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Ecology AS 2.4 Investigate an interrelationship or pattern in an ecological population or community – 3 credits (I) AS 2.5 Describe concepts and processes relating to ecology – 3 credits (E) US 6311 Biodiversity – field work – 3 credits (I) Species definition A species is a group of organisms that can interbreed and produce fertile offspring. They share the same gene pool. A gene pool of a species is the sum total of characteristics that are found within the species. Species are made up of individuals that share the same basic structure, physiology, and behaviour. These are inherited characteristics that we call adaptations. The life history of a species also reflects its adaptations (struggle to survive). Ecological niche The niche of an organism is it’s role or way of life (job or profession). Eg a crab on the seashore is a scavenger. This is different than its habitat, which is the place where an organism lives. In human terms it is an organism’s address. Eg a crab’s habitat is the mid tidal zone on the rocky shore – and perhaps a certain rock The habitat should be where the organism has access to resources, like food, water, space (to live), and members of its own species (mate). Adaptations – (behavioural, physiological, structure and life history) describe what it needs to survive • Paddle crab on sandy shore (predation) – behaviour hold up claws to defend, claws structure, paddles to swim, dig • Barnacle on rocky shore (space) – needs a way of sticking physiological • Kauri tree in forest (other trees) – behaviour grows tall for light • Kiwi in bush (predator) – hides in hole - behaviour • Paramecium in fresh water – contractile vacuole physiological • Shark in ocean (feeding) – teeth structural • Neptune necklace (seaweed) – fix itself to rock physiological • Fantail (eats insect in the air) – structural wings, ability to hover - behaviour • Oyster on rock (predation) – structural hard shell. Life history – produces vast quantities of eggs • Whelk (carnivorous shellfish) – way to cut into shells structural Relationship between organisms and their environment The environment includes all those factors, both living (biotic) and non living (abiotic), that affect the lives of organisms. Abiotic Factors •Light (photo) - duration •water (hydro) - salinity, speed, humidity •temperature (thermo)- average, range (eg. rocky shore has extremes) •chemical (chemo) - CO2, O2, pH, nutrients •touch (thigmo) - solid object •gravity (geo) - orientation in space eg roots go down •Sound •Pressure •Substrate •Wind Biotic factors Interspecific (between two or more species) •competition for food, water, space, light •predator / prey •succession - replacement of one species by another •plant / animals Intra specific (within a species) •competition- for resources, for space, for mates, light, food •reproduction - pair bond, courtship •Aggressive - territory, hierarchy •Cooperation feeding, mating, defence Populations A population is a group organisms of the same species that live in the same habitat. Measuring Populations It is difficult to count all the members in a population, so a sample is taken. The sample should be representative of the population. To measure the size of a population of mobile organisms, markrecapture is used. Some organisms are captured, labelled (ear tags, leg bands) and then release them. Later another sample is taken and population size is calculated from this equation Size of pop = Total sample 1 x total in sample 2 ___________________________ Number marked recaptured in s2 Some population (rare or shy) sizes are estimated from signs of their presence (eg footprints, tracks, droppings etc). Transects A transect is a line placed across a habitat. The transect is divided up into intervals and at each interval the population is sampled. Transects are used where the distribution of the species is affected by some environmental factor, such as tidal movement. A belt transect (metres wide) can be used in a forest where organisms are very large. Quadrat A quadrat is a square frame used to isolate an area so the number of organisms in that area can be counted. The bigger the organism being counted the bigger the quadrat. Quadrats are often used along transect lines. If not they should be thrown down randomly – this can be done by dividing the habitat into a grid and randomly selecting sample sites. Community All plants and animals have two driving forces that make them what they are (not human). These forces or natures relate to the drive to survive and the drive to reproduce. An individual animal does not have to be the best, the fittest, the strongest or the longest living to make its mark on the world. It only has to survive to reproductive age and have reproductive success. An animal or plants genetic makeup means its whole orientation is to survive and reproduce and this is not selfish – it is nature. All biological interactions demonstrate this nature. Some community patterns Zonation Zonation results from the constant change of some environmental factor across a community. On the rocky shore the zones are created by the tides. It is the exposure to air that limits an organism’s distribution. As the environmental conditions exceed the tolerance limits of a species, the zone of distribution for a species finishes. Another species, adapted to the new conditions, forms another zone until it to can no longer cope with conditions. There is usually an optimum range where an organism is dominant. In environmental zones where the organism is under stress other species better suited will out compete them. Competition between species where they meet means zone are usually quite distinct eg tubeworms or oysters on the rocky shore. On the rocky shore it is the sessile organisms that dominate. Zone distributions are often portrayed on kite diagrams. These are obtained by taking quadrat samples along a transect line across a community. Succession Succession is the change is species composition in an area over time. During succession, one species starts to grow and modifies the environment so another organism can grow in its place. This cycle continues until a climax community is established. Primary succession differs from secondary succession in that it occurs in an area that has had no previous vegetation (e.g. a larva flow like Rangitoto Island) where as secondary succession takes place in an area that has a soil layer but has been cleared for some reasons (e.g. by fire) Ecology Energy Flow Food chains show the flow of energy through an ecosystem. For example on the rocky shore algae that settles on rocks is scrapped off by snails which in turn are eaten by oyster borers which are eaten by birds Algae > topshell > oyster borer > sea bird Producer – primary consumer – secondary consumer 3rd trophic level 1st trophic level - 2nd trophic level In reality feeding relationships are more complicated. A food web shows all the feeding relationships in an ecosystem. Energy can only go in one direction and it is passed from one trophic level to the next. Biodiversity The biodiversity of an ecosystem comprises the sum total of different types of species found within. The variety of life in all its forms, including ecosystem diversity, species diversity and genetic diversity, and their relative abundance in particular habitats. SWOT (strengths, weaknesses, opportunities, threats) analysis of biodiversity in NZ. S (of increased ) • Greater tourism • Healthier ecosystems – more complex food chains • More stable to change (storms, pollution) • Less extinction W (of decreased biodiversity) • More vulnerable to change • More extinctions • Unhealthy O (of increased biodiversity) • more habitats and niches • greater use by humans (manuka experiment) T (to biodiversity) • pests (introduced species like possums, stoats, rabbits) • people overfishing or overfarming or making money at the expense of future planning.