Biology B7


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an ecosystem is an area containing a self sustained community of organisms living in non living surroundings eg pond

within an ecosystem there are -

autotrophs (self feeders) they make their own food and an example are plants. these are also known as producers

heterotrophs  for example animals, they are unable to creat their own food so they get their energy from consuming other organisms. these are also know as secondary consumers


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pyramid of number

a pyramid of number -

  • shows the feeding reletionships between organisms in a food chain
  • shows the total number of organisms that feed on each other
  • uses horizontal bars to represent a different organism(trophic level)

typically the bottom bar (the autotroph) is the largest and the top bar (the top consumer) is the smallest. this is because only some of the energy and nutrients are passed on from consumer to consumer

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respiration is the release of energy from food chemicals. there are two types - aerobic respiration and anaerobic respiration

aerobic - releases energy inside living cells by breaking down and combining glucose molecules with oxygen 

anaerobic- releases energy inside living cells by breaking down glucose molecules in the absence of oxygen. anaerobic respiration - takes place when not enough oxygen can get to the muscles,  produces short bursts of energy, is less efficient and produces less energy that aerobic resp, produces lactic acid anaerobic can't be used for long

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respiration in action

during exercise

  • respiration increases in order to deliver a faster supply of glucose and oxygen to the muscles so they are able to work faster and move
  • the heart rate increases in order to pump more blood around the body and to remove the increase levels of carbon dioxide produced by the faster rate of respiration
  • the breathing rate increases in order to ensure that theres enough oxygen circulating round the body in the blood cells

the energy to contract muscles come from the chemical ATP (adenosine triphosphate)

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Sickle cell anaemia

sickle cell anaemia is a disorder that affects the haemoglobin in the red blood cells

if a person has sickle cell, they have an abnormal form of haemoglobin which makes their red blood cells change shape untill they become sickle- shaped. these deformed blood cells block blood vessels and deprive the bodys tissues and organs or oxygen.

symptoms are

  • feeling weak/tired
  • painfull cramps and pain in joints
  • anaemia
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Sickle cell and malaria

malaria can harm or kill poeple who have normal heamoglobin. this means that in areas where malaria is common, the number of people with normal heamoglobin in the population will decrease.

so in area's where malaria is common, carriers are more likely to reproduce and pass on their genes to their offspring, than people who either has normal alleles or who have two sickle cell alleles.

this means the number of people who carry the faulty gene will increase, causing the frequency of sickle cell allele to be higher that it would if malaria didnt exist. this is an example of natural selection.

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evolution of parasites

a parasites body is specifically adapted to survive within a particular host. the evolution of the parasite is closely linked to that of its host,

an example is the tapeworms live inside the intestines of the host. absorbing the food the host eats. the tapeworms shape and features are adapted for its function -

  • the top of the tapeworm has suckers and teeth like structures to hold onto the inside of the intestine
  • tapeworms are flat and very long, so they have a large surface area through which to line the intestine and absorb food
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