1.Ecosystems and environmental factors.Ecosystem:is a system formed by a group of organisms of different species(or biocenosis),the environment in which they live and its physical/chemical characteristics(or biotope) and the interactions.Types of environmental factors.Abiotic factor:are the physical/chemical components of an ecosystem(temperature,light,water).Biotic factors:interactions produced in the biocenosis(wolves when they hunt as a pack).Tolerance ranges and limiting factors:an environmental factor is limiting for a species when its value determines the abundance or distribution of the species.2.Abiotic factors.Temperature:with a few exceptions,living things carry out their activity at temperatures between 0-50·C.Availability of light:sunlight is essencial for all autotrophic organisms to perform photosynthesis and,therefore,to allow them to inhabit a biotope;the absence or scarcy of autotrophic organisms also limits the presence of the organisms also limits the presence of the organisms that feed on them.Availability of water:is the most abundant component of living things and is essencial for plants to perform photosynthesis.Some adaptations.Availability of light:long-day plants which are more of light and short-day plants which are less of light,and neutral plants that are not influenced.Availability of water:In desert areas,in order to avoid losing water,many bushes have small leaves and are covered with impermeable substances.Other plants turn their leaves into spines,while others store water in their stems and leaves,many animals are nocturnal.In tropical forest,there is a lot of water and the trees have large leaves with sharps.To temperature:In low temperatures animals hibernate or migrate,are endotherms(birds and mammals that can control their body temperature),also have insulation.In high temperatures:sweating or panting.Abotic factors in aquatic environment.A photic or sunlight zone is generated(at some 200m from the surface)and an aphotic,or dark,zone(from 200m onwards).The temperature varies according to latitude.Life in aquatic emvironment.Upwelling:are isolated places where marine currents cause nutrient-rich water to rise up.Oceanic areas.Distance from the coast.Neritic zone:water is shallow,well lit,rich in nutrients and in constant movement.Oceanic zone:few nutrients in its waters.Zones by depth:Pelagic zone:sunlight zone,stretches to a depth of 200m and contains species of plankton and nekton,such as dolphins.Bathyl zone:between 200-2000m deep,and there is little light;it is inhabited by species of nekton,like sharks.Abyssal zone:below 2000m and is completely dark;there are benthos organisms(echinoderms) and nekton(flat fish).

3.Biotic factors: Biotic relationships or interactions are those that are established between individuals in a community or biocenosis.They can be interspecific or intraspecific. 3.1 Intraspecific interactions are those which take place in the biocenosis between organisms of the same species. Intraspecific competition: competition by different reasons , such as fighting for territory and hierarchy. Fighting for territory or space in which the animal finds foods,mates,shelters. Establishing dominance hierarchies among the individuals in a group. Associations: Family associations: individuals that are related to each other.Parental, if both parents and the offspring are present: matriarchal, formed by the mother and the offspring: or filial, if only the offspring from the association. Gregarious: individuals not necessary related join with a specific purpose. Colonial associations: are formed by individuals that reproduce asexually and remain close to their parent their whole life, polyps. State associations: societies, there is a division of tasks, from a hierarchy and exhibit some anatomical and psychological differences. 3.2 Intraspecific competition: (-,-) is produced when two species use the same limited sources. Non competitive intraspecific interactions: Predation:an organism , the predators captures and kills the prey for food. Parasitism: the parasite, lives off another, the host feeds off without causing it to die. Commensalism: one species benefits from uses any excess food or secretions of the host , without affecting it in any way . Mutualism: different species in which both benefit. If both organisms are very closely connected, the relationship is known as symbiosis. 4.Ecological balance. Primary succession: Primary succession takes place in a biotope where there is originally no life, such as a newly formed volcanic island. Primary succession stage: Pioneering species colonise the initial biotope.Microorganisms, lichen, mosses establish themselves the bare rocks. New population settle. Bushes and larger consumers. The complexity of the biocenosis increases. complex relationships. The climax stage is reached. the ecosystem has become balanced and adapted. Self- regulation: Dynamic equilibrium thanks to self-regulation mechanisms. The self-regulating mechanisms that enable an ecosystem to be balanced and collectively known as homeostasis.

Tema2 -1. A trophic level consists of all the organisms in an ecosystem which feed in the same way.-Producers are autotrophic organisms that perform photosynthesis and use solar energy to transform inorganic matter into organic matter. They are green plants, algae and some bacteria. They form the first thophic level of the ecosystem. –Consumers are heterotrophic organisms that eat other living things. They can be: Primary consumers (insects , rabbits, elephants…) Secondary consumers (pigeons, shrews…) Tertiary consumers (falcons, tigers, lions,leopards…). Omnivores feed on both producers and other consumers. Humans are omnivores. Decomposers are heterotrophic organisms that obtain their nutrients by decomposing dead organimsm (mainly bacteria and fungi) Detritivores are consumers that feed on dead matter. They can be -carrion feeders that feed on fresh carcasses (vultures). –Saprophages which feed on the remains of plants or very decomposed carcasses. (earthworms) -2.Matter flows in a closed circuit while energy flows in an open circuit. The transfer of energy: energy flows in an open circuit meaning that part of it is lost in each tranfer from one trophic level to another. It is believed that only 10% of the energy stored in a trophic leve lis transfered to the next. (the 10% law). -3. Biomass is the amount of organic matter created in each of the trophic levels. -4. Energy pyramids show the energy available in each trophic level. They always show energy decreasing from bottom to top because of the 10% law (each trophic level has only 10% accumulated energy of the previous level at a specific time) –Biomass pyramids provide information about organic matter accumulated in each trophic level oer unit of surface area) Generally each step is narrower tan those below it. However the trophic level steps sometimes become wider as they get higher (inverted pyremid). –Number pyramids are those with steps that are proportional to the number of individuals found in an ecosystem, per unit of surface area, or biotope volumen,at a specific time.