Properties of water important for life

waterfall in SriLanka- www.imagelanka.com

Water is essential for life. It is the most abundant chemical and also the most abundant inorganic substance.

Main functions of water 

1. Water is the main component of the protoplasm (The  Living content of a cell that is surrounded by a plasma membrane)

2. Water is a reactant in man biochemical reactions e.g: Photosynthesis

3. Water is a good solvent. Therefore it is the medium for many biochemical reactions.

4. Water helps in maintaining turgidity in living organisms.

 In addition to these main functions

In plants water helps in :

1. Absorbing minerals and act as the medium of transport


2. Transporting organic food


3. Germinating seeds


4. Turgor movements  of stomata


5. Acting as a medium for fertilization


6. Medium for pollination


7.  Seed dispersal


8. Maintaining turgidity in herbaceous plants

In Animals water

1. Is the main component in body fluids


2.  Moistens the respiratory surfaces


3. Acts as a lubricant in joints


4. Cools the body surface by evaporation


5. Habitat for some organisms



Water has many important chemical and physical properties making it the main chemical found in living organisms.

chemical and physical properties of water

1. A liquid at room temperature- therefore water is the main medium of protoplasm


2. Polarity- water is a good solvent therefore


3. High surface tension-  small insects such as water skaters can live on the surface of water


4. High specific heat capacity-helps to maintain the body temperature without major fluctuations


5. High latent heat of vaporization-  cools body surfaces because a high heat is absorbed from body surfaces for evaporation


6. High latent heat of fusion- water doesn't freeze easily as a large amount of heat has to be dissipated from water to turn into ice


7. Anomalous expansion of water  when freezing- Due to this property density of water decreases when freezing. It makes ice float on water. Ice is a good insulator. theretofore liquid water remains at the bottom of water bodies without  freezing. Aquatic animals can survive in water dung winter season due to this.


8. Transparent- Water  is a transparent liquid. It allows penetration of light into deep water allowing the growth of aquatic plants and algae in a considerable depth


9. High adhesive and cohesive forces- transport of water in xylem is due to adhesive forces among water molecules and cohesive forces between water molecules and xylem capillary walls.

10. chemical property- water is a common reactant in biochemical reactions

A/L exam results

http://news.stv.tv/

A/L exam results in Sri lanka can be expected to be released by the end of December 2015

Previous exam results can be checked by visiting the link below

/www.doenets.lk/result

Scientific method to solve biological problems

http://science.k12flash.com/scientificmethod.html

In order to interpret conclusions in science, scientists use a set of rules to solve problems in a logical and orderly fashion. This method is known as scientific method. Scientific method can also be applied to solve day to day problems in a systematic way too.

Main steps in scientific method

1. Systemic observation

observations can be taken directly  using our sensory organs or indirectly with the use of instruments such as microscopes.

2. Identification of problem 

Based on the observations the problem can be identified. Problem should be well defined and must have a narrow range

3. formulating  Hypothesis

The possible solutions for the problem is guessed and predicted as the next step

4. Testing hypothesis by experiments
Suitable  experiments has to be carried out to test the hypothesis built in the previous step. Scientific experiments must be well planed and recorded . It s also important to plan control experiments to compare the factor that is being tested.

5. Testing predictions by further experiments

Experiments has to be repeated to arrive in a conclusion. This step is a part of the previous step.

6. Confirming hypothesis supported by evidence/ observations

Based on the results of the experiments  the formulated hypothesis can be either confirmed or rejected.

7. Formulating a theory 

If the hypothesis is confirmed to be true under the testing conditions for many times a theory can be formulated. However the theories can be modified base on new information. If the theory is proven to be true constantly a law can be formulated. usually laws are not modified

a simple example is given below

e.g:

 1.Some plants in the home garden was found to be wilted.

2. Why the plants got wilted?

3. hypothesis 1.  May be the plants were not watered
    hypothesis 2: Fertilizer applied to the plant has caused wilting

4. test 1: water half of the plants with enough water, control experiment is not watering the other half of the plants

   test 2: Add the new fertilizer in to another  set of plants which are not wilted, control is not adding the fertilizer to a another set of plants which are not wilted.    make sure to water the bothe sets of plants since all the other factors has to be kept constant.

6. test 1: observation 1: there was no significant different between the plants which were watered and plants which were not

test 2: observation: Plants which were applied with the new fertilizer was wilted.

7. Based on the observations we can conclude that the new fertilizer has caused the wilting of the plants. Since this a  a simple day to day situation theories and laws are not formulated.

Theories such as  cell theory and relativity theory have been formulated this way. laws such as Newton's first law are laws.

Revised GCE Advanced Level (A/L) time table released

Several dates of the GCE A/L exam has been postponed due to the upcoming elections in Sri lanka. You can download the revised GCE A/L Time table at


 Revised GCE A/L Time table 2015

Characteristics of living organisms

Torque monkey- Sri Lanka- Photo by : Vidura Nishantha- www.imagelanka.com

It is not possible to give one definition to define a living organism. Therefore living organisms are identified by a set of characteristics. Some of those characters can be common to both living and non living. e.g: living organisms can move however a non living object such as a vehicle also can move.

Following are the main characteristics of living organisms

1. Growth

Growth is the irreversible increase in dry mass in an organism e.g: increase in height , weight etc.

2. Development

Irreversible changes that occur during the life span of an organism is development. e.g: Behavioral changes. Growth is also an part of development .

3. Metabolism

The series of biochemical reactions going on in a cell is called metabolism. Biochemical reactions can be
constructive- Anabolism  e.g: synthesis of proteins from amino acids
or
destructive- Catabolism e.g: respiration

4. Irritability and coordination

Irritability is the ability to respond to stimuli from both internal and external environment. coordination is the systematic relationship between stimuli and the response.

5. Adaptation

Adaptation is a peculiarity of structure, physiology or behavior that promotes the
likelihood of an organism’s survival and reproduction in a particular environment. e.g: Camouflage

6.  Reproduction

 Ability to produce a new offspring for continuous existence of species

7. Heredity 

Inheritance of characters of one generation to the next generation

8. Evolution 

Changes in genetics leads to evolution

9. Order and organization

organizational levels

Organizational patterns of living organisms

Red beetles-  Photo by : Vidura Nishantha

Cell is regarded as the basic structural and functional unit of life. The tissues are made up of similar cells. Differentiated  smaller units arranged in an orderly manner  to form larger units is called organization. There are different levels of organizations.

 lower levels include:

molecules ----> organelles  ---->cells  ---->tissues  ----> organs  ----> organ systems  ----> organism

higher levels include:

organisms  ---->population  ----> community  ---->ecosystem  ---->biosphere

Definitions:

• Population: all individuals of a species in a particular area

• Community : Population of different species present in a particular area

• Ecosystem: Living beings interacting with non living components

• Biosphere: Different ecosystems of all geographical regions of the world

Introduction to Biology

photo by : Vidura Nishantha www. imagelanka.com

Biology is the branch of science to study about living beings.

It is important to study biology for many reasons. some the main importance s of studying biology is described below. 

1. Understanding about  biological diversity 

Biology makes us understand that we are only a small part of this living planet.

Thereare around 30 million species of animals and plants in the world. The relationship between living and non living world is a dynamic one.

2. Understanding about  the human body and its functions

study of biology helps us to understand the structure and function of the human body thereby helps us to fight against ailments, cure the diseases and improve the quality of life.

3. Managing  natural resources and environment:

biology deals with the studies on management and conservation of nature and its resources. It warns us about the possible environmental hazards such as ozone depletion, deforestation etc.

4. Sustainable food production:

Since all our food comes from plants and animals, we must find ways to improve the food production by developing agronomy, microbiology, food production etc. It is said that the  current human population of 6 billion and it is expected to double in less than 40 years. Therefore sustainable food production is necessary.

5. Understanding about  causes , effects and cure  of diseases:

Diseases such as cancer , AIDS, malaria  polio and other epidemics can be controlled by the concerted effots of biologists. systematic knowledge of botany can help to discover unknown medicinal plants. understanding of hereditary diseases , a biologist can do genetic counselling.