Resumen Ecology

Ecology= study of organisms within their environment, including the way in which organisms interact with each other and with the non living parts of the environment. Energy enters as light, is transferred from one organism to another as chemical energy and returns to the environment as heat.

Energy transfers between organisms :

Living cells require energy for livin’. The immediate source ofenergy is always ATP which is produced by respiration. Respiration transfers energy from other organic molecules, to ATP molecules.

The energy in these organic molecules is called chemical energy. The original source of almost all of the chemical energy is the light energy, captured by green plants and other photosynthetic organisms. These organisms are called producers. Animals and fungiobtain their supplies of chemical energy by feeding on other organisms. They are consumers. Herbivorous animals which feed on plants, are called primary consumers. Carnivorous animals, which feed on herbivores are secondary consumers. Carnivores which feed on sec. consumers are called tertiary consumers. Most bacteria and fungi which feed on dead organisms or waste organic materials are calleddecomposers.

The level at which an organism feed in this sequence of energy transfer is called a trophic level.

A diagram which shows how energy passes from one organism to another is called food chain. A food web is a combination of different food chains because organisms are used to eat more than one kind of organism. There are some organisms which feed as primary consumers and higher orderconsumers, these are called omnivores.

Energy losses in food webs:

As energy is transferred from 1 organism to another in a food web, a large proportion of it is lost to the surrounding environment. The producers which convert chemical energy from light energy use it fo fuelling active transport. Some of the energy is stored by the producers in chemicals which make up their bodies.

However,the herbivores only receive 10% of the energy in the producers. This percentage is larger in aquatic food webs. The herbivores will use this energy to move, active transport, and a high proportion of this energy will be lost to the environment as heat. Only a small proportion is transferred to the carnivores. This pattern continues along the food chain, with approx. 90% of the energy being lost ateach transfer.

Pyramids of numbers, biomass and energy:

Pyramids can be drawn to represent the proportions of energy which are lost in a food web. Producers at the bottom, with higher trophic levels on top. The area of each box can represent numbers, biomass or energy.

Productivity:

It is the rate of energy passing through a trophic level over a period of time.

Materials required byliving organisms:

Living organisms require more than a supply of energy -> materials from which to build their bodies. Most common: carbon, oxygen, hydrogen and nitrogen. Animals obtain most of the atoms from which they build their bodies in the form of organic molecules. Plants are able to make use of inorganic sources of these atoms, CO2 from the air and H20 from the soil for providingcarbon, oxygen and hydrogen to make carbohydrates and fats. These atoms are passed from organisms to organism, being reused. This cycle is called the atom cycle.

The carbon cycle: (ver cuadros)

The atmosphere contains carbon dioxide. This is present in only very small proportions, 0.04% in air. Plants, algae and blue-greens take carbon dioxide from air and incorporate the carbon intocarbohydrates (organic compounds). Large quantities of carbon are locked up inside tissues of trees and other plants. Animals obtain their supply of carbon by eating plants or by eating other animals. Not all plants or dead animals are used as food sources. Waste materials and dead bodies are used as food source by decomposers. Such as fungi and bacteria. These organisms digest the organic substances and...