B3: Life on Earth

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What is the definition of a species?
A group of organisms that can breed together to produce fertile offspring.
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Why do species adapt to their environments?
They adapt in order to survive, and then they can produce offspring. This makes the entire species more likely to survive.
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How have Cacti adapted to desert conditions?
They have a rounded shape giving them smaller surface area to reduce water loss, they also have a cuticle which reduces water loss. They have a thick stem to store water, and shallow but extensive roots to ensure water is absorbed quickly.
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How have fish adapted?
They have gills which extract oxygen from water for respiration aswell as tall fins with a large surface area to propel themselves through water, their other fins stabalise them. Their bodies are streamlined to reduce resistance as they swim.
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Why do fish have a 'swim bladder'?
So that they can adjust the amount of gas in their bladder and change depth in the water without having to use energy.
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Why are individuals of the same species different?
This is called variation, and it is caused by mutations. Mutations can be casued by outside factors like radiation, or mistakes when genes are copied.
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What is the result of mutations?
If they occur in the body cells- very little.(besides cancer) However if they occur in the formation of the sex cells they have can be passed onto offspring. The offspring will inherit new characteristics which could be harmful or helpful.
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What is natural selection?
It's the process that causes evolution. Some individuals of a particular species will have better chance of survival because of adaptations/mutations they have developed-their mutation may help them to get a resource they need to survive.
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What is natural selection (2)?
The animals who survive as a result of a mutation will pass it down to their offspring, meaning more individuals in the next generation will have the mutation as it will help them to survive.
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What is selective breeding?
This involves humans selecting a feature they want an animal or plant to have and delibratly breeding animals which have the feature. These features will not always help it to survive put could produce more money for the breeder.
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How and when did life begin?
Scientists estimate life began on earth 3500 million years ago. They also believe the very first species were very simple and have evolved to become complex. All living things evolved from the early life forms.
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How does evolution produce new species?
Different mutations create new features, natural selection causes these new features to be passed on. The environment also plays a part, if the climate changes a species will adapt to the new conditions.
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What evidence is there for evolution?
The fossil record- this shows species are getting more complex over time, DNA can also be used because all species have similarities in their DNA proving they evolved from the same simple organism.
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What was Lamarck's theory?
Lamarck believed that any aqquired characteristics e.g having big muscles from doing weights, would be passed on to the offspring. However, this theory was dismissed because aqquired characteristics aren't genetic and can't be passed on.
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What is biodiversity?
It is the variation on earth including, the number of different speices on earth, the range of dfferent types of organisms and the genetic variation between the same species.
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Why is maintaining biodiversity important?
The more plants available the more resources for food, in addition, new medicines are often made from plants e.g. digitails, a drug treating heart disease was discovered in the foxglove.
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Why is the rate of exinction increasing?
There is a correlation between the growth of the worlds population and the number of species extinctions, suggesting it is because pf human activity (hunting, destroying habitiats or introuducing a new species)
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What is classification?
Organising organisms into groups, according to similarities in their characteristics (genetics) and physical features. There are five kingdoms: bacteria, fungi, algae, plants and animals.
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Why is classfication useful?
Because it shows us evolutionary relationships, if two organisms in a similar classification share lots of genetic characteristics it is likley they evolved from the same ancestor organism.
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What resources do organisms need?
Light, (needed by plants to make food), Food, oxygen (for animals and plants) and carbon dioxide (for plants), water. Organisms also depend on eachother for food, this is called interdependence.
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What causes exitinction?
If the environmental conditions change and a species can't adapt to it, a new competitor is introduced (disease organism or preditor-this includes humans hunting), if an organism in the food web becomes extinct.
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Where does all of the energy in a food web come from?
The sun, plants use the energy from the sun for photosynthesis and to make their cells.
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How is energy transferred in a food web?
It is transferred between organisms when animals eat other plants and animals. It is also transferred when decay organisms (decomposers and detritivores) feed on dead organisms.
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Why and how is energy lost at each stage of the food web?
Mostly from life processes (respirations etc) and heat, especially mammals and birds whose bodies need to be kept at a higher constant temperature. Energy is lost through waste and uneaten parts of an animal (bones).
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Why is there usually no more than 5 stages of a food web?
So much energy is lost at each stage, there is usually not enough energy left to support more organisms after around 5 stages.
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How do you work out the energy lost at each stage of a food web?
Take the energy availabe at a stage away from the energy availabe at the previous stage.
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How would you calculate the efficiency of energy transfer in a food web?
efficiency= energy available to the next stage (over) energy available to the previous stage x 100
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How does the carbon cycle work?
CO2 is removed from the atmosphere by photosynthesis, eating passes the carbon in plants along the the animals. Both plant and animals respire which releases carbon back into the air. When plants and animals die and decompose...
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How does the carbon cycle work (2)?
decomposers break them down and release the carbon. The combustion of fossil fuels also releases CO2 into the atmosphere.
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What are the four microorganisms used in the nitrogen cycle?
Decomposers, decompose proteins and urea and turn them into ammonia, Nitrifying bacteria, turn ammonia in decaying matter into nitrates (this is nitrification). Nitrogen-fixing bacteria, turn atmospheric nitrogen into nitrogen compounds for plants.
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Whats are the four microorganisms used in the nitrogen cycle? (2)
Denitrifying bacteria, turn nitrates back into nitrogen gas.
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How can environmental change be measured with non-living indicators?
Temperature- this can indicate that the climate is changing, Nitrate level, this can be used to show change as an increase in the nitrate levels in water can be caused by sewage or fertillisers (showing pollution). CO2 leves, can measure change...
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How can environmental change be measured with non-living indicators? (2)
in the air, an increase in carbon dioxide can be caused by human activity such as burning fossil fuels. An increase in CO2 indicates an increase in the rate of global warming.
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How can environmental change be measured using living indicators?
Linchen, some are very sensitive to levels of sulfur dioxide in the atmosphere, if there are lots of linchen the air is clean and vice verca.
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How can environmental change be measured using living indicators?(2)
Mayfly Nymphs- if there are mayfly nymphs it indicated water is clean because if sewage is emptied into a river the baterial population would increase and more oxygen would be used. Mayflies are sensitive to the level of oxygen in the water.
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How can environmental change be measured using living indicators?(3)
Phytoplankton- their population increases when the levels of nitrates and phosphates in the water increase (this is called algal bloom)- these levels increase when fertillisers or sewage is added to water.
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What is sustainablility?
meeting the needs of today's population without harming the environment so that future generations can still meet their own needs.
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Why is throwing away packaging unsustainable?
The resources used to make the packaging aren't reused and they are no longer available to future generations, lots of energy is used making the packaging, waste is put in landfills which use up space and harm the environment.
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How can we make packaging more sustainable?
use renewable materials, (paper/card) can be replaced by planting new trees. Using less energy, this way the environment isn't damaged as much and less energy is used up. Create less pollution, do this by using biodegradeble materials.
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Card 2

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Why do species adapt to their environments?

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They adapt in order to survive, and then they can produce offspring. This makes the entire species more likely to survive.

Card 3

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How have Cacti adapted to desert conditions?

Back

Preview of the front of card 3

Card 4

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How have fish adapted?

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Card 5

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Why do fish have a 'swim bladder'?

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