Compare and contrast the mode of nutrition of detritivores and saprotrophs.
| Detritivores | Saprotrophs | |
|---|---|---|
| Similarity | heterotrophic OR feed on/obtain nutrients from dead organic matter/dead organisms; | |
| Difference | internal digestion/digestion in gut OR enzymes secreted into gut OR food ingested before digestion | external digestion OR enzymes secreted into surroundings OR food digested before being absorbed; |
Explain the reasons for food chains rarely containing more than four or five trophic levels.
a. energy is lost between the trophic levels
b. transfer between levels is only usually 10% efficient OR energy transformations take place in living organisms / the process is never 100% efficient
c. energy is lost by the organism/used in respiration / released as heat/movement
d. energy is lost as waste/feces/urine/undigested food/uneaten parts
e. as energy is lost between trophic levels and so (higher ones) have less biomass / less biomass available for next level
The amount of food passing into food chains can be affected by the rate of photosynthesis. Explain the effect of one limiting factor on photosynthesis.
Limiting Factor: Temperature
a. the rate of reaction will be limited by the limiting factor that is nearest to its minimum value;
b. enzymes that control photosynthesis are influenced by temperature;
c. as temperature increases, reaction rate will increase;
d. above a certain temperature, the rate of photosynthesis will decrease;
e. (where temperature is limiting) essential enzymes begin to denature/not working to optimum;
Limiting Factor: Light Intensity
f. light is source of energy / converted into chemical energy;
g. as light intensity increases reaction rate will increase;
h. at a certain light intensity, rate of photosynthesis will plateau;
i. another factor becomes limiting;
Limiting Factor: CO2 Concentration
j. CO2 is fixed to form organic molecules;
k. as CO2 concentration increases, reaction rate will increase;
l. at a certain concentration of CO2, rate of photosynthesis will plateau;
m. another factor becomes limiting;
All of the leaves in the image are from Ipomoea, a wild genus of sweet potato.
State one cause of variation in a plant such as the sweet potato.
