- Individual members of populations interact with each other as well as with members of other populations, which can have an impact on the populations involved.
- There is a continuous exchange of materials and energy between the living systems and the Earth and the balance of nature is sustained when losses equal to replacements.
- The energy input to ecosystems is the radiant energy of sunlight and producers are essential to harness this radiant energy and convert it to chemical energy through the process of photosynthesis.
- Energy flow through an ecosystem in the form of chemical energy is present in organic matter and the flow is unidirectional.
- Inter-relationships and inter-dependencies among organisms generate stable ecosystems that fluctuate around a rough state of equilibrium.
- The Sum is the principal source of anergy input to biology systems.
- On Earth, there are lithosphere, atmosphere and hydrosphere.
- Biosphere is composed of ecosystems, each with distinct biotic and abiotic characteristics.
Biotic --> Living
- Relationships between Living Things
- E.g. Predator & Prey
The organisms in any habitat are never completely independent. The life of each organism depends on, and is influenced by, other organisms around it. (Interdependent)
Abiotic --> Non-Living
- Physical Factors
- Light Intensity
- Temperature
- Amount of Water Available
- Oxygen Content
- Salinity of Soil/Water
- pH of Soil/Water
Abiotic Factors --> Type of Plants --> Type of Animals
The physical features of the surroundings and the nature of the soil determine the types of plants found in a region. Since animals rely directly or indirectly on plants for food, the animals that live in a region are determined by the plants growing in that region. Organisms found in a region are usually adapted to the physical features of their environment.
How does light intensity affect organisms?
Light Intensity --> Distribution & Growth of Organisms
Light intensity effects the distribution and growth of both plants and animals. Green plants exist only where there is an adequate supply of sunlight. Some plants develop adaptations to reach the light, for example, climbing plants may twine around or grasp a support to pull themselves upwards. However, bright light causes plant stems to grow more slowly. This is why plants growing in the open usually end up shorter than those in the shade. Certain plants have developed adaptations to block or screen off excessive light. For example, some plants have a dense covering of hairs on the leaf epidermis or a layer of thick-walled cells just beneath the epidermis. These adaptations protect the plant by screening off excessive heat and reducing the rate of transpiration.
Many animals need sunlight to see in order to catch their prey or to detect predators. However, some animals develop special adaptations for living in dark places. For example, bats are especially adapted to move about in dark caves. They locate prey in the dark by bouncing sound waves off objects around them.
How does temperature affect organisms?
Temperature --> Metabolism of Organisms
Temperature affects the rate of reaction of enzymes, which control metabolic or physiological activities of plants and animals. Most organisms cannot tolerate extremes of temperatures. Temperatures that are too high or too low would kill an organism. Many flowering plants are adapted to changing seasons. Such plants are able to survive through a hot and dry season or through winter by storing food in underground storage organs, shedding leaves to reduce water loss, or forming seeds which are resistant to heat, cold or drought, just before these seasons arrive.
How does the amount of available water affect organisms?
Water --> Number & Location of Organisms
No organism can live long without water. Hence, the amount of available water is one of the major factors affecting the number and location of plants and animals in a region. The amount of available water depends on the amount of rain and the pattern in which rain falls throughout the year.
Some organism are adapted to survive under conditions where there is a limited supply of water. For example, camels are able to survive for many days in the dessert without water because they can drink more than 100 litres of water when available, then go for long periods without drinking. Some plants are adapted to survive prolonged drought. These plants may show some of these adaptations:
- They reduce their rate of transpiration by shedding their young leaves or by developing leaves reduced to spines.
- Their stems become fleshy, storing up much water.
- The green stems also take over the function of photosynthesis from the leaves.
Mangrove plants have their roots buried in oxygen-poor mud. Special breathing roots project above the mud surface. The roots have openings through which oxygen oxygen passes downwards to the whole root system.
Aquatic animals also show adaptive features for living in water, such as gills for absorbing oxygen or special structures for swimming. For example, frogs have webbed toes and fish have fins for swimming.
How does oxygen content affect organisms?
Oxygen Content --> Type of Organisms
Most organisms are aerobic, that is, they require oxygen for respiration. They cannot survive in environments of ow oxygen content. However, some aerobic organisms can survive in environments of low oxygen content. This is because they possess special adaptations for obtaining sufficient oxygen, for example, mangrove plants have breathing roots. Fish living in water of low oxygen content are usually air-breathers. They can come to the surface and gulp air.
How does salinity affect organisms?
Salinity Concentration --> Type of Aquatic Organisms
The salinity of water is an important factor affecting aquatic organisms. Animals living in seawater tend to lose water by osmosis as seawater contains a higher salt concentration than the cytoplasm of animal cells. Saltwater/Marine fishes have a waterproof coat consisting of closely-fitting scales covered by a slimy mucous material. This reduces the rate water loss.
How does pH affect organisms?
pH --> Type of Organisms
The pH of soil water or the water in freshwater ponds or the sea affects the types of organisms that can live in such environments. Aquatic organisms are sensitive to the pH of the water in which they live and may die if there are drastic or sudden changes in pH.
Species/Population/Community/Habitat/Niche/Ecosystem
Populations --> Communities --> Ecosystems --> Biosphere
- Habitat - The place where an organism lives.
- There is a mangrove swamp in the Sungei Buloh Nature Reserve.
- Redshanks live in the mud of the mangrove swamp.
- So, the mangrove swamp is the habitat of the redshanks.
- Population - A group of organisms of the same species living in a particular habitat.
- In the mangrove habitat, all the redshanks living in that particular mangrove swamp make up a population.
- Another population is made up of all the mangrove trees living in that particular mangrove swamp.
- Community - All the populations of organisms living and interacting with one another in a particular habitat.
- The mangrove community is made up of mangrove trees and other plants, animals like redshanks, mudskippers and sand flies, and micro-organisms living in the mud of that mangrove swamp.
- Ecosystem - A community and its physical or abiotic environment together.
- The ecosystem of the mangrove swamp is made up of all the organisms in the mangrove community and the all the physical factors that make up its abiotic environment.
- These factors include the salt concentration of the seawater, its pH, the temperature, the amount of oxygen dissolved in the mud, the amount of light falling on the trees and the amount of nutrients in the mud.
- Niche - A position or role taken by a kind of organism.
- Kangaroos in Australia.
Producers --> Consumers --> Decomposers
- Producers - Convert energy from the sun or light energy into chemical energy and store it as food during photosynthesis.
- Producers are mainly green plants, but algae and certain bacteria than can photosynthesis are also producers.
- Producers are the organisms that can manufacture or produce complex organic food from raw material.
- Hence, producers either directly or indirectly affect the lives of other organisms because they provide energy and oxygen.
- Consumers - Obtain their energy by feeding on other organisms.
- All animals are therefore consumers.
- Herbivores feed directly on plant, hence they are know as primary consumers.
- Carnivores feed on other animals.
- Carnivores that feed on herbivores are secondary consumers.
- Carnivores that feed on carnivores are tertiary consumers.
- Decomposers - Obtain energy by breaking down dead organisms and waste products.
- E.g. Fungi, Bacteria and Earthworms
- Parasitism - One benefits at the expenses at another.
- Commensalism - One benefits and the other derives neither benefit nor harm.
- Mutualism - Beneficial to both organisms involved.
- Food Chain - A series of organisms through which energy is transferred in the form of food.
- It is a relationship between organisms in an ecosystem.
- A food chain always begin with a producer.
- Trophic Level
- Autotroph (Producer)
- Heterotroph (Consumer)
- Detritivore (Decomposer)
- Saprotroph (Decomposer)
- Food Web - Food chains that are interlinked.
- Pyramid of Numbers - Compare the number of organisms present in each trophic level at a particular time.
- Pyramid of Biomass - Campare the mass of organisms present in each trophic level at a particular time./Based on the dry mass of organisms in each trophic at any one time. (Standing Mass)
- However, under special conditions, the pyramid may be inverted.
Energy Lost
A lot of energy is lost to the environment as food is transferred from one trophic level to the next. Energy may be lost to the environment:
- as heat during respiration at every trophic level;
- Heat energy is wasted as it cannot be recycled in any way in the ecosystem.
- in uneaten body parts;
- through undigested matter egested by consumers;
- through waste products produced by consumers.
Usually, we can assume that about 90% of the energy is lost when it is transferred from one trophic level to the next. The greatest amount of energy is lost during its transfer from producer to primary consumer.
Non-Cyclic Energy Flow
Energy flow in an ecosystem is non-cyclic. Energy is lost to the environment as heat, which cannot be recycled in the ecosystem.
- In any ecosystem, the ultimate source of energy is the sun.
- Light energy absorbed by chlorophyll in producers is converted into chemical energy during photosynthesis.
- Energy in the producers is passed from one trophic level to another by feeding.
- The flow of energy through the ecosystem is non-cyclic. Energy is released as heat to the environment as it flows through the ecosystem. This heat energy does not return to the same system or organisms that produced it. Hence, it cannot be recycled in the ecosystem.
- Dead organisms and egested and waste materials contain trapped chemical energy. This energy is released by the activity of decomposers. Decomposers use some of this trapped chemical energy for their needs. The rest of the energy is lost as heat.
The Carbon Cycle
Release of Carbon Dioxide: Respiration/Combustion/Decay
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