Biology & our environment

Variation characteristics of organisims vary within & between species. genetic variationMutationsEnvironmental variation

Evolution a gradual process involving gene mutation & natural selection, which can lead to the development of new species

interdependence can be shown using food chains, food webs & predatory-prey relationshipsfood chains - arrows show the direction of energy flow from one organism to the next.  trophic (feeding) level.Producers - start the food chain because carry out photosynthesis& produced own foodConsumers - organisms that obtain energy by eating other organisms or parts of them.Animals that eat plants are called herbivores or primary consumersanimals that eat mainly primary consumers are called secondary consumers or carnivoresenergy is lost as you move from on trophic level to the next in a food chain. energy is lost during movement & as heat from respiration.in any ecosystem, the number of organisms at each trophic level decreases. there are fewer secondary consumers that primary consumers & very few top carnivores. some organisms die without being being eaten. this dead matter is broken down by detritivores like beetles & worms, & decomposers like fungi & bacteria.Food webs - most animals eat, or are eaten, by many other types of organism. a food web shows this variety of food sources & the interdependence of organisms within an ecosystem.Predator-prey relationships - as the predator population increases, more prey is eaten.  the prey population then decreases so there is less food for the predators. the predator numbers fall as they have less food so less predators survive to reproduce. as there are fewer, predators, fewer prey are eaten so more prey animals survive & reproduce. there are more prey animals for predators to eat , so predator numbers increas & the cycle starts all over again.prey populations can also drop if their food source decrease, eg cold weather, so prey numbers can determine predator numbers.

Classification - organisms are classified according to their characteristics.  similarities & differencesthe five Kingdoms: species are grouped into the same genus. genera are grouped into the same family. families are grouped into the same order, orders into the same class, classes into the same phylum & phylum into the same kingdom.bacteria very small, single cell, walls have non cellulose walls, no nucleus, (DNA is free in cytoplasm) many are useful as agents of decay, a fen can infect us & make toxinsprotoctists eukaryotic organisms, many are unicellular, some can photosynthesise, laret than bacteria but still microscopic.  fungi eukaryotic, multicellular, non cellulose sell walls, some live in or on their food (parasitic) & can cause diseases of crop plants, livestock & humans, some feed on dead matter. plants eukaryotic, multicellular, cells have walls made of cellulose, photosynthesise, include mosses, ferns, trees & flowering plants. animals eukaryotic, multicellular, dells do not have walls (can also group animals with backbones (vertebrates) or without backbones (invertebrates))vertebrates - have spinal cord & brain & a backbone (vertebral column)5 vertebrate classes: fish, amphibians, reptiles, birds & mammals.viruses - they are not really living so not fit in the above. they are not made of cells so do not reproduce on their own. they have to invade a living cell & hijack the cells structures to make copies of the virus.

keys - a way of identifying an unknown organisms. need to be able to construct & use keys to show how organisms can be ID'da branching key where questions are yes or no & you move on to the next question. eventually , the answers lead you to the name of a specimen.a numbered identification key where it allows you to ID the oranisms

Agriculture & Ecosystems - understand how human activities alter ecosystems through deforestation & agriculturethe human population increased sharply due to improved hygiene & sanitation, food production & diet, better health care, lower infant mortality (death rate) more people surviving to adulthood & reproducing.how farming affects ecosystems as human population grow,more food is needed. Modern farming is efficient but affect environment because takes up space uses resources & produces pollution. uses chemical fertilisers made in factories that burn fossil fuel (this contribute to climate range) uses machinery that burns fossil fuel, uses pesticides to reduce loss of food but these pesticides accumulate in environment & in food chains & harm other organisms. produce more animal waste (slurry) so cause pollution. rears cows that produce methane that contribute to climate change, reduces genetic diversity when one type of crop is grown (monoculture)deforestation large areas are cleared for crops or animals, or forests are cleared for timber for fuel, building materials or making furniture.   Removing trees means less carbon dioxide is removed from the atmosphere.more carbon dioxide contribute to climate change. clearing forests means that the habitats for wildlife are lost. trees provide wood & many are a source of medicines.  lack of tree roots  to hold hte oil together leads to soil erosion landslides & mudslides may happen. burying villages & killing people & wildlife.  water & minerals may drain quickly from the soil, so fewer minerals are available for plant growth.

ecosystem = all the organisms living in a particular area& the area itself. the organisms interact with each other & with the non living features of the areahabitat = the plaew where an organism lives

evolution = gradual change over a period of timepopulation = a group of organisms of at he same species, living in the same ecosystem at the same time & able to interbreedpredation = the killing & eating of one kind of organism by another. natural selection = mechanism for evolution the best adapted organisms survive & reproduce, & the alleles for the favourable characteristics are passed on to their offspring.

mutation = a change to the structure of genetic material (DNA or chromosomes) that may lead to a change in a characteristic

Transportation and ecosystems Food miles = distance food travels from where it is grown or produced to where it reaches the consumer.                this means: moving animals from farms to slaughter house & then from processing plant to shopmoving fish between countries to be processed  & distributed to supermarketsmoving farm produce to local marketsmoving fruit & vegetables to other countriesmoving anything to a processing plant which may be in other countriestrips made by consumers in their cars to the shops.You need to be able to calculate food miles to see impact of producing the food:transport & refrigeration need fossil fuel & release carbon emissions & other pollutantsCarbon dioxide & oxides of nitrogen are green house gases & contribute to climate changesulphur dioxide & nitrogen dioxide come from fuel burned in car engines & power stations, contribute to acid rain.note:  growing tomatoes in a green house in the UK has more  carbon footprint than a truck of tomatoes from Spain because you have to spend a lot of energy to heat a green house in the UK to grow the tomatoesHuman travel - air travel causes a lot of carbon emissions per person.building roads, railways or airports uses up land that can no longer be used for farming & a lot of the materials that are used as building materials or trains carriages & engines, cars & planes need to be made using fossil fuels.

How fertilisers affect ecosystemsplants grow by photosynthesis & need minerals from soil, light & water  (the minerals are Magnesium (Mg) Nitrogen (N) (in the form of nitrates or ammonium compounds) Phosphorus (P) & Potassium (K))Organic & inorganic fertilisers:organic = manure from animals, unusable parts of plants rotted down, human sewage, crushed animal bones, blood from slaughterhouses & bonfire ashinorganic = since the 1940's fertilisers have been made by chemical processes because there is not enough organic fertiliser available to grow the food that the world population needs.Eutrohication = when too much fertiliser is used. can be organic or inorganic.this is when it rains, excess fertiliser is washed off the land into streams & rivers (this is known as leaching)the extra nitrates & phosphates make algae in water grow this covers the surface of the water & prevents light from reaching the plants below so these plants die so bacteria in the water decomposes themthese bacteria use oxygen for respiration so fish in the water do not get enough oxygen for their respiration & die

key termsbioaccumulation = the accumulation (increase) of a substance in the tissues of a living organism pesticides = a substance that can kill an organism considered to be a pestherbicide = a type of pesticide that kills weeds

Pesticides and Ecosystemsa lot of food produced would be eaten or destroyed by pests like birds, insects & snails if pesticides were not used. weeds are also pests because they compete for space, light & wateruse of DDT - in the 1960's scientists found that many birds were not reproducing because they had a lot of DDT in their tissues & body fatDDT kills useful insects as well as harmful onesit stays in the insects body & when it is eaten by a predator it transfers to the their bodyDDT also stays in soil & water so it can be absorbed by fishanimals at the top of the food chain like eagles build up a lot of DDT in their tissues & this is called bioaccumulationDDT can also enter the human food chain as it stays in soil & water & may cause cancer in humansin the 1970's DDT was banned in agriculture but it is still used in some countries to kill mosquitoes & reduce the spread of malariainterfering with food chains - other pesticides may not bioaccumulate but they can still disrupt the food chain.  if insects are killed then the animals that feed on that insect will not have enough food. they may starve.  also some insecticides may kill useful insects such as bees which help pollinate plants & produce honey herbicides & the environment - these are used to kill weeds. most herbicides interfere with photosynthesis or the growth of the plant.selective herbicides only kill certain types of plants so can be used in a field where the crop will not be killednon selective herbicides kill all plants so is only good for clearing ground like next to railway linesremoving weeds can also disrupt the food chain as it may mean food for some birds or insects are removed as well which means biodiversity is reduced (ie the variety of living organisms within an ecosystem)

Pollution indicators these show you if an area is polluted or notlichens = it is made up of a fungus & an algae. the fungus provides stability & structure & traps water but the algae contains chlorophyll that photosynthesises & so makes its own food. there are different types of lichen on trees, walls & stone surfaces.fresh water shrimps - bacteria use oxygen to decompose organic pollution like sewage or fertilisers in rivers & streams. some fresh water organisms like shrimps can only live in oxygen rich water but others can survive in low oxygen levels.  so you can tell how clean or polluted the water is by seeing what shrimp is found in it.algae - algal bloom in water indicates high levels of organic or inorganic pollution.  filamentous (thread like) algae together with fewer planktonic (single celled) algae indicates water that is more acidic.non living indicators - eutrophication means lots of nitrates dissolved in water causing algal bloom which blocks out light for plants which die so bacteria will use lots of oxygen to break the plants down.  therefore, high nitrate levels & low oxygen levels in water are non living indicators of pollution by sewage or fertilisers. high nitrate levels in drinking water can harm babies. erosion of limestone buildings - burning fossil fuels in power stations or cars may cause acid rain. this cna kill fish & trees & erodes limestone buildings. you get acid rain from : sulphur in the fuel which joins with oxygen in the air to give sulphur dioxide. carbon in fuel combines with oxygen to make carbon dioxide.  both these gases  dissolve in rainwater to make acid rain. acid dissolves calcium carbonate (limestone).  limestone buildings are gradually eroded by acid rain.  you can see this on carvings on buildings or statues. the more erosion, the more sulphur dioxide.

reducing the effects of pollution 

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