Biology - Ecology

ECOLOGY

-is the study of interactions or relationships of organisms with one another and with the living (biotic) & non-living (abiotic) environment

Habitat -> Place where an organism lives and reproduces
(E.g. soil, a rotting log, a tree trunk, a nest, stagnant water, a pond)

Population -> Group of organisms of the same species living in a particular habitat
(E.g. Water lettuces in a pond form a population / A larvae, pupae and adults of lime butterflies in a garden form a population)

Community -> All populations of organisms living & interacting with one another in a particular habitat
(E.g. The different populations of water lettuces, pond skaters, fishes and other populations in a pond form a community)

Ecosystem -> A community and its abiotic environment
(The living organisms and the non-living factors (e.g. air, rock, water, sand) form an ecosystem eg. Forest, mountain, river, pond, ocean, grassland, seashore, mangrove swamp)
Environment -> Everything surrounding an organism is called its environment. The environment affects the organism’s growth, development & survival

- Organisms are interdependent
- Energy is transferred from one organism to another mainly through food
- The Sun is the main source of energy for planet Earth
- Solar energy from the Sun is absorbed by plants and passed on to other organisms as chemical energy
- Most of this energy is eventually lost as heat
- Energy flow is non-cyclical

Living things often have special body features or ways of behaving that help them adapt to their environment for their survival. These special body features and ways of behaving are called adaptations. (E.g. Whales have thick layers of fat under their skin to keep them warm / Cacti have thick stems to store water and strong skins for reducing the loss of water)



When studying an ecosystem, one should consider:

•The abiotic or non-living environment
•The biotic or living environment
•The different kinds of organisms and how they interact with one another and their physical environment
•The adaptations of the different organisms in the ecosystem


ABIOTIC

Temperature

•Most plants and animals survive in temperature between 0°c and 45°c
•Heats up or cools down a habitat
•Controls the process of reproduction in plants as certain fruits and flowers are seasonal
•It affects the proper functioning of enzymes. Extreme temperatures and pH disrupts the hydrophobic, hydrophilic and ionic interactions in enzymes, causing them to lost their shape and functionality
•In humans, optimum for enzymes to work (37°C & below) If surrounding temperature is above 37°C, there would be a change in conformation of the Enzyme. (denaturation)
pH (acidity/ alkalinity)

•pH value of soil solution, freshwater ponds and seawater determines the types of organisms that can live in each environment
•may increase or decrease due to pollution
•when changed may cause death of plants and animals
(E.g. when acid rain falls onto the soil or into water)

•Freshwater organisms live an environment of pH 7 (neutral)
Marine organisms live in an environment of pH 8 (slightly alkaline)

•Most plants grow well in neutral of slightly alkaline soils.
pH of soils determines the type of mineral salts that the plants can absorb from the soil.
Plants cannot absorb mineral salts from acidic soil solutions.
(However, the Cotton Plant & Pitcher Plant both favor the acidic environment)
Air

•Air is a mixture of gases such as nitrogen (78%), oxygen (21%) & carbon dioxide (0.3% to 0.44%)
•Plants require carbon dioxide while most other organisms require oxygen for photosynthesis and respiration respectively
•Oxygen is required for aerobic respiration. Lack of oxygen would slow down metabolism
•Oxygen is toxic to some organisms like certain types of bacteria which live without oxygen
•Land organisms -> Atmospheric oxygen
Aquatic organisms -> Dissolved oxygen

•Some animals like the guppy and goldfish come to the surface of the water to take in air when the content of dissolved oxygen in water is low
•Some plants are adapted to obtain oxygen because their roots are embedded in oxygen-poor water (e.g. Mangrove plants have aerial roots that grow out of oxygen-poor mud. These roots have tiny pores that allows for gaseous exchange to occur)
Humidity

•High humidity slows down the rate of transpiration in plants but is also critical to the survival of epiphytes and organisms living in arid places.
Water

•Affects number and location of flora and fauna. Dependent on rain pattern
•One of the basic necessities for all living things and is present in all environments
•Dissolves nutrients so that plants can absorb them
•Provides a habitat for fishes and other aquatic living things (or hydrophytes – living things that live in water or very wet places)
•More organisms are found where water is available
•Some organisms possess special adaptations to conserve water
(E.g. some plants like the cactus have thick stems to store water
Some animals like camels have humps that contain fats which can be broken down to energy and water) These organisms have the ability to withstand great loss of water and are able to live in dry conditions (or xerophytes – living things in dry or desert-like places)
Wave Action

•Prevents marine organisms from settling down and feeding
Wind Speed

•High wind speed may break the stems of certain plant species and may dissipate humidity
Light

•Provides warmth for organisms to survive
•Is required by green plants to carry on photosynthesis
•Low intensity retards plant growth, but high intensity may bleach chlorophyll & impairs the ability of plants to photosynthesize
•Is required by animals to carry out daily activities eg. Finding food, attracting mates
•Affects the behavior and activities of living things like migration of birds, reproduction of animals and birds and production of fruits in plants
•Some organisms have different adaptations towards the amount of light in their environment
(E.g. Earthworms burrow into the soil to avoid light/ Bats sleep during the day and search for food at night)
Salinity

•Is the concentration of salt in water
•When changed can kill animals and plants which have adapted themselves to different degrees of salinity.
Eg. Fresher water organisms will die when placed in the sea, while those from the sea will die in fresh water
Minerals in the soil

•Are necessary for the healthy growth of plants
•Animals obtain their mineral supply from plants. Plants absorb mineral salts from soil solutions (e.g. nitrates used by plants to make protein)
•Mineral salts are required in the manufacture of substances such as proteins, vitamins and chlorophyll
•Certain bacteria can change the nitrogen in the air to nitrates which are absorbed by plants to make proteins
•Minerals such as potassium and phosphates are required for the growth of healthy flowers and fruits

BIOTIC

In a habitat, living things are dependent on one another to obtain food, shelter and protection. There are many types of relationships in a community listed below:

Predator-prey
•A predator feeds on a prey:
- Herbivore (eats plants)
- Carnivore (eats animals)
- Omnivore (Eats plants & animals)
- Scavenger (feeds on dead animals)
- Goat eats grass
- Eagle eats snake
- Human eats chicken and cabbage
- Vulture eats dead cow

Mutualism or symbiosis
•Relationship between two kinds of organisms in which both benefit
•Clown fish and sea anemones
•Fungi and algae in lichens
•Oxpeckers and ox

Commensalism

•Relationship between two kinds of organisms such that one benefits while the other neither benefits nor is harmed by it
•The remora fish attaches itself to a shark for protection and food. The shark neither benefits nor is harmed by the fish

Parasitism

•Relationship between two kinds of organisms such that one, the parasite, benefits by living in or on the body of the other, the host, which is harmed
•Ticks are parasites which live on the body of the frog, their host – feeding on its blood and harming it

Mimicry

•A form of protection adopted by preys to escape detection by their predators by :
- Camouflage:
A pattern of colouring that disguises an organism or blends it with its surroundings so that it can hide from its prey or predator
- Chameleons, flounders, moths, tigers and horned toads camouflage to avoid being seen by their prey or predator
- Leaf insects look like leaves

Competition

•Between members of the same or different population(s) for food, territory or the right to mate
•Crows, cats and rats compete for food among garbage




Life on Earth is supported by the recycling of natural resources like water, oxygen, carbon, nitrogen, minerals and others.

•In a stable and balanced ecosystem, no nutrients are lost.
•In an ecosystem, nutrients can be recycled but energy that flows through it is not recyclable.
Importance of Nutrient Cycle:
Living things on Earth are primarily made up of the following elements:
•Carbon
•Hydrogen
•Oxygen
•Nitrogen
•Phosphorus
•Sulfur
They also require the following compound as the main solvent/medium in which biochemical processes take place within:
•Water
While the Earth receives a continuous input of solar energy from the Sun, the total amount of each of the elements of Earth remains relatively constant since the formative stages of our planet.
i.e. The Earth does not receive additional amount of carbon, hydrogen, oxygen, nitrogen, phosphorus and sulfur after it is formed.

Hence, as plants and animal grow and die, they cycle these elements between the environment and their bodies through various:

•Biological processes such as photosynthesis, cellular respiration and decomposition
•Geological processes such as sedimentation
•And processes arising from the action of human beings such as deforestation and burning of fossil fuel

Carbon Cycle
The carbon cycle is the circulation of carbon, in the form of carbon dioxide, through the ecosystem. Some processes remove carbon dioxide from the air while other processes return the carbon dioxide to the air so that the amount of carbon in the ecosystem remains constant.

Importance of the carbon cycle:

•Ensures a continuous supply of carbon dioxide for photosynthesis
•Enables carbon compounds rich in energy to be supplied to other organisms in the food chain
•Helps to keep the amount of carbon in the ecosystem constant so that there is neither too much or too little
•Ensures that CO2 and other carbon compounds do not move out and are always available for living things to use
Carbon is an important element in living things. It is part of the proteins, carbohydrates and fats in the tissues of living things.



Carbon exchanges between the atmosphere and the biosphere occur via the following process:
Photosynthesis:
-Carbon is absorbed in the form of CO2 and converted to glucose which may then be used for respiration and for the building of protoplasm in plants.
-Plants are then consumed by primary consumers and the carbon is then transferred into the body tissues of animals.
-Through successive feeding, carbon compounds move up the trophic levels in the ecosystem.
Respiration:
-Plants and animals respire; converting glucose into CO2 which is released back into the atmosphere.
Excretion and Egestion:
-Microorganism ferment carbon-rich food in the stomachs of cattle and releases carbon back into the atmosphere in the form of natural gas or methane, CH4
-Undigested food removed as faeces contains much of the carbon that was initially ingested.
Decomposition:
-As dead organisms decay and become decomposed they release carbon dioxide into the atmosphere
Destruction of vegetation:
-Bush fires or slash-and-burn agriculture may burn away large areas of forests which release large quantity of carbon dioxide from plant material
Sedimentation and mineralization:
-When organisms die and are very quickly buried, they do not undergo decomposition, but may be compacted by layers of mud and rock. Overtime these dead organisms may become fossil fuels. Much of the carbon in the tissues of these organism thus becomes stored in the form of fossil fuel.
-Carbon dioxide from the atmosphere dissolves in the sea in the form of bicarbonate ions or carbonate ions. Marine organisms use carbonate ions to produce hard shells and support structures. When these organisms die, their hard shells will settle down to the bottom of the ocean (sedimentation) and become compacted. This becomes limestone (calcium caronate) over a long period of time, storing the carbon in limestone.
Dissolution (Chemical weathering)
-Precipitation may dissolve limestone structures, thus releasing the carbonate ions back into rivers and streams

Nitrogen Cycle
Nitrogen is also an essential element in living things. It is needed to make proteins that are used for the growth of tissue.

•Keeps the nitrogen level in the atmosphere constant
•Ensures a continuous supply of nitrates for green plants to make proteins and protoplasm
•Enables proteins to be supplied to other organisms in the food chains

Nitrogen is…
Removed from the air
•By nitrogen-fixing bacteria to produce nitrates in the soil
•By lightning that combines nitrogen with oxygen in the air to form oxides of nitrogen. The oxides of nitrogen dissolve in water to from nitric acid. The nitric acid reacts with other substances to form nitrates.
Returned to the air
•By the action of denitrifying bacteria on the nitrates found in the soil, decomposing the nitrates into oxygen for the bacteria’s use and nitrogen for release into the air.
Nitrogen compounds are..
Removed from the soil
•Through the absorption by green plants for their growth
•By leaching; in which nitrates dissolve in rain water or drainage water and are washed away beyond the reach of plant roots.
Returned to the soil
•By the action of decomposers on dead animals and plants

For more information, refer to my Science wikispace that I did about Ecology. It contains mindmaps, images, notes, worksheets all on the topic itself.

http://scienceaceecology.wikispaces.com/