Ecology - Unit 2 - Change and Stability in Ecosystems .  

To maintain life on Earth matter must be recycled

Organic substances always contain atoms of carbon and hydrogen as well as oxygen and nitrogen. Matter that does not contain a combination of carbon and hydrogen atoms is called inorganic.

The focus of this unit is to understand the cycling of organic substances within living things

Decomposers break down complex organic molecules into inorganic matter, which may be used by plants. Plants reassemble these inorganic substances (also called nutrients) to make food for themselves. In turn, animals may eat the plants, continuing the cycle of matter.Copy Figure 3 page 51 into your notes.

2.2 Case Study of Pesticides Pesticides are chemicals designed to kill pests. A pest is an organism that people consider harmful or inconvenient, such as weeds, insects or rodents. Pesticides can be grouped into 4 different categories:

Type of Pesticide Target ExamplePersistence

Insecticide insects DDT high 2-15 years

Malathion moderate 1-12 wks

 

Herbicide weeds 2,4-D low days to wks

Round Up

 

Fungicide moulds and fungus Captan low days

 

Bactericides Bacteria Penicillin low

Bioamplification – Pesticides that contain chlorine, like DDT, are soluble in fat but not in water. As a result, these toxins cannot be released in urine or sweat, so they accumulate in the fatty tissues of animals. As primary consumers are eaten by secondary consumers and these are in turn eaten by tertiary consumers more and more toxins are consumed. The higher the trophic level the greater the concentration of toxins. This process is referred to as Bioamplification. Copy Figure 4 page 54 into your notes.

One of the animals most affected by bioamplification is the Bald Eagle      

- Pesticides are used to kill insects (DDT)

- DDT is washed into the lakes as rivers as runoff

- DDT is eaten by small insects and fish

- Larger fish feed on the insects and small fish

-  Bald Eagles feed on the large fish

-  Lifespan of a bald eagle is 25 years which helps increase the amount of toxins consumed

-   Result is that the toxins weaken the egg shell of the bald eagle making them easily broken when the female tries to incubate the eggs.

Fewer eggs survive = fewer bald eagles

2.5 The Carbon Cycle Carbon is the key element for life on EarthCarbon can be found in:-         atmosphere as carbon dioxide-         dissolved in ocean water as carbon dioxide and bicarbonates  Each year 50 to 70 billion tonnes of carbon is recycled by the process of Photosynthesis.

Plants use light to combine carbon dioxide from the atmosphere and water, into more complex organic substances in the process we call photosynthesis:   Some organic carbon is released back into the environment by cellular respiration as carbon dioxide. Sugar (glucose) + Oxygen Water + Carbon Dioxide + Energy

 Because photosynthesis and cellular respiration are complementary processes, and because the carbon they use is repeatedly cycled through both processes, this relationship is often called the Carbon Cycle.

Carbon dioxide + water + light energy sugar (glucose) + oxygen

Reservoirs (pools) of Inorganic Carbon-  Storage areas of carbon not in an organic form- The oceans (dissolved CO2)- Earth’s Crust (limestone, bicarbonate)- The atmosphere ( CO2)- Industry and vehicles(gasoline)- fossil fuels ( oil and natural gas) 

-Reservoirs (pools) of Organic Carbon-The bodies of living things – animals, bacteria + fungi, vegetation-  decomposing material in bogs ( peat moss)- litter and waste

 

Human impact on the Carbon Cyclehuman industrialization has increased the amount of CO2 being released into the atmosphere and at the same time decreasing the reserve of organic carbon as we burn fossil fuels

The Carbon Cycle Game

Carbon Cycle Terminology

• Carbon Cycle – Movement of carbon atoms through the environment

• Combustion – burning carbon based materials (wood,gas,coal) to do work, releasing carbon dioxide as a byproduct into the atmosphere

• Humification – changing organic matter that is too complex to breakdown by bacteria and fungi, becomes carbon in the soil

• Inorganic – molecules that are not of biological origin (carbon dioxide, bicarbonates)

Carbon Cycle Terminology

• Organic – molecules that are biological in origin(wood, leaves, sugars, starches)

• Organic matter – various molecules and pieces of dead tissue that are biological in origin

• Photosynthesis – conversion of carbon dioxide into sugars by plants using the sun as a source of energy

• Respiration – conversion of sugars into carbon dioxide to release energy used by organisms

2.6 The Nitrogen Cycle Life depends on the cycling of nitrogen. Nitrogen atoms are needed so that animals can make proteins like muscle and also DNA in cells. Nitrogen that is moved through the air and soil is called the nitrogen cycle Nitrogen cycling in the air-         79% of air is nitrogen-         atmospheric nitrogen is unusable by animals-         to be useful it must be turned into nitrates (NO3

-)-         2 methods can change atmospheric nitrogen into useful nitrates by a process called nitrification

1)  nitrogen fixation by lightening2) nitrogen fixation by bacteria in soil

Nitrogen Cycling in the soil-         once the nitrogen has been fixed into the soil in the form of nitrates it is then available to be used by plants (natural fertilizer). -         Plants convert the nitrates into proteins-         Animals eat the nitrogen rich plants making more proteins-         Animal either dies and decays or poops releasing ammonia (NH3) into the soilNitrogen fixing bacteria then turn that ammonia back into useful nitrates by a process called nitrification

Denitrification – at certain stages in the decaying process, denitrifying bacteria can break down nitrates into nitrites (NO2

-), and then nitrites into nitrogen gas which eventually is released back into the atmosphere.Copy Figure 1 Page 66 into your notes

1.9 The Nitrogen Cycle Extension Activity

2.9 Monitoring Changes in PopulationsHuman population increase has had a major impact on the ecosystem and the cycling of matter in the ecosystem.

Year Population Doubling Time1650                          1650                               500 million1850                          1850                             1 billion

200 years 1850                          1850 1 billion 1930 2 billion 80 years 1930                          1930 2 billion 1975 4 billion 45 years 1975                           1975 4 billion 2014 8 billion 39 years

Human population is increasing exponentially

-         Natality – Births or number of offspring born in one year

-         Mortality – deaths or the number of individuals of a species that die in one year

-         Immigration – number of individuals of a species moving into and existing population

-         Emigration – number of individuals of a species moving out of and existing population

Changes in population size in a community occur when individuals are added to or removed from a population

 

Population growth formula

Population growth = (births + immigration) – (deaths + emigrations)

Open populations are populations where all of the above factors are allowed to occur

Closed populations are populations in which only natality and mortality affect their population size

1.12 Case Study: Populations

2.10 Limits on Population Size The maximum number of offspring that a species could produce , if resources are unlimited is called biotic potential

Biotic potential is regulated by 4 factors:

1)      birth potential – maximum # of offspring per birth

2)    capacity for survival – # of offspring that reach reproductive age

3)    procreation - # of times a species reproduces each year

4) length of reproductive life – age of sexual maturity and the number of years the individual can reproduce

Limiting Factors to Population

-         Abiotic factors:

Biotic factors:

O food

o       predators

o       disease and parasites

o       competition for resources

O    Amount of light

o       Temperature

o       Chemical environment

Carrying Capacity

The maximum number of individuals of a species that can be supported indefinitely by an ecosystem. The carrying capacity is determined by:-         the availability of water-         availability of food

If a species exceeds the carrying capacity of the ecosystem poplations will decline.

Limits of Tolerance There are 2 laws that control the survival and reproduction of an organism

2) Law of Tolerance – an organism can survive within (tolerate) a certain range of an abiotic factor.

Above or below the limit it cannot survive

1)      Law of Minimum – the nutrient in least supply is the one that limits growth

Factors that cause changes in populationDensity Independent Factors – affect members of a population regardless of population density (i.e. # of animals/area)-         flood-         fire-         pesticides-         change in climate or temperature-         loss of habitat-         drought

Density Dependent Factors – affect a population because of the density of the population

-         food shortage

- competion for mates

-         disease

-         introduction of an exotic species

-         increased predation

- competion for water and other resources