Community and Ecosystem

9.1

Community and Ecosystem

Interaction of Organism

Organisms do not just interact with each other but they also interact with non-living things to create a balanced system known as ecosystem.

Term

Habitat

Habitat is the natural surrounding or the living place of an organism.

Species

A species is a group of similar organisms, able to interbreed and produce offsprings.

Population

A population is a group of organisms of the same species which live in the same habitat.

Community

A community is the populations of all organisms from different species living in the same habitat whilst interacting with each other.

Ecosystem

An ecosystem is a few communities that live together in a habitat and interact with each other including non-living components (abiotic) such as water, air and soil.

Niche

A niche is the role of an organism in an ecosystem which includes its behaviour and interactions with biotic and abiotic components in the surrounding of its habitat.
- Ecological niche: The role of a species in its surroundings.
- Species niche: The way in which a species interacts with biotic and abiotic components within its surroundings.

Biotic and Abiotic Components in an Ecosystem

An ecosystem consists of two main components, which are biotic components and abiotic components.
Biotic components:
- Refer to all organisms in an ecosystem which interact with other organisms.
Abiotic components:
- Are all the non-living elements including their physical and chemical characteristics that can affect an organism in an ecosystem.

Main Components of An Ecosystem

Biotic Components

Producers.
Consumers.
Decomposers.

Abiotic Components

pH Value

The pH value of the soil greatly affects the distribution of organisms in a habitat
Most suitable organisms live in neutral or almost neutral pH conditions.
Soil is home to hundreds of millions of worms and microorganisms such as bacteria, fungi and protozoa.

Temperature

Ambient temperature affects the physiological activities of plants and animals.
Small temperature changes will lower the rate of metabolism because all the enzymes that catalyze physiological responses are very sensitive to temperature changes.
Although most organisms can survive in a temperature range between 20 degrees Celsius to 40 degrees Celsius, there are also organisms that can survive in extreme temperatures.
Polar bears can live in tundra habitats with temperatures of -14 degrees Celsius while foxes can live in the desert with temperatures reaching 45 degrees Celsius during the day.

Light Intensity

The intensity of light and the length of time that sunlight radiates in an area greatly affects the distribution of organisms, especially plants that carry out photosynthesis.
Tall trees exposed to high light intensity in tropical rainforest areas form a canopy of low light intensity below.
Only small plants such as ferns can live under this canopy.
Moderate climate coniferous forests with low light intensity have less plant density.
The trees in the coniferous forest are small and low in size.

Topography

Topography is the physical feature of the earth's surface that includes altitude, gradient and aspect.
Topography determines humidity, temperature, and light intensity in an ecosystem.
Topography factors:
- Altitude:
  - The higher the altitude, the lower the relative humidity, atmospheric pressure and oxygen content.
  - Plants at different levels of altitudes are different in types, sizes and density.
  - For example, pine trees that grow at higher altitudes are smaller in size compared to meranti trees which can be found in tropical rainforest.
- Gradient:
  - Steeper mountain slopes are easily eroded due to swift water movement.
  - The soil layer becomes thinner and drier.
  - This area has less growth of plants except for some short, thorny shrubs with small and pointed leaves.
- Aspect:
  - Aspect refers to the direction in which wind blows and the rays of sunlight.
  - A mountain slope which faces the sea has denser plants compared to the one facing towards the land.
  - This slope also gains more rainfall distribution.
  - The slope that receives more sunlight is denser with plants.

Microclimate

Microclimate refers to the climatic conditions of a small area that are different from the surrounding area.
The microclimate may occur under rocks or under large thickets of trees in the forest canopy.
The microclimate depends on temperature, humidity, light intensity, heat balance, atmospheric pressure, water evaporation as well as the ability of the soil to retain water in the area to retain moisture.

Air Humidity

Air humidity is the quantity of water vapor in the air that affects the distribution of organisms in a habitat.
More organisms inhabit areas of high humidity.
Low air humidity increases water loss from the stoma through transpiration.
Transpiration also exerts a cooling effect on the plant to maintain the optimum temperature of enzyme action.

Autotrophic and Heterotrophic Nutrition

Nutrition is the way organisms obtain nutrients and energy from food eaten for life processes.
There are two types of nutrients, namely:
- Autotrophic.
- Hheterotrophic.

Classification of Organisms According to their Nutrition
Autotrophic
Photoautotrophic	Chemoautotrophic
Photoautotropic are organisms that synthesize organic compounds from carbon dioxide and light energy. Photoautotrophic can synthesize food on their own through the process of photosynthesis. Example: Green plants.	Chemoautotrophic include several types of bacteria that synthesize organic compounds without the use of light. Chemoautotrophic obtain energy through the oxidation of inorganic substances such as hydrogen sulfide and ammonia through chemosynthesis. Example: Nitrobacter sp.
Heterotrophic
Saprotrophic	Holozoic	Parasitic
Saprotrophic are saprophytic organisms that obtain nutrients from dead and decaying organic matter. Digestion is done outside the body of the organism before nutrients are absorbed into the body. Example: Fungi.	Organisms that consume solid organic matter which then digests it and is absorbed into the body. Humans and almost all types of animals are holozoic. Example: Squirrel.	Parasitic are organisms that absorb nutrients from a host. For example, fleas and tapeworms that absorb nutrients from their hosts are humans. Example: Fleas.

Biotic Components According to Trophic Levels

The biotic component consists of organisms that need energy to carry out life processes.
Humans and animals obtain energy by eating other organisms including photosynthetic plants.
Therefore, the most important source of energy for all organisms comes from the sun.
The components of biosis consist of three groups, namely producers, consumers and decomposers.

Komponen Biosis

Decomposers

Microorganisms decompose waste substances as well as dead or decaying organisms into simpler organic substances such as carbon dioxide and ammonia.

Producers

Autotrophs synthesise organic substances from inorganic substances.
Producers consist of green plants which synthesise glucose from water and carbon dioxide with the help of energy from sunlight.

Primary Consumers

Herbivores which gain energy by feeding on producers.

Secondary Cosumers

Carnivores which feed on primary consumers or omnivores which feed on primary consumers and producers.

Tertiary Consumers

Carnivores which feed on secondary consumers.

Energy Flow in the Food Chain

Organisms in an ecosystem interact with each other in the form of nutritional relationships.
Such relationships are shown in the food chain.
The food chain is a sequence of energy transfers from one trophic level to the next trophic level, starting from the producer.
In a food chain:
- It starts with the producer and ends with the secondary consumers or the tertiary consumers.
- The organism will eat the organism from the previous trophic level.
- Energy is transferred from the organism that eats it to the organism that eats it.
- Organisms that eat other organisms get energy from the body tissues of the organism money is eaten. This energy is transferred to the organism when food is digested and assimilated to form new tissues.
In a food web:
- Describe the nutritional relationship in a community.
- Formed from several food chains.
- Organisms in all food chains are interdependent with each other in aspects of nutrition.
- Initiated by producers who photosynthesize and convert light energy from the sun into chemical energy in the form of food stored in root organs, fruits, stems or leaves.

Ecological Pyramids

Food chains and food webs describe nutritional relationships between organisms.
When one organism eats another organism, energy transfer occurs.
In a nutritional interaction, as the trophy level increases, the number of individuals, biomass and the amount of energy contained in each individual for each trophy level will change.
All these factors can be described in the form of an ecological pyramid consisting of a number pyramid, a biomass pyramid and an energy pyramid.

Pyramid of Numbers

The bottom most has the largest number and is the first trophic level that represents the number of producers.
The next part of the pyramid is the second, third and fourth trophic levels which represent the number of primary users, secondary users and tertiary users.
The higher to the top of the pyramid, the fewer the number of organisms in each of the levels and the larger the size of the organisms.

Pyramid of Biomass

The pyramid also depicts the biomass that can be supplied to organisms in the next trophic level.
For example, the amount of producer biomass that can be consumed by primary consumers is higher than the primary consumer biomass in the ecosystem.
Similarly the total biomass of secondary consumers is lower than that of primary consumers.
The higher to the top of the pyramid, the less the amount of biomass per unit area.

Pyramid of Energy

The source of energy in an ecosystem is light energy from the sun that is absorbed by green plants to carry out photosynthesis and convert it into chemical energy.
Energy will be transferred to the next trophy level when the primary consumer consumes the producer plant.
The energy present in food molecules may be stored in body tissues or transferred to the environment in the form of excrement such as urine or excreted through feces.
When food molecules are broken down for respiration and other reactions, some energy is released into the environment through heat. Only a small portion of the energy in food is converted to energy stored in body tissues as a supplement to the organism's biomass.
Only 10% of the energy is transferred to the next trophy.
90% of energy is lost to the environment through heat, life processes, excretion and decontamination.
Therefore, organisms at lower trophic levels have more available energy content than organisms at higher trophic levels.

Types of Interaction among Biotic Components

There are a few types of main interactions, which are saprophytism, symbiosis, predation and competition.
There are two types of competitions, which are intraspecific competition and interspecific competition.
- Intraspecific competition happens among organisms of the same species.
- Interspecific competition happens among organisms of different species.

Interaction among Biotic Components

Saprophytism

Saprophytism is an interaction in which an organism gets its food from dead organic materials.
For example, mushrooms that live on dead tree trunk.

Symbiosis

Symbiosis occurs when different species that live together, interact with each other.
Types of interaction of symbiosis:
- Mutualism:.
  - Mutualism is an interaction that gives benefits to both organisms.
  - For example, a myna gets its food (lice) from the body of a buffalo whereas the buffalo is free from the lice.
- Commensalism:
  - Commensalism is an interaction that provides benefits to only one organism without causing any harm to the other organism.
  - For example, a shark does not gain any benefit but the remora fish gets scraps of the shark's food.
- Parasitism:
  - Parasitism is an interaction that benefits one organism but harms the other organism.
  - For example, a tapeworm becomes a parasite in the intestines of a human being by absorbing nutrients and causes the human (host) to lack in nutrients.

Predation

It is an interaction involving an organism (predator) that eats another organism (prey).
For example, an owl which is a predator catches and eats rats as its prey.

Competition

Competition occurs when organisms in a habitat compete in order to get basic needs such as food, water, light and mates.
Interspecific competition:
- For example, competition among different species of plants to get sunlight.
Intraspecific competition:
- For example, competition among animals of the same species to get mates.

Mangrove Ecosystem

Abiotic Components

Mangrove trees are tropical plants which are usually found in estuaries.
Estuaries is a place where the sea and river meets.
These plants have successfully adapted themselves to the extreme abiotic components.
Abiotic components of a mangrove ecosystem:
- Germination of seedlings in tidal area.
- Exposed to very strong light intensities.
- Soil with high salt content as well as very low content of dissolved oxygen in water.
- Exposed to strong wind blows.
- Soft, silted and muddy soil that lacks aeration.
- Exposed to waves and water tides.

Biotic Components

Other than the mangrove plants as producers that dominate the ecosystem, many other species of flora and fauna adapt themselves to live in the mangrove forest.
In addition, there are also decomposers such as bacteria and fungi which decompose dead organisms into nutrients for the plants.
These organisms form a food web that helps to maintain the dynamic balance of the mangrove forest.
Biotic components of a mangrove ecosytem:
- Mushroom.
- Mangrove trees.
- Crab.
- Horshoe crab.
- Mudskipper.
- Snake.
- Proboscis monkey.
- Silvered leaf monkey.
- Stork.

Adaptation Features of the Mangrove Trees
Parts of Mangrove Trees	Adaptation Features
Leaves	Mangrove trees have thick cuticle leaves and embedded stomas that can reduce the rate of transpiration. Mangrove trees also have succulent leaves that can store water and have a special structure known as a hydatode to get rid of excess salt. Older leaves can store salt and will fall off when the concentration of stored salt is too much.
Pneumatophere roots	Pneumatophore roots are short root projections from the soil surface for aeration in areas that are often inundated with water. These roots help gas exchange between the submerged roots with the atmosphere through the lenticels. Example: Avicennia sp.
Prop roots	Prop roots grows branching from the bottom of the trunk of a mangrove tree. These roots grip in the soil strongly to provide support against strong winds and waves. Example: Rhizophora sp.
Buttress roots	Buttress root is a type of root with a thickened flake structure to increase the surface area of the base. These roots support trees that grow on soft soil bordering the land. Example: Bruguiera sp.
Seeds	Viviparous seeds germinate and grow while still attached to the parent tree. This allows the seeds to fall strewn on the muddy ground and not be washed away by the waves.

Colonisation and Succession

Colonisation:
- Plants start to conquer an uninhabited area, breed and form colonies in that area.
Sucession:
- A few species of dominant plants in a habitat are gradually being replaced by other species called successor.

Colonisation and Succession of a Mangrove Area

Coastal Zone

The coastline zone is most vulnerable to large waves.
This zone is overgrown by a pioneer species, namely the Avicennia sp. (fire-tree) and Sonneratia sp. (perepat tree).
The extensive root system and pneumatophores help the tree trap mud and organic matter carried by the tide.
This leads to a gradual accumulation of mud. As a result, the soil becomes higher and denser.
Rhizophora sp. displacing and replacing pioneer species.

Middle Zone

The central zone is located along the river near the estuary.
Grown by Rhizophora sp. (oil mangrove tree) which has tangled tap roots that can trap tree twigs and mud that drift and block the flow of water.
Mud trapping causes sedimentation to occur more rapidly.
The cliffs become higher and drier due to less overflow of sea water during high tide.
The soil became less suitable for the growth of Rhizophora sp.
On the other hand more suitable for Bruguiera sp.
Bruguiera sp. displacing and replacing Rhizophora sp.

Inland Zone

The inland zone is located far inland.
The ground becomes higher, harder and only flooded with seawater during high tide.
Grown by the tree Bruguiera sp. (red tumu) which has banir roots to trap more mud and silt.
The sedimentation process forms new swamps that project into the sea.
The old beach is getting further and further away from the sea.
The soil on the coast turns to terrestrial and is suitable for terrestrial trees such as Nypa fruticans and Pandanus sp.
Terrestrial trees displace and replace Bruguiera sp.

The Importance of the Mangrove Ecosystem

Protection Zone

Mangrove swamps serve as a natural buffer to reduce the speed of waves and winds that reach the coastal areas.
The mangrove swamp forest is a refuge for small fish, shrimp and crabs from predators and the movement of water currents and strong waves.
Mangrove swamps serve as sanctuaries and food sources for various species of migrating birds.

Fishery Resources

Seafood such as fish, shrimp, crabs and snails are a source of income for fishermen in mangrove swamps.
The waters in the mangrove swamps support the floating cage industry to breed commercial species.

Forestry Resources

Mangrove wood can be used to make canoes, fish traps and building frames.
Mangrove wood can also be used to make handicraft items.
Mangrove wood is burned in a furnace to produce a source of fuel, namely charcoal.

Food and Medicine Resources

Fruit of Avicennia sp. can be eaten as a vegetable.
Avicennia sp. can be boiled and eaten, while the flowers produce honey.
Fruit Sonneratia sp. used in the manufacture of beverage ingredients.
Fruit of Nypa sp. edible and the water from its fruit can be used in the manufacture of vinegar and nira.
Bark of Bruguiera sp. used to treat diarrhea.