B3 Life On Earth

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a group of living organisms that can breed together to produce fertile offspring
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features that animals have to help them survive in their environments
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what do adaptations do
increase an animals chance of survival making it more likely for them to survive and reproduce
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competition for resources
animal species might compete for food and shelter. plants will compete for space and light
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interdependent species
species in a habitat that rely on each other and their environment for food and other needs
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how much energy from the sun do plants absorb
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plants use the light energy from the sun to produce the chemicals that make up plant cells and to store energy. carbon dioxide + water ---------light energy---------> glucose + oxygen
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what happens to an organism when the environment changes
the organisms aren't as well adapted to it
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energy is transferred between organisms when:
1. when animals (consumers) eat other organisms 2. when decay organisms (decomposers and detritivores) eat dead organisms and waste materials
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only a small percentage of energy at each stage of a food chain is passed on. the rest of the energy:
1. is used for life processes (e.g. moving and keeping warm) 2. escapes to surroundings as heat 3. excreted as waste and passed onto decomposers 4. cannot be eaten and is passed on to decomposers
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why do food chains usually have no more than four species
because so much energy passes out of a food chain
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how to calculate percentage efficiency of energy transfer in a food chain
energy transferred to next level ÷ total energy in × 100
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describe the carbon cycle
plants take in carbon dioxide for photosynthesis. this makes glucose. animals and plants break down glucose in respiration. this returns carbon dioxide to the atmosphere. micro-organisms break down the molecules of dead organisms by decomposition.
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what takes carbon dioxide out of the atmosphere
oceans (CO2 dissolves), plants (photosynthesis)
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what releases carbon dioxide
combustion, decomposition, respiration, oceans
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what are the key processes of the nitrogen cycle
1. nitrogen-fixing bacteria in some roots convert nitrogen into nitrates 2. plants use nitrates to make proteins. animals digest plant proteins and use them to make animal proteins. 3. denitrifying bacteria break down nitrates into nitrogen
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what are some living indicators of environmental change
phytoplankton, to measure ocean temperature changes. lichens, to monitor air quality. mayfly nymphs, to monitor oxygen levels in rivers
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what are some non-living indicators of environmental change
nitrate levels in streams, rivers and lakes. carbon dioxide levels and temperature in air and oceans
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what is genetic variation caused by
caused by mutated genes in sex cells
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how can new characteristics of species be produced
when mutated genes in sex cells are passed on to offspring
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what causes evolution
1. mutations and natural selection 2. environmental changes (adaptation) 3. isolation
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how can isolation cause evolution
if a population of species lives separately from another population of the same species, and changes
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show how natural selection works
individuals of species r not identical (their characteristics vary). environment change/resources become scarce. competition-better adapted organisms have better chance of surviving long enough to reproduce and pass on gene. more organisms with gene
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what evidence is there to support the theory of evolution
simple organisms found in old rocks, complex organisms found in young rocks. recent fossils have features that look like adaptations of older organisms.
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what was darwin's theory
Darwin's theory of evolution states that evolution happens by natural selection
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what was lamark's theory
His theory stipulated that a characteristic which is used more and more by an organism becomes bigger and stronger. One that is not used disappears eventually. Any characteristic of an organism that is improved through use is passed to its offspring
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the variety of plant and animal life in the world or in a particular habitat
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meeting the needs of people today without damaging the earth for people in the future
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what are the pros of monoculture
cheaper and maximises crop yields
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what are the cons of monoculture
reduces biodiversity, no genetic variation between plants - all crops will die if there is an outbreak of disease
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why might species become extinct
changes in environment where organisms cannot adapt. new species arrives that competes with, eats, or causes disease. another species in food web becomes extinct
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features that animals have to help them survive in their environments

Card 3


what do adaptations do


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Card 4


competition for resources


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Card 5


interdependent species


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