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  • Created by: LivviR123
  • Created on: 14-05-16 20:01

Adaption and Variation


  • Species adapt to their environment, adaptions make species more likely to survive and continue to exist. 
  • Cacti are well adpated for hot and dry conditions: small surface area compared to vol. to limit  water loss, they store water in their thick stem, shallow and extensive roots, ensures water is absorbed quickly over a large area
  • Fish are adapted to aquatic environments- gills extract oxygen from water for respiration, tail fins w. large surface ares to propel them, other fins for stability, streamline bodies- little resistance, organ called the swim bladder- adjust amounth of gas in their swim bladder to change their depth without using any energy.

Individuals in species vary- bc genetic variation occurs (when genes change- mutations), can be caused my outside factors (radiation, chemicals) and by mistakes during cell division. Mutations occur in body cells= little/no effect but if in formation of gametes, change will be passed on to offspring, can be helpful or harmful.

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Natural Selection- Survival of the fittest

N.S- process that causes evolution

  • Living things show genetic variation, resources lviing things need to survive are limited, individuals must compete, only some will survive. Some varieties will have a better chance of survival, those varieties will then have an increased chance of reproducing and passing on their genes. This means the characteristic will be spread through the population over time.

Selective Breeding

  • Humans deliberately choose a feature they want to appear in the next generation  and only breeding animals or plants that have it.
  • It does not help survival, it may promote features that don't. 
  • Often done with cows that produce more milk, it helps the farmer make money. 
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  • Estimated that life began approx. 3500 million years ago, first living things were very simple, life evolved to become more complex and varied- everything existing now evolved from the simple early life forms.
  • Evolution can produce new species, when groups of organisms are isolated they can't interbreed, then factors can combine so they become two different species. Different mutations create different new features in the two groups of organisms, natural selection works so they spread if they are useful. Environmental changes also play a part- if it changes inone area but not the other, only the effected ones will adapt.
  • Evidence of evolution- fossil records: newer=more complex. DNA controls characteristics of living things, it also mutates and changes over time, the more closely related two species are, the more similar their DNA is. Scientists can compare to work out how life has evolved. 
  • Evolution by Natural Selection- Charles Darwin, after many observations of organisms.
  • Lamark thought that characteristics used a lot would become more developed and then be passed on. It was dismissed when people realised that acquired characteristics do not have a genetic basis. 
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Biodiversity and Classification

Earth's biodiversity includes: the no. of different species, the range of different types, the genetic variation between organisms of the same species. Maintaining it is important bc: more plants= more resources for developing new food and medicines.

Rate of extinction is increasing- many have become extinct in the past and many are threatened now.  Correlation between growth of the world's population and no. of species extinctions. Suggests suggestion is linked to human activites. Some are hunted to extinction, others are indirect e.g. destroying habitats or introducing a new species it can't compete with. 

Classification- arranging organisms into groups

  • scientists group organisms together according to their similarities in their characteristics, genetics snd physical features. Five different kingdoms= bacteria, fungi, algae, plants and animals. Each kingdom is divided into more groups until you get to species. As you go down these groups, no. of types of organisms in each one decreases, but the characteristics increase. Classification is useful bc, it shows evoltionary relationships that can be shown for all living and fossilised organisms. 
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Interactions between organisms

Every living thing needs resources from its environment- light, food, oxygen (+carbon dioxide for plants), water. If an essential factor is limited, species must compete, not enough= some won't survive- limting their population in that habitat- organisms also depend on other organisms -interdependence. 

Changes in environment have knock-on-effects- interedependence means that any major changes can have far-reaching effects. Food chains are effective. 

  • Blackfly lavae-loss=less competition for algae (increase), more likely to be eaten by predators (decrease).
  • Water spider, loss= less food= decrease
  • Stickleback, loss=less food=decrease.

Extinction-fossil record provides evidence of extinct organisms. Rapid changes can cause animals to becomes extinct e.g. Environmental conditions- can't adapt. New species introduced- can't compete. An organism it's reliant on becomes extinct.  

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Energy in an ecosystem


plants use a small amount during photosynthesis, light energy is stored by converting it to chemcials which make up the plants' cells. Energy is transferred by eating, when decay organisms feed on dead organisms/ waste materials. Energy is lost at each stage- a lot used for staying alive (i.e respiration). Most is then lost to the surroundings as heat, especially for mammals (they require a constant internal temp). Also lost at differnt stage of food chain- waste (excretion and urine). This is why after 4-5 stages food chains stop, energy runs out/too low. 

Energy flows allow you to work out energy lost and efficiency.

Efficiency= energy available to next stage/ energy that was available to previous stage x100

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The Carbon Cycle

  • Only one arrow going down- the whole thing is powered by photosynthesis
  • Photosynthesis removes CO2 from air into sugars, plants can then incorporate this carbon into carbs, fats and proteins too.
  • Eating passes carbon compounds in the plants along to aniamls in the food chain/web
  • Respiration (plants and animals) realeases CO2.
  • Plants eventually die and decompose
  • When they decompose they're broken down by microorganisms. Thse decomposers release CO2 back into the air by respiration as they break down the material. 
  • Combustion of fossil fuels release CO2 back into the air
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The Nitrogen Cycle

  • The atmosphere is 78 percent gas- N2- very unreactive and it can't be used directly by plants or animals.
  • Nitrogen is needed for making proteins for growth- plants get their nitrogen from the soil but it needs to be turned into nitrates first. Animals can only get proteins by eating plants- other animals.
  • Nitrogen fixation is a process turning N2 from the air into nitrogen compounds (e.g nitrates)  in the soil that plants can use. Two main ways are: lightning- so much energy in a bolt that it's enough to make nitrogen react with oxygen to give nitrates. Nitrogen-fixing bacteria in roots and soil. 
  • Decomposers break down proteins in dead plants and animals , and urea in excreted animal waste, into ammonia. Ammonia is turned into nitrates by nitrifying bacteria found in the soil.


  • Decomposers- decompose proteins and urea and turn them into ammonia
  • Nitrifying bacteria- turn ammonia in decaying matter into nitrates (nitrification) 
  • Nitrogen-fixing bacteria- turn atmospheric N2 into nitrogen compounds plants can use
  • Denitrifying bacteria- turn nitrates back into N2 gas- no benefit to living organisms. 
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Measuring Environmental Change

Non-living indicators:

Temperature- variation over a long period of time indicates climate of the environment is changing- e.g. global warming. Nitrate level- indicator for environmental change in a body of water. Increase in nitrate level could be caused by seage or fertilisers entering the water- could show pollution. Carbon Dioxide level- environmental change in air, increase in CO2 could be caused by lots of factors, including human activites- burning fossil fuels. 

Living indicators

Lichen-  v. sensitive to levels of sulfur dioxide in atmosphere, give a good idea about pollution from car exhausts, power stations etc. No. and type at a particular location will indicate how clean the air is. Lots= clean air. Mayfly Nymphs-  raw sewerage released into river, bacterial pop. increases and uses up oxygen. V. sensitive to level of oxygen, lots= clean water. Phytoplankton- pop. increases when levels of nitrates and phosphates in water increase- algae bloom. Lots indicate water pollution- eutrophication. 

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  • Human activities damage the environment, some damage can't be repaired, means environment won't be the same for future generations.
  • Greater pressure on our planet's limited resources e.g fossil fiels
  • Maintaining biodiversity is important

Packaging can be made more sustainable

  • Thrown away packaging isn't sustainable because: resources can't be reused, lots of energy has been put into making it, landfill sites use up space and damage the environment. 
  • Can be improved by using renewable materials- resources can be replaced (e.g trees), using less energy (e.g using recycled materials), creating less pollution- using biodegradable materials- more sustainable. 
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Very good revision resource! Thanks

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