The Abiotic and Biotic Components of the Environment

Brief Account

• Ecology is the study of interactions among organisms and interactions between organisms and their environment.
• Biotic components: the living organisms: producers, consumers, decomposers.
• Take note of the definitions...
• Abiotic components: Non living factors such as temperature, pH, humidity, microclimate, topography and light intensity

Food chain, food web and trophic levels

Food chain :

• shows the feeding relationship of biotic components in an ecosystem
• shows how energy is transferred from one organism to another.
• as one organism feeds on another, energy is transferred from one trophic level to another.
• about 90% of the energy is lost to the environment
• while only 10% is passed on
  energy is lost tru processes sucha s respiration, excretion and defaecation

Example:

The Marine Food Chain

• Phytoplankton is the first level of the food chain,


• followed by the zooplankton, which feeds on the phytoplankton.


• The zooplankton are then eaten by krill, fish and other crustaceans,


• which all go on to be eaten by big fish, penguins, seals, walruses and whales.


• The food chain continues when these are eaten by mammals like polar bears.
  If you think about the food chain logically it is easy to understand how, without plankton, all of the oceans animals would die.


• Without phytoplankton, zooplankton would not have food and die.


• Without zooplankton, krill, smaller fish and other crustaceans would have nothing to eat and they would die, etc, etc.


• Until finally you get all the way out to large mammals like whales, dolphins, and manatees.


• All animals in the ocean depend on plankton for survival.

Useful tips:

• You should be able to differentiate between food chain and food web.


• Question might want you to draw/construct Food Chain...or may be Food Web..So please response to the question!!


• Use the organisms given in the question...Unless the qs ask you to construct any...


• Always start with The Producer!! Apart from plants, phytoplanktons are producers too...and algae!!!( Any photosynthetic organism...)

As for the interactions between biotic components, please check my blogspot : http://mahadiahgc.blogspot.com/ because i've posted some notes about it earlier.

..And please take note of all Diagrams/pictures in your Text Book and also in your reference books...which show the interactions between organisms...

You should be able to explain their interactions: Either Win-win or Win-Lose

Sample Question:




(a) Diagram shows a plant species P with green leaves on a tree trunk.
(i) Describe the relationship between species P and the host plant, Q. [4 marks]
(ii) Explain how species P obtains their needs and adapted to the environment [6 marks]

Answer:

Able to explain how species P obtains their needs and adapted to the environment :
F : adapted structures
E : function of adaptation


Sample answer :
F1 : Roots system is occupied by ants
E1 : the ants bring all kinds of rubbish and remnants of food to the roots
E2 : These materials gradually decompose into humus


F2 : Leaf arrangement in the form of a basket
E1 : can collect falling leaves
E2 : the leaves then decomposes into humus

F3 : Corrugated leaves with grooves
E1 : can direct rainwater and dew to the roots

F4 : Leaf with thick cuticle
E1 : to reduce transpiration

.Prey-predator Relationship:
If graph is produced, you should be able to explain the relationship.

Question: Diagram 8 shows types of interaction between two organisms in an ecosystem.
Explain how the interaction between the two organisms controls each other population. [10 marks]

Answer:

• The interaction is Prey-predator interaction ( 1 m)


• The interaction is where an organism which is smaller (rabbit) called prey (1m)


• Is hunted and eaten by a stronger animal, the predator ( wolf) (1m)


• F1: When the population of a predator (wolf) is high, the population of its prey (rabbit) decreases


• E1: because the prey is eaten by the predator


• F2: When the population of the prey falls, there is insufficient food for the predator


• E2: results in a decline of the predator population


• F3: When the population of predator is low, the prey recovers and its population increases


• E3: result in an increase in the population of the predator (have enough food)


• The interaction takes place in a cycle that keeps the population of both organisms in a dynamic equilibrium. ( 10 marks)

..Competition relationship:

Sample Qs:

1. In natural ecosystems, there is competition between members of the same species as
well as between different species.
a) Explain how competition between members of the same species helps to control
population growth. [2m]
b) Crop plants must compete with weeds for the same resources. Farmers control weeds by spraying herbicides(weedkillers). State two factors that the crop plants and weed may compete for and explain the importance of each. [2+2]

Answer:

a)
F: intraspecific competition
E: Plants which grow quickly,will obtain sufficient light ,thus will survive at the expanse of others//control other plants population growth.


b) F1: light intensity
E1: light is important for photosynthesis that produce energy for a crop plants and weed
F2: water
E2: to replace the water lost caused transpiration






















...There are intraspecific competition and interspecific competition...Dont get confused!

As for both, please take note of the experiments involved!!


Questions:

1. If almost all the snakes in the field are killed because of a disease, which organism in the food chain will immediately increased in number?
A Cats C Caterpillars
B Eagles D Rats

2. Which of the following are primary consumers ?
A Decomposers C Herbivors
B Autotrophs D Carnivores

3. The factors which influence the distribution of organisms in pond include

I the pH
II light intensity
III the presence of predators
IV concentration of carbon dioxide

A I and II C II, III and IV
B I, II and III D I, II and IV


4. Diagram below shows an ecosystem in a pond.Discuss the flow of energy in the food chain of the ecosystem. (10 marks)






Answer:

• 
  - In a pond ecosystem, the source of energy is sunlight
  
  - Producers such as lotus plants and sedges absorb solar energy from the sun and convert it into chemical energy stored in food during photosynthesis
  
  - Some of this energy is used by the lotus plants for cell division, growth and excretion
  
  - When the producers die, the energy becomes available to decomposers such as saprophytic bacteria
  
  - As one organism eats another in the pond, there is a transfer of energy from one consumer to another
  
  - When primary consumers such as mosquito larvae feed on the leaves of the lotus plant, some of the energy stored in the lotus plant is passed on to the mosquito larvae
  
  - About 10% of the plant’s available energy is passed on to the primary consumers
  
  - The primary consumers released energy during respiration , etc and used the energy for growth, movement
  
  - Some of this energy becomes available to the decomposers through excretion and defeacation of the primary consumers
  
  - When the secondary consumers like the small fish eat mosquito larvae, the primary consumers available energy is passed on to the secondary consumers
  
  - The small fish loses energy through respiration, excretion and defeacation
  
  - The small fish is then eaten by the big fish. Energy flows through the food chain in the ecosystem when a consumer eats another organism
  
  - When the mosquito larvae, the big fish and the small fish die, they are decomposed by saprophytic bacteria.
  
  ..10 marks (max)
  
• HAPPY REVISING..