Biology 4.2

Question 1

Energy Source

Answer 1

Light is the initial source of energy for almost all communities
- all green plants, and some bacteria are phototrauphic

light energy is absorbed by phototrauphs and converted into chemical energy via photosynthesis
- this light energy is used to make organic compounds (e.g. sugars) from inorganic sources (e.g. CO2)
- heterotrophs ingests these organic compounds in order to derive their chemical energy (ATP)
- when organic compounds are broken down via cell respiration, ATP is produces to fuel metabolic processes

Question 2

Energy Flow

Answer 2

energy enters most ecosystems as sunlight, where it is converted into chemical energy by producers
- this energy is stored in Carbon compound, and moves throught the trophic levels via feeding

Question 3

Trophic levels

Answer 3

producer–> primary consumer –> secondary consumer –> tertiary consumer

Question 4

Food chain

Answer 4

shows the linear feeding relationship between species in a community
first organisms is always a producer

Question 5

Energy Loss

Answer 5

energy stores in inorganic molecules can be released by cell respiration to produce ATP
- ATP can be used to fuel metabolic reactions require for growth and homeostatis
- by-product of these chemical reactions is heat, which is released from the organism

Chemical energy is lost by:
- being excreted as part of the organisms faeces
- remaining unconsumed as uneaten portion of the food
- Input: 100%, Stored: 25%, Lost: 25% respiration, 40% heat, 10% excretion

Chemical energy produced by an organism can be converted into a number of forms:
- kinetic energy
- electrical energy
- light energy

All of these reactions are exothermic and release thermal energy
- living organisms cannot turn this heat into other forms of usable energy
- heat is lost to the environment

Question 6

Energy efficiency

Answer 6

Energy transformation take place in living organisms is never 100% efficient
- most energy is lost to organisms
- only 10% efficient
- 90% lost between trophic levels

As energy is lost between trophic levels, higher trophic levels store less energy as carbon compounds and have less biomass
- biomass is total mass of a group of organisms

AS energy and biomass is lost between each level of food chain, the number of potential trophic levels are limited
- higher trophic levels recieve less energy/biomass from feeding and so need to eat larger quantities to obtain sufficient amounts
- bc higher trophic levels need to eat more, they expand more energy hunting for food
- if the energy to hunt is more than the energy available from the food eaten = trophic level is unviable

Question 7

Pyramids of Energy

Answer 7

graphical representation of the amount energy at each trophic level of food chain
each level is 1/10 of the size preceding it.