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Interactions within Ecosystems

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R Abetria

on 18 September 2013

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Transcript of Interactions within Ecosystems

Interactions within Ecosystems

- study of how organisms interact with each other
Cycling of Matter
Levels of Biological Organization
- an organism
- all members of the same species in the same habitat

– collection of all the populations of all the species in an ecosystem
– describes relationships among the many species in an environment and relationships of those organisms and the non-living components of the environment
Biotic factors

– factors caused by the presence and roles of other living things

Abiotic factors

– non-living factors or influences on organisms
The Sun

-source of all energy in ecosystems
-30% reflected by clouds
-70% absorbed by Earth’s surface

-process by which green plants use sunlight energy to produce carbohydrates
Food Chain

-step by step sequence linking organisms that feed on each other
1st trophic level
2nd trophic level
3rd trophic level
4th trophic level
top carnivore

- organisms that make their own food
- plants, algae, some bacteria
-relies on the primary consumer but indirectly relies on producers

-organisms that can’t make their own food
Energy flow in Ecosystems
- eat dead organisms releasing nutrients into the soil and water
Ecological Niche
- combination of the “job” of an organism and its habitat; specific role to play in an ecosystem
- places where a species live

-a feeding relationship consisting of multiple food chains
Food Web

-compare a stable (diverse) ecosystem to an unstable ecosystem
-as you go up any food chain, energy is transferred (not created nor destroyed) but some of it is converted into an unusable form
-therefore, less energy is available to higher trophic levels
Ecological Pyramid
-graph used to describe energy flow in food chains/webs (pyramid of energy)
-a pyramid of biomass – the dry mass of the dry tissue in organisms is measured and graphed
Cycling of matter
-there are two types of substances within organisms
1. Organic
- always contain C and H atoms, sometimes O and N atoms
Proteins, sugars, fats
2. Inorganic
- Doesn’t contain a combination of C and H atoms
- CO2, H2O, NH3
-their complex structures are broken and rebuilt in a continuous cycling of matter
-to maintain life, matter must be recycled
The Carbon Cycle
key element for living things
- found in the atmosphere and dissolved in oceans (as inorganic substance, CO2)
- all movements between carbon reservoirs makes up the carbon cycle, a biogeochemical cycle
5 Movements of Carbon in the Carbon Cycle
1) Photosynthesis
Producers use the Sun’s energy to combine CO2 and H2O to produce glucose and oxygen gas.
energy + CO2 + H2O -> C6H12O6 (glucose) + O2
2) Consumption
Consumers eat plants and other animals that have glucose stored in them. The carbon is transferred to the consumer.
3) Cellular Respiration
The glucose stored in the things we eat reacts with oxygen gas to produce carbon dioxide, water, and energy. This energy is used to live.
C6H12O6 + O2 -> CO2 + H2O + energy
4) Decomposition and Decay

Decomposers break down dead material, which releases carbon dioxide into the atmosphere, soil and sediment.
Under certain conditions, the decay process is delayed: organic matter is converted to rock or fossil fuels.
5) Combustion

The burning of fossil fuels release carbon dioxide into the atmosphere too.
The Nitrogen Cycle
-movement of nitrogen through ecosystems
-life depends on cycling of nitrogen
* needed to make amino acids, protein, DNA
-N2 = very stable molecule

-nitrogen can be converted into nitrates through nitrogen fixation
Nitrogen fixation by lightning
-energy from lightning causes nitrogen gas to react with oxygen, forming nitrates (NO3)
-nitrates dissolve in rain, enter the soil, move to plants through its roots

-plants use it to make DNA, amino acids, protein
- animals eat plants; they break down plant protein to amino acids, then use the amino acids to build animal proteins
Nitrogen fixation by bacteria
-nitrogen-fixing bacteria found in nodules (small lumps) on legume (soybean, peas, alfalfa) roots produce nitrates
-excess nitrates move into the soil
Nitrogen and decomposers
- all organisms produce waste and die

- decomposers break down the nitrogen-containing chemicals into simpler chemicals like ammonia (NH3)
- other bacteria: comvert from ammonia to nitrites (NO2), some from nitrites to nitrates
-use of manure and decaying matter of farmers/gardeners
* soil bacteria converts decaying matter into nitrates
* plants absorb nitrates
- denitrifying bacteria break down nitrates -> nitrites, then nitrites -> nitrogen gas
- carried out by bacteria that doesn’t require oxygen
-gardeners often aerate their lawns in early spring to reduce denitrifying bacteria (i.e. less nitrates are converted to N2)
-plants require nitrates to produce chlorophyll (protein, green colour)
-denitrification process speeds up in acidic or water-logged soil
* insect-eating plants survive in poor nitrogen environments by digesting trapped animals
- chemicals designed to kill pests (harmful or inconvenient organisms)
1. First generation
a. 15th century – heavy metals (mercury, arsenic, lead) as insecticides
b. 1763 – French gardeners use nicotine sulfate (extracted from the tobacco plant) to kill aphids
2. Second generation
a. synthetic chemicals
b.1939 – Dichlorodiphenyltrichloroethane (DDT, known since 1874) – Paul Mueller
c. other pesticides: Malathion, Captan, penicillin

-some of these pesticides/toxins/chemicals that are released in the environment persist for a long period of time
-also called bioamplification or biological magnification
-pesticides containing chlorine are soluble in fat but not in water

-it can’t be released in urine or sweat so it accumulates in fatty tissues of animals
-it starts when toxins enter primary consumers (prey)

-a secondary consumer eats many prey
-when the secondary consumer is eaten, the higher-level predator gets all the toxins + those of all the other prey it eats
-toxin concentration becomes greater as you move up the food chain
-result of non-cycling of matter in ecosystems

Growth Patterns
- birth rate
– number of individuals moving into an existing population
– death rate
- number of individuals moving out of an existing population
Population growth = (births + immigration) – (deaths + emigration)
-populations in mature ecosystems remain stable because of constant or predictable availability of resources (pop. growth = 0)

dynamic equilibrium
or steady state
1. open
– all four factors acts upon populations
2. Closed
– only natality and mortality affect pop size
Population Histograms
-used to study populations and examine it in terms of its age structure and male and female proportions at a specific time
-young vs. stabilizing vs. declining populations – look at the pyramid shapes
Biotic Potential
-max number of offspring a species can produce if resources are unlimited
-regulated by four factors
birth potential
– max number of offspring per birth
capacity for survival
– number of offspring that reach reproductive age
– number of times a species reproduce each year
4.length of reproductive life – age of sexual maturity and number of years an individual can reproduce
-abiotic factors prevent populations from attaining their biotic potential
-optimum number of organisms of a species that can be supported by a particular environment
Carrying capacity
-depends on changing biotic and abiotic components
-can be exceeded but not for long
Factors that cause changes in populations
1.density-independent factors
a.affect members of a population regardless of pop density
2. density-dependent factors
a.affect a population because of its density
Predator-prey relations
- organism that eats another organism
- organism which the predator eats
the same concept applies to animal-plant interactions
Invasive Species
-species not native or non-indigenous to a particular ecosystem; “alien” species
-come from other countries or other parts of the country
-accidental or intentional
Why are we concerned?
-reduce, eliminate, or outcompete native species
-expensive damage costs
What can be done?
-targeted control
-monitoring, research, education
Species at Risk
-organisms that are at-risk of disappearing
- because of environmental or human-induced changes
Why should we care?
– number of species in an ecosystem
-all species depend on each other to survive
Classification system for at-risk species
- A species no longer found anywhere
- a species close to extinction in all parts of Canada
- any species that non longer exists in one part of Canada but can be found in others
- any species likely to become endangered if factors that make it vulnerable are not reversed
- any species at risk because of low or declining numbers at the fringe of its range or in some restricted area
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