds gross…but isn’t because of the water cycle.cycle.

D. The Water CycleD. The Water Cycle1.1. The water cycle (like all The water cycle (like all

the other cycles) is the other cycles) is driven by the energy of driven by the energy of the sun.the sun.

2.2. The purpose of the water The purpose of the water cycle is to collect, purify cycle is to collect, purify and distribute the water and distribute the water found on the Earth.found on the Earth.

3.3. There are six major steps There are six major steps to the water cycle.to the water cycle.

I.I. EvaporationEvaporation – the – the energy of the sun energy of the sun causes water to causes water to evaporate (from evaporate (from mainly the oceans), mainly the oceans), changing from liquid changing from liquid water to water vapor.water to water vapor.

II.II. CondensationCondensation – as – as the water vapor the water vapor cools, it condenses cools, it condenses into cloud droplets.into cloud droplets.

III.III. PrecipitationPrecipitation – as – as the cloud droplets the cloud droplets grow, they form rain grow, they form rain (or snow or both) (or snow or both) which falls back to which falls back to the earth.the earth.

IV.IV. RunoffRunoff – if the – if the precipitation falls on precipitation falls on land, it washes land, it washes downhill by gravity downhill by gravity into lakes, rivers, or into lakes, rivers, or ponds and ponds and eventually the eventually the ocean.ocean.

V.V. Percolation/infiltrationPercolation/infiltration – – some of the water seeps some of the water seeps into the ground and into the ground and becomes groundwater.becomes groundwater.

VI.VI. TranspirationTranspiration – – groundwater is absorbed groundwater is absorbed by plants and given off by by plants and given off by the leaves of plants due to the leaves of plants due to the energy of the sun and the energy of the sun and respiration. respiration.

4.4. The water cycle can be The water cycle can be extremely fast or slow extremely fast or slow depending on the depending on the location and climate.location and climate.

5.5. Humans are affecting Humans are affecting the water cycle through the water cycle through pollution. Pollution pollution. Pollution limits the amount of limits the amount of water that is available water that is available for use by humans and for use by humans and other living organisms. other living organisms.

Condensation

Runoff

LET’S REVIEW….

E.E. CarbonCarbon1.1. We are considered carbon-based life forms. We are considered carbon-based life forms.

Carbon is the building block of life. It is Carbon is the building block of life. It is essential for DNA, proteins, fats, and essential for DNA, proteins, fats, and carbohydrates. carbohydrates.

2.2. Carbon dioxide, COCarbon dioxide, CO22, is an essential greenhouse , is an essential greenhouse gas that helps maintain heat in Earth’s gas that helps maintain heat in Earth’s atmosphere.atmosphere.

3.3. Carbon can be found in the atmosphere, oceans, Carbon can be found in the atmosphere, oceans, and in rocks. Let’s review the carbon cycle…and in rocks. Let’s review the carbon cycle…

4.4. The carbon cycle has The carbon cycle has three natural steps.three natural steps.

I. I. PhotosynthesisPhotosynthesis – – Producers (Plants) on Producers (Plants) on the land and in the the land and in the ocean take in COocean take in CO22 and build organic and build organic molecules with the molecules with the carbon.carbon.

Decomposition

II. II. RespirationRespiration – the carbon – the carbon stored in organic stored in organic molecules (like sugars) molecules (like sugars) are used by the producers are used by the producers and consumers for energy. and consumers for energy. (These carbon molecules (These carbon molecules travel through the food travel through the food web). Cellular respiration web). Cellular respiration releases COreleases CO22 back into the back into the atmosphere or water.atmosphere or water.

Decomposition

III. III. DecompositionDecomposition – – when the waste when the waste products or remains products or remains of dead organisms are of dead organisms are broken down by broken down by decomposers, COdecomposers, CO22 is is released back into the released back into the atmosphere and atmosphere and oceans or oceans or settle/combine with settle/combine with sediments in the soil.sediments in the soil.

5.5. The carbon cycle has parts that exchange The carbon cycle has parts that exchange carbon very quickly (photosynthesis and carbon very quickly (photosynthesis and respiration) and has parts that can take respiration) and has parts that can take millions of years. (formation of fossil fuels – millions of years. (formation of fossil fuels – coal and oil)coal and oil)

6.6. Humans affect through deforestation and the Humans affect through deforestation and the burning of fossil fuels. Fewer trees result in burning of fossil fuels. Fewer trees result in less COless CO22 absorbed from the atmosphere. absorbed from the atmosphere. Burning fossil fuels releases carbon that was Burning fossil fuels releases carbon that was stored deep in the ground for millions of stored deep in the ground for millions of years.years.

Let’s review the Carbon cycle…Let’s review the Carbon cycle…

F.F. NitrogenNitrogen1.1. Nitrogen is the most abundant gas found in the Nitrogen is the most abundant gas found in the

Earth’s atmosphere.Earth’s atmosphere.

2.2. Nitrogen is also an important component in Nitrogen is also an important component in organic compounds such as proteins, DNA, and organic compounds such as proteins, DNA, and chlorophyll.chlorophyll.

3.3. However, the form of nitrogen that is most However, the form of nitrogen that is most abundant, Nabundant, N22, is not usable by producers or , is not usable by producers or consumers.consumers.

4.4. So how do we get the nitrogen that we need…So how do we get the nitrogen that we need…enter the nitrogen cycle.enter the nitrogen cycle.

5.5. The nitrogen cycle is The nitrogen cycle is driven by bacteria and has driven by bacteria and has five basic steps.five basic steps.

I.I. Nitrogen-fixationNitrogen-fixation – – bacteria found in the roots bacteria found in the roots of plants (mainly legumes) of plants (mainly legumes) convert Nconvert N22 gas into gas into ammonia (NHammonia (NH33))

II.II. AmmonificationAmmonification – – decomposers break down decomposers break down organism remains and organism remains and releases ammoniareleases ammonia..

III. III. NitrificationNitrification – another – another type of bacteria convert type of bacteria convert the ammonia (NHthe ammonia (NH33) into ) into nitrates (NOnitrates (NO33). Nitrates ). Nitrates are a form of nitrogen are a form of nitrogen that are usable by that are usable by producers. (Lightening producers. (Lightening can also change Ncan also change N22 into into NONO33))

IV. IV. AssimilationAssimilation – is the – is the uptake of nitrates by uptake of nitrates by producers. Consumers producers. Consumers get nitrogen by get nitrogen by consuming producers or consuming producers or other consumers.other consumers.

V. V. DenitrificationDenitrification – – another type of another type of bacteria breaks bacteria breaks down the nitrates down the nitrates back into nitrogen back into nitrogen

gas. (Ngas. (N22)) Nitrogen Nitrogen content is a limiting content is a limiting factor for plant factor for plant growth.growth.

6.6. Humans are affecting the nitrogen cycle by adding Humans are affecting the nitrogen cycle by adding nitrogen-containing fertilizers to the environment nitrogen-containing fertilizers to the environment and through the burning of fossil fuels. (Nitrogen and through the burning of fossil fuels. (Nitrogen oxides are emitted which can cause acid rain)oxides are emitted which can cause acid rain)

Let’s review the Nitrogen cycle…Let’s review the Nitrogen cycle…

Any Questions????Any Questions????

Ecological Succession

1. Ecological Succession is a process in which the communities of an ecosystem change over time.

2. There are two types of succession: primary and secondary. Both types of succession follow a similar pattern.

3. Let’s focus on primary succession.A. Primary succession occurs in places where an

ecosystem has never existed before. This could be a newly formed volcanic island or land exposed from a receding glacier.

B. As the exposed rock is weathered, the first species appear. These species are called pioneer species. They are small, grow quickly, and need minimal resources to survive. Often are mosses and lichens.

C. The pioneer species breakdown the rock to form soil. This allows other species to grow among the mosses and lichens. Eventually the other species out compete with the pioneer species and change the community.

D. At each stage, competition among the species causes a change in the dominant community. In the later stages, larger, slower growing species displace the smaller, faster growing species.

E. As the ecosystem ages, the community becomes more diverse. The process of succession will continue until the ecosystem reaches a climax community.

A climax community is the last stage of succession. If left undisturbed, the ecosystem will stay at the climax community.

The Oak-Hickory forests of PA is a climax community.

F. Disturbances in the ecosystem, such as fire, flood or human activity, can slow the process of succession down.

G. If the disturbance is catastrophic, like a tornado or volcanic eruptions, the process may have to start over from the beginning.

Which leads us to….

H. Secondary succession is the process that begins in an ecosystem that has been disturbed or destroyed. Typically occurs

on abandoned farmlands, burned or cut forests, etc…

I. Secondary succession has similar stages compared with primary succession. Remember that secondary is regenerating an existing ecosystem. Primary is forming a new ecosystem where none existed before.