Chapter 19: Organisms and their environment Flashcards
Principle Source of energy
the Sun is the principal source of energy input to biological systems
Transfer of energy
- Energy flows from the sun to the first trophic level (producers) in the form of light
- Producers convert light energy into chemical energy and it flows in this form from one consumer to the next
- Eventually all energy is transferred to the environment
– Energy is passed on from one level to the next with some being used and lost at each stage
Describe a food chain
showing the transfer of energy from one organism to the next, beginning with a producer
Describe a food web
a network of interconnected food chains and interpret food webs
Describe a producer as
an organism that makes its own organic nutrients, usually using energy from sunlight, through photosynthesis
Describe a consumer as
an organism that gets its energy by feeding on other organisms
Describe a herbivore
an animal that gets its energy by eating plants
Describe a carnivore
an animal that gets its energy by eating other animals
Describe a decomposer as
an organism that gets its energy from dead or waste organic material
Discuss the advantages of using a pyramid of biomass rather than a pyramid of numbers to represent a food chain
It is more accurate as the organism’s size is taken into account.
Discuss the advantages of using a pyramid of energy rather than pyramids of numbers or biomass to represent a food chain
Pyramid of energy shows amount of energy trapped per unit time and area at each stage of a food chain.
for weight two species do not necessarily have the same energy content.
Explain why the transfer of energy from one trophic level to another is often not efficient
Only 10% is passed on to next trophic level
Because
-not all of the organism is consumed.
-not all of the consumed energy is available for the next trophic level. (Metabolic reaction, respiration, movement and reproduction)
- some energy is lost in the form of waste products.
why food chains usually have fewer than five trophic levels
due to the loss of energy between each level of consumers. Remaining energy can’t benefit a consumer
why it is more energy efficient for humans to eat crop plants than to eat livestock that have been fed on crop plants
In term of conversations of energy, there is an increased efficiency in supplying green plants as human food
Short food chains are more efficient than long ones in providing energy to the top consumer
Describe the carbon cycle
Carbon moves into and out of the atmosphere mainly in the form of carbon dioxide.
Plants take carbon dioxide out of the air by photosynthesis.
Plants convert carbon dioxide into organic materials (carbohydrates, fats, proteins)
Herbivores obtain carbon compounds by eating plants.
Carnivores gain carbon compounds by eating other animals.
Animals and plants release carbon dioxide back into the air through respiration.
When organisms die they usually rot (decompose).
Decomposers break down the organic molecules through the process of respiration to release energy. Thus decomposers also release carbon dioxide.
If a dead organism does not decompose, the carbon compounds are trapped in its body. Over a long period of time, this can form fossil fuels.
Combustion of fossil fuels releases carbon dioxide back into the air.
Describe the nitrogen cycle
• decomposition of plant and animal protein to ammonium ions
• nitrification (The conversion of ammonium ions to nitrate ions by nitrifying bacteria.)
• nitrogen fixation ( nitrogen gas is converted into nitrates) by lightning and bacteria
• absorption of nitrate ions by plants
• production of amino acids and proteins
• feeding and digestion of proteins
• deamination (the removal of an amine group from a molecule.)
• denitrification (the nitrates from the soil are then converted into nitrogen gas by denitrifying bacteria)
roles of microorganisms in the nitrogen cycle
decomposition, nitrification, nitrogen fixation and denitrification
Describe a population
a group of organisms of one species, living in the same area, at the same time
Describe a community as
all of the populations of different species in an ecosystem
Describe an ecosystem as
a unit containing the community of organisms and their environment, interacting together
factors affecting the rate of population growth for a population of an organism
food supply, competition, predation and disease
Lag phase: organisms are adapting to the environment before they are able to reproduce
Log:food supply is abundant, birth rate is rapid and death rate is low; growth is exponential
Stationary phase: population levels out due to a factor in the environment, such as a nutrient
Death phase: population decreases as death rate is now greater than birth rate
