TEMA 5

UNIT 5: BIOSPHERE AND ECOSYSTEMS

• INDEX
• The Earth : a complex system.
• Structure of ecosystems.
• Dynamics of ecsystems.
• Adaptation of organisms.
• Evolution of ecosystems.

BIOSPHERE

• 
• It refers to the subsystem of the Earth which is made up of all the living things which inhabit our planet and all the relationships between them.
• It is the part of the Earth that supports life.
• The top portion of the Earth crust - Geosphere.
• All the waters on Earth - Hydrosphere
• Surrounding by the Atmosphere

Slide 3

Slide 4

Slide 5

ECOSYSTEMS

• - An ecosystem is a natural system, made up of a group of living organisms (Biocenosis) which interact with one another and with the physical enviroment or biotope, that they inhabit.
• - Physical enviroment: precipitations, humidity, light, wind, weather, temperature etc.
• 

BIOTOPE

• - Are the natural physical surroundings of an ecosystem including its physical and chemical properties (Abiotic factors)
• 
• Legenda: NON-LIVING ORGANISMS

BIOCENOSIS

• - Set of populations of different species within an specific area.
• Biocenosis = community.
• 
• Legenda: LIVING ORGANISMS

LEVELS OF ORGANISATION

• 1. SPECIES
• Group of similar organisms which can reproduce with one another and produce fertile offsprings.
• 

LEVELS OF ORGANISATION

• 2. POPULATIONS
• The individual organisms of a single species which inhabit a specific area make up the populations.
• 

LEVELS OF ORGANISATION

• 3. COMMUNAITY OR BIOCENOSIS
• A group of populations whch live together in the same ecosystem form a community or biocenosis.
• 

ECOLOGY

• It is the science that studies ecosystems.
• 

ABIOTIC FACTORS

• DEFINITION:
• They are the variables of the physical enviroment that affect living beings in term of its survival and distribution. (Tolerance limits and adaptations)
• 

ABIOTIC FACTORS

• TEMPERATURE
• Freezing occurs below 0ºC and over 50ºC, proteins that form part of living things lose their natural structure.
• Aquatic enviroments have usually a constant temperature, while in terrestial enviroments, temperature changes a lot.
• It affects reproduction (eggs and seeds development)
• 

ABIOTIC FACTORS

• LIGHT
• For plants, light is essential to perfom photosynthesis. It is different for light to penetrate on aqutic enviroments and it can only enter until certain depth.
• 

ABIOTIC FACTORS

• HUMIDITY
• Water is essential for all living things. When the humidity of the air is very low, orgnisms fight against dehydratation throught adaptations.
• 

ABIOTIC FACTORS

• SALINITY
• The concentration of salt in water. In aquatic enviroments, water can be freshwater or salt water depending on the amount of salt it contains.
• 

INFLUENCE OF ABIOTIC FACTORS

• The influence of abiotic factors can be more or less intense depending on the enviroment.
• -Terrestial enviroment: more affected by temperature and humidity
• -Aquatic enviroment: more affected by light and salinity.
• 

TOLERANCE LIMITS

• The maximum or minimum values of a variable which species can tolerate.
• When variables exceed these limits, organisms cannot survive. In this case, the factor is called - limiting factor.
• -In order to survive, living things adapt to th enviroment.
• -Adaptation is the progressive adjustment of a species. The special conditions of the enviroment it lives in.
• 

TYPES OF SPECIES

• EURYTOPIC SPECIES: are undemanding in relation to the values of a given enviromental factor. Their tolerance limits are wide and their ecologicak amplitude is high. "Generalist" species with a wide geographical distribution.
• STENOTOPIC SPECIES: are highly demanding in terms of the vlues of given enviromental factor. Their tolerance limits are narrow and their ecological amplitude is low. "Specialist" species whose geographical distribution is low.

BIOTIC FACTORS

• -Are those that will influence the distribution and abundance of living things.
• -There are 2 types: intraspecific relationships (organisms of the same species.) and interspecific relationships (with organisms of different species.)
• 

INTRASPECIFIC RELATIONSHIPS

• 
• Legenda: CASTES: (permanent association that is established among the members of the same species. They include labour divisions (morphological differences among individuals. (ants, bees etc) TERRITORIALITY: several members of the same species cannot ocupy the same territoty, so to avoid this, they fight.

INTERSPECIFIC RELATIONSHIPS

• 
• Legenda: MUTUALISM, COMMENSALISM, SYMBIOSIS, COMPETITION, PREDATION, PARASITISMS.

TROPHIC LEVELS

• -Are those organisms which share the same kind of food.
• -The 1st level is made up off consumers: autotrophic organisms which consume matter with low energy from the soil and the atmosphere. The majority of them are photosynthesisers, they ue light as their source of energy.
• -All organisms, both producers and cosumers, respire in order to acess the energy stored in the form of chemical bonds in nutrients.
• 

FOOD CHAIN

• -Linear sequence of organisms of different trophic levels in which each organisms consumes the preceding one. Several interlinked food chains form the food web of an ecosystem.
• 

FOOD WEB

• Are made up of food chains. All the interactions in the ecosystem. We have more information of how a structure in an ecosystem is working.
• 

ECOLOGICAL PYRAMIDS

• They are graphic represetations of the general structure of an ecosystem. They are organised into trophic levels and producers always form teh base layer. Above them are the primary consumers, then the secondary sonsumers and finally the tertiary consumers.
• -The trophic levels are represented in the form of superimposed bars which always have the same height and whose width is appropiated to the value of the variable they represented, either the number of individuals, the biomass or the energy.
• They help us study the structure and fucntions of ecosystems using trophic parameters.
• 

INVERTED PYRAMIDS

• Is when they are narrower at their base (tree at the base and bacteria at the top level)
• 

BIOMASS PYRAMIDS

• Is when producers reproce rapidly in order to feed higher levels.
• 

BIOMASS

• Is the amount of organic material per unit of areo or volumen in each trophic level.
• 

PRODUCTIVITY

• Energy flow. Amount of biomass that is generated in an ecosystem in a set period of time.
• 

ENERGY AND ECOSYSTEMS

• -An ecosystem needs matter and energy to work: matter is recycled in cycles while energy is constantly entering as light (through producers) and leaving as heat.
• .The 10% rule states that, on average, only 10% of the energy consumed by living things from the trophic level below is stored as biomass. The remaining 90% is used up in cell respiration or expelled.
•