B3-Life on Earth-OCR 21st Century

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What is a species?
A group of organisms that can breed together to produce fertile offspring
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How are cacti are adapted to their environment?
1)a rounded shape giving them a small surface area compared to their volume to reduce water loss 2)they store water in their thick stem which they can use to survive when there's no water 3)shallow but extensive roots water is absorbed alot+quickly
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Why do mutations in sex cells have a greater effect than mutations in body cells?
Mutations in sex cells will be passed onto an organisms offspring
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How does selective breeding differ from natural selection?
Selective breeding involves humans deliberately choosing a feature they want to appear in the next generation and only breeding from animals or plants that have it, natural selection which only selects features that help survival.
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How could evolution lead to the formation of new species?
Sometimes groups of organisms of the same species become isolated from each other so they cant interbreed, factors combine to make the two groups so different that they become two different species
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How do fossils provide evidence that we evolved from simpler life forms?
There is evidence for evolution in the fossil record, which shows species getting more and more complex as time goes on
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How do scientists use DNA evidence to show evolution?
All living things have some similarities in their DNA because they all evolved from the same simple life forms. The more closesly related 2 species are the more similar their DNA is. Scientists use this to work out how life has evolved
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What was Lamarcks theory?
If a characteristic was used a lot by an animal then it would become more developed and these acquired characteristics could be passed onto the animals offspring
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Why was Lamarck's theory rejected?
Acquired characteristics dont have a genetic basis and so are unable to be passed onto the next generation
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What is biodiversity?
The variety of life on earth
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What are the likely causes of the increasing rate of extinction?
Human activites: there is a correlation between the growth of the worlds population and the number of species extinction, humans can indirectly cause extinction by destroying a habitat or introducing a new species which it cannot compete with
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Why do scientists classify organisms?
It shows us the evolutionary relationships between different organisms eg 2 organisms that are in similar classification groups will share lots of genetic and structural characteristics so its likely that they evolved from a shared ancestor
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How do scientists classify organisms?
According to similarities in their genetics (DNA) and physical features
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What 4 things are essential for life?
1)Light (needed by plants for photosythesis) 2)Food (for animals) and Minerals (for plants) 3)Oxygen (for animals and plants) and CO2 (for plants) 4)Water (vital for all living organisms)
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Why do organisms have to compete for resources?
If any essential resource in an environment is in low supply the organisms must compete or they will not survive
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If one organism in a food web dies why are other organisms affected?
The interdependence of all living things in a habitat means that any major change in the habitat can have far reaching effects
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What are the 3 main causes of extinction?
Environmental change which a species cannot adapt to, a new species (competitor,disease organism or predator) is introduced, an organism in its food web which it relies on becomes extinct
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What is the source of all the energy in an ecosystem?
The sun
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How is energy lost in a food chain?
through heat or respiration, excreted as waste products, trapped in materials such as bone and fur
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How is carbon dioxide removed from the atmosphere?
By plants in photosyntheis and it is incorporated into their cells as carbon compounds
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How is carbon passed between animals in an ecosystem?
Animals consume the carbon compounds in plants and pass them along to other animals in a food chain or web
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How does carbon return to the air?
Respiration,combustion of fossil fuels,decomposing plants and animals are broken down by microorganisms which release co2 back into the air by respiration as they break down the material
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What is the role of decomposers in the nitrogen cycle?
They decompose proteins and urea and turn them into ammonia
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What is the role of nitrifying bacteria in the nitrogen cycle?
They turn ammonia in decaying matter into nitrates (called nitrification)
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What is the role of nitrogen-fixing bacteria in the nitrogen cycle?
They turn atmospheric nitrogen into nitrogen compounds that plants can use
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What is the role of denitrifying bacteria in the nitrogen cycle?
They turn nitrates back in nitrogen gas which has no benefit to living organisms
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How is temperature used as a non-living indicator to measure environmental change?
Temperature measurements taken using instruments over a long period of time could indicate that the climate of the environment is changing eg global warming
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How are nitrate levels used as a non-living indicator to measure environmental change?
Nitrate level can we used as an indicator of environmental change in a body of water. An increase in nitrate level could be caused by sewage or fertilisers entering the water which could show that the water is being polluted
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How are CO2 levels used as a non-living indicator to measure environmental change?
CO2 level can be used to measure environmental change in the air. An increase in CO2 could be caused by lots of factors including human activities such as burning fossil fuels. Increases in CO2 increase the rate of global warming
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How can mayfly nymphs be used to measure environmental change?
If raw sewage is released into a river the bacterial population in the water increases and uses up the oxygen. Mayfly Nymphs are very sensitive to the level of oxygen in the water. Finding mayfly nymphs in a river indicates the water is clean
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What is monoculture and how does it affect biodiversity?
Large scale monoculture crop production (where farmers grow fields containing only 1 type of crop) is not sustainable because it doesnt maintain biodiversity. A single type of crop will support fewer species than a field containing different species
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Explain 2 ways that packaging materials can be made more sustainable
Making packaging from recycled materials uses less energy than producing new materials, using biodegradable packaging means they can be broken down naturally by microorganisms and will not pollute the land for hundreds of years
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Why is decreasing the amount of packaging more sustainable than anything else?
Even when biodegradable materials are used they still take a while to break down in landfill sites because there's not much oxygen available, making and transporting any packaging material uses up energy
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Card 2

Front

How are cacti are adapted to their environment?

Back

1)a rounded shape giving them a small surface area compared to their volume to reduce water loss 2)they store water in their thick stem which they can use to survive when there's no water 3)shallow but extensive roots water is absorbed alot+quickly

Card 3

Front

Why do mutations in sex cells have a greater effect than mutations in body cells?

Back

Preview of the front of card 3

Card 4

Front

How does selective breeding differ from natural selection?

Back

Preview of the front of card 4

Card 5

Front

How could evolution lead to the formation of new species?

Back

Preview of the front of card 5
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merisha

excellent resource!!!!!!!!

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