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Succession

Succession. Succession – orderly natural changes that take place in an ecosystem. There are two types. Primary succession. colonization of new sites by communities of organisms. Occurs where no life before. Starts with bare rock (often lava)→soil (dead organisms or transfer)

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Succession

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  1. Succession

  2. Succession – orderly natural changes that take place in an ecosystem. There are two types.

  3. Primary succession • colonization of new sites by communities of organisms. • Occurs where no life before. • Starts with bare rock (often lava)→soil (dead organisms or transfer) • First organisms to colonize a site are often lichens (fungus and photosynthetic organisms) • Larger plants over time replace smaller species until climax community reached.

  4. Pioneer species– first species/organisms to inhabit an area (usually small – example weeds) • Climax community – stable, mature community that undergoes little or no succession • Biome – large group of ecosystems with the same climax community (determined by climate)

  5. Bare rock → lichen → soil with small plants (weeds, mosses, grass) → larger plants (shrubs) → trees

  6. Aquatic ecosystems– will “fill in” with dirt over time to create a land ecosystem – if no manmade intervention primary succession.

  7. Secondary succession • changes that occur when a community is disrupted by natural disaster or humans. • Leads to new climax community. • Starts from soil → small plants → large plants • Examples – fire, flood, hurricane, abandoned farm

  8. Close relationships between organisms often exist • Many organisms living in the same environment are in a continuous battle for survival (predator vs. prey) • Other times the relationships among organisms helps them survive

  9. Sometimes there is a close, permanent relationship between organisms of two different species – this is called a symbiotic relationship • Def. – symbiosis – living together

  10. Several types of symbiosis • Parasitism- one organism lives off another and causes it harm – ex. tapeworm, fleas (+, -)

  11. Commensalism – one of the organism benefits while the other is not affected – ex. barnacles attached to whales (+, 0)

  12. Mutualism – both species benefit – ex. the bacteria E. coli in human intestines (+, +)

  13. Populations and Predator Prey • Population – group of organisms that belong to the same species and live in a given area • If conditions are ideal for growth and reproduction there will be a rapid increase in population that continues to accelerate until some factor stops it

  14. Produces an exponential growth curve

  15. Most organisms go through a number of growth phases which are represented on a logistic growth curve E D C B A

  16. There are 5 distinct phases on a logistic growth curve • A – only a few individuals introduced to the environment • B – period of very rapid growth (mimics exponential growth) with few organisms dying and many being born birthrate > deathrate • C – speed of population growth slows (still growing just slower) • D – population grows more and more slowly **In C and D birthrate slowing and deathrate increasing • E – steady state – on average birthrate = deathrate – so zero overall growth – reaches carrying capacity

  17. Carrying capacity – optimum number of organisms of a particular species that can be supported by that environment • Once a population reaches its carrying capacity, factors will keep the population from growing faster

  18. These factors are density dependent limiting factors (ex. lack of food and water, overcrowding (crowding and stress), predation, parasitism, competition) and work best on a large and concentrated population • competition – populations struggle with each other for food, water, space, sunlight etc. so that the number of organisms directly related to the amount of resources

  19. predation – almost every species serves as food for another species • predator-prey relationship – organisms become accustomed to each other strengths and weaknesses and try to take advantage of each other

  20. if an organism is introduced into an area where it has no natural predator it will grow uncontrolled until some factor stops it (ex. no more food) ex. rabbits in Australia reindeer in Michigan

  21. parasitism – parasites act like predators by living off of their host and weakening it • crowding and stress – most organisms need a certain amount of space (territory) and if too many in too little space they will fight with each other

  22. There are other factors that control populations that don’t depend on the number of organisms – called density independent limiting factors (ex. seasonal weather such as a freeze, flood or hurricane; earthquakes, fire)

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