Topic 19 Flashcards
“What is the main source of energy in biological systems?
The sun
Describe the flow of energy in biological systems
“Light energy from the sun is trapped by photosynthetic organisms
Energy is stored as chemical energy in organisms
Energy is eventually lost to the environment”
What is a food chain?
A way of showing the flow of energy between organisms starting with a producer
How is energy transferred between organisms in a food chain?
By ingestion (organisms eating other organisms)
What is a trophic level?
The position that an organism holds in a food chain, food web, pyramid of numbers or pyramid of biomass
Why are biomass transfers not 100% efficient?
“Energy is lost through:
Egestion (removal of faeces)
Excretion (removal of waste products e.g. urine)
Respiration
The production of inedible bones and shells”
Why do food chains usually have fewer than 5 trophic levels?
Biomass transfers are not 100% efficient and so there is often not enough energy to support 5 trophic levels
Why is it most efficient to supply plants as food for humans?
“Using the plants as food for livestock wastes energy as the biomass transfers are not 100% efficient
Eating plant transfers can maximise the amount of energy gained as there is only one transfer”
What is a food web?
Multiple interconnected food chains
What is a producer?
An organism that makes its own food (usually through photosynthesis)
What is a consumer?
An organism that gets its energy by eating other organisms
What is a primary consumer?
An organism that feeds on producers
What is a secondary consumer?
An organism that feeds on primary consumers
What is a tertiary consumer?
An organism that feeds on secondary consumers
What are herbivores?
Herbivores are animals that only eat plants
What are carnivores?
Organisms that mainly eat animals
What are decomposers?
Organisms that get Theo energy from dead/waste organic material
Explain the impact humans have on food chains and webs by overharvesting certain species
Many organisms rely on other organisms for food, overharvesting can reduce the amount of food available for other animals
Explain the impact humans have on food chains and webs by introducing other species into a habitat
Introducing new organisms increases competition and can interfere with the food chain, causing organisms who cannot compete to die
What is a pyramid of numbers?
A pyramid of numbers shows the number of organisms at each trophic level
What is a biomass pyramid?
A pyramid that shows the total dry mass of organisms at each trophic level
Why is a pyramid of biomass a better way of representing a food chain than a pyramid of numbers?
Pyramids of biomass take into account the size of the organisms and are less easily misinterpreted
Describe the carbon cycle
1) Carbon present in atmosphere as CO2
2) CO2 taken by planks in photosynthesis & transferred to other molecules (eg. proteins & carbohydrates)
3) molecules (w/ C) passed on through food chains during feeding
4) C returned to atmosphere through
-respiration
-decomposition
-burned fossil fuel or combustion or deforestation
State the effect of burning fossil fuels on carbon dioxide concentration in the environment
Burning fossil fuels releases more carbon dioxide into the atmosphere, increasing the concentration of CO2
State the effect of deforestation on carbon dioxide concentration in the environment
“Trees take in carbon dioxide during photosynthesis (decreasing the atmospheric carbon dioxide concentration)
Cutting down trees prevents this and so the atmospheric carbon dioxide concentration does not decrease”
Briefly describe how nitrogen is cycled through an ecosystem
“Nitrogen is fixed by lightning and bacteria
Decomposers break proteins / urea down into ammonium ions
Nitrifying bacteria convert ammonia, ions into nitrites and nitrates
Plants absorb nitrate ions
Denitrifying bacteria release nitrogen back to the atmosphere”
What is deamination?
The removal of the amine group in an amino acid
State 4 roles of bacteria in the nitrogen cycle
“Decomposition
Nitrification
Denitrification
Nitrogen fixation”
Define population
A species that occupy the same habitat at the same time
Define community
All the different populations in an ecosystem
Define ecosystem
Both the community and their physical environment e.g. a pond
State 3 factors that affect population growth rates
Disease, Predation, Availability of food
Describe and explain the lag phase in population growth
Population size increases slowly at the beginning as there are few individuals so reproduction rate is slow
Describe and explain the log phase in population growth
The growth of the population is increasing at a fast (exponential) rate- many individuals and lots of resources available
Describe and explain the stationary phase in population growth
The amount of births and deaths are equal so population size does not increase- resources are limited so population does not increase further
Describe and explain the death phase in population growth
Once the resources begin to be used up, organisms begin to compete for resources and organisms will die as resources become scarce and toxins build up
