Chapter 10(404)

Ecosystems

p.318-334

• An ecosystem refers to all the animals and plants found in one place, and the way they all live together.

• Some animals belong to several ecosystems.

• In an ecosystem, the living organisms need energy to survive. They get this energy by eating the food in their environment.

Food Chains A food chain shows the relationships

between the living organism and shows who eats who.

The lettuce is eaten by the rabbit.

Feeding Relationships

• There are 3 main trophic levels.

• They are are producers, consumers, and decomposers

• Autotrophs are groups of organisms that can use the energy in sunlight to convert water and carbon dioxide into glucose (food).

• Autotrophs are also called producers because they produce all of the food that heterotrophs use.

• Without autotrophs, there would be no life on this planet.

• Ex. Plants and Algae

(p321)

• Organisms that do not make their own food

• Another term for heterotroph is consumer because they consume other organisms in order to live.

• Ex. Rabbits, Deer,...

First Order Consumers

• Eat ONLY eat plants, seeds and fruitsEx. – Cows, Elephants, Giraffes

Second, Third and Fourth Order Consumers

• Carnivores – eat ONLY meatEx. – Lions, Tigers, Sharks

Second Order Consumers….

• Omnivores – eat BOTH plants and animals

Ex. – Bears and Humans

Decomposers

• Decomposers – absorb any dead material and break it down into simple nutrients or fertilizers

• Decomposers are also called DetritivoresEx. – Bacteria and Mushrooms

Food Webs

• Most organisms eat more than just one organism

• When more organisms are involved, it is known as a FOOD WEB.

• Food webs are more complex and involve lots of organisms.

Transfer of Energy 404 (p.323)

• According to Antoine Lavoisier’s Law of Conservation of Energy “Energy is not lost or created; energy is transformed.”

• This law applies in the lab but also applies to ecosystems.

• When a zebra eats grass, it does not obtain all of the energy the grass has (much of it is not eaten).

• When a lion eats a zebra, it does not get all of the energy from a zebra (much of it is lost as heat).

• The two previous examples of energy transfer show that no organism EVER receives all of the energy from the organism they just ate.

• Only 10% of the energy from one trophic level is transferred to the next – this is called the 10% law.

• Energy moves from one organism to another when it is eaten.

• CHEMICAL RECYCLING is a natural phenomena. Producers take inorganic matter (ex.sun energy) and convert it to organic matter(ex.C6H12O6). Decomposers take this organic matter and convert it to inorganic matter (ex. nitrogen, phosphorus, potassium).

Trophic Levels

Producers- Autotrophs

Primary consumers- Herbivores

Secondary consumers-small

carnivores

Tertiary consumers-

top carnivores

E

N

E

R

G

Y

Biomass (404) (p.325)

• The total mass of the organic matter at each trophic level is called biomass.

• As you move up a food chain, both energy and biomass decrease.

• The transfer of energy from one level to another is very inefficient (10% Law).

Primary Productivity 404(p.326)

• PRIMARY PRODUCTIVITY of an ecosystem is the amount of new biomass generated by its producers.

• This is a very important because it represents the amount of energy available to the primary consumers and will directly influence the number of living organisms that live in an ecosystem.

• Primary productivity depends on several factors such as amount of light, amount of water, temperature, access to nutrients….

Disturbances (404)p.327

• Sooner or later, all ecosystems are subjected to disturbances such as drought, snowstorms, oil spills, flooding,….

• Natural disturbances: storms, forest fires, frost, heat waves,….

• Human disturbances: oil spills, littering, building large scale shopping centers,...

Ecological Succession (404) p.329

• After suffering a disturbance, an ecosystem will begin a series of gradual changes spread over hundreds of years to re-establish a state of balance. These series of changes is called ecological succession.

• We can estimate the area that a person takes up or uses to satisfy all their needs and to ensure the disposal of our waste. This is called our ecological footprint.

• To calculate our footprint we can use the formula described on page 330.

ECOTOXICOLOGY (466)

• Ecotoxicology is the scientific study of the harm that humans cause on the ecosystems of the Earth.

• Any substance or radiation that can cause harm to the environment is called a contaminant.

Types of Contaminants (466)

• Inorganic contaminants: lead, arsenic, mercury, phosphorus

• Organic contaminants: pesticides, PCB’s, benzene

• Microbial contaminants: Viruses and harmful bacteria

• Radioactive contaminants: Uranium, plutonium, radon

When a contaminant harms an organism, it is said to be toxic.

Toxicity depends on:• Concentration: The more concentrated a

contaminant, the higher the risk that it is toxic. (in Qc, the [ ] of lead in water must not exceed 0.01 ppm)

• The type of organism: Certain contaminants are toxic to some organisms but not to others.

• Length of exposure:The longer an organism is exposed to a contaminant, the greater the toxicity.

466

• Toxicity: is the degree to which something is able to produce illness or damage to an organism.

• Ex: Experiments have shown that 0.075g of Tylenol has toxic effects on rats.

• Lethal Dose: Represents a dose at which a given percentage of subjects will die.

• LD50 = a dose at which 50% of subjects will die.

Bioaccumulation (p.335) 466

• It is the tendency among certain contaminants to accumulate over time in the tissues of living organisms.

• In a food chain, when a trophic level feeds on a lower trophic level, the organism absorbs the contaminants that have accumulated.

• As you go higher up the food chain, there is a greater concentration of contaminants.

• This is called bioconcentration.

• Humans are at the top of food chains, so we are faced with high concentrations of contaminants.

Biotechnology (p.337)

• Pollution can be cleaned up through bioremediation or phytoremediation.

• We already know that bacteria and fungi are decomposers who break down organic matter into inorganic matter. This is called biodegradation.

• Bioremediation is when a polluted site can be cleaned up with microorganisms that decompose the contaminants.

Wastewater Treatment (p.339)

• Water is essential to many activities. In our home, water is used for various chores.

• After water is used in a household it is discharged and called wastewater.

• To treat wastewater, various biotechnological methods exist to treat and clean wastewater before returning it to the environment.