Organisms and their environment Details Flashcards
Principal source of energy input to biological systems
The Sun
Flow of energy through living organisms
-Plants use photosynthesis to convert light energy(from sunlight) into chemical energy in nutrients
-Chemical energy in nutrients is passed down to other organisms by feeding
-When these animals die, they are broken down by decomposers which return their nutrients to the soil
Advantages of pyramids of biomass over pyramids of numbers
-In pyramids of biomass, biomass is lost at each level which corresponds to energy lost
-Pyramids of biomass give an indication of the amount of energy being passed on at each stage of the food chain
Advantages of pyramids of energy over pyramids of biomass and numbers
-Most accurate presentation of the flow of energy in ecosystems
-Account for the difference in lifespan of two species of similar biomass(even if they have a similar biomass, one may live longer than the other, meaning that they have more energy overall)
Why the transfer of energy from one trophic level to another is often not efficient
-Not all animal and plant energy can be digested to gain energy from(eg. fur and bones)
-Energy is lost through excretion and decay
-Energy is used in other processes(eg. movement and keeping warm)
Why food chains usually have fewer than five tropic levels
-Organisms later on in the food chain gain less energy than organisms earlier on, as energy is lost at each level
-Organisms later on in the food chain must eat a larger amounts to gain enough energy for survival
-Too much energy would be lost to sustain another trophic level
Why it is more energy efficient for humans to eat crop plants than to eat livestock that have fed on crop plants
There are more stages in the food chain if more animals are present(because plants have more energy than animals)
Nitrogen cycle
-Decomposition of plant and animal protein to ammonium ions
-Nitrification
-Nitrogen fixation by lightning and bacteria
-Absorption of nitrate ions by plants
-Production of amino acids and proteins
-Feeding and digestion of proteins
-Deamination
-Denitrification
Role of microorganisms
Help to convert nitrogen to different forms so that they can be used(eg. in decomposition, nitrification, nitrogen fixation and denitrification)
Factors affecting the rate of population growth for a population of an organism
-Food supply
-Competition
-Predation
-Disease
What happens at lag phase
-Population growth begins slowly from a few organisms
-Organisms getting used to surroundings
What happens at log phase
-Exponential growth(due to lots of resources and mates)
-Maximum growth rate is achieved
What happens at stationary phase
-Carrying capacity of the environment reached(maximum population size that the environment can support)
-This may be due to limited resources(eg. food, space)
-Death rate is equal to birth rate
What happens at death phase
-Sudden environmental change causes an inability of the environment to support the population
-Death rate is higher than birth rate
-Population decreases
