why are short food chains better?

As energy is lost at each tropic level, lesser energy is available for the organism at the next level, the the food chain . thus a shorter food chain is more efficient than a longer one as more energy is available to the final consumer as less energy is loss to the surroundings

ECOLOGICAL PYRAMIDS

http://www.envf.port.ac.uk/geog/teaching/environ/sect2-3c.htm
http://resources.edb.gov.hk/biology/english/images/environment/pyramid.gif


It allows us to compare the tropic levels in a food chain. There are three types.
Pyramids of numbers
This allows us to compare the number of organisms present in each trophic level at a particular time.

In this pyramid, all the numbers at each trophic level are counted regardless of size and stage development.
http://www.sturgeon.ab.ca/rw/Pyramids/pyrakind.htm







Pyramid of biomass

This allows us to compare the mass of organisms present in each trophic level at a particular time

The pyramid of biomass is constructed based on the dry mass of organisms in each trophic level at any one time. This is called the standing mass of organisms.
The unit of biomass is dry weight of organic matter( per square metre)

pyramid of energy

The total energy at various trophies levels of a food chain represented in a pyramid is called a pyramid of energy.

This is constructed based on total energy level in each trophic level over a certain period of time . down a food chain as energy is transferred from one trophic level to the next, energy is loss. Which is why a this pyramid is always broad at the base and narrow toward the top .


http://resources.edb.gov.hk/biology/english/images/environment/pyramid.gif

Relationship between predator and prey

http://www.tiem.utk.edu/bioed/bealsmodules/pred-prey.gph1.gif
Let me first explain the definitions.

Predator : A predator is an organism that kills and feeds on other organisms
Prey: the organisms that are eaten are called prey.

An increase in the population size would provide more food for the predator, thus the increase in predator will in turn result in a decrease in population of the prey as more predator feed on them and eventually the predator population will decrease as well, and there would be a rise in the prey population again.
This cycle repeats itself but the average size of the prey population is greater than that of the predator population.
Two predators with the same prey

The land snail is eaten by fishes and frogs

food chains and food web

Food chain− series of organisms through which energy is transferred in the form of food
grass→ chicken→ snake→ man

Foodweb
−food chains interlinked
http://www.vtaide.com/png/foodchains.htm

How do energy and nutrients flow through ecosysytem?

The organisms in an ecosystem consist of produces , consumers and decomposers . energy is passed from the producers to consumers to decomposes.

Produces
Produces converts the energy from the sun to chemical energy and stored as food during photosynthesis thus they are either directly or indirectly affect other organisms as they provide energy and oxygen.
Consumers
they feed on other organisms thus all animals are consumer. Herbivores are primary consumers while carnivores are secondary consumers and carnivores that feed on carnivores are tertiary consumers.
www.longleat.co.uk

Decomposes
They achieve their energy by breaking down dead faeces and excretory products

http://infohost.nmt.edu/~klathrop/East%20Mountain%20High%20School%20Virtual%20Nature%20Trail.htm

no organism is independent

Organisms rely on one another , they are interdependent on each other . the populations in a community live interdependently , any change one population affects the other populations and eventually the whole system.

physical features of environment which affect organisms

1) light intensity: It affects the distribution and growth of both plants . green plants grow in areas where there are sufficient light .for survival the plants have got adaptations which enable them to get light .there are also some plants which are adapted to screen off excess light.
2) Temperature: it affects rate of reactions of enzymes , which control metabolic activities of plants and animals .many organisms are not able to tolerate extreme temperature. This is hazardous as too high or low a temperature is able to kill an organism. some flowering plants are adapted to change in seasons as they have special attributes like storing food during winter
3) Amount of available water: this is one of the most essential factors as no organism is able to sustain without water for a prolonged period of time. This factor is also dependent on amount of rain and pattern in which rain falls the whole year. Only those organisms with certain adaptation are able to survive in places where water is scarce. Xerophytes reduce their rate of transpiration by shedding leaves or reducing leaves to spine.
4) Oxygen content: most organisms are aerobic thus they require oxygen for respiration , and are not able to survive in places with a lack of oxygen. However there are a few exceptions . these organisms possessed unique adaptations so as to get oxygen. Like mangrove plants which have pneuatophores.
5) Salinity: this refers to the salt concentrations of water and soil . the organisms living in sea have adaptations , to prevent water loss from body . amoeba have contractile vacuoles to prevent excess water in body which enters by osmosis
6) Ph: this term refers to the acidity or alkalinity of a solution . the ph in the habitat affects the organism as some species are ph sensitive , and drastic change in ph could cause death. Some fishes adapt by secreting the excess salts taken by the body through the skin