B2 - Understanding Our Environment Flashcards
Which groups are organisms classified into?
- Kingdom
- Phylum
- Class
- Order
- Family
- Genus
- Species
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What are the two different forms of classifying species?
- **Artificial system **- based on one or two characteristics to make identification easier
- Natural system - based on evolutionary relationships and genetic similarities between organisms
How could the classification of an organism change overtime?
DNA Sequencing allows scientists to see the genetic diffrence between organisms, therefore some organisms could be re-classified into different groups
What does the term **Species **mean?
A groups of organisms that can interbreed to produce fertile offspring
How are organisms named?
Organisms are named by the binomial system, there are two parts to the name
- Genus - starts with capital
- Species - starts with lower case
What are the problems with classifying?
- There are different organisms that are in different stages of evolution & new organisms are being discovered therefore its hard to put them into a distinct group
- Bacteria - they don’t interbreed and reproduce asexually, therefore they can’t be classed as different species.
- Hybrids- produced by two members of different species interbreeding, the offspring is infertile so it can’t be classes as species
What is the pyramid of biomass?
It shows the dry mass of a living material at each stage of a food chain
Why might a pyramid of biomass look different compared to a pyramid of numbers?
- If the producers are very large
- If small parasites live on a large animal
Why might a POB (pyramid of biomass) be more difficult to construct even though it shows the different trophic levels better?
- some organisms feed on organisms from different trophic levels
- Measuring dry mass is difficult as it involves removing alll of the water from an organism. therefore killing it
What can the energy along the food chain be wasted as?
- heat from respiration
- egestion
- excretion
Why might the material at each stage of a trophic level, not be wasted?
The lost energy is used by decomposers that can start another food chain
Why can’t there be more than roughly five trophic levels in a pyramid of biomass?
So much energy is lost at each stage that it isn’t sustainable for the organism at the top of the food chain
How do you work out the efficiency of energy transfer?
efficiency = _energy used for growth _
energy input X 100
How is CO2 released into air?
- plants & animals **respiring **
- soil bacteria & fungi acting as decomposers
- burning of fossil fuels (combustion)
How can CO2 be absorbed from the air by the ocean and how is it released again?
- There are marine organisms that make shells made out of carbonate, this becomes limestone rocks
- the carbon in limestone can return in the air as CO2 during volcanic eruptions or weathering
carbon cycle diagram
What do plants use nitrogen for?
What happens to the nitrogen compounds in dead organisms?
They are broken down by decomposers & returned to the soil
What are the microorganisms responsible for recycling nitrogen?
- Soil bacteria/fungi - known as decomposers & they convert proteins into ammonia
- **Nitrifying bacteria - **converting ammonia to nitrates
- **Denitrifying bacteria - **converts nitrates to nitrogen gas
- Nitrogen-fixing bacteria - live in root nodules of legume plants and they fix nitrogen gas into nitrogen compounds through lightening. They have a mutualistic relationship with the plant, the bacterua gets food (sugar) from the plant and the plant gets the nitrogen compounds it need in able to make proteins and grow