Environment and Evolution



  • Desert aminals have adapted to save water and keep cool
  • Large Surface Area compared to Volume-this lets the desert animals lose more body heat-stops them overheating
  • Efficient with water-They lose less water by producing small amounts of concentrated urine. They also make very little sweat. Camels are able to tolerate big changes in body temperature, kangaroo rats live in burrows underground where it's cool
  • Good in Hot Conditions-They have very thin layers of body fatand a thin coat to help them lose body heat. Camels keep nearly all their fat in their humps
  • Camouflage-Helps to avoid predators, or to sneak up on prey
  • Artic animals have adapted to reduce heat loss
  • Small Surface Area compared to Volume-Animals living in cold conditions have a compact (round) shape to keep their surface area to a minimum-this reduces heat loss
  • Well Insulated-They have a thick layer of blubber for insulation-acts as an energy store when food is scarce. Thick hairy coats keep body heat in and greasy fur sheds water-this prevents cooling because of evaporation
  • Camouflage-Help them avoid predators, or to sneak up on prey
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Adaptations 2

  • Desert Plants have adapted to having little water
  • Small Surface Area compared to Volume-Plants lose water vapour from the surface of their leaves. Cacti have spikes instead of leaves to reduce water loss. Small surface area reduces water loss
  • Water Storage Tissue-A cactus stores water in its thick stem
  • Maximising Water Absorption-Some cacti have shallow but large roots to absorb water quickly over a large area. Others have deep roots to access underground water
  • Some plants and animals are adapted to deter predators
  • Some plants and animals have armour- like roses(thorns), cacti(sharp spines) and tortoises(shells)
  • Others produce poisons-like bees and poison ivy
  • Some have amazing warning colours to scare off predators-like wasps

Microorganisms have a huge variety of adaptations so that they can live in a wide range of environments. e.g. bacteria is known as an extremophiles-they're adapted to live in seriously extreme conditions like super hot volcanic vents, in very salty lakes or at high pressure on the sea bed

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Competition and Environmental Change

  • Organisms compete for resources to survive
  • Plants need light,space,water and minerals from the soil
  • Animals need territory,food,water and mates
  • Organisms compete with other species and members of their own species for the same resources
  • Environmental Changes are caused by different factors
  • Living Factors-A change in occurance of infectious diseases, a change in the number of predators, prey,availability of food sources and types of competitors
  • Non-Living Factors-A change in average temperature,rainfall and level of air or water pollution
  • Environmental Changes affect populations in different ways
  • Population size increases-there's more food available,predators survive and reproduce
  • Population size decreases-e.g. the no. of bees decreasing: pesticides, less food, more disease
  • Population distribution changes-e.g. the distribution of bird species in Germany is changing because of the rise in average temperatures. Mediterranean species now present in parts of Germany
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Measuring Environmental Change

Environmental Changes can be measured using living factors

  • Some organisms are very sensitive to changes in their environment and so can be studied to see the effect of human activities- these organisms are known as indicator species
  • Air pollution can be monitored by looking at particular types of lichen that are very sensitive to the concentration of sulphur dioxide in the atmosphere-this will give a good idea about the level pollution from car pollution and power stations etc.
  • The number and type of lichen at a particular location will indicate how clean the air is- if there is lots of lichen it means the air is clean
  • If raw sewage is released into a river, the bacterial population in the water increases and uses up the oxygen. Some invertebrate animals, like mayfly larvae, are good indicators for water pollution because they're sensitive to the concentration of dissolved oxygen in the water. If you find mayfly larvae in a river, it indicates the water is clean
  • Other invertebrate species have adapted to live in polluted conditions- so if you see a lot of them you know there's a problem. e.g. rat-tailed maggots and sludgeworms indicate a very high level of water pollution
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Measuring Environmental Change 2

Environmental Changes can be measured using non-living indicators

  • To find out about environmental change, scientists are busy collecting data about the environment
    • They use satellites to measure the temperature of the sea surface and the amount of snow and ice cover. These are modern, accurate instruments and give us global coverage.
    • Automatic weather stations tell us the atmospheric temperature at various locations. They contain thermometers that are sensitive and accurate-they can measure to very small fractions of a degree
    • They measure rainfall using rain gauges, to find out how much the average rainfall changes year on year
    • They use dissolved oxygen meters, which measure the concentration of dissolved oxygen in the water, to discover how the level of water pollution is changing
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Energy Transfer and Decay

  • Trophic level is a feeding level
  • Why is there less energy and biomass each time you move up a trophic level?
  • Energy from the Sun is the source of energy for nearly all life on Earth
  • Green plants and algae use a small percentage of the light energy from the Sun to make food during photosynthesis. This energy's stored in the substances which make up the cells of plants and algae, and then works its way through the food chain as animals eat them and each other
  • Respiration supplies the energy for all life processes including movement. Most of the energy is eventually lost to the surroundings as heat
  • Some of the materials which makes up plants and animals is inedible, so it doesn't pass to the next stage of the food chain. Material and energy are also lost from the food chain in the organisms' waste materials
  • This explains why you get biomass pyramids. Most of the biomass is lost and does not become biomass in the next level uo
  • This is why you hardly get food chains with more than five tropic levels. So much energy is lost at each stage that there's not enough left to support more organisms after four or five stages
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The Carbon Cycle

  • The Carbon Cycle shows how Carbon is recycled
  • The whole thing is powered by photosynthesis. C02 is removed from the atmosphere by green plants and algae, and the carbon is used to make carbohydrates, fats and proteins in the plants and algae
  • Some of the carbon is returned to the atmosphere as CO2 when the plants and algae respire. Some of the carbon becomes part of the fats and proteins in animals when the plants and algae are eaten. The carbon then moves through the food chain
  • Some of the carbon is returned to the atmosphere as CO2 when the animals respire
  • When plants, algae and animals die, other animals (detritus feeders) and microorganisms feed on their remains. When these organisms respire, CO2 is returned to the atmosphere
  • Animals also produce waste, and this too is broken down by detritus feeders and microorganisms. Compounds in the waste are taken up from the soil by plants as nutrients-they're put back into the food chain again
  • Some useful plant and animal products e.g. wood and fossil fuels, are burnt (combustion). This also releases CO2 back into the air.
  • So the carbon is constantly being cycled-from the air, through food chains and eventually back out into the air again
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Organisms of the same species have differences

  • Organisms of the same species will usually have slight differences- different hair colour, individually shaped noses, different height
  • There are two types of variation--genetic and environmental

Different genes cause genetic variation

  • All plants and animals have characteristics that are in some ways similar to their parents'
  • This is because an organism's characteristics are determined by the genes inherited from their parents.
  • These genes are passed on in sex cells (gametes), which the offspring develop from
  • This combining of genes from two parents causes genetic variation--no two of the species are genetically identical
  • Some characteristics are determined only by genes. In animals these include eye colour, blood group and inherited disorders
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Variation 2

Characteristics are also influenced by the environment

  • The environment that organisms live and grow in also causes differences between members of the same species--environmental variation
  • Environmental variation covers a wide range of differences-from losing your toes in a piranha attack to getting a suntan
  • Any differences that has been caused by the conditions something lives in, is an environmental variation

Most characteristics are due to genes and the environments

  • Most characteristics e.g. body weight, height, skin colour are determined by a mixture of genetic and environmental factors
  • The maximum height that an animal or plant could grow to is determined by its genes, but whether it actually grows that tall depends on its environment
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Genes, Chromosomes and DNA

  • Most cells in your body have a nucleus. The nucleus contains your genetic material in the form of chromosomes
  • The human cell nucleus contains 23 pairs of chromosomes
  • Chromosomes carry genes. Different genes control the development of different characteristics e.g. hair colour
  • A gene is a short length of the chromosome, which is quite a long length of DNA
  • The DNA is coiled up to form the arms of the chromosomes

There can be different versions of the same gene, which gives different versions of a characteristic, like blue or brown eyes

The different versions of the same gene are called alleles instead of genes

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Sexual reproduction produces genetically different cells

  • Sexual reproduction is where genetic information from two organisms (a mother and a father) is combined to produce offspring which are genetically different to either parent
  • In sexual reproduction the mother and father produce gametes--egg and sperm cells
  • The egg and the sperm cell then fuse together (fertilisation) to form a cell with the full number of chromosomes (half from the mother and half from the father)
  • This is why the offspring inherits features from both parents-it's received a mixture of chromosomes from its mum and its dad
  • This mixture of genetic material produces variation in the offspring

Asexual reproduction produces genetically identical cells

  • An ordinary cell can make a new cell by dividing into two. The new cell has exactly the same genetic information as the parent cell
  • This is how all plants and animals grow and produce replacement cells
  • Some organisms also produce offspring using asexual reproduction e.g. bacteria and certain plants
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