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B3 INTERDEPENDENCE
Classification
Use of similarities and differences between living
things on earth in order to group them
separately
Species
A group of organisms that can breed together to
produce fertile offspring
Adaptations
 Features that help an organism survive in the environment it lives in
 These increase survival chances of an organism and therefore increase the chance
of it successfully reproducing.
 Change in environment – organisms not so adapted and therefore affects survival
rate.
 If poorly adapted to environment - less likely to survive and reproduce than those
who are. Also possible for them to become extinct.
http://www.youtube.com/watch?v=Boo1nSo73Gs
Food web
 A number of food chains joined together and shows how the
importance of each organism for the survival of the rest –
interdependence of living things.
Extinction
Fossil records show many species have become extinct
since the beginning of life on earth.
Still occurring mainly due to human activity
Northern elephant seals as a result of direct activity of
humans.
Extinction Factors
Sudden environmental changes
Diseases
Predators (when one food source disappears, predator
must find new one to survive)
New competitors
Indirect activity of humans
 Caused dodo extinction
 Lived in uninhabited islands with no natural predators
then colonised by the Dutch who hunted them for food
as they were easy to catch due to them being flightless
and large.
 Also brought new competitors to the island (dogs, cats)
which ate their eggs.
The Sun
 Most organisms dependant on energy from the sun
 Plants use photosynthesis as a process of harnessing light
energy to convert carbon dioxide into glucose .
Energy Transfer
 Animals don’t make their own food so energy transferred between
organisms and used for a number of life processes.
 10% passed on – rest passes out of food chain through;
- heat energy
- life processes like movement
- uneaten parts passed to decomposers
 Less energy transferred at each level therefore number of
organisms decrease
Producers to primary consumers efficiency:
4,500kJ + 500kJ = 5,000kJ
500kJ ÷ 5,000kJ) X 100 = 10%
Energy transferred to next level
X 100
Total energy in
Carbon cycle
All cells contain carbon as they all contain fats,
carbohydrates and proteins.
Passed from atmosphere as carbon dioxide to living things
then to different organisms then returns to atmosphere.
Explained
 Photosynthesis by green plants and carbon becomes part of their complex
molecules
 Animals eat plants and carbon as part of their proteins and fats and when they
die microorganisms feed on waste material and carbon becomes part of them
 Carbon dioxide returns to atmosphere – respiration (plants, micro organisms and
animals)
 http://www.youtube.com/watch?v=a6n54IlhDM8
Decay
Living things decay as digested by
microorganisms
Happens faster in warm, moist conditions
and plenty of oxygen – otherwise slow
Nitrogen cycle
 Need nitrogen to make proteins and not get directly from air as gas
unreactive.
 Plants take it up as compounds (nitrates and ammonium salts) from
soil.
Nitrogen fixation
 Making nitrogen compounds from air.
 Happens in;
1. Energy in lightening splits nitrogen molecules into separate atoms which react
with
oxygen to form Nitrogen Oxides. These then washed to ground by rain to
form nitrates in soil.
2. Nitrogen fixing bacteria (in soil and some plants) fix the gas
into compounds.
3. Haber process by industry to produce ammonia (which is then
make compounds used as fertilisers) from N & H.
used to
Nitrogen compounds
 In living things –returned to soil through excretion and egestion by animals and decay of
dead plants and animals
 Denitrifying bacteria in soil break down the compounds and release gas into air.
Evolution
Theories
 Know Earth is 4500 million years old and evidence living things existed 3500 million
years ago
 Earth was hotter and atmosphere consisted of mostly carbon dioxide
 Main theory: living things developed from molecules that could replicate and
originate from either conditions of earth at that time or from somewhere else
(another planet)
 Over millions of years molecules joined together with other molecules and
became more complex and dependant on each other
 Evolution by natural selection lead to life on earth today
Darwin’s theory
 All different species evolved from simple life forms which first developed 3 billion
years ago
 Evolution happens by natural selection ;
- individuals show wide range of variation due to differences in genes
- those with characteristics most suited to environment will survive and
reproduce and
genes passed on
 Those poorly adapted less likely therefore genes not passed on and species
gradually evolve.
 Although variation caused by genes and environment, only genetic can be
passed on.
Selective breeding
 Only occurs when humans intervene – different to natural selection
 Choose desired characteristics then breed them together and form offspring –
repeated over many generations
 Used by farmers to increase cattle milk yield and larger chicken eggs..etc
Mutations
 Changes that occur in genes at random and sometimes severe so cells die or
divide uncontrollably and become cancerous but changes very rarely useful
 Caused by e.g. background radiation and chemicals
 In normal body cells – die and in sex cells (sperm and ova) possibility genes
passed on.
 When passed on – natural selection ensure selection if useful or disappear from
gene pool if not
 Combined effect of mutations, environmental changes and natural selection
sometimes produces great changes causing new species but rare as only
happens when mutated no longer breed with original.
Developing explanations
 Lamarck another scientist developed alternative theory involving;
- law of use and disuse
- law of inheritance of acquired characteristics
 Characteristics used more by organism becomes bigger and stronger and those
not useful disappear and only improved features passed to offspring.
 Doesn’t account for all organisms as “simple ones disappear”
Differences – why do giraffes have long necks?
Lamarck
Darwin
A giraffe stretches its neck to reach
food high up
A giraffe with a longer neck can
reach food high up
The giraffe's neck gets longer
because it is used a lot
The giraffe is more likely to get
enough food to survive and to
reproduce
The giraffe's offspring inherit its long
neck
The giraffe's offspring inherit its long
neck
Evidence
 Fossil records – show how much organisms changed over time.
 Problem: contains gaps and not all organisms fossilise well. Also
many destroyed by Earth movements or not yet discovered.
 E.g. moths during industrial revolution – most pale birch trees then
black with soot so black camouflaged. Resistant bacteria.
 Scientists use DNA to see how closely two species related and
eventually how evolved. Found DNA supports evolution theory.
Biodiversity
Classification
Organisms classified into different groups
according to characteristics, similarities and
differences including physical features and DNA.
Into large group like kingdom with little in common
or small group with more like species.
Biodiversity
 Having a wide range of different species
 Maintaining important for sustainability of the environment e.g.
cutting down trees
 Monoculture (continuous production of one type of crop often
genetically identical) disadvantages:
- chemical pesticides used in large amounts to prevent pests
harming it. Harms environment therefore not sustainable.
- whole crop wiped out in case of natural disaster
Improving sustainability
 Recycle packaging
 Using biodegradable packaging – decomposes
quickly in landfill sites. However, oxygen presence
required for decomposition to produce carbon
dioxide only but this not the case in landfills causing
production of methane greenhouse gas