Organisms and their environment Flashcards iGCSE Biology

[q] Which animal is called a Herbivore?

[a] An animal that gets its energy by eating plants is called a Herbivore animal.  

[q] Which animal is called a Carnivore?

[a] An animal that gets its energy by eating other animals is called a Carnivore animal.

[q] What is called a Community?

[a] All of the populations of different species in an ecosystem is called a Community.

[q] Which Organism is called as Decomposer?

[a] An organism that gets its energy from dead or waste organic material is called as Decomposer.

[q] How the Decomposition of Organisms occurs?

[a] Bacteria or fungi decompose the body and the protein is broken into ammonium ions and is released into the soil.

[q] What is Nitrification?

[a] Nitrification is done by nitrifying bacteria, who turn these ammonium ions into nitrates, which are used by plants.

[q] What is Nitrogen fixation?

[a] Nitrogen fixation is the transfer of nitrogen in the air into the soil,

• by the work of lightning; which makes nitrogen combine with oxygen, and which dissolves in rain,
  
• or by nitrogen-fixing bacteria; which lives in the soil or in root nodule and use nitrogen in the air spaces and combines it with other substances to make ammonium ions and other compounds.

[q] How does Absorption occurs in plants?

[a] Plants absorb the nitrate ions in the soil by the root, or through root nodules. In the soil method, active transport is used.

• Usage: Amino acids then portions are built for plants. 

[q] How the Digestion occurs in plants?

[a] Animals feeding on plants digest the proteins into amino acids.

[q] What is Deamination?

[a] Animals with excess amino acids deaminate them and release ammonium ions in forms like urea and ammonia into the environment, which will be further be made into nitrates by the nitrifying bacteria. 

[q] What does the Denitrifying bacteria actually do?

[a] Denitrifying bacteria turns nitrates and ammonia in the soil into nitrogen gas.

[q] Describe how nitrogen in proteins in dead leaves is recycled to be absorbed by plants?

[a]

• Proteins → Amino Acids → Ammonia → Nitrite ions → Nitrate ions
  
• Ref to, decomposers / bacteria / fungi;
  
• Proteins are broken down to amino acids;
  
  
  • By proteases;
    
• Amino acids converted to, ammonia / ammonium (ions);
  
  
  • Deamination;
    
• Ammonia / ammonium ions, converted to nitrite ions;
  
• Nitrites converted to nitrate ions;
  
  
  • Nitrification / oxidation / nitrifying bacteria;
    
• Nitrate ions absorbed by plants

[q] What is a Ecosystem?

[a] A unit containing the community of organisms and their environment, interacting together is called Ecosystem.

e.g. a decomposing log, or a lake.

[q] Explain the importance of recycling nitrogen in ecosystems, such as the African savanna?

[a] The importance of recycling nitrogen in ecosystems, such as the African savanna is

• Idea that (fixed) nitrogen is in limited supply;
  
• Idea that if not recycled is not available for plants to absorb;
  
• Needed for many biological compounds;
  
• (Required by organisms to make) amino acids / proteins / DNA / chlorophyll;
  
• For growth / for repair / for enzymes / for genes / AW

[q] Explain why there are far fewer predators (cheetah) than prey (impala)?

[a]

• General idea of energy loss (in food chain);
  Cheetahs do not eat, all impalas / all parts of an impala
  ‘lose energy’, in respiration / as heat to environment;
  And in movement / excretion / egestion / reproduction;
• Cheetahs are at a higher trophic level (than impala) / impala are the primary consumers / prey;
• Each cheetah eats many impala;
• Large population of cheetahs cannot be sustained / number of impala controls or determines the number of cheetahs;
• Hunted / poached (for skins);
• Killed by local people as they feed on animals
• Reference to balanced ecosystem / food chain / food web;
• Offspring killed / die (while growing) by other predators / their prey
• Avp ;

[q] What is called a Food chain?

[a] Showing the transfer of energy from one organism to the next, beginning with a producer is called a Food Chain.

[q] What is a Food web?

[a] A network of interconnected food chains is called a Food web.

[q] Identify the phases in the sigmoid population growth curve.

[a]

[q] What is the Importance of decomposers?

[a] Importance of decomposers are

• Removes organic waste;
  
• Recycles nutrients;
  
• Releases (carbon as) carbon dioxide;
  
• Carbon dioxide for photosynthesis;
  
• Decreases particle size of food for decomposers;
  
• Ref to energy flow in, food chain / food web / ecosystem;

[q] Label the carbon cycle

[a]

A: Combustion
B: Feeding
C: Photosynthesis
D: Respiration
E: Fossilisation
F: Decomposition

[q] Label the processes in the Nitrogen Cycle

[a]

[q] Label the Water Cycle

[a]

[q] What is Nitrogen Fixation?

[a]

• Root nodules (on legumes);
  
  
  • Contain free living bacteria;
    
    
    • Called nitrogen-fixing bacteria;
      
• Converts nitrogen into ammonia / ammonium ions
  
  
  • and converts ammonia to amino acids;

[q] What is Population?

[a] A group of organisms of one species, living in the same area, at the same time is called Population.

[q] What is Producer?

[a] An autotrophic organism that makes its own organic nutrients, usually using energy from sunlight, through photosynthesis is called Producer.

[q] What is a Trophic level?

[a] The position of an organism in a food chain, food web, pyramid of numbers or pyramid of biomass is called a Trophic level.

[q] What are the factors affecting rate of population growth?

[a]

• Interspecific competition;
  
• Food supply;
  
• Water;
  
• Shelter / ‘nest’ sites / space / territory;
  
• Mates (Intraspecific competition;
  
• Competition with other types of predators;
  
• Disease;
  
• Hunting;
  
• Pollution;
  
• Rate of reproduction;
  
• Habitat loss / destruction;

[q] Why are there rarely more than 5 trophic levels?

[a] Energy is passed between trophic levels, although this process is highly inefficient due to a variety of reasons:

• Small percentage of energy from Sun is ‘fixed’ by photosynthesis because light is of the wrong wavelength;
  
• Energy is lost between and within trophic levels
  
  
  • Some material ingested by consumers are inedible or indigestible.
    
  • Energy is lost by
    
    
    • Respiration.
      
    • Excretion.
      
    • Movement
      
    • Maintaining body temperature
      
• 90% of energy lost per trophic level
  
• So only a small total percentage of energy reaches fourth trophic level.
  
• Thus, there is not enough energy in fourth trophic level to support another level.

[q] Why are there rarely more than 5 trophic levels?

[a]

1. A small percentage of energy from sun is ’fixed’ by photosynthesis;
   
   
   • Because light is of the wrong wavelength;
     
2. 90% of energy is lost within trophic levels;
   
   
   • To material that is, inedible / not digestible / egested / not absorbed / not consumed;
     
   • Energy lost, in respiration / heat / movement;
     
   • To energy loss to (named) decomposers;
     
3. Not enough energy in fourth trophic level to support another level;
   
4. Population of predators in fifth trophic level unlikely to survive;
   
5. Fifth trophic level may be parasites which are very small;

[q] Why is it more efficient to eat plants, and less efficient to feed crop plants to livestock?

[a]

• Energy transfer from one trophic level to another is inefficient.
  
  
  • Eating producer is more energy efficient than consumer.
    
• Feeding crop plants to lifestock is inefficient.
  
  
  • More vegetation fed to animals for meat instead of eating vegetables directly for same energy gain.
    
  • Animals lose energy to environment and doesn’t use up all plant material.