ECOLOGY - FOOD CHAIN AND WEB

An ecosystem is a community of living organisms interacting with the non-living components of the environment (air, water, mineral, soil). The living component is referred to as biotic component and the non-living component is the abiotic component. There is flow of energy through the ecosystem. The energy comes from the sunlight which is used in the process of photosynthesis. The energy trapped in the plants is transferred to other animals through feeding interactions. Once the plants and animal die, the energy is released back into the environment through the process of decomposition.

A population is defined as a group of organisms of the the same species, example, dog or cat population.

A community is a group of different population living within a specific area.

A biosphere  is the part of the earth where living organisms exist.

This is a link to more info on the ecosystem

FOOD CHAIN AND FOOD WEB

 A food chain is a simple linear diagram that shows organisms feeding and being fed upon by another organism.
 It looks like this: Organism 1 -----> Organism 2 ------> Organism 3 ------> Organism 4
This means that Organism 1 provides food for Organism 2, and Organism 3 provides food for Organism 4.

This is an example:



It is made up of producers and consumers. Decomposers such as bacteria are important in the food chain but they are not shown on the food chain.

Producers are the first in any food chain. They are the plants. They produce their food using the energy from the sun via photosynthesis.

Consumers can be classified as primary consumers, secondary consumers, tertiary consumers, and quartenary consumers, etc.

• primary consumers - They are the first to feed on the producers.
• secondary consumers - They feed on the primary consumers
•  tertiary consumers - They feed on the secondary consumers
• quartenary consumers -They feed on the tertiary consumers

Producers are also known as autotrophs because they can produce their own food.

Consumers are also known as heterotrophs because they cannot produce their own food.

Consumers can also be classified as herbivores, carnivores, or omnivores.

•  herbivore - Feeds on plants
• carnivore - Feeds on other animals
• omnivore - Feeds on both plants and animals

A food web is made up of a network of food chains. It is a more complex feeding relationship and interactions. This is an example of a food web.



Start with the producers (plants) and follow the arrows to show the feeding relationships. One organism can be a source of food for more than one organism. In the example above, grass provides food for rabbit which then is feed upon by the hawk. As you can see, the hawk also feeds on the field mouse and sparrow. You can come out with so many relationships in the above diagram.

As you study, think about the effect of  eliminating an organism from the food chain or web on the other organisms.

TYPES OF MIXTURES

Mixtures

Mixture Definition: A mixture consists of two or more substances which have been combined such that each substance retains its own chemical identity.That is,  a combination of substances which are not chemically joined together. The key characteristics are:

• They have the same properties as their components
• There is no fixed proportion between the components
• The components can be separated from the mixture

Examples

• A mixture of sugar and salt
• Air is a mixture of gases with nitrogen, oxygen, carbon dioxide, etc.
• A mixture of flour and sugar.
• Salt and sand mixture
• Salt and water

Types of mixtures: There are three types of mixtures.

• Solutions
• Suspensions
• Colloids

Solutions

Definition: A solution is a mixture in which other substances (solutes) are dissolved. The dissolve substance is known as the solute and the substance that does the dissolving is known as the solvent. For example, in a salt solution, the water is the solvent and the salt is the solute.The components in a solution may not be separated from the solution by leaving it to stand or by filtration. Another example is sugar in water.

Degrees of saturation: A solution can be unsaturated, saturated or supersaturated.A solution is unsaturated if it can dissolve more solute at a given temperate. A solution is saturated if no more solute can be dissolved with temperature remaining constant. Note that changing the temperature will affect the solubility. The solubility increases with temperature. A supersaturated solution is the one in which no more solute can dissolve no matter the temperature increase.

Suspensions

A suspension is a mixture of liquids with particles of a solid which may not dissolve in the liquid.The solid may be separated from the liquid by leaving it to stand or by filtration.

Examples

• Sand in water

Colloids

These are homogeneous, noncrystalline substances consisting of large molecules or particles of one substance dispersed through a second substance. 

Examples of colloids are gels, sols, and emulsions; the particles do not settle and cannot be separated out by ordinary filtering or centrifuging like those in a suspension.

Emulsions

This is a fine dispersion of minute droplets of one liquid in another in which it is not soluble or 

miscible. That is, a colloidal suspension of one liquid in another. Emulsions may be temporary or permanent. Temporary ones separate when left to stand for some time.

Examples: Oil and vinegar (temporary emulsion), Mayonnaise (egg yoke in oil) (permanent emulsion)

Certain substances act as emulsifiers. They help two liquids to come together and stay together. Lecithin in the egg yolks acts as emulsifier. It is a fatty substance soluble in both fat and water. In mayonnaise, It combines readily with both the egg yolk and the oil or butter, essentially holding the two liquids together.

Sol

These are colloidal suspensions of small solid particles in a continuous liquid medium. Examples include blood, pigmented ink and paints. If the dispersion medium is water, the colloid is referred to as a hydrosol and if air, an aerosol.

Gels

Gels are colloids in a more solid form than sols. The disperse phase has combined with the dispersion medium to produce a semisolid material. An example is jelly.

QUESTIONS FOR THE DAY

 Two vehicles with masses 1500 kg and 3000 kg ,respectively, are moving in the same direction and with the same speed on a highway. Both drivers apply their brakes at the same time and both vehicles begin sliding. If the coefficient of kinetic friction is the same for both vehicles, which vehicle stops first?

A. The 1500 kg vehicle

B. The 3000 kg vehicle

C. Both vehicles stop at the same time

D. More information is needed to answer this question.

2. If a 40-kg child lifts a chair from the floor unto a table whose top is 1 meter above the floor, and a 70-kg adult lifts the same chair onto the same table, who does more work?

A. The child

B. The adult

C. They both do the same work.

D. More information is needed to answer this question.

Answers: 1. C   2. C