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Ecology Year 12 What is ecology? • the scientific study of the distribution and abundance of living organisms and the interactions among and between the organisms and their environment http://en.wikipedia.org/wiki/Ecology Ecosystem • natural unit consisting of all plants, animals and micro-organisms in an area functioning together with all the non-living physical factors of the environment http://en.wikipedia.org/wiki/Ecosystem Components of an Ecosystem • All systems are made up of both biotic (living) and abiotic (non-living) components • In any ecosystem many factors exert an influence on living organisms and their environment. These factors can be broadly classified integrating or limiting Habitat • The particular place an organism lives is called its habitat. • Each habitat is likely to be the home for several species. • Usually these species will not be able to survive in other habitats where conditions can be quite different but some organisms can tolerate a range of conditions and can therefore live in a variety of habitats, eg flax. Niche • Within a habitat each species will have a special role or way of living. Generally this is related to how the species obtain food, eg as a producer, predator etc. • The role of a species in a habitat is called its ecological niche. • The area which the organism can occupy is called its fundamental niche. • Sometimes however due to competition the niche becomes smaller, this is the realised niche. Factors that affect organisms in their habitat Biotic Abiotic Predators Parasites Food supply Human influence Competition Light intensity Salinity Tidal Exposure Day Length Rainfall Humidity Temperature Wind pH levels Wave action Carbon dioxide Tolerance & Limiting Factors • The environmental factors that can affect an organism do not remain constant • For a species to be able to survive in its habitat it must be able to tolerate variation in these factors • If it cannot, members will either die or migrate to a more suitable habitat • A species is usually adapted to tolerate a range of variation in most environmental factors • The range in which it thrives is called the optimum range for that factor • When an environmental factor exceeds the tolerance limits of an organism, the organism suffers stress Tolerance & Limiting Factors cont… Tolerance & Limiting Factors cont… • Organisms can adjust their tolerance limits. This is called acclimation. It can be either: – Temporary – such as developing a suntan to prevent harmful UV rays affecting skin cells – Seasonal – such as the thick coat that domestic animals such as cats develop in autumn to withstand winter conditions. Liebig’s Law of the Minimum • The functioning of an organism is limited or controlled by whatever essential environmental factor/s is present in the least favourable amount Gause’s Competitive Exclusion Principle • “No two species can occupy the same ecological niche in the same habitat for an indefinite period” Gause’s Principle • This shows that although both species appear similar, they do not have the same Niche requirements • Competition between species within habitats that overlap may be reduced by character displacement Biological Relationships • The relationships between the organisms making up a community are sometimes based on cooperation, but more often on competition or exploitation. If a relationship is between members of the same species it is described as intraspecific. Relationships between members of different species are inter-specific. Group Co-operation • Some animals rely on intra-specific co-operation. • Members work together to ensure mutual survival • Many groups have developed complex social behaviour eg: hunting in packs, shared rearing of young Inter-specific Competition • Competition between different species in a community • Often over resources • More specifically there are feeding relationships Adaptations • All organisms inherit characteristics that increase their chances of survival. • These are commonly divided into three categories: – Behavioural – how the organism behaves – Structural – the shape and size of an organism – Physiological – the working of an organisms body Population Attributes • • • • • • • • Natality: birth rate Mortality: death rate Net Migration Rate Density Age Structure Distribution Survivorship Curves Population Growth Curves Population Counting • Can be difficult as they often cover a large area • Measuring methods should be chosen in accordance to what is being measured • Sampling methods include: • • • • • Quadrats Counting Line transects Belt transects Mark and recapture Food and Energy • The main interaction between organisms involve food • Green plants produce their own food via photosynthesis (producers) • Animals eat other plants and animals (consumers) • Food chain and food webs show the interactions • Energy flows along the food chains Food Chains PRODUCERS Producer Photosynthetic plant CONSUMERS Primary Secondary Tertiary Herbivore Browses or grazes plants 10 Carnivore Eats herbivore 2o Carnivore Eats 1o carnivore Food Webs • Groups of food chains joined together • Represent entire feeding relationships in community • Show that individual organisms can exist in more than one trophic level Energy and Food • Ecosystems rely on a regular supply of energy, this comes mainly from the sun • Radiant energy arrives as heat and light and is converted into chemical energy in food molecules by plants in photosynthesis • Only 1-5% is used this way • The energy is then passed along the food as one organism eats another, flows in one direction • About 10% of the stored energy in a trophic level gets stored in the tissue of the next • Decomposers release the remaining energy as heat Nutrient Cycling • Nutrients cycle through an ecosystem • Carried out mainly by decomposers and detritivores • The chemical elements needed in significant amounts are: – – – – Carbon Hydrogen Oxygen Nitrogen Community Patterns • Variations in habitat conditions can cause changes in communities • The three main patterns of change are: – Succession – Stratification – Zonation