Ecology is the study of the interactions between organisms as well as their environment.
What comprises ecology?
1) Habitat - the place where an organism lives
eg. redshanks(wading birds) live in the mud of the mangrove swamp, so the mangrove swamp is the habitat of the redshanks
2) Population - a group of organisms of the same spiecies living in a specific habitat
eg. all the redshanks living in that particular mangrove swamp make up a population
3) Community - all the populations of organisms(includes organisms of different species) living and interacting with one another in a particular habitat
eg. the mangrove community is made up of mangrove trees and other plants, animals like redshanks, mudskippers and sand flies and microorganisms living in the mud of that mangrove swamp 4) Ecosystem - community of species and all abiotic enviornments that exist in a certain area
eg. the ecosystem of the mangrove swamp is made up of all the organisms in the mangrove community and all the physical factors that make up its abiotic environment Factors include: - the salt concentration of the seawater - pH - amount of oxygen dissolved in the mud, etc
5) Biosphere - sum of all the ecosystems established on Earth
How are they linked?
groups of organisms interact with one another and the non-living environment to form levels of organisation that get bigger and more complex:
How do the physical features of the surroundings affect organisms? Biomes are main ecological regions in which the land surfaces can be devided.
These are the major types of ecosystems(those that occupy broad geographic regions). - coniferous forests - deserts - temperate grassland
Each of these places has its own type of abiotic environment(eg. the nature of the soil) which determines the type of plants found in that particular habitat. Since animals rely directly or indirectly on plants for food, the animals living in a region is determined by the plants growing there. So, living organisms have to adapt to the abiotic environment of the region in order not to be affected by the surroundings.
What are the physical factors? Abiotic emvironments consists of non-living factors such as climate and physical features that influencace ecological systems.
These physical factors include: - temperature - light intensity - amount of water available - oxygen content - salinity(salt concentration) of soil/water - pH of soil/water How organisms adapt to these physical factors 1) Temperature - affects the rate of biological processes(reactions of enzymes, which control metabolic activities of plants and animals); - and the inability of most organisms to regulate body temperature.
Most organisms cannot tolerate extremes of temperature; temperature that are too low or high would kill an organism.
eg. - a cell may rupture if the water is below 0°C or above 45 °C, most protein will denature rendering the organisms ability to function;
- desert plants :
~have small/spiny leaves limit the surface area exposed to the drying heat
~glossy leaves reflect the sun's rays, reducing leaf temperatures and evaporation rates ~waxy leaves prevent moisture from escaping ~some plants only open their leaf pores at night when it is cool and water loss from leaves is low
- desert animals :
~staying in the shade of plants or rocks or by burrowing underground in the heat of the day ~they stay inactive in shelter during the day and hunt at night when it is cool[nocturnal]
2) Light Intensity - the sun provides energy that drives almost all ecosystems on Earth - light intensity allows photosynthesis to take place which affect the plants growth, which in turn affect the animals growth too ;D - and the distribution of aquatic life
eg. - in a forest, the canopy layer tend to be denser as it recieves most of the sunlight, while the undergrowth layer(growing plant) at the bottom is less dense as it recieves little or no light at all - undergrowth layers : have large, broad leaves packed with extra chlorophyll to capture and absorb what little light is available.
- low light intensity : ~the anglerfish has a long protrusion on its head which is used lik a fishing rod to 'fish' for smaller fishes instead of relying on its poor eyesight to locate prey
3) Amount of water available - affect the number and location of plants and animals in a region - depend on the amount of rain
NO ORGANISMS CAN LIVE LONG WITHOUT WATER!
eg. - desert animals : ~can go 5-7 days with little or no food and water ~fat inside the hump is used to keep the animal going when there is no food or water
- desert plants ~plants have developed very long roots that go deep into the ground to reach underground water
~others have developed spreading root systems lying just below the surface and stretching widely ~this gives the plant many tiny roots that capture water when it rains.
4) Oxygen content - most organisms require oxygen for aerobic respiration - thus, they cannot survive in environments of low oxygen content
eg. in low oxygen content : - mangrove plants ~these air roots, called pneumatophores, extend upward from the underground roots above the soil surface ~during low tides, oxygen is taken up through open passages in the pneumatophores and transported to living root tissues.
- koi
~living in water of low oxygen content ~come to the surface of the water to gulp oxygen
5a) Salinity of water
- in aquatic habitats, the organisms are surrounded by water but there can still be problems due to osmosis
eg. - marine fish :
~in salt-water environments animals can lose water by osmosis as seawater has a higher salt concentration than the fish`s cells and must constantly replace it by taking in the water to replace water loss
- freshwater organisms
~in fresh-water, osmosis causes water to flow into the organism’s body as the freshwater has a higher water potential than the organism`s cells and water must be constantly "pumped out"
5b) Salinity of soil
- mangrove plants
as mangrove grew near the sea area, therefore the soil has a higher salt content
~secreting salts from their leaves, the salt can often be seen sitting on the surface
~excluding salt; prevent larger salt molecules from entering but allow smaller water molecules to pass through ~salt storage; salt is stored in leaves which then fall off the plant taking the salt with them
6a) pH of soil
- soil pH is a measure of soil acidity
- as soils become more acid/alkaline, this has a negative effect on the growth of plants - when soil become too alkaline, leafs would produce insufficient amounts of chlorophyll
6b) pH of water
- seawater has a pH of 8
- aquatic organisms may die when there is a sudden change in pH as they are sensitive to the pH of water
- hydrogencarbonates determine the pH of water
eg. - in daylight, photosynthesis in aquatic plants use up the carbon dioxide in the water, making the water more alkaline
- during the night, photosynthesis stops and the carbon dioxide produced in respiration makes the water more acidic
2:45 PM
Thursday, January 8, 2009
21.3
Are organisms interdependent? YES!
Plants provide food, shelter, and nesting sites for other organisms
Many plants depend upon animals for help in reproduction
eg.bees pollinate flowers 1) plants make their own food 2) in turn, they are food for animals 3) which may be eaten by other animals 4) when aniamls die, they are food for decomposers 5) which break down their bodies into simple materials 6) and now, plants can use the materials to make food SO, organisms depend on each other to survive - the various populations in a community live interdependently - a change in one population will affect the other population of the community
Why are organisms interdependent? - all living organisms in a community depend on other living and non-living things in some way to survive - each population must be strong enough to ensure the survival of all organisms involved - when one population is weakened or broken, the rest of the organisms is affected either directly or indirectly - a single change in the environment can affect the organisms living in it and thus upset the balance of nature. - SO, organisms are interdependent to maintain the balance of nature, aye?
10:07 PM
Sunday, January 4, 2009
21.4 (nutrients flow)
How do energy and nutrients flow through an ecosystem? Let me tell you a short story ;D
The sun shines on a field of grass and gives it energy to grow. A rabbit comes hopping along, stops to nibble on the grass, and gets energy from the meal. Hiding behind a bush, a fox comes out and tries to catch the rabbit. The rabbit sees the fox and tries to escape. The fox chases the rabbit. the chase ends when the fox catches the rabbit, and it becomes food for the fox, which in turn gets energy from this meal.
This is how energy and nutrients transfer from one organisms to another. Energy and nutrients are transferred from producers to consumers to decomposers.
Producers : - produce food not only for themselves but for all other organisms, either directly or indirectly
eg. when the rabbit eats the grass, it gets the food energy stored in the plants directly, but when the fox eats the rabbit, the fox gets the plant food energy indirectly through the rabbit.
Consumers : - cannot make their own food, and obtain energy by feeding on other organisms
1) Herbivores(plant-eaters) - feed directly on plant(producers) to gain energy, hence they are known as primary consumers
2) Carnivores(meat-eaters) - feed on meat to gain energy BUT, i) those that feed on herbivores are known as secondary consumers ii) those that feed on carnivores are known as tertiary consumers
3) Omnivores - feed on both plant(producers) and animal(consumers) to gain energy
4) Decomposers i) obtain energy by : - breaking down the remains of dead plants and animals into nutrients - break down the waste materials of living organisms ii) allow materials to be used again by green plants
Food chain
- a food chain is like a ladder, with animals at each step
- series of organisms through which energy is transferred in the form of food
- each organism in a food chain feeds on the organism before it and provides food for the organism after it
- each step is known as a trophic level(usually not more than 4 levels) :
What would it be like if animals in the wild ate the same thing day after day? Not only would their life lack variety, but it would also be precarious.
What would happen if lion could eat only zrbras? If a natural disater wiped out the entire zrbra population in an area, the lions that live there would lose their only food source. Soon, they too would die out.
- food chains combine together to form a food web - food chains are interrelated because animals do not eat the same food every meal
Lets use a spider web as an example if a couple of strands are broken, a spider web can still keep its shape. but if too many strands break, the whole web is in danger of collapsing
jus lik a food web, when one population dies out, the other populations can still depend on other food sources to survive as they do not eat the same food every meal right? but if too many populations dies out, the whole community might 'collapse'
7:12 PM
Tuesday, December 30, 2008
21.4 (predator prey)
What is the relationship between a predator and a prey? A predator is an organism that eats another organism. A prey is an organism which the predator eats.
Predator and prey evolve together.
The prey is part of the predator's environment, and the predator dies if it does not get food. The decrease in the number of predator allows an increase in the number of prey. Likewise, the predator is part of the prey's environment, and the prey dies if it is eaten by the predator. The decrease in the number of prey causes the number of predators to decrease as less food is available.
So, the increase and decrease in the population of the predator follows the corresponding increase and decrease in the population of its prey
Two predators with the same prey?
If there are two predators after the same prey, the population of the prey would decrease. Thus, there is less food for both the predators causing a decrease in population size of both predators. Which would then cause a big increase in the number of prey since the population of both its predator decreased.
This cycle would then repeats overtime.
10:44 PM
Thursday, December 25, 2008
21.4 (pyramid)
What are ecological pyramids? - pyramid-shaped diagrams - pyramid is divided into sections, each representing one trophic level - showing the relative numbers, biomass(weight), or energy content of organisms in an ecosystem - feeding relationship among organisms at different trophic levels
The bottom level of the pyramid include the producers The second level include the primary consumers The third level include the secondary consumers The fourth level include the tertiary consumers
Pyramid of numbers
- shows the number of organisms at each trophic level
- each consecutive level contains fewer organisms than the level below it
- thus the number of herbivores like zebras is greater than the carnivores like lions
The shape of the pyramid of numbers vary from ecosystem to ecosystem. eg,
In aquatic ecosystems and herbaceous communities, autotrophs are present in large numbers per unit area. They support a lesser number of herbivores, which inturn support fewer carnivores.
So, the producers are smallest sized but maximum in number while carnivores are larger in size but lesser in number, so these cannot be used as prey by another.
Hence the pyramid of numbers is upright.
Pyramid of biomass
- shows the total biomass at each successive trophic level
- biomass is the total amount of living matter at a trophic level
- the pyramids of mass show a progressive reduction of biomass in the successive trophic level
- an enormous mass of grass is required to support a smaller mass of buck, which in turn would support a smaller mass of lions.
In a terrestrial ecosystem, the maximum biomass occurs in producers, and there is progressive decrease in biomass from lower to higher trophic levels. Thus, the pyramid of biomass in a terrestrial ecosystem is upright.
Pyramid of energy
- indicates the total amount of energy present in each trophic level
- shows the loss of energy from one trophic level to the next as food is transferred from one trophic level to the next
Energy is lost:
1) as heat during respiration at every trophic level
2) in uneaten parts
3) through undigested matter egested by consumers
4) through waste products excreted consumers, eg, urea
Pyramid of energy is always upright.
It is so because at each transfer about 80 - 90% of the energy available at lower trophic level is used up to overcome its entropy and to perform metabolic activities. Only 10% of the energy is available to next trophic level (as per Lindemann's ten percent rule), so there are usually no more than 4 or 5 links in a food chain.
Going up each level of the pyramid, less and less energy is available. The number of organisms the pyramid can support is small. This explains why there are typically more prey than predators in a community. Thus, the pyramid of numbers, the pyramid of biomass and the pyramid of energy all describe relationships among organisms in a single ecosystem.
Variations
- In a parasitic food chain, for e.g., an oak tree, the large tree provides food to several herbivorous birds. The birds support larger population of ectoparasites leading to the formation of an inverted pyramid.
When a large tree support larger number of herbivorous birds which inturn are eaten by carnivorous birds like falcon and eagle, which are smaller in number, it forms a spindle shaped pyramid.
- In an aquatic habitat the pyramid of biomass is inverted or spindle shaped where the biomass of trophic level depends upon the reproductive potential and longivity of the member.
8:26 PM
Monday, December 22, 2008
21.4 (short food chain)
Why are short food chain better? Going up each level of the pyramid, less and less energy is available for the organisms at the next level as we go down the food chain. The number of organisms the pyramid can support is small. Hence, food chains are generally short. This explains why there are typically more prey than predators in a community. A shorter food chain means more energy is available to the final consumer beacuse less energy is lost to the environment.
eg, more energy will be available to a man if he feeds directly on crop plants grown on a given area, rather than eating the cattle that feed on his crop plants.
10:10 PM
Sunday, December 21, 2008
21.4 (energy)
What happen to most of the energy in the ecosystem? The main energy source in an ecosystem is the sun which provides light energy. Once energy is lost to the environment as heat, it cannot be recycled as energy flow is non-linear . Thus, energy has to be continually be supplied to the ecosystem. In this case it is in the form of light energy.
1) in all ecosystem, the ultimate source of energy comes from the sun
2) light energy from the sun is converted to chemical energy by plants during photosynthesis
3) Energy in these plants is passed from each trophic level to another by feeding. some of these energy is used up by the animals and some energy is lost to its surrounding by heat energy
4) the flow of energy through the ecosystem is non-cyclic. this means that once the energy is lost to the environment, it will never be able to return to the same system orr organism that produced it hence, energy cannot be recycled
5)Trapped chemical energy in dead organisms, egested and excreted materials are released by decomposers. These decomposers use some of this trapped energy for respiration and lose the rest as heat
EVENTUALLY, all the energy is lost to the environment in the form of heat.
11:11 PM
Saturday, December 20, 2008
21.5
The carbon cycle - process through which carbon is cycled through the air, ground, plants, animals, and fossil fuels - large amounts of carbon exist in the atmosphere as carbon dioxide (CO2) and - is constantly being removed from and released into the environment thus CO2 concentration remains relatively constant
Removal of CO2 from the environment 1. carbon dioxide from the atmosphere is absorbed by the green plants to synthesis carbohydrates(glucose)
2. glucose may be changed to other organic compunds lik fats, amino acids, proteins
3. this carbon compound then become part of the bodies of those animals who feed on the freen plants
4. some carcass or dead plants may not decay immediately and the carbon compound is preserved as fossil fuel Release of CO2 into the environment Carbon dioxide is released through:
1) Decay - When a green plant dies, the carbohydrates are usually broken down by fungi or bacteria, which are decomposers. The Fungi and bacteria undergo respiration, which allows them to release the carbon back into the atmosphere as carbon dioxide
2) Respiration - carbon compounds are broken down in the bodies and carbon dioxide is released into the environment when living organisms respire
3) Combustion - carbon compound preserved in fossile fuels are broken down when burnt and carbon dioxide is released into the environment
carbon cycle
10:53 PM
Saturday, December 13, 2008
22.1
What are the impacts of human activities on our ecosystem? Human beings are continually using and depleting the Earth's natural resources and upsetting the balance of nature in the process. The uncontrolled use of the Earth's natural resources has caused lasting or permanent damage to the environment. Thus, human activities must be carefully monitored to preserve and conserve whats left of the Earth for the future.
Impacts of deforestation Deforestation: Deforestation means clearing of forests. Forests are cleared to meet increasing demands of land and raw materials such as for wood and agriculture. With today's modern technology, the forests are being cleared at a rate that they cannot be replaced. With forests being cleared not only will wildlife lose their habitat, it also causes other harmful effects.
Effects:
soil erosion:
When the trees are removed, the topsoil is exposed to rain and wind. Without the roots to hold soil together, the topsoil which is the most fertile layer is vulnerable to rain. It will get washed away or eroded during heavy rain, which causes soil erosion.
flooding:
When the soil get washed into the river, eroded soil causes water level to rise, increasing the chances of flooding.
desertification: Sunlight now falls directly onto the soil. Water beneath evaporate rapidly, causing the soil to become hard and barren. Plants can no longer grow and organisms that feed on these plants will die off. Consequently, habitats are lost, species of organisms become extinct.
climate change: Rainwater is retained and absorbed by roots of trees which is lost as water vapour during transpiration. This water vapour eventually falls as rain after condensation. Without the presence of trees, rainfall will decrease and causes the land to become warm and dry, thus annual rainfall decrease.
Impacts of over-fishing As human population increases, the demand of fish also increases. Some species of fish have been caught in large number which cause the fish population to decrease and thus affecting the balance in the environment. With the advancement of fishing gear, marine life are caught indiscriminately. Marine life such as turtles and dolphins are caught unintentionally which are then dumped back into the sea, but they often die.
Other types of overfishing: 1)Trawlers drag large fish nets along the bottom of the sea, many unwanted species are trapped in the process.
2)Dredges scrape the seabed destroying coral reefs and other organisms that live on the seabed.
3)Cyanide fishing uses poison or dynamite to stun the fish but kills corals and other reefs organisms. The stunned fish are sold as pets.
Effects: If over fishing is not controlled, this will lead to the extinction of a particular species as they are caught faster than they can be replaced. Fishes are unable to have a chance to grow and reproduce, therefore populations drop.
Impacts of entrophication Overuse of chemical fertilisers containing nitrates and phosphates which are used to increase crop yield may cause water pollution.
Fertilisers: contain nitrates and phosphates are used to increase yield of crops.These fertilisers are not absorbed immediately and can be washed into water bodies.This results in algae and water plants getting the nutrients instead."algae bloom" the rapid multiplication of algae,will block out sunlight that reaches submerged plants.These submerged plants die,and organisms feeding on the plants will die.Bacteria growth is rapid and dissolved oxygen is used up.Other organism dies too due to lack of oxygen
Insecticides: used to kill insects are usually non-biodegradable such as dichlorodiphenyltrichloroethane. They can remain in the soil or water for many years and may poison fish or animals when consumed in high concentrations. DDT is insoluble in water, and when accumulated in bodies of consumers will be passed to the top of the food chain. Top consumers of food chain will suffer from toxic effects due to bioaccumulation.
Impacts of biomagnification The increase in concentration of a substance such as dichlorodiphenyltrichloroethane that occurs in food chains. Biomagnification occurs across all trophic levels.
9:11 PM
Wednesday, December 10, 2008
22.2
Why is there a need for conservation? Conservation is necessary for the maintenance of the Earth's biodiversity. Conservation is the protection and preservation of natural resources in the environment.
reason: 1) to prevent thee extinction of plant and animal species 2) to maintain a large gene pool for cross breeding 3) to maintain a stable and balanced ecosystem to prevent disruption 4) to ensure the conservation of marine life as they are a major source of food 5) allow the study of wildlife which provides useful infomation 6) preserve natural scenery and wildlife for people to appreciate 7) to maintain biodiversity, where tropical plants provide raw materials
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